perf/jit: various improvements

PATCH In review Stephane Eranian 4 participants 29 messages Oct 13, 2016 – Oct 24, 2016 perf events

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Stephane Eranian

author

2016-10-13 11:01 UTC #0 lore raw

cover perf/jit: various improvements

From: Stephane Eranian <[email protected]>

This patch series provides several important enhancements to the perf jit code profiling support. The following is changed:
- enable building pref jitdump support without DWARF (Maciej)
- Add Exception Handling (EH) Frame record type to support unwinding
- remove useless padding of data in jitdump file
- provide a specification document for the jitdump format to help jit runtime developers add support

Note that the runtime needs to emit the unwind information. This is not supported for openJDK via JVMTI.

Thanks to Maciej, Stefano, and Ross for their contributions.

Maciej Debski (1):
perf/jit: enable jitdump support without dwarf

Stefano Sanfilippo (5):
perf/jit: make perf skip unknown records perf/jit: do not assume pgoff is zero perf/jit: add unwinding support
perf/jit: generate .eh_frame/.eh_frame_hdr in DSO perf/jit: Check JITHEADER_VERSION

Stephane Eranian (3):
perf/jit: improve error messages from JVMTI perf/jit: remove unecessary padding in jitdump file perf/jit: add jitdump format specification document

 tools/perf/Documentation/jitdump-specification.txt | 170 +++++++++++++++++++++
 tools/perf/Makefile.config                         |   2 -
 tools/perf/jvmti/jvmti_agent.c                     |  38 +----
 tools/perf/jvmti/libjvmti.c                        |  37 +++--
 tools/perf/util/Build                              |   2 +-
 tools/perf/util/genelf.c                           | 109 ++++++++++++-
 tools/perf/util/genelf.h                           |   5 +-
 tools/perf/util/jitdump.c                          |  80 ++++++++--
 tools/perf/util/jitdump.h                          |  12 ++
 tools/perf/util/unwind-libunwind-local.c           |   4 +-
 10 files changed, 393 insertions(+), 66 deletions(-)
 create mode 100644 tools/perf/Documentation/jitdump-specification.txt

Signature · 1 line

1.9.1

Stephane Eranian

author

2016-10-13 11:02 UTC #1 lore raw

PATCH 1/9 perf/jit: improve error messages from JVMTI

This patch improves the usefulness of error messages generated by the JVMTI interfac.e This can help identify the root cause of a problem by printing the actual error code. The patch adds a new helper function called print_error().

Signed-off-by Stephane Eranian <[email protected]>

---
 tools/perf/jvmti/libjvmti.c | 37 +++++++++++++++++++++++++++----------
 1 file changed, 27 insertions(+), 10 deletions(-)

tools/perf/jvmti/libjvmti.c +27 ~~-10~~

index ac12e4b91a92..2d9bc04b79a8 100644
@@ -12,6 +12,17 @@
 static int has_line_numbers;
 void *jvmti_agent;
 
+static void print_error(jvmtiEnv *jvmti, const char *msg, jvmtiError ret)
+{
+	char *err_msg = NULL;
+	jvmtiError err;
+	err = (*jvmti)->GetErrorName(jvmti, ret, &err_msg);
+	if (err == JVMTI_ERROR_NONE) {
+		warnx("%s failed with %s", msg, err_msg);
+		(*jvmti)->Deallocate(jvmti, (unsigned char *)err_msg);
+	}
+}
+
 static jvmtiError
 do_get_line_numbers(jvmtiEnv *jvmti, void *pc, jmethodID m, jint bci,
 		    jvmti_line_info_t *tab, jint *nr)

@@ -22,8 +33,10 @@ do_get_line_numbers(jvmtiEnv *jvmti, void *pc, jmethodID m, jint bci,
 	jvmtiError ret;
 
 	ret = (*jvmti)->GetLineNumberTable(jvmti, m, &nr_lines, &loc_tab);
-	if (ret != JVMTI_ERROR_NONE)
+	if (ret != JVMTI_ERROR_NONE) {
+		print_error(jvmti, "GetLineNumberTable", ret);
 		return ret;
+	}
 
 	for (i = 0; i < nr_lines; i++) {
 		if (loc_tab[i].start_location < bci) {

@@ -71,6 +84,8 @@ get_line_numbers(jvmtiEnv *jvmti, const void *compile_info, jvmti_line_info_t **
 					/* free what was allocated for nothing */
 					(*jvmti)->Deallocate(jvmti, (unsigned char *)lne);
 					nr_total += (int)nr;
+				} else {
+					print_error(jvmti, "GetLineNumberTable", ret);
 				}
 			}
 		}

@@ -130,7 +145,7 @@ compiled_method_load_cb(jvmtiEnv *jvmti,
 	ret = (*jvmti)->GetMethodDeclaringClass(jvmti, method,
 						&decl_class);
 	if (ret != JVMTI_ERROR_NONE) {
-		warnx("jvmti: cannot get declaring class");
+		print_error(jvmti, "GetMethodDeclaringClass", ret);
 		return;
 	}

@@ -144,21 +159,21 @@ compiled_method_load_cb(jvmtiEnv *jvmti,
 
 	ret = (*jvmti)->GetSourceFileName(jvmti, decl_class, &file_name);
 	if (ret != JVMTI_ERROR_NONE) {
-		warnx("jvmti: cannot get source filename ret=%d", ret);
+		print_error(jvmti, "GetSourceFileName", ret);
 		goto error;
 	}
 
 	ret = (*jvmti)->GetClassSignature(jvmti, decl_class,
 					  &class_sign, NULL);
 	if (ret != JVMTI_ERROR_NONE) {
-		warnx("jvmti: getclassignature failed");
+		print_error(jvmti, "GetClassSignature", ret);
 		goto error;
 	}
 
 	ret = (*jvmti)->GetMethodName(jvmti, method, &func_name,
 				      &func_sign, NULL);
 	if (ret != JVMTI_ERROR_NONE) {
-		warnx("jvmti: failed getmethodname");
+		print_error(jvmti, "GetMethodName", ret);
 		goto error;
 	}

@@ -253,7 +268,7 @@ Agent_OnLoad(JavaVM *jvm, char *options, void *reserved __unused)
 
 	ret = (*jvmti)->AddCapabilities(jvmti, &caps1);
 	if (ret != JVMTI_ERROR_NONE) {
-		warnx("jvmti: acquire compiled_method capability failed");
+		print_error(jvmti, "AddCapabilities", ret);
 		return -1;
 	}
 	ret = (*jvmti)->GetJLocationFormat(jvmti, &format);

@@ -264,7 +279,9 @@ Agent_OnLoad(JavaVM *jvm, char *options, void *reserved __unused)
 		ret = (*jvmti)->AddCapabilities(jvmti, &caps1);
                 if (ret == JVMTI_ERROR_NONE)
                         has_line_numbers = 1;
-        }
+        } else if (ret != JVMTI_ERROR_NONE)
+		print_error(jvmti, "GetJLocationFormat", ret);
+
 
 	memset(&cb, 0, sizeof(cb));

@@ -273,21 +290,21 @@ Agent_OnLoad(JavaVM *jvm, char *options, void *reserved __unused)
 
 	ret = (*jvmti)->SetEventCallbacks(jvmti, &cb, sizeof(cb));
 	if (ret != JVMTI_ERROR_NONE) {
-		warnx("jvmti: cannot set event callbacks");
+		print_error(jvmti, "SetEventCallbacks", ret);
 		return -1;
 	}
 
 	ret = (*jvmti)->SetEventNotificationMode(jvmti, JVMTI_ENABLE,
 			JVMTI_EVENT_COMPILED_METHOD_LOAD, NULL);
 	if (ret != JVMTI_ERROR_NONE) {
-		warnx("jvmti: setnotification failed for method_load");
+		print_error(jvmti, "SetEventNotificationMode(METHOD_LOAD)", ret);
 		return -1;
 	}
 
 	ret = (*jvmti)->SetEventNotificationMode(jvmti, JVMTI_ENABLE,
 			JVMTI_EVENT_DYNAMIC_CODE_GENERATED, NULL);
 	if (ret != JVMTI_ERROR_NONE) {
-		warnx("jvmti: setnotification failed on code_generated");
+		print_error(jvmti, "SetEventNotificationMode(CODE_GENERATED)", ret);
 		return -1;
 	}
 	return 0;

Signature · 1 line

1.9.1

Nilay Vaish

2016-10-13 20:22 UTC #2 lore raw

Re: [PATCH 1/9] perf/jit: improve error messages from JVMTI

Quoted 8 lines · Stephane Eranian

tools/perf/jvmti/libjvmti.c +0 -0

index ac12e4b91a92..2d9bc04b79a8 100644
@@ -12,6 +12,17 @@
 static int has_line_numbers;
 void *jvmti_agent;

tools/perf/jvmti/libjvmti.c line 24

Quoted 10 lines

tools/perf/jvmti/libjvmti.c +10 -0

+static void print_error(jvmtiEnv *jvmti, const char *msg, jvmtiError ret)
+{
+       char *err_msg = NULL;
+       jvmtiError err;
+       err = (*jvmti)->GetErrorName(jvmti, ret, &err_msg);
+       if (err == JVMTI_ERROR_NONE) {
+               warnx("%s failed with %s", msg, err_msg);
+               (*jvmti)->Deallocate(jvmti, (unsigned char *)err_msg);
+       }
+}

Do we not need to release the memory for err_msg if the condition for the 'if' statement evaluates to false? Is it that we are going to kill the process, so no need to release the memory?

--
Nilay

Arnaldo Carvalho de Melo

maintainer

2016-10-14 11:15 UTC #3 lore raw

Re: [PATCH 1/9] perf/jit: improve error messages from JVMTI

Em Thu, Oct 13, 2016 at 03:05:40PM -0500, Nilay Vaish escreveu:

Quoted 9 lines · Stephane Eranian

Quoted 8 lines

+++ b/tools/perf/jvmti/libjvmti.c

tools/perf/jvmti/libjvmti.c +6 -0

@@ -12,6 +12,17 @@
+static void print_error(jvmtiEnv *jvmti, const char *msg, jvmtiError ret)
+{
+       char *err_msg = NULL;
+       jvmtiError err;
+       err = (*jvmti)->GetErrorName(jvmti, ret, &err_msg);
+       if (err == JVMTI_ERROR_NONE) {

Quoted 8 lines

tools/perf/jvmti/libjvmti.c line 24
Quoted 4 lines
tools/perf/jvmti/libjvmti.c +4 -0
+               warnx("%s failed with %s", msg, err_msg);
+               (*jvmti)->Deallocate(jvmti, (unsigned char *)err_msg);
+       }
+}
Do we not need to release the memory for err_msg if the condition for the 'if' statement evaluates to false? Is it that we are going to kill the process, so no need to release the memory?

I guess that print_error() is called only when an error was returned somewhere, that ret parameter, then if there was no error (JVMTI_ERROR_NONE) in translating that numeric code to an string, err_msg, it can then be used with warnx() (the main purpose of print_error()) and then deallocated.

For err != JVMTI_ERROR_NONE it silently goes back to the caller that expected it to print something.

I.e. probably it should have an else clause, something like:

	if (err == JVMTI_ERROR_NONE) {
		warnx("%s failed with %s", msg, err_msg);
		(*jvmti)->Deallocate(jvmti, (unsigned char *)err_msg);
	} else {
		warnx("%s failed with an unknown error %d", msg, (int)ret);
	}

Stephane?

- Arnaldo

Stephane Eranian

author

2016-10-14 13:26 UTC #4 lore raw

Re: [PATCH 1/9] perf/jit: improve error messages from JVMTI

Quoted 41 lines · Arnaldo Carvalho de Melo

Em Thu, Oct 13, 2016 at 03:05:40PM -0500, Nilay Vaish escreveu:
Quoted 9 lines · Stephane Eranian
Quoted 8 lines
+++ b/tools/perf/jvmti/libjvmti.c
tools/perf/jvmti/libjvmti.c +6 -0
@@ -12,6 +12,17 @@
+static void print_error(jvmtiEnv *jvmti, const char *msg, jvmtiError ret)
+{
+       char *err_msg = NULL;
+       jvmtiError err;
+       err = (*jvmti)->GetErrorName(jvmti, ret, &err_msg);
+       if (err == JVMTI_ERROR_NONE) {
Quoted 8 lines
tools/perf/jvmti/libjvmti.c line 24
Quoted 4 lines
tools/perf/jvmti/libjvmti.c +4 -0
+               warnx("%s failed with %s", msg, err_msg);
+               (*jvmti)->Deallocate(jvmti, (unsigned char *)err_msg);
+       }
+}
Do we not need to release the memory for err_msg if the condition for the 'if' statement evaluates to false? Is it that we are going to kill the process, so no need to release the memory?
I guess that print_error() is called only when an error was returned somewhere, that ret parameter, then if there was no error (JVMTI_ERROR_NONE) in translating that numeric code to an string, err_msg, it can then be used with warnx() (the main purpose of print_error()) and then deallocated.
For err != JVMTI_ERROR_NONE it silently goes back to the caller that expected it to print something.
I.e. probably it should have an else clause, something like:
        if (err == JVMTI_ERROR_NONE) {
                warnx("%s failed with %s", msg, err_msg);
                (*jvmti)->Deallocate(jvmti, (unsigned char *)err_msg);
        } else {
                warnx("%s failed with an unknown error %d", msg, (int)ret);
        }
Stephane?
'I will fix all of the comments over the week-end. I am away from office today.
- Arnaldo

Arnaldo Carvalho de Melo

maintainer

2016-10-14 15:21 UTC #5 lore raw

Re: [PATCH 1/9] perf/jit: improve error messages from JVMTI

Em Fri, Oct 14, 2016 at 05:57:25AM -0700, Stephane Eranian escreveu:

Quoted 24 lines · Arnaldo Carvalho de Melo

Quoted 23 lines
Em Thu, Oct 13, 2016 at 03:05:40PM -0500, Nilay Vaish escreveu:
Quoted 3 lines
Do we not need to release the memory for err_msg if the condition for the 'if' statement evaluates to false? Is it that we are going to kill the process, so no need to release the memory?
I guess that print_error() is called only when an error was returned somewhere, that ret parameter, then if there was no error (JVMTI_ERROR_NONE) in translating that numeric code to an string, err_msg, it can then be used with warnx() (the main purpose of print_error()) and then deallocated.
For err != JVMTI_ERROR_NONE it silently goes back to the caller that expected it to print something.
I.e. probably it should have an else clause, something like:
        if (err == JVMTI_ERROR_NONE) {
                warnx("%s failed with %s", msg, err_msg);
                (*jvmti)->Deallocate(jvmti, (unsigned char *)err_msg);
        } else {
                warnx("%s failed with an unknown error %d", msg, (int)ret);
        }

Quoted 2 lines

Quoted 1 line
Stephane?
I will fix all of the comments over the week-end. I am away from office today.

I have almost all of them fixed, will fix this one too, if you agree with the analysis.

- Arnaldo

Stephane Eranian

author

2016-10-17 13:52 UTC #6 lore raw

Re: [PATCH 1/9] perf/jit: improve error messages from JVMTI

Quoted 25 lines · Arnaldo Carvalho de Melo

Em Fri, Oct 14, 2016 at 05:57:25AM -0700, Stephane Eranian escreveu:
Quoted 24 lines · Arnaldo Carvalho de Melo
Quoted 23 lines
Em Thu, Oct 13, 2016 at 03:05:40PM -0500, Nilay Vaish escreveu:
Quoted 3 lines
Do we not need to release the memory for err_msg if the condition for the 'if' statement evaluates to false? Is it that we are going to kill the process, so no need to release the memory?
I guess that print_error() is called only when an error was returned somewhere, that ret parameter, then if there was no error (JVMTI_ERROR_NONE) in translating that numeric code to an string, err_msg, it can then be used with warnx() (the main purpose of print_error()) and then deallocated.
For err != JVMTI_ERROR_NONE it silently goes back to the caller that expected it to print something.
I.e. probably it should have an else clause, something like:
        if (err == JVMTI_ERROR_NONE) {
                warnx("%s failed with %s", msg, err_msg);
                (*jvmti)->Deallocate(jvmti, (unsigned char *)err_msg);
        } else {
                warnx("%s failed with an unknown error %d", msg, (int)ret);
        }

Quoted 6 lines

Quoted 2 lines
Quoted 1 line
Stephane?
I will fix all of the comments over the week-end. I am away from office today.
I have almost all of them fixed, will fix this one too, if you agree with the analysis.

