Adjust objdump start/end range per map pgoff parameter

PATCH Superseded Steve Clevenger 2 participants 11 messages Aug 26, 2024 – Aug 28, 2024 1 message not in the archive perf events

lore

Share & tools

lore

A message that is not in the archive (sent off-list or not yet received): [email protected]

Steve Clevenger

author

2024-08-26 21:36 UTC #1 lore raw

v2 cover arm-cs-trace-disasm.py/perf must accommodate non-zero DSO text offset

Changes in V2:
- Updated mailing list distribution

Fedora 37 distributed shared binary and executable mapped files show a zero text section offset. Starting with the Fedora 38 distribution, the shared binary and executable mapped files show a non-zero text section offset for some binaries. The text offset parameter is never passed into the arm-cs-trace-disasm.py script to allow the script to adjust the start/end address range passed to objdump. This adjustment is required to correctly offset into the dso text section. Not doing so results in an incorrect user instruction trace display for Fedora 38 (and later) user trace output.

Steve Clevenger (5):
Add dso__is_pie call to identify ELF PIE
Add dso__is_pie prototype
Force MAPPING_TYPE__IDENTIY for PIE
Add map pgoff to python dictionary based on MAPPING_TYPE Adjust objdump start/end range per map pgoff parameter

 .../scripts/python/arm-cs-trace-disasm.py     | 17 +++++-
 tools/perf/util/map.c                         |  5 +-
 .../scripting-engines/trace-event-python.c    | 13 +++-
 tools/perf/util/symbol-elf.c                  | 60 +++++++++++++++++++
 tools/perf/util/symbol.h                      |  1 +
 5 files changed, 90 insertions(+), 6 deletions(-)

Signature · 1 line

2.25.1

Steve Clevenger

author

2024-08-26 21:36 UTC #2 lore raw

PATCH v2 2/5 Add dso__is_pie prototype

Changes in V2:
- Updated mailing list distribution

Add prototype to dso__is_pie() global.

Signed-off-by Steve Clevenger <[email protected]>

---
 tools/perf/util/symbol.h | 1 +
 1 file changed, 1 insertion(+)

tools/perf/util/symbol.h +1 -0

index 3fb5d146d9b1..33ea2596ce31 100644
@@ -127,6 +127,7 @@ void dso__insert_symbol(struct dso *dso,
 			struct symbol *sym);
 void dso__delete_symbol(struct dso *dso,
 			struct symbol *sym);
+bool dso__is_pie(struct dso *dso);
 
 struct symbol *dso__find_symbol(struct dso *dso, u64 addr);
 struct symbol *dso__find_symbol_nocache(struct dso *dso, u64 addr);

Signature · 1 line

2.25.1

Leo Yan

2024-08-27 19:29 UTC #3 lore raw

Re: [PATCH V2 2/5] Add dso__is_pie prototype

Quoted 3 lines · Steve Clevenger

Changes in V2:
- Updated mailing list distribution

Usually, we record the change history into the cover letter, or put it under the line starting with --- in the commit. This can avoid the change history to be merged into the mainline.

Quoted 1 line

Add prototype to dso__is_pie() global.

Please squash the patch 02 into 01. Otherwise, the patch 01 will introduce building regression:

util/symbol-elf.c:669:6: error: no previous prototype for ‘dso__is_pie’ [-Werror=missing-prototypes]
669 | bool dso__is_pie(struct dso *dso)

      |      ^~~~~~~~~~~

Thanks,
Leo

Quoted 20 lines

Signed-off-by Steve Clevenger <[email protected]>

---
 tools/perf/util/symbol.h | 1 +
 1 file changed, 1 insertion(+)

tools/perf/util/symbol.h +1 -1

index 3fb5d146d9b1..33ea2596ce31 100644
@@ -127,6 +127,7 @@ void dso__insert_symbol(struct dso *dso,
                        struct symbol *sym);
 void dso__delete_symbol(struct dso *dso,
                        struct symbol *sym);
+bool dso__is_pie(struct dso *dso);
 
 struct symbol *dso__find_symbol(struct dso *dso, u64 addr);
 struct symbol *dso__find_symbol_nocache(struct dso *dso, u64 addr);
--

