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perf test llvm: Avoid error when PROFILE_ALL_BRANCHES is set

PATCH New Wang Nan 2 participants 2 messages Jun 19, 2017 – Jun 20, 2017 perf events

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Wang Nan

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PATCH 1/1 perf test llvm: Avoid error when PROFILE_ALL_BRANCHES is set

'if' is defined to complex code when CONFIG_PROFILE_ALL_BRANCHES is selected, which cause a 'perf test LLVM' failure like:

 $ ./perf test LLVM
 35: LLVM search and compile                    :
 35.1: Basic BPF llvm compile                    : Ok
 35.2: kbuild searching                          : Ok
 35.3: Compile source for BPF prologue generation: FAILED!
 35.4: Compile source for BPF relocation         : Skip

The only affected test case is bpf-script-test-prologue.c because it uses kernel headers and has 'if' inside.

This patch undefines 'if' to make it passes perf test.

Signed-off-by Wang Nan <[email protected]>
Cc Arnaldo Carvalho de Melo <[email protected]>
Cc Thomas-Mich Richter <[email protected]>
Cc Hendrik Brueckner <[email protected]>
Cc Alexei Starovoitov <[email protected]>
Cc Li Zefan <[email protected]>
---
 tools/perf/tests/bpf-script-test-prologue.c | 9 +++++++++
 1 file changed, 9 insertions(+)
tools/perf/tests/bpf-script-test-prologue.c +9 -0
index 7230e62..b4ebc75 100644
@@ -10,6 +10,15 @@
 
 #include <uapi/linux/fs.h>
 
+/*
+ * If CONFIG_PROFILE_ALL_BRANCHES is selected,
+ * 'if' is redefined after include kernel header.
+ * Recover 'if' for BPF object code.
+ */
+#ifdef if
+# undef if
+#endif
+
 #define FMODE_READ		0x1
 #define FMODE_WRITE		0x2
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#1 lore raw
perf test llvm: Avoid error when PROFILE_ALL_BRANCHES is set
Commit-ID:  9b57fb7e35957c6838f89f4ed7e3f8433a4bbfc5
Gitweb:     http://git.kernel.org/tip/9b57fb7e35957c6838f89f4ed7e3f8433a4bbfc5
Author:     Wang Nan <[email protected]>
AuthorDate: Wed, 21 Jun 2017 02:32:03 +0800
Committer:  Arnaldo Carvalho de Melo <[email protected]>
CommitDate: Mon, 19 Jun 2017 16:11:26 -0300

perf test llvm: Avoid error when PROFILE_ALL_BRANCHES is set

The 'if' keyword is a define that expands to complex code when CONFIG_PROFILE_ALL_BRANCHES is selected, which causes a 'perf test LLVM' failure like:

  $ ./perf test LLVM
  35: LLVM search and compile                    :
  35.1: Basic BPF llvm compile                    : Ok
  35.2: kbuild searching                          : Ok
  35.3: Compile source for BPF prologue generation: FAILED!
  35.4: Compile source for BPF relocation         : Skip

The only affected test case is bpf-script-test-prologue.c because it uses kernel headers and has 'if' inside.

This patch undefines 'if' to make it passes perf test.

More detailed analysis from a message in this thread, also by Wang:

The problem is caused by following relocation information:

  $ readelf -a ./llvmsubtest3
  ...
     [ 5] _ftrace_branch    PROGBITS         0000000000000000  00000260
          00000000000000a0  0000000000000000  WA       0     0     4
  ...
  Relocation section '.relfunc=null_lseek file->f_mode offset orig' at
  offset 0x490 contains 4 entries:
     Offset          Info           Type           Sym. Value    Sym. Name
  000000000038  000b00000001 unrecognized: 1       0000000000000000 _ftrace_branch
  0000000000b0  000b00000001 unrecognized: 1       0000000000000000 _ftrace_branch
  000000000128  000b00000001 unrecognized: 1       0000000000000000 _ftrace_branch
  0000000001c0  000b00000001 unrecognized: 1       0000000000000000 _ftrace_branch

Relocation section '.rel_ftrace_branch' at offset 0x4d0 contains 8 entries:

     Offset          Info           Type           Sym. Value    Sym. Name
  000000000000  000200000001 unrecognized: 1       0000000000000000 .L__func__.bpf_func__n
  000000000008  000100000001 unrecognized: 1       0000000000000015 .L.str
  000000000028  000200000001 unrecognized: 1       0000000000000000 .L__func__.bpf_func__n
  000000000030  000100000001 unrecognized: 1       0000000000000015 .L.str
  000000000050  000200000001 unrecognized: 1       0000000000000000 .L__func__.bpf_func__n
  000000000058  000100000001 unrecognized: 1       0000000000000015 .L.str
  000000000078  000200000001 unrecognized: 1       0000000000000000 .L__func__.bpf_func__n
  000000000080  000100000001 unrecognized: 1       0000000000000015 .L.str

...

So I think the failure is because you enabled CONFIG_PROFILE_ALL_BRANCHES.

I can reproduce your buggy result by selecting
CONFIG_PROFILE_ALL_BRANCHES in my kbuild:

  $ ./perf test LLVM
  35: LLVM search and compile                    :
  35.1: Basic BPF llvm compile                    : Ok
  35.2: kbuild searching                          : Ok
  35.3: Compile source for BPF prologue generation: FAILED!
  35.4: Compile source for BPF relocation         : Skip

Simply undef CONFIG_PROFILE_ALL_BRANCHES in clang opts not working because it is introduced by "#include <uapi/linux/fs.h>", which override cmdline options. So I think the best way is to undefine 'if' inside BPF script.

Reported-and-Tested-by Thomas-Mich Richter <[email protected]>
Signed-off-by Wang Nan <[email protected]>
Cc Alexei Starovoitov <[email protected]>
Cc Hendrik Brueckner <[email protected]>
Cc Zefan Li <[email protected]>
Link http://lkml.kernel.org/r/[email protected] open here
Signed-off-by Arnaldo Carvalho de Melo <[email protected]>
---
 tools/perf/tests/bpf-script-test-prologue.c | 9 +++++++++
 1 file changed, 9 insertions(+)
tools/perf/tests/bpf-script-test-prologue.c +9 -0
index 7230e62..b4ebc75 100644
@@ -10,6 +10,15 @@
 
 #include <uapi/linux/fs.h>
 
+/*
+ * If CONFIG_PROFILE_ALL_BRANCHES is selected,
+ * 'if' is redefined after include kernel header.
+ * Recover 'if' for BPF object code.
+ */
+#ifdef if
+# undef if
+#endif
+
 #define FMODE_READ		0x1
 #define FMODE_WRITE		0x2