Ok, the proposed fix is correct.
Thanks for fixing issues.

Now, I am tracking down another issue with the injection of jitdump. It seems something goes wrong with ordering and timestamps and some valid jitdump samples are not symbolized. It is not clear what is causing this yet. It may be the issue raised by Adrian a while ago about the finished_round processing.

Quoted 1 line

- Arnaldo

tip-bot for Stephane Eranian

merge bot

2016-10-24 19:00 UTC #7 lore raw

[tip:perf/core] perf jit: Improve error messages from JVMTI

In reply to Stephane Eranian

perf jit: Improve error messages from JVMTI

Commit-ID:  cdd75e3b0d1e668bc498f18f0ea8353f9f955114
Gitweb:     http://git.kernel.org/tip/cdd75e3b0d1e668bc498f18f0ea8353f9f955114
Author:     Stephane Eranian <[email protected]>
AuthorDate: Thu, 13 Oct 2016 03:59:35 -0700
Committer:  Arnaldo Carvalho de Melo <[email protected]>
CommitDate: Mon, 24 Oct 2016 11:07:37 -0300

perf jit: Improve error messages from JVMTI

Signed-off-by Stephane Eranian <[email protected]>

Cc Anton Blanchard <[email protected]>

Cc Jiri Olsa <[email protected]>

Cc Namhyung Kim <[email protected]>

Cc Nilay Vaish <[email protected]>

Cc Peter Zijlstra <[email protected]>

Link http://lkml.kernel.org/r/[email protected] open here

[ Handle failure to convert numeric error to a string in print_error() ]

Signed-off-by Arnaldo Carvalho de Melo <[email protected]>

---
 tools/perf/jvmti/libjvmti.c | 39 +++++++++++++++++++++++++++++----------
 1 file changed, 29 insertions(+), 10 deletions(-)

tools/perf/jvmti/libjvmti.c +29 ~~-10~~

index ac12e4b..5612641 100644
@@ -12,6 +12,19 @@
 static int has_line_numbers;
 void *jvmti_agent;
 
+static void print_error(jvmtiEnv *jvmti, const char *msg, jvmtiError ret)
+{
+	char *err_msg = NULL;
+	jvmtiError err;
+	err = (*jvmti)->GetErrorName(jvmti, ret, &err_msg);
+	if (err == JVMTI_ERROR_NONE) {
+		warnx("%s failed with %s", msg, err_msg);
+		(*jvmti)->Deallocate(jvmti, (unsigned char *)err_msg);
+	} else {
+		warnx("%s failed with an unknown error %d", msg, ret);
+	}
+}
+
 static jvmtiError
 do_get_line_numbers(jvmtiEnv *jvmti, void *pc, jmethodID m, jint bci,
 		    jvmti_line_info_t *tab, jint *nr)

@@ -22,8 +35,10 @@ do_get_line_numbers(jvmtiEnv *jvmti, void *pc, jmethodID m, jint bci,
 	jvmtiError ret;
 
 	ret = (*jvmti)->GetLineNumberTable(jvmti, m, &nr_lines, &loc_tab);
-	if (ret != JVMTI_ERROR_NONE)
+	if (ret != JVMTI_ERROR_NONE) {
+		print_error(jvmti, "GetLineNumberTable", ret);
 		return ret;
+	}
 
 	for (i = 0; i < nr_lines; i++) {
 		if (loc_tab[i].start_location < bci) {

@@ -71,6 +86,8 @@ get_line_numbers(jvmtiEnv *jvmti, const void *compile_info, jvmti_line_info_t **
 					/* free what was allocated for nothing */
 					(*jvmti)->Deallocate(jvmti, (unsigned char *)lne);
 					nr_total += (int)nr;
+				} else {
+					print_error(jvmti, "GetLineNumberTable", ret);
 				}
 			}
 		}

@@ -130,7 +147,7 @@ compiled_method_load_cb(jvmtiEnv *jvmti,
 	ret = (*jvmti)->GetMethodDeclaringClass(jvmti, method,
 						&decl_class);
 	if (ret != JVMTI_ERROR_NONE) {
-		warnx("jvmti: cannot get declaring class");
+		print_error(jvmti, "GetMethodDeclaringClass", ret);
 		return;
 	}

@@ -144,21 +161,21 @@ compiled_method_load_cb(jvmtiEnv *jvmti,
 
 	ret = (*jvmti)->GetSourceFileName(jvmti, decl_class, &file_name);
 	if (ret != JVMTI_ERROR_NONE) {
-		warnx("jvmti: cannot get source filename ret=%d", ret);
+		print_error(jvmti, "GetSourceFileName", ret);
 		goto error;
 	}
 
 	ret = (*jvmti)->GetClassSignature(jvmti, decl_class,
 					  &class_sign, NULL);
 	if (ret != JVMTI_ERROR_NONE) {
-		warnx("jvmti: getclassignature failed");
+		print_error(jvmti, "GetClassSignature", ret);
 		goto error;
 	}
 
 	ret = (*jvmti)->GetMethodName(jvmti, method, &func_name,
 				      &func_sign, NULL);
 	if (ret != JVMTI_ERROR_NONE) {
-		warnx("jvmti: failed getmethodname");
+		print_error(jvmti, "GetMethodName", ret);
 		goto error;
 	}

@@ -253,7 +270,7 @@ Agent_OnLoad(JavaVM *jvm, char *options, void *reserved __unused)
 
 	ret = (*jvmti)->AddCapabilities(jvmti, &caps1);
 	if (ret != JVMTI_ERROR_NONE) {
-		warnx("jvmti: acquire compiled_method capability failed");
+		print_error(jvmti, "AddCapabilities", ret);
 		return -1;
 	}
 	ret = (*jvmti)->GetJLocationFormat(jvmti, &format);

@@ -264,7 +281,9 @@ Agent_OnLoad(JavaVM *jvm, char *options, void *reserved __unused)
 		ret = (*jvmti)->AddCapabilities(jvmti, &caps1);
                 if (ret == JVMTI_ERROR_NONE)
                         has_line_numbers = 1;
-        }
+        } else if (ret != JVMTI_ERROR_NONE)
+		print_error(jvmti, "GetJLocationFormat", ret);
+
 
 	memset(&cb, 0, sizeof(cb));

@@ -273,21 +292,21 @@ Agent_OnLoad(JavaVM *jvm, char *options, void *reserved __unused)
 
 	ret = (*jvmti)->SetEventCallbacks(jvmti, &cb, sizeof(cb));
 	if (ret != JVMTI_ERROR_NONE) {
-		warnx("jvmti: cannot set event callbacks");
+		print_error(jvmti, "SetEventCallbacks", ret);
 		return -1;
 	}
 
 	ret = (*jvmti)->SetEventNotificationMode(jvmti, JVMTI_ENABLE,
 			JVMTI_EVENT_COMPILED_METHOD_LOAD, NULL);
 	if (ret != JVMTI_ERROR_NONE) {
-		warnx("jvmti: setnotification failed for method_load");
+		print_error(jvmti, "SetEventNotificationMode(METHOD_LOAD)", ret);
 		return -1;
 	}
 
 	ret = (*jvmti)->SetEventNotificationMode(jvmti, JVMTI_ENABLE,
 			JVMTI_EVENT_DYNAMIC_CODE_GENERATED, NULL);
 	if (ret != JVMTI_ERROR_NONE) {
-		warnx("jvmti: setnotification failed on code_generated");
+		print_error(jvmti, "SetEventNotificationMode(CODE_GENERATED)", ret);
 		return -1;
 	}
 	return 0;

Stephane Eranian

author

2016-10-13 11:02 UTC #8 lore raw

PATCH 2/9 perf/jit: enable jitdump support without dwarf

In reply to Stephane Eranian

From: Maciej Debski <[email protected]>

This patch modifies the build dependencies on the jitdump support in perf. As it stands jitdump was wrongfully made dependent 100% on using DWARF. However, the dwarf dependency, only exist if generating the source line table in genelf_debug.c. The rest of the support does not need DWARF.

This patch removes the dependency on DWARF for the entire jitdump support. It keeps it only for the genelf_debug.c support.

Signed-off-by Maciej Debski <[email protected]>

Reviewed-by Stephane Eranian <[email protected]>

---
 tools/perf/Makefile.config | 2 --
 tools/perf/util/Build      | 2 +-
 tools/perf/util/genelf.c   | 9 +++++++--
 tools/perf/util/genelf.h   | 2 ++
 4 files changed, 10 insertions(+), 5 deletions(-)

tools/perf/Makefile.config +0 -2

index 72edf83d76b7..8cfc310d4358 100644
@@ -366,10 +366,8 @@ ifndef NO_SDT
 endif
 
 ifdef PERF_HAVE_JITDUMP
-  ifndef NO_DWARF
     $(call detected,CONFIG_JITDUMP)
     CFLAGS += -DHAVE_JITDUMP
-  endif
 endif
 
 ifeq ($(ARCH),powerpc)

tools/perf/util/Build +1 -1

index eb60e613d795..1dc67efad634 100644
@@ -120,7 +120,7 @@ libperf-y += demangle-rust.o
 ifdef CONFIG_JITDUMP
 libperf-$(CONFIG_LIBELF) += jitdump.o
 libperf-$(CONFIG_LIBELF) += genelf.o
-libperf-$(CONFIG_LIBELF) += genelf_debug.o
+libperf-$(CONFIG_DWARF) += genelf_debug.o
 endif
 
 CFLAGS_config.o   += -DETC_PERFCONFIG="BUILD_STR($(ETC_PERFCONFIG_SQ))"

tools/perf/util/genelf.c +7 -2

index c1ef805c6a8f..14a73acc549c 100644
@@ -19,7 +19,9 @@
 #include <limits.h>
 #include <fcntl.h>
 #include <err.h>
+#ifdef HAVE_DWARF_SUPPORT
 #include <dwarf.h>
+#endif
 
 #include "perf.h"
 #include "genelf.h"

@@ -157,7 +159,7 @@ gen_build_id(struct buildid_note *note, unsigned long load_addr, const void *cod
 int
 jit_write_elf(int fd, uint64_t load_addr, const char *sym,
 	      const void *code, int csize,
-	      void *debug, int nr_debug_entries)
+	      void *debug __maybe_unused, int nr_debug_entries __maybe_unused)
 {
 	Elf *e;
 	Elf_Data *d;

@@ -386,11 +388,14 @@ jit_write_elf(int fd, uint64_t load_addr, const char *sym,
 	shdr->sh_size = sizeof(bnote);
 	shdr->sh_entsize = 0;
 
+#ifdef HAVE_DWARF_SUPPORT
 	if (debug && nr_debug_entries) {
 		retval = jit_add_debug_info(e, load_addr, debug, nr_debug_entries);
 		if (retval)
 			goto error;
-	} else {
+	} else
+#endif
+	{
 		if (elf_update(e, ELF_C_WRITE) < 0) {
 			warnx("elf_update 4 failed");
 			goto error;

tools/perf/util/genelf.h +2 -0

index 2fbeb59c4bdd..5c933ac71451 100644
@@ -4,8 +4,10 @@
 /* genelf.c */
 int jit_write_elf(int fd, uint64_t code_addr, const char *sym,
 		  const void *code, int csize, void *debug, int nr_debug_entries);
+#ifdef HAVE_DWARF_SUPPORT
 /* genelf_debug.c */
 int jit_add_debug_info(Elf *e, uint64_t code_addr, void *debug, int nr_debug_entries);
+#endif
 
 #if   defined(__arm__)
 #define GEN_ELF_ARCH	EM_ARM

Signature · 1 line

1.9.1

Arnaldo Carvalho de Melo

maintainer

2016-10-13 18:17 UTC #9 lore raw

Re: [PATCH 2/9] perf/jit: enable jitdump support without dwarf

Em Thu, Oct 13, 2016 at 03:59:36AM -0700, Stephane Eranian escreveu:

Quoted 10 lines

From: Maciej Debski <[email protected]>
This patch modifies the build dependencies on the jitdump support in perf. As it stands jitdump was wrongfully made dependent 100% on using DWARF. However, the dwarf dependency, only exist if generating the source line table in genelf_debug.c. The rest of the support does not need DWARF.
This patch removes the dependency on DWARF for the entire jitdump support. It keeps it only for the genelf_debug.c support.

Please add a:

Fixes e12b202f8fb9 ("perf jitdump: Build only on supported archs")

Next time, so that scripts can pick patches for stable kernels, etc.

Adding it this time.

Thanks,

- Arnaldo

Quoted 93 lines

Signed-off-by Maciej Debski <[email protected]>

Reviewed-by Stephane Eranian <[email protected]>

---
 tools/perf/Makefile.config | 2 --
 tools/perf/util/Build      | 2 +-
 tools/perf/util/genelf.c   | 9 +++++++--
 tools/perf/util/genelf.h   | 2 ++
 4 files changed, 10 insertions(+), 5 deletions(-)

tools/perf/Makefile.config +0 -2

index 72edf83d76b7..8cfc310d4358 100644
@@ -366,10 +366,8 @@ ifndef NO_SDT
 endif
 
 ifdef PERF_HAVE_JITDUMP
-  ifndef NO_DWARF
     $(call detected,CONFIG_JITDUMP)
     CFLAGS += -DHAVE_JITDUMP
-  endif
 endif
 
 ifeq ($(ARCH),powerpc)

tools/perf/util/Build +1 -1

index eb60e613d795..1dc67efad634 100644
@@ -120,7 +120,7 @@ libperf-y += demangle-rust.o
 ifdef CONFIG_JITDUMP
 libperf-$(CONFIG_LIBELF) += jitdump.o
 libperf-$(CONFIG_LIBELF) += genelf.o
-libperf-$(CONFIG_LIBELF) += genelf_debug.o
+libperf-$(CONFIG_DWARF) += genelf_debug.o
 endif
 
 CFLAGS_config.o   += -DETC_PERFCONFIG="BUILD_STR($(ETC_PERFCONFIG_SQ))"

tools/perf/util/genelf.c +7 -2

index c1ef805c6a8f..14a73acc549c 100644
@@ -19,7 +19,9 @@
 #include <limits.h>
 #include <fcntl.h>
 #include <err.h>
+#ifdef HAVE_DWARF_SUPPORT
 #include <dwarf.h>
+#endif
 
 #include "perf.h"
 #include "genelf.h"

@@ -157,7 +159,7 @@ gen_build_id(struct buildid_note *note, unsigned long load_addr, const void *cod
 int
 jit_write_elf(int fd, uint64_t load_addr, const char *sym,
 	      const void *code, int csize,
-	      void *debug, int nr_debug_entries)
+	      void *debug __maybe_unused, int nr_debug_entries __maybe_unused)
 {
 	Elf *e;
 	Elf_Data *d;

@@ -386,11 +388,14 @@ jit_write_elf(int fd, uint64_t load_addr, const char *sym,
 	shdr->sh_size = sizeof(bnote);
 	shdr->sh_entsize = 0;
 
+#ifdef HAVE_DWARF_SUPPORT
 	if (debug && nr_debug_entries) {
 		retval = jit_add_debug_info(e, load_addr, debug, nr_debug_entries);
 		if (retval)
 			goto error;
-	} else {
+	} else
+#endif
+	{
 		if (elf_update(e, ELF_C_WRITE) < 0) {
 			warnx("elf_update 4 failed");
 			goto error;

tools/perf/util/genelf.h +2 -0

index 2fbeb59c4bdd..5c933ac71451 100644
@@ -4,8 +4,10 @@
 /* genelf.c */
 int jit_write_elf(int fd, uint64_t code_addr, const char *sym,
 		  const void *code, int csize, void *debug, int nr_debug_entries);
+#ifdef HAVE_DWARF_SUPPORT
 /* genelf_debug.c */
 int jit_add_debug_info(Elf *e, uint64_t code_addr, void *debug, int nr_debug_entries);
+#endif
 
 #if   defined(__arm__)
 #define GEN_ELF_ARCH	EM_ARM

Signature · 1 line

1.9.1

Arnaldo Carvalho de Melo

maintainer Reviewed-by Stephane Eranian

2016-10-13 19:31 UTC #10 lore raw

Re: [PATCH 2/9] perf/jit: enable jitdump support without dwarf

Em Thu, Oct 13, 2016 at 03:16:43PM -0300, Arnaldo Carvalho de Melo escreveu:

Quoted 12 lines

Em Thu, Oct 13, 2016 at 03:59:36AM -0700, Stephane Eranian escreveu:
Quoted 10 lines
From: Maciej Debski <[email protected]>
This patch modifies the build dependencies on the jitdump support in perf. As it stands jitdump was wrongfully made dependent 100% on using DWARF. However, the dwarf dependency, only exist if generating the source line table in genelf_debug.c. The rest of the support does not need DWARF.
This patch removes the dependency on DWARF for the entire jitdump support. It keeps it only for the genelf_debug.c support.