2.25.1

Steve Clevenger

author

2024-08-26 21:36 UTC #4 lore raw

PATCH v2 3/5 Force MAPPING_TYPE__IDENTIY for PIE

In reply to Steve Clevenger

Changes in V2:
- Updated mailing list distribution

Use dso__is_pie() to check whether the DSO file is a Position Independent Executable (PIE). If PIE, change the MAPPING_TYPE to MAPPING_TYPE__IDENTITY so a zero map pgoff (text offset) is passed into the script.

Signed-off-by Steve Clevenger <[email protected]>

---
 tools/perf/util/map.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

tools/perf/util/map.c +4 -1

index e1d14936a60d..df7c06fc373e 100644
@@ -171,8 +171,11 @@ struct map *map__new(struct machine *machine, u64 start, u64 len,
 		assert(!dso__kernel(dso));
 		map__init(result, start, start + len, pgoff, dso);
 
+		if (map->pgoff && !no_dso)
+			no_dso = dso__is_pie(dso);	// PIE check
+
 		if (anon || no_dso) {
-			map->mapping_type = MAPPING_TYPE__IDENTITY;
+			map__set_mapping_type(map, MAPPING_TYPE__IDENTITY);
 
 			/*
 			 * Set memory without DSO as loaded. All map__find_*

Signature · 1 line

2.25.1

Leo Yan

2024-08-27 19:55 UTC #5 lore raw

Re: [PATCH V2 3/5] Force MAPPING_TYPE__IDENTIY for PIE

Quoted 20 lines · Steve Clevenger

Changes in V2:
- Updated mailing list distribution
Use dso__is_pie() to check whether the DSO file is a Position Independent Executable (PIE). If PIE, change the MAPPING_TYPE to MAPPING_TYPE__IDENTITY so a zero map pgoff (text offset) is passed into the script.
Signed-off-by Steve Clevenger <[email protected]>
---
 tools/perf/util/map.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)
tools/perf/util/map.c +0 -0
index e1d14936a60d..df7c06fc373e 100644

tools/perf/util/map.c struct map *map__new(struct machine *machine, u64 start, u64 len, · line 175

Quoted 5 lines

tools/perf/util/map.c +2 -0

@@ -171,8 +171,11 @@ struct map *map__new(struct machine *machine, u64 start, u64 len,
                assert(!dso__kernel(dso));
                map__init(result, start, start + len, pgoff, dso);
 
+               if (map->pgoff && !no_dso)
+                       no_dso = dso__is_pie(dso);      // PIE check

Here the logic is whatever the pgoff is (zero or non-zero), we need to always set the mapping type as MAPPING_TYPE__IDENTITY. It is no need to check pgoff and is no matter with 'no_dso'. So we can simply check dso__is_pie() and set IDENTITY flag for the true case.

    if (dso__is_pie(dso)) {
            map__set_mapping_type(map, MAPPING_TYPE__IDENTITY);
    } else if (anon || no_dso) {
            ...
    }

BTW, please rebase the series on the top of the perf-tools-next branch [1], I saw this patch has merging conflict on it.

Thanks,
Leo

[1] https://git.kernel.org/pub/scm/linux/kernel/git/acme/linux.git
branch: perf-tools-next

Quoted 10 lines

tools/perf/util/map.c +2 -2

+
                if (anon || no_dso) {
-                       map->mapping_type = MAPPING_TYPE__IDENTITY;
+                       map__set_mapping_type(map, MAPPING_TYPE__IDENTITY);
 
                        /*
                         * Set memory without DSO as loaded. All map__find_*
--