Quoted 7 lines

Please add a:
Fixes e12b202f8fb9 ("perf jitdump: Build only on supported archs")
Next time, so that scripts can pick patches for stable kernels, etc.
Adding it this time.

But, this introduces a bug, breaking the perf's static build:

[acme@jouet linux]$ git bisect bad
Bisecting: 0 revisions left to test after this (roughly 0 steps)
[f5722b101fb37339001e9524262d3eb08b7b1bfe] perf jit: Enable jitdump support without dwarf
[acme@jouet linux]$ rm -rf /tmp/build/perf/ ; mkdir -p /tmp/build/perf ; make -C tools/perf LDFLAGS=-static O=/tmp/build/perf install-bin

/tmp/build/perf/perf-in.o: In function `perf_event__jit_repipe_mmap2':
/home/acme/git/linux/tools/perf/builtin-inject.c:298: undefined reference to jit_process' /tmp/build/perf/perf-in.o: In function perf_event__jit_repipe_mmap':
/home/acme/git/linux/tools/perf/builtin-inject.c:260: undefined reference to `jit_process'
collect2: error: ld returned 1 exit status
Makefile.perf:470: recipe for target '/tmp/build/perf/perf' failed
make[1]: *** [/tmp/build/perf/perf] Error 1
Makefile:108: recipe for target 'install-bin' failed
make: *** [install-bin] Error 2
make: Leaving directory '/home/acme/git/linux/tools/perf'
[acme@jouet linux]$ git bisect bad
f5722b101fb37339001e9524262d3eb08b7b1bfe is the first bad commit
commit f5722b101fb37339001e9524262d3eb08b7b1bfe

Author: Maciej Debski <[email protected]>
Date:   Thu Oct 13 03:59:36 2016 -0700

perf jit: Enable jitdump support without dwarf

This patch removes the dependency on DWARF for the entire jitdump support. It keeps it only for the genelf_debug.c support.

Signed-off-by Maciej Debski <[email protected]>

Reviewed-by Stephane Eranian <[email protected]>

Cc Anton Blanchard <[email protected]>

Cc Jiri Olsa <[email protected]>

Cc Namhyung Kim <[email protected]>

Cc Peter Zijlstra <[email protected]>

Link http://lkml.kernel.org/r/[email protected] open here

Fixes e12b202f8fb9 ("perf jitdump: Build only on supported archs")

Signed-off-by Arnaldo Carvalho de Melo <[email protected]>

:040000 040000 281764609ccfd745f984caae6a331b5b9ebd15b0 4f1ebed718481cacdd901f28a05b347a135e46cf M tools
[acme@jouet linux]$

Please use:

make -C tools/perf build-test

That will do may build tests, including this one, the static build.

I'm trying to figure this out...

- Arnaldo

Quoted 98 lines

Thanks,

- Arnaldo

Quoted 93 lines

Signed-off-by Maciej Debski <[email protected]>

Reviewed-by Stephane Eranian <[email protected]>

---
 tools/perf/Makefile.config | 2 --
 tools/perf/util/Build      | 2 +-
 tools/perf/util/genelf.c   | 9 +++++++--
 tools/perf/util/genelf.h   | 2 ++
 4 files changed, 10 insertions(+), 5 deletions(-)

tools/perf/Makefile.config +0 -2

index 72edf83d76b7..8cfc310d4358 100644
@@ -366,10 +366,8 @@ ifndef NO_SDT
 endif
 
 ifdef PERF_HAVE_JITDUMP
-  ifndef NO_DWARF
     $(call detected,CONFIG_JITDUMP)
     CFLAGS += -DHAVE_JITDUMP
-  endif
 endif
 
 ifeq ($(ARCH),powerpc)

tools/perf/util/Build +1 -1

index eb60e613d795..1dc67efad634 100644
@@ -120,7 +120,7 @@ libperf-y += demangle-rust.o
 ifdef CONFIG_JITDUMP
 libperf-$(CONFIG_LIBELF) += jitdump.o
 libperf-$(CONFIG_LIBELF) += genelf.o
-libperf-$(CONFIG_LIBELF) += genelf_debug.o
+libperf-$(CONFIG_DWARF) += genelf_debug.o
 endif
 
 CFLAGS_config.o   += -DETC_PERFCONFIG="BUILD_STR($(ETC_PERFCONFIG_SQ))"

tools/perf/util/genelf.c +7 -2

index c1ef805c6a8f..14a73acc549c 100644
@@ -19,7 +19,9 @@
 #include <limits.h>
 #include <fcntl.h>
 #include <err.h>
+#ifdef HAVE_DWARF_SUPPORT
 #include <dwarf.h>
+#endif
 
 #include "perf.h"
 #include "genelf.h"

@@ -157,7 +159,7 @@ gen_build_id(struct buildid_note *note, unsigned long load_addr, const void *cod
 int
 jit_write_elf(int fd, uint64_t load_addr, const char *sym,
 	      const void *code, int csize,
-	      void *debug, int nr_debug_entries)
+	      void *debug __maybe_unused, int nr_debug_entries __maybe_unused)
 {
 	Elf *e;
 	Elf_Data *d;

@@ -386,11 +388,14 @@ jit_write_elf(int fd, uint64_t load_addr, const char *sym,
 	shdr->sh_size = sizeof(bnote);
 	shdr->sh_entsize = 0;
 
+#ifdef HAVE_DWARF_SUPPORT
 	if (debug && nr_debug_entries) {
 		retval = jit_add_debug_info(e, load_addr, debug, nr_debug_entries);
 		if (retval)
 			goto error;
-	} else {
+	} else
+#endif
+	{
 		if (elf_update(e, ELF_C_WRITE) < 0) {
 			warnx("elf_update 4 failed");
 			goto error;

tools/perf/util/genelf.h +2 -0

index 2fbeb59c4bdd..5c933ac71451 100644
@@ -4,8 +4,10 @@
 /* genelf.c */
 int jit_write_elf(int fd, uint64_t code_addr, const char *sym,
 		  const void *code, int csize, void *debug, int nr_debug_entries);
+#ifdef HAVE_DWARF_SUPPORT
 /* genelf_debug.c */
 int jit_add_debug_info(Elf *e, uint64_t code_addr, void *debug, int nr_debug_entries);
+#endif
 
 #if   defined(__arm__)
 #define GEN_ELF_ARCH	EM_ARM

Signature · 1 line

1.9.1

Arnaldo Carvalho de Melo

maintainer

2016-10-13 18:51 UTC #11 lore raw

Re: [PATCH 2/9] perf/jit: enable jitdump support without dwarf

Em Thu, Oct 13, 2016 at 03:37:42PM -0300, Arnaldo Carvalho de Melo escreveu:

Quoted 1 line

I'm trying to figure this out...

So, building with:

make -C tools/perf LDFLAGS=-static O=/tmp/build/perf install-bin

I get:

[acme@jouet linux]$ grep libelf /tmp/build/perf/FEATURE-DUMP feature-libelf=0
feature-libelf-getphdrnum=0 feature-libelf-gelf_getnote=0 feature-libelf-getshdrstrndx=0 feature-libelf-mmap=0
[acme@jouet linux]$

And jitdump is only linked if:

[acme@jouet linux]$ grep jitdump tools/perf/*/Build tools/perf/util/Build:libperf-$(CONFIG_LIBELF) += jitdump.o [acme@jouet linux]$

But:

#ifdef HAVE_JITDUMP
static int perf_event__jit_repipe_mmap(struct perf_tool *tool, .
.
.

        ret = jit_process(inject->session, &inject->output, machine,
                          event->mmap.filename, sample->pid, &n);

.
.
.
#endif

So we need:

[acme@jouet linux]$ git diff

tools/perf/Makefile.config +2 -0

index 8cfc310d4358..cffdd9cf3ebf 100644
@@ -366,8 +366,10 @@ ifndef NO_SDT
 endif
 
 ifdef PERF_HAVE_JITDUMP
+  ifndef NO_LIBELF
     $(call detected,CONFIG_JITDUMP)
     CFLAGS += -DHAVE_JITDUMP
+  endif
 endif
 
 ifeq ($(ARCH),powerpc)

[acme@jouet linux]$

To get that fixed.

Please let me know if this suits your needs.

I'll now try building with elfutils static libraries to see if in that case it all gets linked.

- Arnaldo

Arnaldo Carvalho de Melo

maintainer

2016-10-13 19:12 UTC #12 lore raw

Re: [PATCH 2/9] perf/jit: enable jitdump support without dwarf

Em Thu, Oct 13, 2016 at 03:51:35PM -0300, Arnaldo Carvalho de Melo escreveu:

Quoted 20 lines

So we need:

[acme@jouet linux]$ git diff

tools/perf/Makefile.config +2 -0

index 8cfc310d4358..cffdd9cf3ebf 100644
@@ -366,8 +366,10 @@ ifndef NO_SDT
 endif
 
 ifdef PERF_HAVE_JITDUMP
+  ifndef NO_LIBELF
     $(call detected,CONFIG_JITDUMP)
     CFLAGS += -DHAVE_JITDUMP
+  endif
 endif
 
 ifeq ($(ARCH),powerpc)

[acme@jouet linux]$

Quoted 6 lines

To get that fixed.
Please let me know if this suits your needs.
I'll now try building with elfutils static libraries to see if in that case it all gets linked.

After installing these packages, on fedora, i.e. installing what is needed to statically link against libelf:

elfutils-devel-static
elfutils-libelf-devel-static
zlib-static

Then it all works, libelf is statically linked and we also statically link the jitdump code:

  $ make -C tools/perf LDFLAGS=-static O=/tmp/build/perf install-bin
  $ grep libelf /tmp/build/perf/FEATURE-DUMP 
  feature-libelf=1
  feature-libelf-getphdrnum=1
  feature-libelf-gelf_getnote=1
  feature-libelf-getshdrstrndx=1
  feature-libelf-mmap=1
  $

And:

[acme@jouet linux]$ size /tmp/build/perf/perf
text data bss dec hex filename
4478822 581702 23919240 28979764 1ba3234 /tmp/build/perf/perf
[acme@jouet linux]$
[acme@jouet linux]$ file /tmp/build/perf/perf
/tmp/build/perf/perf: ELF 64-bit LSB executable, x86-64, version 1 (GNU/Linux), statically linked, for GNU/Linux 2.6.32, BuildID[sha1]=c2950590a0f24d76baa0ce4896414e5d523fefba, not stripped [acme@jouet linux]$
[acme@jouet linux]$ nm /tmp/build/perf/perf | grep jit
00000000005007f0 T jit_process
0000000000501920 T jit_write_elf
0000000000431a50 t perf_event__jit_repipe_mmap
0000000000431b20 t perf_event__jit_repipe_mmap2
[acme@jouet linux]$

- Arnaldo

Arnaldo Carvalho de Melo

maintainer

2016-10-13 19:44 UTC #13 lore raw

Re: [PATCH 2/9] perf/jit: enable jitdump support without dwarf

Em Thu, Oct 13, 2016 at 04:03:11PM -0300, Arnaldo Carvalho de Melo escreveu:

Quoted 49 lines

Em Thu, Oct 13, 2016 at 03:51:35PM -0300, Arnaldo Carvalho de Melo escreveu:
Quoted 20 lines
So we need:
[acme@jouet linux]$ git diff
tools/perf/Makefile.config +2 -0
index 8cfc310d4358..cffdd9cf3ebf 100644
@@ -366,8 +366,10 @@ ifndef NO_SDT
 endif
 
 ifdef PERF_HAVE_JITDUMP
+  ifndef NO_LIBELF
     $(call detected,CONFIG_JITDUMP)
     CFLAGS += -DHAVE_JITDUMP
+  endif
 endif
 
 ifeq ($(ARCH),powerpc)
[acme@jouet linux]$
Quoted 6 lines
To get that fixed.
Please let me know if this suits your needs.
I'll now try building with elfutils static libraries to see if in that case it all gets linked.
After installing these packages, on fedora, i.e. installing what is needed to statically link against libelf:
elfutils-devel-static
elfutils-libelf-devel-static
zlib-static
Then it all works, libelf is statically linked and we also statically link the jitdump code:
  $ make -C tools/perf LDFLAGS=-static O=/tmp/build/perf install-bin
  $ grep libelf /tmp/build/perf/FEATURE-DUMP 
  feature-libelf=1
  feature-libelf-getphdrnum=1
  feature-libelf-gelf_getnote=1
  feature-libelf-getshdrstrndx=1
  feature-libelf-mmap=1
  $
And:

Quoted 13 lines

[acme@jouet linux]$ size /tmp/build/perf/perf
text data bss dec hex filename
4478822 581702 23919240 28979764 1ba3234 /tmp/build/perf/perf
[acme@jouet linux]$
[acme@jouet linux]$ file /tmp/build/perf/perf
/tmp/build/perf/perf: ELF 64-bit LSB executable, x86-64, version 1 (GNU/Linux), statically linked, for GNU/Linux 2.6.32, BuildID[sha1]=c2950590a0f24d76baa0ce4896414e5d523fefba, not stripped [acme@jouet linux]$
[acme@jouet linux]$ nm /tmp/build/perf/perf | grep jit
00000000005007f0 T jit_process
0000000000501920 T jit_write_elf
0000000000431a50 t perf_event__jit_repipe_mmap
0000000000431b20 t perf_event__jit_repipe_mmap2
[acme@jouet linux]$

Ok, now this cset is bisected as causing this problem when built on Alpine Linux 3.4:

  CC       /tmp/build/perf/util/demangle-java.o
  CC       /tmp/build/perf/util/demangle-rust.o
  CC       /tmp/build/perf/util/jitdump.o
  CC       /tmp/build/perf/util/genelf.o

util/jitdump.c: In function 'jit_process':
util/jitdump.c:622:3: error: 'ret' may be used uninitialized in this function [-Werror=maybe-uninitialized]
fprintf(stderr, "injected: %s (%d)\n", path, ret);
^
util/jitdump.c:584:6: note: 'ret' was declared here

  int ret;
      ^

FLEX /tmp/build/perf/util/parse-events-flex.c

/ $ gcc -v
Using built-in specs.
COLLECT_GCC=gcc
COLLECT_LTO_WRAPPER=/usr/libexec/gcc/x86_64-alpine-linux-musl/5.3.0/lto-wrapper
Target: x86_64-alpine-linux-musl
Configured with: /home/buildozer/aports/main/gcc/src/gcc-5.3.0/configure --prefix=/usr --mandir=/usr/share/man --infodir=/usr/share/info --build=x86_64-alpine-linux-musl --host=x86_64-alpine-linux-musl --target=x86_64-alpine-linux-musl --with-pkgversion='Alpine 5.3.0' --enable-checking=release --disable-fixed-point --disable-libstdcxx-pch --disable-multilib --disable-nls --disable-werror --disable-symvers --enable-__cxa_atexit --enable-esp --enable-cloog-backend --enable-languages=c,c++,objc,java,fortran,ada --disable-libssp --disable-libmudflap --disable-libsanitizer --enable-shared --enable-threads --enable-tls --with-system-zlib Thread model: posix
gcc version 5.3.0 (Alpine 5.3.0)
/ $

Investigating...

- Arnaldo

tip-bot for Maciej Debski

merge bot

2016-10-24 18:59 UTC #14 lore raw

[tip:perf/core] perf jit: Enable jitdump support without dwarf

In reply to Stephane Eranian

perf jit: Enable jitdump support without dwarf

Commit-ID:  621cb4e7837e39d25a5af5a785ad282cdd2b4ce8
Gitweb:     http://git.kernel.org/tip/621cb4e7837e39d25a5af5a785ad282cdd2b4ce8
Author:     Maciej Debski <[email protected]>
AuthorDate: Thu, 13 Oct 2016 03:59:36 -0700
Committer:  Arnaldo Carvalho de Melo <[email protected]>
CommitDate: Mon, 24 Oct 2016 11:07:37 -0300

perf jit: Enable jitdump support without dwarf

This patch removes the dependency on DWARF for the entire jitdump support. It keeps it only for the genelf_debug.c support.

Signed-off-by Maciej Debski <[email protected]>

Reviewed-by Stephane Eranian <[email protected]>

Cc Anton Blanchard <[email protected]>

Cc Jiri Olsa <[email protected]>

Cc Namhyung Kim <[email protected]>

Cc Peter Zijlstra <[email protected]>

Link http://lkml.kernel.org/r/[email protected] open here

Fixes e12b202f8fb9 ("perf jitdump: Build only on supported archs")

[ Make it build only if NO_LIBELF isn't defined, as jitdump.o will only be built in that case ]

Signed-off-by Arnaldo Carvalho de Melo <[email protected]>

---
 tools/perf/Makefile.config | 2 +-
 tools/perf/util/Build      | 2 +-
 tools/perf/util/genelf.c   | 9 +++++++--
 tools/perf/util/genelf.h   | 2 ++
 4 files changed, 11 insertions(+), 4 deletions(-)

tools/perf/Makefile.config +1 -1

index 72edf83..cffdd9c 100644
@@ -366,7 +366,7 @@ ifndef NO_SDT
 endif
 
 ifdef PERF_HAVE_JITDUMP
-  ifndef NO_DWARF
+  ifndef NO_LIBELF
     $(call detected,CONFIG_JITDUMP)
     CFLAGS += -DHAVE_JITDUMP
   endif

tools/perf/util/Build +1 -1

index eb60e61..1dc67ef 100644
@@ -120,7 +120,7 @@ libperf-y += demangle-rust.o
 ifdef CONFIG_JITDUMP
 libperf-$(CONFIG_LIBELF) += jitdump.o
 libperf-$(CONFIG_LIBELF) += genelf.o
-libperf-$(CONFIG_LIBELF) += genelf_debug.o
+libperf-$(CONFIG_DWARF) += genelf_debug.o
 endif
 
 CFLAGS_config.o   += -DETC_PERFCONFIG="BUILD_STR($(ETC_PERFCONFIG_SQ))"

tools/perf/util/genelf.c +7 -2

index 8a2995e..30dece3 100644
@@ -19,7 +19,9 @@
 #include <limits.h>
 #include <fcntl.h>
 #include <err.h>
+#ifdef HAVE_DWARF_SUPPORT
 #include <dwarf.h>
+#endif
 
 #include "perf.h"
 #include "genelf.h"

@@ -161,7 +163,7 @@ gen_build_id(struct buildid_note *note, unsigned long load_addr, const void *cod
 int
 jit_write_elf(int fd, uint64_t load_addr, const char *sym,
 	      const void *code, int csize,
-	      void *debug, int nr_debug_entries)
+	      void *debug __maybe_unused, int nr_debug_entries __maybe_unused)
 {
 	Elf *e;
 	Elf_Data *d;

@@ -390,11 +392,14 @@ jit_write_elf(int fd, uint64_t load_addr, const char *sym,
 	shdr->sh_size = sizeof(bnote);
 	shdr->sh_entsize = 0;
 
+#ifdef HAVE_DWARF_SUPPORT
 	if (debug && nr_debug_entries) {
 		retval = jit_add_debug_info(e, load_addr, debug, nr_debug_entries);
 		if (retval)
 			goto error;
-	} else {
+	} else
+#endif
+	{
 		if (elf_update(e, ELF_C_WRITE) < 0) {
 			warnx("elf_update 4 failed");
 			goto error;

tools/perf/util/genelf.h +2 -0

index 2fbeb59..5c933ac 100644
@@ -4,8 +4,10 @@
 /* genelf.c */
 int jit_write_elf(int fd, uint64_t code_addr, const char *sym,
 		  const void *code, int csize, void *debug, int nr_debug_entries);
+#ifdef HAVE_DWARF_SUPPORT
 /* genelf_debug.c */
 int jit_add_debug_info(Elf *e, uint64_t code_addr, void *debug, int nr_debug_entries);
+#endif
 
 #if   defined(__arm__)
 #define GEN_ELF_ARCH	EM_ARM

Stephane Eranian

author

2016-10-13 11:03 UTC #15 lore raw

PATCH 3/9 perf/jit: remove unecessary padding in jitdump file

In reply to Stephane Eranian

This patch removes all the string padding generated in the jitdump file. There are nonecessary and were adding unecessary complexity. Modern processors can handle unaligned accesses quite well. The perf.data/jitdump file are always postp-processed, no need to add extra complexity for no real gain.

Signed-off-by Stephane Eranian <[email protected]>

---
 tools/perf/jvmti/jvmti_agent.c | 38 +-------------------------------------
 1 file changed, 1 insertion(+), 37 deletions(-)

tools/perf/jvmti/jvmti_agent.c +1 ~~-37~~

index 55daefff0d54..e9651a9d670e 100644
@@ -44,11 +44,6 @@
 static char jit_path[PATH_MAX];
 static void *marker_addr;
 
-/*
- * padding buffer
- */
-static const char pad_bytes[7];
-
 static inline pid_t gettid(void)
 {
 	return (pid_t)syscall(__NR_gettid);

@@ -230,7 +225,6 @@ init_arch_timestamp(void)
 
 void *jvmti_open(void)
 {
-	int pad_cnt;
 	char dump_path[PATH_MAX];
 	struct jitheader header;
 	int fd;

@@ -288,10 +282,6 @@ void *jvmti_open(void)
 	header.total_size = sizeof(header);
 	header.pid        = getpid();
 
-	/* calculate amount of padding '\0' */
-	pad_cnt = PADDING_8ALIGNED(header.total_size);
-	header.total_size += pad_cnt;
-
 	header.timestamp = perf_get_timestamp();
 
 	if (use_arch_timestamp)

@@ -301,13 +291,6 @@ void *jvmti_open(void)
 		warn("jvmti: cannot write dumpfile header");
 		goto error;
 	}
-
-	/* write padding '\0' if necessary */
-	if (pad_cnt && !fwrite(pad_bytes, pad_cnt, 1, fp)) {
-		warn("jvmti: cannot write dumpfile header padding");
-		goto error;
-	}
-
 	return fp;
 error:
 	fclose(fp);

@@ -349,7 +332,6 @@ jvmti_write_code(void *agent, char const *sym,
 	static int code_generation = 1;
 	struct jr_code_load rec;
 	size_t sym_len;
-	size_t padding_count;
 	FILE *fp = agent;
 	int ret = -1;

@@ -366,8 +348,6 @@ jvmti_write_code(void *agent, char const *sym,
 
 	rec.p.id           = JIT_CODE_LOAD;
 	rec.p.total_size   = sizeof(rec) + sym_len;
-	padding_count      = PADDING_8ALIGNED(rec.p.total_size);
-	rec.p. total_size += padding_count;
 	rec.p.timestamp    = perf_get_timestamp();
 
 	rec.code_size  = size;

@@ -393,9 +373,6 @@ jvmti_write_code(void *agent, char const *sym,
 	ret = fwrite_unlocked(&rec, sizeof(rec), 1, fp);
 	fwrite_unlocked(sym, sym_len, 1, fp);
 
-	if (padding_count)
-		fwrite_unlocked(pad_bytes, padding_count, 1, fp);
-
 	if (code)
 		fwrite_unlocked(code, size, 1, fp);

@@ -412,7 +389,6 @@ jvmti_write_debug_info(void *agent, uint64_t code, const char *file,
 {
 	struct jr_code_debug_info rec;
 	size_t sret, len, size, flen;
-	size_t padding_count;
 	uint64_t addr;
 	const char *fn = file;
 	FILE *fp = agent;

@@ -443,16 +419,10 @@ jvmti_write_debug_info(void *agent, uint64_t code, const char *file,
 	 * int      : line number
 	 * int      : column discriminator
 	 * file[]   : source file name
-	 * padding  : pad to multiple of 8 bytes
 	 */
 	size += nr_lines * sizeof(struct debug_entry);
 	size += flen * nr_lines;
-	/*
-	 * pad to 8 bytes
-	 */
-	padding_count = PADDING_8ALIGNED(size);
-
-	rec.p.total_size = size + padding_count;
+	rec.p.total_size = size;
 
 	/*
 	 * If JVM is multi-threaded, nultiple concurrent calls to agent

@@ -486,12 +456,6 @@ jvmti_write_debug_info(void *agent, uint64_t code, const char *file,
 		if (sret != 1)
 			goto error;
 	}
-	if (padding_count) {
-		sret = fwrite_unlocked(pad_bytes, padding_count, 1, fp);
-		if (sret != 1)
-			goto error;
-	}
-
 	funlockfile(fp);
 	return 0;
 error:

Signature · 1 line

1.9.1

tip-bot for Stephane Eranian

merge bot

2016-10-24 18:59 UTC #16 lore raw

[tip:perf/core] perf jit: Remove unecessary padding in jitdump file

perf jit: Remove unecessary padding in jitdump file

Commit-ID:  13b9012ab42ee93dabe8555f2e701ca139180f85
Gitweb:     http://git.kernel.org/tip/13b9012ab42ee93dabe8555f2e701ca139180f85
Author:     Stephane Eranian <[email protected]>
AuthorDate: Thu, 13 Oct 2016 03:59:37 -0700
Committer:  Arnaldo Carvalho de Melo <[email protected]>
CommitDate: Mon, 24 Oct 2016 11:07:38 -0300

perf jit: Remove unecessary padding in jitdump file

This patch removes all the string padding generated in the jitdump file. They are not necessary and were adding unnecessary complexity. Modern processors can handle unaligned accesses quite well. The perf.data/ jitdump file are always post-processed, no need to add extra complexity for no real gain.

Signed-off-by Stephane Eranian <[email protected]>

Cc Anton Blanchard <[email protected]>

Cc Jiri Olsa <[email protected]>

Cc Namhyung Kim <[email protected]>

Cc Peter Zijlstra <[email protected]>

Link http://lkml.kernel.org/r/[email protected] open here

Signed-off-by Arnaldo Carvalho de Melo <[email protected]>

---
 tools/perf/jvmti/jvmti_agent.c | 38 +-------------------------------------
 1 file changed, 1 insertion(+), 37 deletions(-)

tools/perf/jvmti/jvmti_agent.c +1 ~~-37~~

index 55daeff..e9651a9 100644
@@ -44,11 +44,6 @@
 static char jit_path[PATH_MAX];
 static void *marker_addr;
 
-/*
- * padding buffer
- */
-static const char pad_bytes[7];
-
 static inline pid_t gettid(void)
 {
 	return (pid_t)syscall(__NR_gettid);

@@ -230,7 +225,6 @@ init_arch_timestamp(void)
 
 void *jvmti_open(void)
 {
-	int pad_cnt;
 	char dump_path[PATH_MAX];
 	struct jitheader header;
 	int fd;

@@ -288,10 +282,6 @@ void *jvmti_open(void)
 	header.total_size = sizeof(header);
 	header.pid        = getpid();
 
-	/* calculate amount of padding '\0' */
-	pad_cnt = PADDING_8ALIGNED(header.total_size);
-	header.total_size += pad_cnt;
-
 	header.timestamp = perf_get_timestamp();
 
 	if (use_arch_timestamp)

@@ -301,13 +291,6 @@ void *jvmti_open(void)
 		warn("jvmti: cannot write dumpfile header");
 		goto error;
 	}
-
-	/* write padding '\0' if necessary */
-	if (pad_cnt && !fwrite(pad_bytes, pad_cnt, 1, fp)) {
-		warn("jvmti: cannot write dumpfile header padding");
-		goto error;
-	}
-
 	return fp;
 error:
 	fclose(fp);

@@ -349,7 +332,6 @@ jvmti_write_code(void *agent, char const *sym,
 	static int code_generation = 1;
 	struct jr_code_load rec;
 	size_t sym_len;
-	size_t padding_count;
 	FILE *fp = agent;
 	int ret = -1;

@@ -366,8 +348,6 @@ jvmti_write_code(void *agent, char const *sym,
 
 	rec.p.id           = JIT_CODE_LOAD;
 	rec.p.total_size   = sizeof(rec) + sym_len;
-	padding_count      = PADDING_8ALIGNED(rec.p.total_size);
-	rec.p. total_size += padding_count;
 	rec.p.timestamp    = perf_get_timestamp();
 
 	rec.code_size  = size;

@@ -393,9 +373,6 @@ jvmti_write_code(void *agent, char const *sym,
 	ret = fwrite_unlocked(&rec, sizeof(rec), 1, fp);
 	fwrite_unlocked(sym, sym_len, 1, fp);
 
-	if (padding_count)
-		fwrite_unlocked(pad_bytes, padding_count, 1, fp);
-
 	if (code)
 		fwrite_unlocked(code, size, 1, fp);

@@ -412,7 +389,6 @@ jvmti_write_debug_info(void *agent, uint64_t code, const char *file,
 {
 	struct jr_code_debug_info rec;
 	size_t sret, len, size, flen;
-	size_t padding_count;
 	uint64_t addr;
 	const char *fn = file;
 	FILE *fp = agent;

@@ -443,16 +419,10 @@ jvmti_write_debug_info(void *agent, uint64_t code, const char *file,
 	 * int      : line number
 	 * int      : column discriminator
 	 * file[]   : source file name
-	 * padding  : pad to multiple of 8 bytes
 	 */
 	size += nr_lines * sizeof(struct debug_entry);
 	size += flen * nr_lines;
-	/*
-	 * pad to 8 bytes
-	 */
-	padding_count = PADDING_8ALIGNED(size);
-
-	rec.p.total_size = size + padding_count;
+	rec.p.total_size = size;
 
 	/*
 	 * If JVM is multi-threaded, nultiple concurrent calls to agent

@@ -486,12 +456,6 @@ jvmti_write_debug_info(void *agent, uint64_t code, const char *file,
 		if (sret != 1)
 			goto error;
 	}
-	if (padding_count) {
-		sret = fwrite_unlocked(pad_bytes, padding_count, 1, fp);
-		if (sret != 1)
-			goto error;
-	}
-
 	funlockfile(fp);
 	return 0;
 error:

Stephane Eranian

author

2016-10-13 11:02 UTC #17 lore raw

PATCH 4/9 perf/jit: make perf skip unknown records

In reply to Stephane Eranian

From: Stefano Sanfilippo <[email protected]>

The behaviour before this commit was to skip the remaining portion of the jitdump in case an unknown record was found, including those records that perf could handle.

With this change, parsing a record with an unknown id will cause a warning to be emitted, the record will be skipped and parsing will resume from the next (valid) one.

The patch aims at making perf more future proof, by extracting as much information as possible from jitdumps.

Signed-off-by Stefano Sanfilippo <[email protected]>

Signed-off-by Ross McIlroy <[email protected]>

Reviewed-by Stephane Eranian <[email protected]>

---
 tools/perf/util/jitdump.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

tools/perf/util/jitdump.c +3 -3

index 95f0884aae02..5db2feb90060 100644
@@ -263,8 +263,7 @@ jit_get_next_entry(struct jit_buf_desc *jd)
 		return NULL;
 
 	if (id >= JIT_CODE_MAX) {
-		pr_warning("next_entry: unknown prefix %d, skipping\n", id);
-		return NULL;
+		pr_warning("next_entry: unknown record type %d, skipping\n", id);
 	}
 	if (bs > jd->bufsize) {
 		void *n;

@@ -322,7 +321,8 @@ jit_get_next_entry(struct jit_buf_desc *jd)
 		break;
 	case JIT_CODE_MAX:
 	default:
-		return NULL;
+		/* skip unknown record (we have read them) */
+		break;
 	}
 	return jr;
 }

Signature · 1 line

1.9.1

tip-bot for Stefano Sanfilippo

merge bot

2016-10-24 19:00 UTC #18 lore raw

[tip:perf/core] perf jit: Make perf skip unknown records

perf jit: Make perf skip unknown records

Commit-ID:  7354ec7a86c0cc03bebb7f86af8f20a88b27c262
Gitweb:     http://git.kernel.org/tip/7354ec7a86c0cc03bebb7f86af8f20a88b27c262
Author:     Stefano Sanfilippo <[email protected]>
AuthorDate: Thu, 13 Oct 2016 03:59:38 -0700
Committer:  Arnaldo Carvalho de Melo <[email protected]>
CommitDate: Mon, 24 Oct 2016 11:07:38 -0300

perf jit: Make perf skip unknown records

The behavior before this commit was to skip the remaining portion of the jitdump in case an unknown record was found, including those records that perf could handle.