2.25.1

Steve Clevenger

author

2024-08-28 01:41 UTC #6 lore raw

Re: [PATCH V2 3/5] Force MAPPING_TYPE__IDENTIY for PIE

Quoted 38 lines · Leo Yan

Quoted 20 lines · Steve Clevenger
Changes in V2:
- Updated mailing list distribution
Use dso__is_pie() to check whether the DSO file is a Position Independent Executable (PIE). If PIE, change the MAPPING_TYPE to MAPPING_TYPE__IDENTITY so a zero map pgoff (text offset) is passed into the script.
Signed-off-by Steve Clevenger <[email protected]>
---
 tools/perf/util/map.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)
tools/perf/util/map.c +0 -0
index e1d14936a60d..df7c06fc373e 100644
tools/perf/util/map.c struct map *map__new(struct machine *machine, u64 start, u64 len, · line 175
Quoted 5 lines
tools/perf/util/map.c +2 -0
@@ -171,8 +171,11 @@ struct map *map__new(struct machine *machine, u64 start, u64 len,
                assert(!dso__kernel(dso));
                map__init(result, start, start + len, pgoff, dso);
 
+               if (map->pgoff && !no_dso)
+                       no_dso = dso__is_pie(dso);      // PIE check
Here the logic is whatever the pgoff is (zero or non-zero), we need to always set the mapping type as MAPPING_TYPE__IDENTITY. It is no need to check pgoff and is no matter with 'no_dso'. So we can simply check dso__is_pie() and set IDENTITY flag for the true case.
    if (dso__is_pie(dso)) {
            map__set_mapping_type(map, MAPPING_TYPE__IDENTITY);
    } else if (anon || no_dso) {
            ...
    }

Quoted 5 lines

BTW, please rebase the series on the top of the perf-tools-next branch [1], I saw this patch has merging conflict on it.
Thanks,
Leo

Hi Leo,

I combined the dso__is_pie() call onto the end of the existing 'if' statement you now show as an 'else if'. Please see V3 of the patch series.

Steve

Quoted 13 lines

[1] https://git.kernel.org/pub/scm/linux/kernel/git/acme/linux.git
branch: perf-tools-next

Quoted 10 lines

tools/perf/util/map.c +2 -2

+
                if (anon || no_dso) {
-                       map->mapping_type = MAPPING_TYPE__IDENTITY;
+                       map__set_mapping_type(map, MAPPING_TYPE__IDENTITY);
 
                        /*
                         * Set memory without DSO as loaded. All map__find_*
--

2.25.1

Steve Clevenger

author

2024-08-26 21:36 UTC #7 lore raw

PATCH v2 4/5 Add map pgoff to python dictionary based on MAPPING_TYPE

In reply to Steve Clevenger

Changes in V2:
- Updated mailing list distribution

Add map_pgoff parameter to python dictionary so it can be seen by the python script, arm-cs-trace-disasm.py. map_pgoff is forced to zero in the dictionary if file type is MAPPING_TYPE__IDENTITY. Otherwise, the map_pgoff value is directly added to the dictionary.

Signed-off-by Steve Clevenger <[email protected]>

---
 .../util/scripting-engines/trace-event-python.c     | 13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

tools/perf/util/scripting-engines/trace-event-python.c +10 -3

index fb00f3ad6815..8a056c3574ec 100644
@@ -798,7 +798,8 @@ static int set_regs_in_dict(PyObject *dict,
 static void set_sym_in_dict(PyObject *dict, struct addr_location *al,
 			    const char *dso_field, const char *dso_bid_field,
 			    const char *dso_map_start, const char *dso_map_end,
-			    const char *sym_field, const char *symoff_field)
+			    const char *sym_field, const char *symoff_field,
+			    const char *map_pgoff)
 {
 	char sbuild_id[SBUILD_ID_SIZE];