With this change, parsing a record with an unknown id will cause a warning to be emitted, the record will be skipped and parsing will resume from the next (valid) one.

The patch aims at making perf more future proof, by extracting as much information as possible from jitdumps.

Signed-off-by Stefano Sanfilippo <[email protected]>

Signed-off-by Ross McIlroy <[email protected]>

Reviewed-by Stephane Eranian <[email protected]>

Cc Anton Blanchard <[email protected]>

Cc Jiri Olsa <[email protected]>

Cc Namhyung Kim <[email protected]>

Cc Peter Zijlstra <[email protected]>

Link http://lkml.kernel.org/r/[email protected] open here

Signed-off-by Arnaldo Carvalho de Melo <[email protected]>

---
 tools/perf/util/jitdump.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

tools/perf/util/jitdump.c +3 -3

index f3ed3c9..75b66bb 100644
@@ -263,8 +263,7 @@ jit_get_next_entry(struct jit_buf_desc *jd)
 		return NULL;
 
 	if (id >= JIT_CODE_MAX) {
-		pr_warning("next_entry: unknown prefix %d, skipping\n", id);
-		return NULL;
+		pr_warning("next_entry: unknown record type %d, skipping\n", id);
 	}
 	if (bs > jd->bufsize) {
 		void *n;

@@ -322,7 +321,8 @@ jit_get_next_entry(struct jit_buf_desc *jd)
 		break;
 	case JIT_CODE_MAX:
 	default:
-		return NULL;
+		/* skip unknown record (we have read them) */
+		break;
 	}
 	return jr;
 }

Stephane Eranian

author

2016-10-13 11:01 UTC #19 lore raw

PATCH 5/9 perf/jit: do not assume pgoff is zero

In reply to Stephane Eranian

From: Stefano Sanfilippo <[email protected]>

When calculating .eh_frame_hdr base and LUT offsets do not always assume that pgoff is zero.

The assumption is false for DSOs built from the jitdump by perf inject, because the ELF header did not exist in memory at sampling time.

Signed-off-by Stefano Sanfilippo <[email protected]>

Signed-off-by Ross McIlroy <[email protected]>

Reviewed-by Stephane Eranian <[email protected]>

---
 tools/perf/util/unwind-libunwind-local.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

tools/perf/util/unwind-libunwind-local.c +2 -2

index 20c2e5743903..6fec84dff3f7 100644
@@ -357,8 +357,8 @@ find_proc_info(unw_addr_space_t as, unw_word_t ip, unw_proc_info_t *pi,
 		di.format   = UNW_INFO_FORMAT_REMOTE_TABLE;
 		di.start_ip = map->start;
 		di.end_ip   = map->end;
-		di.u.rti.segbase    = map->start + segbase;
-		di.u.rti.table_data = map->start + table_data;
+		di.u.rti.segbase    = map->start + segbase - map->pgoff;
+		di.u.rti.table_data = map->start + table_data - map->pgoff;
 		di.u.rti.table_len  = fde_count * sizeof(struct table_entry)
 				      / sizeof(unw_word_t);
 		ret = dwarf_search_unwind_table(as, ip, &di, pi,

Signature · 1 line

1.9.1

tip-bot for Stefano Sanfilippo

merge bot

2016-10-24 19:00 UTC #20 lore raw

[tip:perf/core] perf jit: Do not assume pgoff is zero

perf jit: Do not assume pgoff is zero

Commit-ID:  eac05af2bf33aa9474482f1f19555adfd2cdf69d
Gitweb:     http://git.kernel.org/tip/eac05af2bf33aa9474482f1f19555adfd2cdf69d
Author:     Stefano Sanfilippo <[email protected]>
AuthorDate: Thu, 13 Oct 2016 03:59:39 -0700
Committer:  Arnaldo Carvalho de Melo <[email protected]>
CommitDate: Mon, 24 Oct 2016 11:07:39 -0300

perf jit: Do not assume pgoff is zero

When calculating .eh_frame_hdr base and LUT offsets do not always assume that pgoff is zero.

The assumption is false for DSOs built from the jitdump by perf inject, because the ELF header did not exist in memory at sampling time.

Signed-off-by Stefano Sanfilippo <[email protected]>

Signed-off-by Ross McIlroy <[email protected]>

Reviewed-by Stephane Eranian <[email protected]>

Cc Anton Blanchard <[email protected]>

Cc Jiri Olsa <[email protected]>

Cc Namhyung Kim <[email protected]>

Cc Peter Zijlstra <[email protected]>

Link http://lkml.kernel.org/r/[email protected] open here

Signed-off-by Arnaldo Carvalho de Melo <[email protected]>

---
 tools/perf/util/unwind-libunwind-local.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

tools/perf/util/unwind-libunwind-local.c +2 -2

index 20c2e57..6fec84d 100644
@@ -357,8 +357,8 @@ find_proc_info(unw_addr_space_t as, unw_word_t ip, unw_proc_info_t *pi,
 		di.format   = UNW_INFO_FORMAT_REMOTE_TABLE;
 		di.start_ip = map->start;
 		di.end_ip   = map->end;
-		di.u.rti.segbase    = map->start + segbase;
-		di.u.rti.table_data = map->start + table_data;
+		di.u.rti.segbase    = map->start + segbase - map->pgoff;
+		di.u.rti.table_data = map->start + table_data - map->pgoff;
 		di.u.rti.table_len  = fde_count * sizeof(struct table_entry)
 				      / sizeof(unw_word_t);
 		ret = dwarf_search_unwind_table(as, ip, &di, pi,

Stephane Eranian

author

2016-10-13 11:03 UTC #21 lore raw

PATCH 6/9 perf/jit: add unwinding support

In reply to Stephane Eranian

From: Stefano Sanfilippo <[email protected]>

This record is intended to provide unwinding information in the eh_frame format. This is required to unwind JITed code which does not maintain the frame pointer register during function calls.

The eh_frame unwinding information can be emitted by V8 / Chromium when the --perf_prof_unwinding_info is passed.

A record of type jr_code_unwinding_info comes before the jr_code_load it referred to and contains both the .eh_frame and .eh_frame_hdr.

The fields in the header have the following meaning:

* unwinding_size: size of the eh_frame and eh_frame_hdr, necessary for distinguishing the content from the padding.

* eh_frame_hdr_size: as the name says.

* mapped_size: size of the payload that was in memory at runtime. typically unwinding_size if the .eh_frame_hdr and .eh_frame were mapped, or 0 if they weren't. It should always be the former case, since the .eh_frame is guaranteed to be mapped in memory. However, certain JITs might want to inject an .eh_frame_hdr with an empty LUT to trigger fp-based unwinding fallback in libunwind. The only part of the .eh_frame_hdr that libunwind reads from remote memory is the LUT, and since there is none, mapping the unwinding info in memory is not necessary, and 0 in this field signifies that it wasn't. This practical hack allows to save bytes in code memory for those JIT compilers that might or might not maintain a valid frame pointer.

The payload that follows is assumed to contain first the .eh_frame and then the .eh_header_hdr, with no padding between the two.

Signed-off-by Stefano Sanfilippo <[email protected]>

Signed-off-by Ross McIlroy <[email protected]>

Reviewed-by Stephane Eranian <[email protected]>

---
 tools/perf/util/jitdump.c | 57 ++++++++++++++++++++++++++++++++++++++++++++---
 tools/perf/util/jitdump.h | 12 ++++++++++
 2 files changed, 66 insertions(+), 3 deletions(-)

tools/perf/util/jitdump.c +54 -3

index 5db2feb90060..fdddeca26545 100644
@@ -37,6 +37,10 @@ struct jit_buf_desc {
 	bool		 needs_bswap; /* handles cross-endianess */
 	bool		 use_arch_timestamp;
 	void		 *debug_data;
+	void		 *unwinding_data;
+	uint64_t	 unwinding_size;
+	uint64_t	 unwinding_mapped_size;
+	uint64_t         eh_frame_hdr_size;
 	size_t		 nr_debug_entries;
 	uint32_t         code_load_count;
 	u64		 bytes_written;

@@ -295,6 +299,13 @@ jit_get_next_entry(struct jit_buf_desc *jd)
 			}
 		}
 		break;
+	case JIT_CODE_UNWINDING_INFO:
+		if (jd->needs_bswap) {
+			jr->unwinding.unwinding_size = bswap_64(jr->unwinding.unwinding_size);
+			jr->unwinding.eh_frame_hdr_size = bswap_64(jr->unwinding.eh_frame_hdr_size);
+			jr->unwinding.mapped_size = bswap_64(jr->unwinding.mapped_size);
+		}
+		break;
 	case JIT_CODE_CLOSE:
 		break;
 	case JIT_CODE_LOAD:

@@ -370,7 +381,7 @@ static int jit_repipe_code_load(struct jit_buf_desc *jd, union jr_entry *jr)
 	u16 idr_size;
 	const char *sym;
 	uint32_t count;
-	int ret, csize;
+	int ret, csize, usize;
 	pid_t pid, tid;
 	struct {
 		u32 pid, tid;

@@ -380,6 +391,7 @@ static int jit_repipe_code_load(struct jit_buf_desc *jd, union jr_entry *jr)
 	pid   = jr->load.pid;
 	tid   = jr->load.tid;
 	csize = jr->load.code_size;
+	usize = jd->unwinding_mapped_size;
 	addr  = jr->load.code_addr;
 	sym   = (void *)((unsigned long)jr + sizeof(jr->load));
 	code  = (unsigned long)jr + jr->load.p.total_size - csize;

@@ -408,6 +420,14 @@ static int jit_repipe_code_load(struct jit_buf_desc *jd, union jr_entry *jr)
 		jd->nr_debug_entries = 0;
 	}
 
+	if (jd->unwinding_data && jd->eh_frame_hdr_size) {
+		free(jd->unwinding_data);
+		jd->unwinding_data = NULL;
+		jd->eh_frame_hdr_size = 0;
+		jd->unwinding_mapped_size = 0;
+		jd->unwinding_size = 0;
+	}
+
 	if (ret) {
 		free(event);
 		return -1;

@@ -422,7 +442,7 @@ static int jit_repipe_code_load(struct jit_buf_desc *jd, union jr_entry *jr)
 
 	event->mmap2.pgoff = GEN_ELF_TEXT_OFFSET;
 	event->mmap2.start = addr;
-	event->mmap2.len   = csize;
+	event->mmap2.len   = usize ? ALIGN_8(csize) + usize : csize;
 	event->mmap2.pid   = pid;
 	event->mmap2.tid   = tid;
 	event->mmap2.ino   = st.st_ino;

@@ -473,6 +493,7 @@ static int jit_repipe_code_move(struct jit_buf_desc *jd, union jr_entry *jr)
 	char *filename;
 	size_t size;
 	struct stat st;
+	int usize;
 	u16 idr_size;
 	int ret;
 	pid_t pid, tid;

@@ -483,6 +504,7 @@ static int jit_repipe_code_move(struct jit_buf_desc *jd, union jr_entry *jr)
 
 	pid = jr->move.pid;
 	tid =  jr->move.tid;
+	usize = jd->unwinding_mapped_size;
 	idr_size = jd->machine->id_hdr_size;
 
 	/*

@@ -511,7 +533,8 @@ static int jit_repipe_code_move(struct jit_buf_desc *jd, union jr_entry *jr)
 			(sizeof(event->mmap2.filename) - size) + idr_size);
 	event->mmap2.pgoff = GEN_ELF_TEXT_OFFSET;
 	event->mmap2.start = jr->move.new_code_addr;
-	event->mmap2.len   = jr->move.code_size;
+	event->mmap2.len   = usize ? ALIGN_8(jr->move.code_size) + usize
+				   : jr->move.code_size;
 	event->mmap2.pid   = pid;
 	event->mmap2.tid   = tid;
 	event->mmap2.ino   = st.st_ino;

@@ -578,6 +601,31 @@ static int jit_repipe_debug_info(struct jit_buf_desc *jd, union jr_entry *jr)
 }
 
 static int
+jit_repipe_unwinding_info(struct jit_buf_desc *jd, union jr_entry *jr)
+{
+	void *unwinding_data;
+	uint32_t unwinding_data_size;
+
+	if (!(jd && jr))
+		return -1;
+
+	unwinding_data_size  = jr->prefix.total_size - sizeof(jr->unwinding);
+	unwinding_data = malloc(unwinding_data_size);
+	if (!unwinding_data)
+		return -1;
+
+	memcpy(unwinding_data, &jr->unwinding.unwinding_data,
+	       unwinding_data_size);
+
+	jd->eh_frame_hdr_size = jr->unwinding.eh_frame_hdr_size;
+	jd->unwinding_size = jr->unwinding.unwinding_size;
+	jd->unwinding_mapped_size = jr->unwinding.mapped_size;
+	jd->unwinding_data = unwinding_data;
+
+	return 0;
+}
+
+static int
 jit_process_dump(struct jit_buf_desc *jd)
 {
 	union jr_entry *jr;

@@ -594,6 +642,9 @@ jit_process_dump(struct jit_buf_desc *jd)
 		case JIT_CODE_DEBUG_INFO:
 			ret = jit_repipe_debug_info(jd, jr);
 			break;
+		case JIT_CODE_UNWINDING_INFO:
+			ret = jit_repipe_unwinding_info(jd, jr);
+			break;
 		default:
 			ret = 0;
 			continue;

tools/perf/util/jitdump.h +12 -0

index bcacd20d0c1c..c6b9b67f43bf 100644
@@ -19,6 +19,7 @@
 #define JITHEADER_MAGIC_SW	0x4454694A
 
 #define PADDING_8ALIGNED(x) ((((x) + 7) & 7) ^ 7)
+#define ALIGN_8(x) (((x) + 7) & (~7))
 
 #define JITHEADER_VERSION 1

@@ -48,6 +49,7 @@ enum jit_record_type {
         JIT_CODE_MOVE           = 1,
 	JIT_CODE_DEBUG_INFO	= 2,
 	JIT_CODE_CLOSE		= 3,
+	JIT_CODE_UNWINDING_INFO	= 4,
 
 	JIT_CODE_MAX,
 };

@@ -101,12 +103,22 @@ struct jr_code_debug_info {
 	struct debug_entry entries[0];
 };
 
+struct jr_code_unwinding_info {
+	struct jr_prefix p;
+
+	uint64_t unwinding_size;
+	uint64_t eh_frame_hdr_size;
+	uint64_t mapped_size;
+	const char unwinding_data[0];
+};
+
 union jr_entry {
         struct jr_code_debug_info info;
         struct jr_code_close close;
         struct jr_code_load load;
         struct jr_code_move move;
         struct jr_prefix prefix;
+        struct jr_code_unwinding_info unwinding;
 };
 
 static inline struct debug_entry *

Signature · 1 line

1.9.1

tip-bot for Stefano Sanfilippo

merge bot

2016-10-24 19:01 UTC #22 lore raw

[tip:perf/core] perf jit: Add unwinding support

perf jit: Add unwinding support

Commit-ID:  0284fecd13b6db3ecd4c2b1bf3e72b105edce24b
Gitweb:     http://git.kernel.org/tip/0284fecd13b6db3ecd4c2b1bf3e72b105edce24b
Author:     Stefano Sanfilippo <[email protected]>
AuthorDate: Thu, 13 Oct 2016 03:59:40 -0700
Committer:  Arnaldo Carvalho de Melo <[email protected]>
CommitDate: Mon, 24 Oct 2016 11:07:39 -0300

perf jit: Add unwinding support

This record is intended to provide unwinding information in the eh_frame format. This is required to unwind JITed code which does not maintain the frame pointer register during function calls.

The eh_frame unwinding information can be emitted by V8 / Chromium when the --perf_prof_unwinding_info is passed.

A record of type jr_code_unwinding_info comes before the jr_code_load it referred to and contains both the .eh_frame and .eh_frame_hdr.

The fields in the header have the following meaning:

* unwinding_size: size of the eh_frame and eh_frame_hdr, necessary for distinguishing the content from the padding.

* eh_frame_hdr_size: as the name says.

The payload that follows is assumed to contain first the .eh_frame and then the .eh_header_hdr, with no padding between the two.

Signed-off-by Stefano Sanfilippo <[email protected]>

Signed-off-by Ross McIlroy <[email protected]>

Reviewed-by Stephane Eranian <[email protected]>

Cc Anton Blanchard <[email protected]>

Cc Jiri Olsa <[email protected]>

Cc Namhyung Kim <[email protected]>

Cc Peter Zijlstra <[email protected]>

Link http://lkml.kernel.org/r/[email protected] open here

Signed-off-by Arnaldo Carvalho de Melo <[email protected]>

---
 tools/perf/util/jitdump.c | 57 ++++++++++++++++++++++++++++++++++++++++++++---
 tools/perf/util/jitdump.h | 12 ++++++++++
 2 files changed, 66 insertions(+), 3 deletions(-)

tools/perf/util/jitdump.c +54 -3

index 75b66bb..9bae66c 100644
@@ -37,6 +37,10 @@ struct jit_buf_desc {
 	bool		 needs_bswap; /* handles cross-endianess */
 	bool		 use_arch_timestamp;
 	void		 *debug_data;
+	void		 *unwinding_data;
+	uint64_t	 unwinding_size;
+	uint64_t	 unwinding_mapped_size;
+	uint64_t         eh_frame_hdr_size;
 	size_t		 nr_debug_entries;
 	uint32_t         code_load_count;
 	u64		 bytes_written;

@@ -295,6 +299,13 @@ jit_get_next_entry(struct jit_buf_desc *jd)
 			}
 		}
 		break;
+	case JIT_CODE_UNWINDING_INFO:
+		if (jd->needs_bswap) {
+			jr->unwinding.unwinding_size = bswap_64(jr->unwinding.unwinding_size);
+			jr->unwinding.eh_frame_hdr_size = bswap_64(jr->unwinding.eh_frame_hdr_size);
+			jr->unwinding.mapped_size = bswap_64(jr->unwinding.mapped_size);
+		}
+		break;
 	case JIT_CODE_CLOSE:
 		break;
 	case JIT_CODE_LOAD:

@@ -370,7 +381,7 @@ static int jit_repipe_code_load(struct jit_buf_desc *jd, union jr_entry *jr)
 	u16 idr_size;
 	const char *sym;
 	uint32_t count;
-	int ret, csize;
+	int ret, csize, usize;
 	pid_t pid, tid;
 	struct {
 		u32 pid, tid;

@@ -380,6 +391,7 @@ static int jit_repipe_code_load(struct jit_buf_desc *jd, union jr_entry *jr)
 	pid   = jr->load.pid;
 	tid   = jr->load.tid;
 	csize = jr->load.code_size;
+	usize = jd->unwinding_mapped_size;
 	addr  = jr->load.code_addr;
 	sym   = (void *)((unsigned long)jr + sizeof(jr->load));
 	code  = (unsigned long)jr + jr->load.p.total_size - csize;

@@ -408,6 +420,14 @@ static int jit_repipe_code_load(struct jit_buf_desc *jd, union jr_entry *jr)
 		jd->nr_debug_entries = 0;
 	}
 
+	if (jd->unwinding_data && jd->eh_frame_hdr_size) {
+		free(jd->unwinding_data);
+		jd->unwinding_data = NULL;
+		jd->eh_frame_hdr_size = 0;
+		jd->unwinding_mapped_size = 0;
+		jd->unwinding_size = 0;
+	}
+
 	if (ret) {
 		free(event);
 		return -1;

@@ -422,7 +442,7 @@ static int jit_repipe_code_load(struct jit_buf_desc *jd, union jr_entry *jr)
 
 	event->mmap2.pgoff = GEN_ELF_TEXT_OFFSET;
 	event->mmap2.start = addr;
-	event->mmap2.len   = csize;
+	event->mmap2.len   = usize ? ALIGN_8(csize) + usize : csize;
 	event->mmap2.pid   = pid;
 	event->mmap2.tid   = tid;
 	event->mmap2.ino   = st.st_ino;

@@ -473,6 +493,7 @@ static int jit_repipe_code_move(struct jit_buf_desc *jd, union jr_entry *jr)
 	char *filename;
 	size_t size;
 	struct stat st;
+	int usize;
 	u16 idr_size;
 	int ret;
 	pid_t pid, tid;

@@ -483,6 +504,7 @@ static int jit_repipe_code_move(struct jit_buf_desc *jd, union jr_entry *jr)
 
 	pid = jr->move.pid;
 	tid =  jr->move.tid;
+	usize = jd->unwinding_mapped_size;
 	idr_size = jd->machine->id_hdr_size;
 
 	/*

@@ -511,7 +533,8 @@ static int jit_repipe_code_move(struct jit_buf_desc *jd, union jr_entry *jr)
 			(sizeof(event->mmap2.filename) - size) + idr_size);
 	event->mmap2.pgoff = GEN_ELF_TEXT_OFFSET;
 	event->mmap2.start = jr->move.new_code_addr;
-	event->mmap2.len   = jr->move.code_size;
+	event->mmap2.len   = usize ? ALIGN_8(jr->move.code_size) + usize
+				   : jr->move.code_size;
 	event->mmap2.pid   = pid;
 	event->mmap2.tid   = tid;
 	event->mmap2.ino   = st.st_ino;

@@ -578,6 +601,31 @@ static int jit_repipe_debug_info(struct jit_buf_desc *jd, union jr_entry *jr)
 }
 
 static int
+jit_repipe_unwinding_info(struct jit_buf_desc *jd, union jr_entry *jr)
+{
+	void *unwinding_data;
+	uint32_t unwinding_data_size;
+
+	if (!(jd && jr))
+		return -1;
+
+	unwinding_data_size  = jr->prefix.total_size - sizeof(jr->unwinding);
+	unwinding_data = malloc(unwinding_data_size);
+	if (!unwinding_data)
+		return -1;
+
+	memcpy(unwinding_data, &jr->unwinding.unwinding_data,
+	       unwinding_data_size);
+
+	jd->eh_frame_hdr_size = jr->unwinding.eh_frame_hdr_size;
+	jd->unwinding_size = jr->unwinding.unwinding_size;
+	jd->unwinding_mapped_size = jr->unwinding.mapped_size;
+	jd->unwinding_data = unwinding_data;
+
+	return 0;
+}
+
+static int
 jit_process_dump(struct jit_buf_desc *jd)
 {
 	union jr_entry *jr;

@@ -594,6 +642,9 @@ jit_process_dump(struct jit_buf_desc *jd)
 		case JIT_CODE_DEBUG_INFO:
 			ret = jit_repipe_debug_info(jd, jr);
 			break;
+		case JIT_CODE_UNWINDING_INFO:
+			ret = jit_repipe_unwinding_info(jd, jr);
+			break;
 		default:
 			ret = 0;
 			continue;

tools/perf/util/jitdump.h +12 -0

index bcacd20..c6b9b67 100644
@@ -19,6 +19,7 @@
 #define JITHEADER_MAGIC_SW	0x4454694A
 
 #define PADDING_8ALIGNED(x) ((((x) + 7) & 7) ^ 7)
+#define ALIGN_8(x) (((x) + 7) & (~7))
 
 #define JITHEADER_VERSION 1

@@ -48,6 +49,7 @@ enum jit_record_type {
         JIT_CODE_MOVE           = 1,
 	JIT_CODE_DEBUG_INFO	= 2,
 	JIT_CODE_CLOSE		= 3,
+	JIT_CODE_UNWINDING_INFO	= 4,
 
 	JIT_CODE_MAX,
 };

@@ -101,12 +103,22 @@ struct jr_code_debug_info {
 	struct debug_entry entries[0];
 };
 
+struct jr_code_unwinding_info {
+	struct jr_prefix p;
+
+	uint64_t unwinding_size;
+	uint64_t eh_frame_hdr_size;
+	uint64_t mapped_size;
+	const char unwinding_data[0];
+};
+
 union jr_entry {
         struct jr_code_debug_info info;
         struct jr_code_close close;
         struct jr_code_load load;
         struct jr_code_move move;
         struct jr_prefix prefix;
+        struct jr_code_unwinding_info unwinding;
 };
 
 static inline struct debug_entry *

Stephane Eranian

author

2016-10-13 11:03 UTC #23 lore raw

PATCH 7/9 perf/jit: generate .eh_frame/.eh_frame_hdr in DSO

In reply to Stephane Eranian

From: Stefano Sanfilippo <[email protected]>

When the jit_buf_desc contains unwinding information, it is emitted as eh_frame unwinding sections in the DSOs generated by perf inject.

The unwinding information is required to unwind of JITed code which do not maintain the frame pointer register during function calls. It can be emitted by V8 / Chromium when the --perf_prof_unwinding_info is passed to V8.

The eh_frame and eh_frame_hdr sections are emitted immediately after the .text.

The .eh_frame is aligned at a 8-byte boundary, and .eh_frame_hdr at a 4-byte one. Since size of the .eh_frame is required to be a multiple of the word size, which means there will never be additional padding between it and the .eh_frame_hdr on machines where the word size is 4 or 8 bytes.

However, additional padding might be inserted between .text and .eh_frame to reach the correct alignment, which will always be 8 bytes, also on 32bit machines. The reasoning behind this choice is that 4 extra bytes of padding worst case are not a large cost for the advantage of removing word-size dependent offset calculations when emitting the jitdump.

Signed-off-by Stefano Sanfilippo <[email protected]>

Signed-off-by Ross McIlroy <[email protected]>

Reviewed-by Stephane Eranian <[email protected]>

---
 tools/perf/util/genelf.c  | 102 ++++++++++++++++++++++++++++++++++++++++++++--
 tools/perf/util/genelf.h  |   3 +-
 tools/perf/util/jitdump.c |  11 +++--
 3 files changed, 109 insertions(+), 7 deletions(-)

tools/perf/util/genelf.c +99 -3

index 14a73acc549c..57845109e662 100644
@@ -69,6 +69,8 @@ static char shd_string_table[] = {
 	'.', 'd', 'e', 'b', 'u', 'g', '_', 'l', 'i', 'n', 'e', 0, /* 52 */
 	'.', 'd', 'e', 'b', 'u', 'g', '_', 'i', 'n', 'f', 'o', 0, /* 64 */
 	'.', 'd', 'e', 'b', 'u', 'g', '_', 'a', 'b', 'b', 'r', 'e', 'v', 0, /* 76 */
+	'.', 'e', 'h', '_', 'f', 'r', 'a', 'm', 'e', '_', 'h', 'd', 'r', 0, /* 90 */
+	'.', 'e', 'h', '_', 'f', 'r', 'a', 'm', 'e', 0, /* 104 */
 };
 
 static struct buildid_note {

@@ -149,6 +151,86 @@ gen_build_id(struct buildid_note *note, unsigned long load_addr, const void *cod
 }
 #endif
 
+static int
+jit_add_eh_frame_info(Elf *e, void* unwinding, uint64_t unwinding_header_size,
+		      uint64_t unwinding_size, uint64_t base_offset)
+{
+	Elf_Data *d;
+	Elf_Scn *scn;
+	Elf_Shdr *shdr;
+	uint64_t unwinding_table_size = unwinding_size - unwinding_header_size;
+
+	/*
+	 * setup eh_frame section
+	 */
+	scn = elf_newscn(e);
+	if (!scn) {
+		warnx("cannot create section");
+		return -1;
+	}
+
+	d = elf_newdata(scn);
+	if (!d) {
+		warnx("cannot get new data");
+		return -1;
+	}
+
+	d->d_align = 8;
+	d->d_off = 0LL;
+	d->d_buf = unwinding;
+	d->d_type = ELF_T_BYTE;
+	d->d_size = unwinding_table_size;
+	d->d_version = EV_CURRENT;
+
+	shdr = elf_getshdr(scn);
+	if (!shdr) {
+		warnx("cannot get section header");
+		return -1;
+	}
+
+	shdr->sh_name = 104;
+	shdr->sh_type = SHT_PROGBITS;
+	shdr->sh_addr = base_offset;
+	shdr->sh_flags = SHF_ALLOC;
+	shdr->sh_entsize = 0;
+
+	/*
+	 * setup eh_frame_hdr section
+	 */
+	scn = elf_newscn(e);
+	if (!scn) {
+		warnx("cannot create section");
+		return -1;
+	}
+
+	d = elf_newdata(scn);
+	if (!d) {
+		warnx("cannot get new data");
+		return -1;
+	}
+
+	d->d_align = 4;
+	d->d_off = 0LL;
+	d->d_buf = unwinding + unwinding_table_size;
+	d->d_type = ELF_T_BYTE;
+	d->d_size = unwinding_header_size;
+	d->d_version = EV_CURRENT;
+
+	shdr = elf_getshdr(scn);
+	if (!shdr) {
+		warnx("cannot get section header");
+		return -1;
+	}
+
+	shdr->sh_name = 90;
+	shdr->sh_type = SHT_PROGBITS;
+	shdr->sh_addr = base_offset + unwinding_table_size;
+	shdr->sh_flags = SHF_ALLOC;
+	shdr->sh_entsize = 0;
+
+	return 0;
+}
+
 /*
  * fd: file descriptor open for writing for the output file
  * load_addr: code load address (could be zero, just used for buildid)

@@ -159,13 +241,15 @@ gen_build_id(struct buildid_note *note, unsigned long load_addr, const void *cod
 int
 jit_write_elf(int fd, uint64_t load_addr, const char *sym,
 	      const void *code, int csize,
-	      void *debug __maybe_unused, int nr_debug_entries __maybe_unused)
+	      void *debug __maybe_unused, int nr_debug_entries __maybe_unused,
+	      void *unwinding, uint64_t unwinding_header_size, uint64_t unwinding_size)
 {
 	Elf *e;
 	Elf_Data *d;
 	Elf_Scn *scn;
 	Elf_Ehdr *ehdr;
 	Elf_Shdr *shdr;
+	uint64_t eh_frame_base_offset;
 	char *strsym = NULL;
 	int symlen;
 	int retval = -1;

@@ -196,7 +280,7 @@ jit_write_elf(int fd, uint64_t load_addr, const char *sym,
 	ehdr->e_type = ET_DYN;
 	ehdr->e_entry = GEN_ELF_TEXT_OFFSET;
 	ehdr->e_version = EV_CURRENT;
-	ehdr->e_shstrndx= 2; /* shdr index for section name */
+	ehdr->e_shstrndx= unwinding ? 4 : 2; /* shdr index for section name */
 
 	/*
 	 * setup text section

@@ -233,6 +317,18 @@ jit_write_elf(int fd, uint64_t load_addr, const char *sym,
 	shdr->sh_entsize = 0;
 
 	/*
+	 * Setup .eh_frame_hdr and .eh_frame
+	 */
+	if (unwinding) {
+		eh_frame_base_offset = ALIGN_8(GEN_ELF_TEXT_OFFSET + csize);
+		retval = jit_add_eh_frame_info(e, unwinding,
+					       unwinding_header_size, unwinding_size,
+					       eh_frame_base_offset);
+		if (retval)
+			goto error;
+	}
+
+	/*
 	 * setup section headers string table
 	 */
 	scn = elf_newscn(e);

@@ -300,7 +396,7 @@ jit_write_elf(int fd, uint64_t load_addr, const char *sym,
 	shdr->sh_type = SHT_SYMTAB;
 	shdr->sh_flags = 0;
 	shdr->sh_entsize = sizeof(Elf_Sym);
-	shdr->sh_link = 4; /* index of .strtab section */
+	shdr->sh_link = unwinding ? 6 : 4; /* index of .strtab section */
 
 	/*
 	 * setup symbols string table

tools/perf/util/genelf.h +2 -1

index 5c933ac71451..2424bd9862a3 100644
@@ -3,7 +3,8 @@
 
 /* genelf.c */
 int jit_write_elf(int fd, uint64_t code_addr, const char *sym,
-		  const void *code, int csize, void *debug, int nr_debug_entries);
+		  const void *code, int csize, void *debug, int nr_debug_entries,
+		  void *unwinding, uint64_t unwinding_header_size, uint64_t unwinding_size);
 #ifdef HAVE_DWARF_SUPPORT
 /* genelf_debug.c */
 int jit_add_debug_info(Elf *e, uint64_t code_addr, void *debug, int nr_debug_entries);

tools/perf/util/jitdump.c +8 -3

index fdddeca26545..c47fba63274b 100644
@@ -72,7 +72,10 @@ jit_emit_elf(char *filename,
 	     const void *code,
 	     int csize,
 	     void *debug,
-	     int nr_debug_entries)
+	     int nr_debug_entries,
+	     void *unwinding,
+	     uint32_t unwinding_header_size,
+	     uint32_t unwinding_size)
 {
 	int ret, fd;

@@ -85,7 +88,8 @@ jit_emit_elf(char *filename,
 		return -1;
 	}
 
-        ret = jit_write_elf(fd, code_addr, sym, (const void *)code, csize, debug, nr_debug_entries);
+	ret = jit_write_elf(fd, code_addr, sym, (const void *)code, csize, debug, nr_debug_entries,
+			    unwinding, unwinding_header_size, unwinding_size);
 
         close(fd);

@@ -412,7 +416,8 @@ static int jit_repipe_code_load(struct jit_buf_desc *jd, union jr_entry *jr)
 
 	size = PERF_ALIGN(size, sizeof(u64));
 	uaddr = (uintptr_t)code;
-	ret = jit_emit_elf(filename, sym, addr, (const void *)uaddr, csize, jd->debug_data, jd->nr_debug_entries);
+	ret = jit_emit_elf(filename, sym, addr, (const void *)uaddr, csize, jd->debug_data, jd->nr_debug_entries,
+			   jd->unwinding_data, jd->eh_frame_hdr_size, jd->unwinding_size);
 
 	if (jd->debug_data && jd->nr_debug_entries) {
 		free(jd->debug_data);

Signature · 1 line

1.9.1

tip-bot for Stefano Sanfilippo

merge bot

2016-10-24 19:01 UTC #24 lore raw

[tip:perf/core] perf jit: Generate .eh_frame/.eh_frame_hdr in DSO

perf jit: Generate .eh_frame/.eh_frame_hdr in DSO

Commit-ID:  086f9f3d7897d8081b18b949caa631b937c5891e
Gitweb:     http://git.kernel.org/tip/086f9f3d7897d8081b18b949caa631b937c5891e
Author:     Stefano Sanfilippo <[email protected]>
AuthorDate: Thu, 13 Oct 2016 03:59:41 -0700
Committer:  Arnaldo Carvalho de Melo <[email protected]>
CommitDate: Mon, 24 Oct 2016 11:07:40 -0300

perf jit: Generate .eh_frame/.eh_frame_hdr in DSO

When the jit_buf_desc contains unwinding information, it is emitted as eh_frame unwinding sections in the DSOs generated by perf inject.