@@ -814,6 +815,12 @@ static void set_sym_in_dict(PyObject *dict, struct addr_location *al,
 			PyLong_FromUnsignedLong(map__start(al->map)));
 		pydict_set_item_string_decref(dict, dso_map_end,
 			PyLong_FromUnsignedLong(map__end(al->map)));
+		if (al->map->mapping_type == MAPPING_TYPE__DSO)
+			pydict_set_item_string_decref(dict, map_pgoff,
+				PyLong_FromUnsignedLongLong(al->map->pgoff));
+		else
+			pydict_set_item_string_decref(dict, map_pgoff,
+				PyLong_FromUnsignedLongLong(0));
 	}
 	if (al->sym) {
 		pydict_set_item_string_decref(dict, sym_field,

@@ -898,7 +905,7 @@ static PyObject *get_perf_sample_dict(struct perf_sample *sample,
 	pydict_set_item_string_decref(dict, "comm",
 			_PyUnicode_FromString(thread__comm_str(al->thread)));
 	set_sym_in_dict(dict, al, "dso", "dso_bid", "dso_map_start", "dso_map_end",
-			"symbol", "symoff");
+			"symbol", "symoff", "map_pgoff")
 
 	pydict_set_item_string_decref(dict, "callchain", callchain);

@@ -923,7 +930,7 @@ static PyObject *get_perf_sample_dict(struct perf_sample *sample,
 			PyBool_FromLong(1));
 		set_sym_in_dict(dict_sample, addr_al, "addr_dso", "addr_dso_bid",
 				"addr_dso_map_start", "addr_dso_map_end",
-				"addr_symbol", "addr_symoff");
+				"addr_symbol", "addr_symoff", "map_pgoff");
 	}
 
 	if (sample->flags)

Signature · 1 line

2.25.1

Steve Clevenger

author

2024-08-26 21:36 UTC #8 lore raw

PATCH v2 5/5 Adjust objdump start/end range per map pgoff parameter

In reply to Steve Clevenger

Changes in V2:
- Updated mailing list distribution

Extract map_pgoff parameter from the dictionary, and adjust start/end range passed to objdump based on the value.

The start_addr/stop_addr address checks are changed to print a warning only if verbose == True. This script repeatedly sees a zero value passed in for
start_addr = cpu_data[str(cpu) + 'addr']

These zero values are not a new problem. The start_addr/stop_addr warning clutters the instruction trace output, hence this change.

Signed-off-by Steve Clevenger <[email protected]>

---
 .../perf/scripts/python/arm-cs-trace-disasm.py  | 17 +++++++++++++++--
 1 file changed, 15 insertions(+), 2 deletions(-)

tools/perf/scripts/python/arm-cs-trace-disasm.py +15 -2

index d973c2baed1c..6bf806078f9a 100755
@@ -187,6 +187,7 @@ def process_event(param_dict):
 	dso_start = get_optional(param_dict, "dso_map_start")
 	dso_end = get_optional(param_dict, "dso_map_end")
 	symbol = get_optional(param_dict, "symbol")
+	map_pgoff = get_optional(param_dict, "map_pgoff")
 
 	cpu = sample["cpu"]
 	ip = sample["ip"]

@@ -250,13 +251,25 @@ def process_event(param_dict):
 		return
 
 	if (start_addr < int(dso_start) or start_addr > int(dso_end)):
-		print("Start address 0x%x is out of range [ 0x%x .. 0x%x ] for dso %s" % (start_addr, int(dso_start), int(dso_end), dso))
+		if (options.verbose == True):
+			print("Start address 0x%x is out of range [ 0x%x .. 0x%x ] for dso %s" % (start_addr, int(dso_start), int(dso_end), dso))
 		return
 
 	if (stop_addr < int(dso_start) or stop_addr > int(dso_end)):
-		print("Stop address 0x%x is out of range [ 0x%x .. 0x%x ] for dso %s" % (stop_addr, int(dso_start), int(dso_end), dso))
+		if (options.verbose == True):
+			print("Stop address 0x%x is out of range [ 0x%x .. 0x%x ] for dso %s" % (stop_addr, int(dso_start), int(dso_end), dso))
 		return
 