The eh_frame and eh_frame_hdr sections are emitted immediately after the .text.

Signed-off-by Stefano Sanfilippo <[email protected]>

Signed-off-by Ross McIlroy <[email protected]>

Reviewed-by Stephane Eranian <[email protected]>

Cc Anton Blanchard <[email protected]>

Cc Jiri Olsa <[email protected]>

Cc Namhyung Kim <[email protected]>

Cc Peter Zijlstra <[email protected]>

Link http://lkml.kernel.org/r/[email protected] open here

Signed-off-by Arnaldo Carvalho de Melo <[email protected]>

---
 tools/perf/util/genelf.c  | 102 ++++++++++++++++++++++++++++++++++++++++++++--
 tools/perf/util/genelf.h  |   3 +-
 tools/perf/util/jitdump.c |  11 +++--
 3 files changed, 109 insertions(+), 7 deletions(-)

tools/perf/util/genelf.c +99 -3

index 30dece3..c540d47 100644
@@ -73,6 +73,8 @@ static char shd_string_table[] = {
 	'.', 'd', 'e', 'b', 'u', 'g', '_', 'l', 'i', 'n', 'e', 0, /* 52 */
 	'.', 'd', 'e', 'b', 'u', 'g', '_', 'i', 'n', 'f', 'o', 0, /* 64 */
 	'.', 'd', 'e', 'b', 'u', 'g', '_', 'a', 'b', 'b', 'r', 'e', 'v', 0, /* 76 */
+	'.', 'e', 'h', '_', 'f', 'r', 'a', 'm', 'e', '_', 'h', 'd', 'r', 0, /* 90 */
+	'.', 'e', 'h', '_', 'f', 'r', 'a', 'm', 'e', 0, /* 104 */
 };
 
 static struct buildid_note {

@@ -153,6 +155,86 @@ gen_build_id(struct buildid_note *note, unsigned long load_addr, const void *cod
 }
 #endif
 
+static int
+jit_add_eh_frame_info(Elf *e, void* unwinding, uint64_t unwinding_header_size,
+		      uint64_t unwinding_size, uint64_t base_offset)
+{
+	Elf_Data *d;
+	Elf_Scn *scn;
+	Elf_Shdr *shdr;
+	uint64_t unwinding_table_size = unwinding_size - unwinding_header_size;
+
+	/*
+	 * setup eh_frame section
+	 */
+	scn = elf_newscn(e);
+	if (!scn) {
+		warnx("cannot create section");
+		return -1;
+	}
+
+	d = elf_newdata(scn);
+	if (!d) {
+		warnx("cannot get new data");
+		return -1;
+	}
+
+	d->d_align = 8;
+	d->d_off = 0LL;
+	d->d_buf = unwinding;
+	d->d_type = ELF_T_BYTE;
+	d->d_size = unwinding_table_size;
+	d->d_version = EV_CURRENT;
+
+	shdr = elf_getshdr(scn);
+	if (!shdr) {
+		warnx("cannot get section header");
+		return -1;
+	}
+
+	shdr->sh_name = 104;
+	shdr->sh_type = SHT_PROGBITS;
+	shdr->sh_addr = base_offset;
+	shdr->sh_flags = SHF_ALLOC;
+	shdr->sh_entsize = 0;
+
+	/*
+	 * setup eh_frame_hdr section
+	 */
+	scn = elf_newscn(e);
+	if (!scn) {
+		warnx("cannot create section");
+		return -1;
+	}
+
+	d = elf_newdata(scn);
+	if (!d) {
+		warnx("cannot get new data");
+		return -1;
+	}
+
+	d->d_align = 4;
+	d->d_off = 0LL;
+	d->d_buf = unwinding + unwinding_table_size;
+	d->d_type = ELF_T_BYTE;
+	d->d_size = unwinding_header_size;
+	d->d_version = EV_CURRENT;
+
+	shdr = elf_getshdr(scn);
+	if (!shdr) {
+		warnx("cannot get section header");
+		return -1;
+	}
+
+	shdr->sh_name = 90;
+	shdr->sh_type = SHT_PROGBITS;
+	shdr->sh_addr = base_offset + unwinding_table_size;
+	shdr->sh_flags = SHF_ALLOC;
+	shdr->sh_entsize = 0;
+
+	return 0;
+}
+
 /*
  * fd: file descriptor open for writing for the output file
  * load_addr: code load address (could be zero, just used for buildid)

@@ -163,13 +245,15 @@ gen_build_id(struct buildid_note *note, unsigned long load_addr, const void *cod
 int
 jit_write_elf(int fd, uint64_t load_addr, const char *sym,
 	      const void *code, int csize,
-	      void *debug __maybe_unused, int nr_debug_entries __maybe_unused)
+	      void *debug __maybe_unused, int nr_debug_entries __maybe_unused,
+	      void *unwinding, uint64_t unwinding_header_size, uint64_t unwinding_size)
 {
 	Elf *e;
 	Elf_Data *d;
 	Elf_Scn *scn;
 	Elf_Ehdr *ehdr;
 	Elf_Shdr *shdr;
+	uint64_t eh_frame_base_offset;
 	char *strsym = NULL;
 	int symlen;
 	int retval = -1;

@@ -200,7 +284,7 @@ jit_write_elf(int fd, uint64_t load_addr, const char *sym,
 	ehdr->e_type = ET_DYN;
 	ehdr->e_entry = GEN_ELF_TEXT_OFFSET;
 	ehdr->e_version = EV_CURRENT;
-	ehdr->e_shstrndx= 2; /* shdr index for section name */
+	ehdr->e_shstrndx= unwinding ? 4 : 2; /* shdr index for section name */
 
 	/*
 	 * setup text section

@@ -237,6 +321,18 @@ jit_write_elf(int fd, uint64_t load_addr, const char *sym,
 	shdr->sh_entsize = 0;
 
 	/*
+	 * Setup .eh_frame_hdr and .eh_frame
+	 */
+	if (unwinding) {
+		eh_frame_base_offset = ALIGN_8(GEN_ELF_TEXT_OFFSET + csize);
+		retval = jit_add_eh_frame_info(e, unwinding,
+					       unwinding_header_size, unwinding_size,
+					       eh_frame_base_offset);
+		if (retval)
+			goto error;
+	}
+
+	/*
 	 * setup section headers string table
 	 */
 	scn = elf_newscn(e);

@@ -304,7 +400,7 @@ jit_write_elf(int fd, uint64_t load_addr, const char *sym,
 	shdr->sh_type = SHT_SYMTAB;
 	shdr->sh_flags = 0;
 	shdr->sh_entsize = sizeof(Elf_Sym);
-	shdr->sh_link = 4; /* index of .strtab section */
+	shdr->sh_link = unwinding ? 6 : 4; /* index of .strtab section */
 
 	/*
 	 * setup symbols string table

tools/perf/util/genelf.h +2 -1

index 5c933ac..2424bd9 100644
@@ -3,7 +3,8 @@
 
 /* genelf.c */
 int jit_write_elf(int fd, uint64_t code_addr, const char *sym,
-		  const void *code, int csize, void *debug, int nr_debug_entries);
+		  const void *code, int csize, void *debug, int nr_debug_entries,
+		  void *unwinding, uint64_t unwinding_header_size, uint64_t unwinding_size);
 #ifdef HAVE_DWARF_SUPPORT
 /* genelf_debug.c */
 int jit_add_debug_info(Elf *e, uint64_t code_addr, void *debug, int nr_debug_entries);

tools/perf/util/jitdump.c +8 -3

index 9bae66c..6a2688d 100644
@@ -72,7 +72,10 @@ jit_emit_elf(char *filename,
 	     const void *code,
 	     int csize,
 	     void *debug,
-	     int nr_debug_entries)
+	     int nr_debug_entries,
+	     void *unwinding,
+	     uint32_t unwinding_header_size,
+	     uint32_t unwinding_size)
 {
 	int ret, fd;

@@ -85,7 +88,8 @@ jit_emit_elf(char *filename,
 		return -1;
 	}
 
-        ret = jit_write_elf(fd, code_addr, sym, (const void *)code, csize, debug, nr_debug_entries);
+	ret = jit_write_elf(fd, code_addr, sym, (const void *)code, csize, debug, nr_debug_entries,
+			    unwinding, unwinding_header_size, unwinding_size);
 
         close(fd);

@@ -412,7 +416,8 @@ static int jit_repipe_code_load(struct jit_buf_desc *jd, union jr_entry *jr)
 
 	size = PERF_ALIGN(size, sizeof(u64));
 	uaddr = (uintptr_t)code;
-	ret = jit_emit_elf(filename, sym, addr, (const void *)uaddr, csize, jd->debug_data, jd->nr_debug_entries);
+	ret = jit_emit_elf(filename, sym, addr, (const void *)uaddr, csize, jd->debug_data, jd->nr_debug_entries,
+			   jd->unwinding_data, jd->eh_frame_hdr_size, jd->unwinding_size);
 
 	if (jd->debug_data && jd->nr_debug_entries) {
 		free(jd->debug_data);

Stephane Eranian

author

2016-10-13 11:01 UTC #25 lore raw

PATCH 8/9 perf/jit: Check JITHEADER_VERSION

In reply to Stephane Eranian

From: Stefano Sanfilippo <[email protected]>

Check the version number when opening a jitdump file. Accept older versions, but not newer ones.

Signed-off-by Stefano Sanfilippo <[email protected]>

Signed-off-by Ross McIlroy <[email protected]>

Reviewed-by Stephane Eranian <[email protected]>

---
 tools/perf/util/jitdump.c | 6 ++++++
 1 file changed, 6 insertions(+)

tools/perf/util/jitdump.c +6 -0

index c47fba63274b..c5dabb3a81fd 100644
@@ -180,6 +180,12 @@ jit_open(struct jit_buf_desc *jd, const char *name)
 			header.elf_mach,
 			jd->use_arch_timestamp);
 
+	if (header.version > JITHEADER_VERSION) {
+	  pr_err("wrong jitdump version %u, expected " STR(JITHEADER_VERSION),
+		 header.version);
+	  goto error;
+	}
+
 	if (header.flags & JITDUMP_FLAGS_RESERVED) {
 		pr_err("jitdump file contains invalid or unsupported flags 0x%llx\n",
 		       (unsigned long long)header.flags & JITDUMP_FLAGS_RESERVED);

Signature · 1 line

1.9.1

tip-bot for Stefano Sanfilippo

merge bot

2016-10-24 19:02 UTC #26 lore raw

[tip:perf/core] perf jit: Check JITHEADER_VERSION

perf jit: Check JITHEADER_VERSION

Commit-ID:  6760d77b708571b925e2dd2b61f847cbee6e0f21
Gitweb:     http://git.kernel.org/tip/6760d77b708571b925e2dd2b61f847cbee6e0f21
Author:     Stefano Sanfilippo <[email protected]>
AuthorDate: Thu, 13 Oct 2016 03:59:42 -0700
Committer:  Arnaldo Carvalho de Melo <[email protected]>
CommitDate: Mon, 24 Oct 2016 11:07:40 -0300

perf jit: Check JITHEADER_VERSION

Check the version number when opening a jitdump file. Accept older versions, but not newer ones.

Signed-off-by Stefano Sanfilippo <[email protected]>

Signed-off-by Ross McIlroy <[email protected]>

Reviewed-by Stephane Eranian <[email protected]>

Cc Anton Blanchard <[email protected]>

Cc Jiri Olsa <[email protected]>

Cc Namhyung Kim <[email protected]>

Cc Peter Zijlstra <[email protected]>

Link http://lkml.kernel.org/r/[email protected] open here

Signed-off-by Arnaldo Carvalho de Melo <[email protected]>

---
 tools/perf/util/jitdump.c | 6 ++++++
 1 file changed, 6 insertions(+)

tools/perf/util/jitdump.c +6 -0

index 6a2688d..c9a941e 100644
@@ -180,6 +180,12 @@ jit_open(struct jit_buf_desc *jd, const char *name)
 			header.elf_mach,
 			jd->use_arch_timestamp);
 
+	if (header.version > JITHEADER_VERSION) {
+		pr_err("wrong jitdump version %u, expected " STR(JITHEADER_VERSION),
+			header.version);
+		goto error;
+	}
+
 	if (header.flags & JITDUMP_FLAGS_RESERVED) {
 		pr_err("jitdump file contains invalid or unsupported flags 0x%llx\n",
 		       (unsigned long long)header.flags & JITDUMP_FLAGS_RESERVED);

Stephane Eranian

author

2016-10-13 11:02 UTC #27 lore raw

PATCH 9/9 perf/jit: add jitdump format specification document

In reply to Stephane Eranian

This patch adds a formal specification of the jitdump format. The goal is to help jit runtime developers implement the jitdump support without having to read the jvmti code.