+	if map_pgoff != None and map_pgoff != '[unknown]':
+		if (dso == "[kernel.kallsyms]"):
+			dso_vm_start = 0
+			map_pgoff = '[unknown]'
+		else:
+			dso_vm_start = int(dso_start)
+			start_addr += map_pgoff
+			stop_addr += map_pgoff
+			map_pgoff = '[unknown]'
+
 	if (options.objdump_name != None):
 		# It doesn't need to decrease virtual memory offset for disassembly
 		# for kernel dso and executable file dso, so in this case we set

Signature · 1 line

2.25.1

Leo Yan

2024-08-27 20:23 UTC #9 lore raw

Quoted 46 lines · Steve Clevenger

Changes in V2:
- Updated mailing list distribution

Extract map_pgoff parameter from the dictionary, and adjust start/end range passed to objdump based on the value.

The start_addr/stop_addr address checks are changed to print a warning only if verbose == True. This script repeatedly sees a zero value passed in for
start_addr = cpu_data[str(cpu) + 'addr']

These zero values are not a new problem. The start_addr/stop_addr warning clutters the instruction trace output, hence this change.

Signed-off-by Steve Clevenger <[email protected]>

---
 .../perf/scripts/python/arm-cs-trace-disasm.py  | 17 +++++++++++++++--
 1 file changed, 15 insertions(+), 2 deletions(-)

tools/perf/scripts/python/arm-cs-trace-disasm.py +5 -2

index d973c2baed1c..6bf806078f9a 100755
@@ -187,6 +187,7 @@ def process_event(param_dict):
        dso_start = get_optional(param_dict, "dso_map_start")
        dso_end = get_optional(param_dict, "dso_map_end")
        symbol = get_optional(param_dict, "symbol")
+       map_pgoff = get_optional(param_dict, "map_pgoff")
 
        cpu = sample["cpu"]
        ip = sample["ip"]

@@ -250,13 +251,25 @@ def process_event(param_dict):
                return
 
        if (start_addr < int(dso_start) or start_addr > int(dso_end)):
-               print("Start address 0x%x is out of range [ 0x%x .. 0x%x ] for dso %s" % (start_addr, int(dso_start), int(dso_end), dso))
+               if (options.verbose == True):
+                       print("Start address 0x%x is out of range [ 0x%x .. 0x%x ] for dso %s" % (start_addr, int(dso_start), int(dso_end), dso))
                return
 
        if (stop_addr < int(dso_start) or stop_addr > int(dso_end)):
-               print("Stop address 0x%x is out of range [ 0x%x .. 0x%x ] for dso %s" % (stop_addr, int(dso_start), int(dso_end), dso))
+               if (options.verbose == True):
+                       print("Stop address 0x%x is out of range [ 0x%x .. 0x%x ] for dso %s" % (stop_addr, int(dso_start), int(dso_end), dso))
                return

tools/perf/scripts/python/arm-cs-trace-disasm.py def process_event(param_dict): · line 271

Quoted 10 lines

tools/perf/scripts/python/arm-cs-trace-disasm.py +9 -0

 
+       if map_pgoff != None and map_pgoff != '[unknown]':
+               if (dso == "[kernel.kallsyms]"):
+                       dso_vm_start = 0
+                       map_pgoff = '[unknown]'
+               else:
+                       dso_vm_start = int(dso_start)
+                       start_addr += map_pgoff
+                       stop_addr += map_pgoff
+                       map_pgoff = '[unknown]'

Every sample has its own field map_pgoff. So I am confused why we need the
sentence: map_pgoff = '[unknown]'. And you can see with above change, we will set dso_vm_start delicately with below code section.

How about a simple change like below?

@@ -267,7 +268,7 @@ def process_event(param_dict):

dso_fname = get_dso_file_path(dso, dso_bid)
if path.exists(dso_fname):
- print_disam(dso_fname, dso_vm_start, start_addr, stop_addr)
+ print_disam(dso_fname, dso_vm_start, start_addr + map_pgoff, stop_addr +
map_pgoff)

If this change does not work, I am curious if anything we missed to handle in the perf's C code (frontend).

Thanks,
Leo

Quoted 6 lines

tools/perf/scripts/python/arm-cs-trace-disasm.py +0 -1

        if (options.objdump_name != None):
                # It doesn't need to decrease virtual memory offset for disassembly
                # for kernel dso and executable file dso, so in this case we set
--

2.25.1

Steve Clevenger

author

2024-08-28 01:49 UTC #10 lore raw

Quoted 75 lines · Leo Yan

Quoted 46 lines · Steve Clevenger
Changes in V2:
- Updated mailing list distribution
Extract map_pgoff parameter from the dictionary, and adjust start/end range passed to objdump based on the value.
The start_addr/stop_addr address checks are changed to print a warning only if verbose == True. This script repeatedly sees a zero value passed in for
start_addr = cpu_data[str(cpu) + 'addr']
These zero values are not a new problem. The start_addr/stop_addr warning clutters the instruction trace output, hence this change.
Signed-off-by Steve Clevenger <[email protected]>
---
 .../perf/scripts/python/arm-cs-trace-disasm.py  | 17 +++++++++++++++--
 1 file changed, 15 insertions(+), 2 deletions(-)
tools/perf/scripts/python/arm-cs-trace-disasm.py +5 -2
index d973c2baed1c..6bf806078f9a 100755
@@ -187,6 +187,7 @@ def process_event(param_dict):
        dso_start = get_optional(param_dict, "dso_map_start")
        dso_end = get_optional(param_dict, "dso_map_end")
        symbol = get_optional(param_dict, "symbol")
+       map_pgoff = get_optional(param_dict, "map_pgoff")
 
        cpu = sample["cpu"]
        ip = sample["ip"]
@@ -250,13 +251,25 @@ def process_event(param_dict):
                return
 
        if (start_addr < int(dso_start) or start_addr > int(dso_end)):
-               print("Start address 0x%x is out of range [ 0x%x .. 0x%x ] for dso %s" % (start_addr, int(dso_start), int(dso_end), dso))
+               if (options.verbose == True):
+                       print("Start address 0x%x is out of range [ 0x%x .. 0x%x ] for dso %s" % (start_addr, int(dso_start), int(dso_end), dso))
                return
 
        if (stop_addr < int(dso_start) or stop_addr > int(dso_end)):
-               print("Stop address 0x%x is out of range [ 0x%x .. 0x%x ] for dso %s" % (stop_addr, int(dso_start), int(dso_end), dso))
+               if (options.verbose == True):
+                       print("Stop address 0x%x is out of range [ 0x%x .. 0x%x ] for dso %s" % (stop_addr, int(dso_start), int(dso_end), dso))
                return
tools/perf/scripts/python/arm-cs-trace-disasm.py def process_event(param_dict): · line 271
Quoted 10 lines
tools/perf/scripts/python/arm-cs-trace-disasm.py +9 -0
 
+       if map_pgoff != None and map_pgoff != '[unknown]':
+               if (dso == "[kernel.kallsyms]"):
+                       dso_vm_start = 0
+                       map_pgoff = '[unknown]'
+               else:
+                       dso_vm_start = int(dso_start)
+                       start_addr += map_pgoff
+                       stop_addr += map_pgoff
+                       map_pgoff = '[unknown]'
Every sample has its own field map_pgoff. So I am confused why we need the
sentence: map_pgoff = '[unknown]'. And you can see with above change, we will set dso_vm_start delicately with below code section.
How about a simple change like below?
(quoted diff) +1 -1
@@ -267,7 +268,7 @@ def process_event(param_dict):
 
  dso_fname = get_dso_file_path(dso, dso_bid)
  if path.exists(dso_fname):
-     print_disam(dso_fname, dso_vm_start, start_addr, stop_addr)
+     print_disam(dso_fname, dso_vm_start, start_addr + map_pgoff, stop_addr +
 map_pgoff)
 
If this change does not work, I am curious if anything we missed to handle in the perf's C code (frontend).