Signed-off-by Stephane Eranian <[email protected]>

---
 tools/perf/Documentation/jitdump-specification.txt | 170 +++++++++++++++++++++
 1 file changed, 170 insertions(+)
 create mode 100644 tools/perf/Documentation/jitdump-specification.txt

tools/perf/Documentation/jitdump-specification.txt new file +170 -0

new file mode 100644
index 000000000000..f32397dbcb29
@@ -0,0 +1,170 @@
+JITDUMP specification version 2
+Last Revised: 09/15/2016
+Author: Stephane Eranian <[email protected]>
+
+--------------------------------------------------------
+| Revision  |    Date    | Description                 |
+--------------------------------------------------------
+|   1       | 09/07/2016 | Initial revision            |
+--------------------------------------------------------
+|   2       | 09/15/2016 | Add JIT_CODE_UNWINDING_INFO |
+--------------------------------------------------------
+
+
+I/ Introduction
+
+
+This document describes the jitdump file format. The file is generated by Just-In-time compiler runtimes to save meta-data information about the generated code, such as address, size, and name of generated functions, the native code generated, the source line information. The data may then be used by performance tools, such as Linux perf to generate function and assembly level profiles.
+
+The format is not specific to any particular programming language. It can be extended as need be.
+
+The format of the file is binary. It is self-describing in terms of endianness and is portable across multiple processor architectures.
+
+
+II/ Overview of the format
+
+
+The format requires only sequential accesses, i.e., append only mode. The file starts with a fixed size file header describing the version of the specification, the endianness.
+
+The header is followed by a series of records, each starting with a fixed size header describing the type of record and its size. It is, itself, followed by the payload for the record. Records can have a variable size even for a given type.
+
+Each entry in the file is timestamped. All timestamps must use the same clock source. The CLOCK_MONOTONIC clock source is recommended.
+
+
+III/ Jitdump file header format
+
+Each jitdump file starts with a fixed size header containing the following fields in order:
+
+
+* uint32_t magic     : a magic number tagging the file type. The value is 4-byte long and represents the string "JiTD" in ASCII form. It is 0x4A695444 or 0x4454694a depending on the endianness. The field can be used to detect the endianness of the file
+* uint32_t version   : a 4-byte value representing the format version. It is currently set to 2
+* uint32_t total_size: size in bytes of file header
+* uint32_t elf_mach  : ELF architecture encoding (ELF e_machine value as specified in /usr/include/elf.h)
+* uint32_t pad1      : padding. Reserved for future use
+* uint32_t pid       : JIT runtime process identification (OS specific)
+* uint64_t timestamp : timestamp of when the file was created
+* uint64_t flags     : a bitmask of flags
+
+The flags currently defined are as follows:
+ * bit 0: JITDUMP_FLAGS_ARCH_TIMESTAMP : set if the jitdump file is using an architecture-specific timestamp clock source. For instance, on x86, one could use TSC directly
+
+IV/ Record header
+
+The file header is immediately followed by records. Each record starts with a fixed size header describing the record that follows.
+
+The record header is specified in order as follows:
+* uint32_t id        : a value identifying the record type (see below)
+* uint32_t total_size: the size in bytes of the record including the header.
+* uint64_t timestamp : a timestamp of when the record was created.
+
+The following record types are defined:
+ * Value 0 : JIT_CODE_LOAD      : record describing a jitted function
+ * Value 1 : JIT_CODE_MOVE      : record describing an already jitted function which is moved
+ * Value 2 : JIT_CODE_DEBUG_INFO: record describing the debug information for a jitted function
+ * Value 3 : JIT_CODE_CLOSE     : record marking the end of the jit runtime (optional)
+ * Value 4 : JIT_CODE_UNWINDING_INFO: record describing a function unwinding information
+
+ The payload of the record must immediately follow the record header without padding.
+
+V/ JIT_CODE_LOAD record
+
+
+  The record has the following fields following the fixed-size record header in order:
+  * uint32_t pid: OS process id of the runtime generating the jitted code
+  * uint32_t tid: OS thread identification of the runtime thread generating the jitted code
+  * uint64_t vma: virtual address of jitted code start
+  * uint64_t code_addr: code start address for the jitted code. By default vma = code_addr
+  * uint64_t code_size: size in bytes of the generated jitted code
+  * uint64_t code_index: unique identifier for the jitted code (see below)
+  * char[n]: function name in ASCII including the null termination
+  * native code: raw byte encoding of the jitted code
+
+  The record header total_size field is inclusive of all components:
+  * record header
+  * fixed-sized fields
+  * function name string, including termination
+  * native code length
+  * record specific variable data (e.g., array of data entries)
+
+The code_index is used to uniquely identify each jitted function. The index can be a monotonically increasing 64-bit value. Each time a function is jitted it gets a new number. This value is used in case the code for a function is moved and avoids having to issue another JIT_CODE_LOAD record.
+
+The format supports empty functions with no native code.
+
+
+VI/ JIT_CODE_MOVE record
+
+  The record type is optional.
+
+  The record has the following fields following the fixed-size record header in order:
+  * uint32_t pid          : OS process id of the runtime generating the jitted code
+  * uint32_t tid          : OS thread identification of the runtime thread generating the jitted code
+  * uint64_t vma          : new virtual address of jitted code start
+  * uint64_t old_code_addr: previous code address for the same function
+  * uint64_t new_code_addr: alternate new code started address for the jitted code. By default it should be equal to the vma address.
+  * uint64_t code_size    : size in bytes of the jitted code
+  * uint64_t code_index   : index referring to the JIT_CODE_LOAD code_index record of when the function was initially jitted
+
+
+The MOVE record can be used in case an already jitted function is simply moved by the runtime inside the code cache.
+
+The JIT_CODE_MOVE record cannot come before the JIT_CODE_LOAD record for the same function name. The function cannot have changed name, otherwise a new JIT_CODE_LOAD record must be emitted.
+
+The code size of the function cannot change.
+
+
+VII/ JIT_DEBUG_INFO record
+
+The record type is optional.
+
+The record contains source lines debug information, i.e., a way to map a code address back to a source line. This information may be used by the performance tool.
+
+The record has the following fields following the fixed-size record header in order:
+  * uint64_t code_addr: address of function for which the debug information is generated
+  * uint64_t nr_entry : number of debug entries for the function
+  * debug_entry[n]: array of nr_entry debug entries for the function
+
+The debug_entry describes the source line information. It is defined as follows in order:
+* uint64_t code_addr: address of function for which the debug information is generated
+* uint32_t line     : source file line number (starting at 1)
+* uint32_t discrim  : column discriminator, 0 is default
+* char name[n]      : source file name in ASCII, including null termination
+
+The debug_entry entries are saved in sequence but given that they have variable sizes due to the file name string, they cannot be indexed directly.
+They need to be walked sequentially. The next debug_entry is found at sizeof(debug_entry) + strlen(name) + 1.
+
+IMPORTANT:
+  The JIT_CODE_DEBUG for a given function must always be generated BEFORE the JIT_CODE_LOAD for the function. This facilitates greatly the parser for the jitdump file.
+
+
+VIII/ JIT_CODE_CLOSE record
+
+
+The record type is optional.
+
+The record is used as a marker for the end of the jitted runtime. It can be replaced by the end of the file.
+
+The JIT_CODE_CLOSE record does not have any specific fields, the record header contains all the information needed.
+
+
+IX/ JIT_CODE_UNWINDING_INFO
+
+
+The record type is optional.
+
+The record is used to describe the unwinding information for a jitted function.
+
+The record has the following fields following the fixed-size record header in order:
+
+uint64_t unwind_data_size   : the size in bytes of the unwinding data table at the end of the record
+uint64_t eh_frame_hdr_size  : the size in bytes of the DWARF EH Frame Header at the start of the unwinding data table at the end of the record
+uint64_t mapped_size        : the size of the unwinding data mapped in memory
+const char unwinding_data[n]: an array of unwinding data, consisting of the EH Frame Header, followed by the actual EH Frame
+
+
+The EH Frame header follows the Linux Standard Base (LSB) specification as described in the document at https://refspecs.linuxfoundation.org/LSB_1.3.0/gLSB/gLSB/ehframehdr.html
+
+
+The EH Frame follows the LSB specicfication as described in the document at https://refspecs.linuxbase.org/LSB_3.0.0/LSB-PDA/LSB-PDA/ehframechpt.html
+
+
+NOTE: The mapped_size is generally either the same as unwind_data_size (if the unwinding data was mapped in memory by the running process) or zero (if the unwinding data is not mapped by the process). If the unwinding data was not mapped, then only the EH Frame Header will be read, which can be used to specify FP based unwinding for a function which does not have unwinding information.

Signature · 1 line

1.9.1

tip-bot for Stephane Eranian

merge bot

2016-10-24 19:02 UTC #28 lore raw

[tip:perf/core] perf jit: Add jitdump format specification document

perf jit: Add jitdump format specification document

Commit-ID:  b3151ea500655f232255ddcdf2bbcf691cb39646
Gitweb:     http://git.kernel.org/tip/b3151ea500655f232255ddcdf2bbcf691cb39646
Author:     Stephane Eranian <[email protected]>
AuthorDate: Thu, 13 Oct 2016 03:59:43 -0700
Committer:  Arnaldo Carvalho de Melo <[email protected]>
CommitDate: Mon, 24 Oct 2016 11:07:41 -0300

perf jit: Add jitdump format specification document

This patch adds a formal specification of the jitdump format. The goal is to help jit runtime developers implement the jitdump support without having to read the jvmti code.

Signed-off-by Stephane Eranian <[email protected]>

Cc Anton Blanchard <[email protected]>

Cc Jiri Olsa <[email protected]>

Cc Namhyung Kim <[email protected]>

Cc Peter Zijlstra <[email protected]>

Link http://lkml.kernel.org/r/[email protected] open here

Signed-off-by Arnaldo Carvalho de Melo <[email protected]>

---
 tools/perf/Documentation/jitdump-specification.txt | 170 +++++++++++++++++++++
 1 file changed, 170 insertions(+)

tools/perf/Documentation/jitdump-specification.txt new file +170 -0

new file mode 100644
index 0000000..4c62b07
@@ -0,0 +1,170 @@
+JITDUMP specification version 2
+Last Revised: 09/15/2016
+Author: Stephane Eranian <[email protected]>
+
+--------------------------------------------------------
+| Revision  |    Date    | Description                 |
+--------------------------------------------------------
+|   1       | 09/07/2016 | Initial revision            |
+--------------------------------------------------------
+|   2       | 09/15/2016 | Add JIT_CODE_UNWINDING_INFO |
+--------------------------------------------------------
+
+
+I/ Introduction
+
+
+This document describes the jitdump file format. The file is generated by Just-In-time compiler runtimes to save meta-data information about the generated code, such as address, size, and name of generated functions, the native code generated, the source line information. The data may then be used by performance tools, such as Linux perf to generate function and assembly level profiles.
+
+The format is not specific to any particular programming language. It can be extended as need be.
+
+The format of the file is binary. It is self-describing in terms of endianness and is portable across multiple processor architectures.
+
+
+II/ Overview of the format
+
+
+The format requires only sequential accesses, i.e., append only mode. The file starts with a fixed size file header describing the version of the specification, the endianness.
+
+The header is followed by a series of records, each starting with a fixed size header describing the type of record and its size. It is, itself, followed by the payload for the record. Records can have a variable size even for a given type.
+
+Each entry in the file is timestamped. All timestamps must use the same clock source. The CLOCK_MONOTONIC clock source is recommended.
+
+
+III/ Jitdump file header format
+
+Each jitdump file starts with a fixed size header containing the following fields in order:
+
+
+* uint32_t magic     : a magic number tagging the file type. The value is 4-byte long and represents the string "JiTD" in ASCII form. It is 0x4A695444 or 0x4454694a depending on the endianness. The field can be used to detect the endianness of the file
+* uint32_t version   : a 4-byte value representing the format version. It is currently set to 2
+* uint32_t total_size: size in bytes of file header
+* uint32_t elf_mach  : ELF architecture encoding (ELF e_machine value as specified in /usr/include/elf.h)
+* uint32_t pad1      : padding. Reserved for future use
+* uint32_t pid       : JIT runtime process identification (OS specific)
+* uint64_t timestamp : timestamp of when the file was created
+* uint64_t flags     : a bitmask of flags
+
+The flags currently defined are as follows:
+ * bit 0: JITDUMP_FLAGS_ARCH_TIMESTAMP : set if the jitdump file is using an architecture-specific timestamp clock source. For instance, on x86, one could use TSC directly
+
+IV/ Record header
+
+The file header is immediately followed by records. Each record starts with a fixed size header describing the record that follows.
+
+The record header is specified in order as follows:
+* uint32_t id        : a value identifying the record type (see below)
+* uint32_t total_size: the size in bytes of the record including the header.
+* uint64_t timestamp : a timestamp of when the record was created.
+
+The following record types are defined:
+ * Value 0 : JIT_CODE_LOAD      : record describing a jitted function
+ * Value 1 : JIT_CODE_MOVE      : record describing an already jitted function which is moved
+ * Value 2 : JIT_CODE_DEBUG_INFO: record describing the debug information for a jitted function
+ * Value 3 : JIT_CODE_CLOSE     : record marking the end of the jit runtime (optional)
+ * Value 4 : JIT_CODE_UNWINDING_INFO: record describing a function unwinding information
+
+ The payload of the record must immediately follow the record header without padding.
+
+V/ JIT_CODE_LOAD record
+
+
+  The record has the following fields following the fixed-size record header in order:
+  * uint32_t pid: OS process id of the runtime generating the jitted code
+  * uint32_t tid: OS thread identification of the runtime thread generating the jitted code
+  * uint64_t vma: virtual address of jitted code start
+  * uint64_t code_addr: code start address for the jitted code. By default vma = code_addr
+  * uint64_t code_size: size in bytes of the generated jitted code
+  * uint64_t code_index: unique identifier for the jitted code (see below)
+  * char[n]: function name in ASCII including the null termination
+  * native code: raw byte encoding of the jitted code
+
+  The record header total_size field is inclusive of all components:
+  * record header
+  * fixed-sized fields
+  * function name string, including termination
+  * native code length
+  * record specific variable data (e.g., array of data entries)
+
+The code_index is used to uniquely identify each jitted function. The index can be a monotonically increasing 64-bit value. Each time a function is jitted it gets a new number. This value is used in case the code for a function is moved and avoids having to issue another JIT_CODE_LOAD record.
+
+The format supports empty functions with no native code.
+
+
+VI/ JIT_CODE_MOVE record
+
+  The record type is optional.
+
+  The record has the following fields following the fixed-size record header in order:
+  * uint32_t pid          : OS process id of the runtime generating the jitted code
+  * uint32_t tid          : OS thread identification of the runtime thread generating the jitted code
+  * uint64_t vma          : new virtual address of jitted code start
+  * uint64_t old_code_addr: previous code address for the same function
+  * uint64_t new_code_addr: alternate new code started address for the jitted code. By default it should be equal to the vma address.
+  * uint64_t code_size    : size in bytes of the jitted code
+  * uint64_t code_index   : index referring to the JIT_CODE_LOAD code_index record of when the function was initially jitted
+
+
+The MOVE record can be used in case an already jitted function is simply moved by the runtime inside the code cache.
+
+The JIT_CODE_MOVE record cannot come before the JIT_CODE_LOAD record for the same function name. The function cannot have changed name, otherwise a new JIT_CODE_LOAD record must be emitted.
+
+The code size of the function cannot change.
+
+
+VII/ JIT_DEBUG_INFO record
+
+The record type is optional.
+
+The record contains source lines debug information, i.e., a way to map a code address back to a source line. This information may be used by the performance tool.
+
+The record has the following fields following the fixed-size record header in order:
+  * uint64_t code_addr: address of function for which the debug information is generated
+  * uint64_t nr_entry : number of debug entries for the function
+  * debug_entry[n]: array of nr_entry debug entries for the function
+
+The debug_entry describes the source line information. It is defined as follows in order:
+* uint64_t code_addr: address of function for which the debug information is generated
+* uint32_t line     : source file line number (starting at 1)
+* uint32_t discrim  : column discriminator, 0 is default
+* char name[n]      : source file name in ASCII, including null termination
+
+The debug_entry entries are saved in sequence but given that they have variable sizes due to the file name string, they cannot be indexed directly.
+They need to be walked sequentially. The next debug_entry is found at sizeof(debug_entry) + strlen(name) + 1.
+
+IMPORTANT:
+  The JIT_CODE_DEBUG for a given function must always be generated BEFORE the JIT_CODE_LOAD for the function. This facilitates greatly the parser for the jitdump file.
+
+
+VIII/ JIT_CODE_CLOSE record
+
+
+The record type is optional.
+
+The record is used as a marker for the end of the jitted runtime. It can be replaced by the end of the file.
+
+The JIT_CODE_CLOSE record does not have any specific fields, the record header contains all the information needed.
+
+
+IX/ JIT_CODE_UNWINDING_INFO
+
+
+The record type is optional.
+
+The record is used to describe the unwinding information for a jitted function.
+
+The record has the following fields following the fixed-size record header in order:
+
+uint64_t unwind_data_size   : the size in bytes of the unwinding data table at the end of the record
+uint64_t eh_frame_hdr_size  : the size in bytes of the DWARF EH Frame Header at the start of the unwinding data table at the end of the record
+uint64_t mapped_size        : the size of the unwinding data mapped in memory
+const char unwinding_data[n]: an array of unwinding data, consisting of the EH Frame Header, followed by the actual EH Frame
+
+
+The EH Frame header follows the Linux Standard Base (LSB) specification as described in the document at https://refspecs.linuxfoundation.org/LSB_1.3.0/gLSB/gLSB/ehframehdr.html
+
+
+The EH Frame follows the LSB specicfication as described in the document at https://refspecs.linuxbase.org/LSB_3.0.0/LSB-PDA/LSB-PDA/ehframechpt.html
+
+
+NOTE: The mapped_size is generally either the same as unwind_data_size (if the unwinding data was mapped in memory by the running process) or zero (if the unwinding data is not mapped by the process). If the unwinding data was not mapped, then only the EH Frame Header will be read, which can be used to specify FP based unwinding for a function which does not have unwinding information.