Quoted 2 lines

Thanks,
Leo

Leo,

Sorry, the map_pgoff = '[unknown]' instances are actually leftover debug artifacts used for print type debug. I resorted to print debug after I didn't see success attempting mixed-mode debug with Visual Studio Code on AARCH64. If you have a known working launch configuration, please share it. See V3 of the patch series. I've rebased to the perf-tools-next branch.

Steve

Quoted 7 lines

tools/perf/scripts/python/arm-cs-trace-disasm.py +0 -1

        if (options.objdump_name != None):
                # It doesn't need to decrease virtual memory offset for disassembly
                # for kernel dso and executable file dso, so in this case we set
--

2.25.1

Steve Clevenger

author

2024-08-26 21:36 UTC #11 lore raw

PATCH v2 1/5 Add dso__is_pie call to identify ELF PIE

In reply to a message not in the archive

Changes in V2:
- Updated mailing list distribution
- Decrease indentation, add null pointer checks per Leo Yan review

Add dso__is_pie global to read the .dynamic section DT_FLAGS_1 entry for the DF_1_PIE flag. This identifies position executable code.

Signed-off-by Steve Clevenger <[email protected]>

---
 tools/perf/util/symbol-elf.c | 60 ++++++++++++++++++++++++++++++++++++
 1 file changed, 60 insertions(+)

tools/perf/util/symbol-elf.c +60 -0

index e398abfd13a0..0e49c1345a67 100644
@@ -662,6 +662,66 @@ static int dso__synthesize_plt_got_symbols(struct dso *dso, Elf *elf,
 	return err;
 }
 
+/*
+ * Check dynamic section DT_FLAGS_1 for a Position Independent
+ * Executable (PIE).
+ */
+bool dso__is_pie(struct dso *dso)
+{
+	Elf *elf = NULL;
+	Elf_Scn *scn = NULL;
+	GElf_Ehdr ehdr;
+	GElf_Shdr shdr;
+	bool is_pie = false;
+	char dso_path[PATH_MAX];
+	int fd = -1;
+
+	if (!dso || (elf_version(EV_CURRENT) == EV_NONE))
+		goto exit;	// false
+
+	dso__build_id_filename(dso, dso_path, sizeof(dso_path), false);
+
+	fd = open(dso_path, O_RDONLY);
+
+	if (fd < 0) {
+		pr_debug("%s: cannot read cached %s.\n", __func__, dso_path);
+		goto exit;	// false
+	}
+
+	elf = elf_begin(fd, ELF_C_READ, NULL);
+	gelf_getehdr(elf, &ehdr);
+
+	if (ehdr.e_type == ET_DYN) {
+		Elf_Data *data;
+		GElf_Dyn *entry;
+		int n_entries = shdr.sh_size / sizeof(GElf_Dyn);
+
+		scn = elf_section_by_name(elf, &ehdr, &shdr, ".dynamic", NULL);
+		if (!scn)
+			goto exit;	// false
+
+		data = (Elf_Data *) elf_getdata(scn, NULL);
+		if (!data || !data->d_buf)
+			goto exit;	// false
+
+		// check DT_FLAGS_1
+		for (int i = 0; i < n_entries; i++) {
+			entry = ((GElf_Dyn *) data->d_buf) + i;
+			if (entry->d_tag == DT_FLAGS_1) {
+				if ((entry->d_un.d_val & DF_1_PIE) != 0) {
+					is_pie = true;
+					break;
+				}
+			}
+		} // end for
+	}
+
+	elf_end(elf);
+	close(fd);
+exit:
+	return is_pie;
+}
+
 /*
  * We need to check if we have a .dynsym, so that we can handle the
  * .plt, synthesizing its symbols, that aren't on the symtabs (be it

Signature · 1 line

2.25.1