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authorSteve MacLean <Steve.MacLean@microsoft.com>2019-09-28 01:53:08 +0000
committerArnaldo Carvalho de Melo <acme@redhat.com>2019-09-30 17:29:51 -0300
commit2657983b4c0d81632c6a73bae469951b0d341251 (patch)
treebc21967fb57bd2ec729bd7cdc848ff29cb03a951 /tools
parentb59711e9b0d22fd47abfa00602fd8c365cdd3ab7 (diff)
perf docs: Correct and clarify jitdump spec
Specification claims latest version of jitdump file format is 2. Current jit dump reading code treats 1 as the latest version. Correct spec to match code. The original language made it unclear the value to be written in the magic field. Revise language that the writer always writes the same value. Specify that the reader uses the value to detect endian mismatches. Signed-off-by: Steve MacLean <Steve.MacLean@Microsoft.com> Acked-by: Stephane Eranian <eranian@google.com> Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com> Cc: Andi Kleen <ak@linux.intel.com> Cc: Brian Robbins <brianrob@microsoft.com> Cc: Davidlohr Bueso <dave@stgolabs.net> Cc: Eric Saint-Etienne <eric.saint.etienne@oracle.com> Cc: Jiri Olsa <jolsa@redhat.com> Cc: John Keeping <john@metanate.com> Cc: John Salem <josalem@microsoft.com> Cc: Leo Yan <leo.yan@linaro.org> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Namhyung Kim <namhyung@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Song Liu <songliubraving@fb.com> Cc: Tom McDonald <thomas.mcdonald@microsoft.com> Link: http://lore.kernel.org/lkml/BN8PR21MB1362F63CDE7AC69736FC7F9EF7800@BN8PR21MB1362.namprd21.prod.outlook.com Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Diffstat (limited to 'tools')
-rw-r--r--tools/perf/Documentation/jitdump-specification.txt4
1 files changed, 2 insertions, 2 deletions
diff --git a/tools/perf/Documentation/jitdump-specification.txt b/tools/perf/Documentation/jitdump-specification.txt
index 4c62b0713651..52152d156ad9 100644
--- a/tools/perf/Documentation/jitdump-specification.txt
+++ b/tools/perf/Documentation/jitdump-specification.txt
@@ -36,8 +36,8 @@ 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 magic : a magic number tagging the file type. The value is 4-byte long and represents the string "JiTD" in ASCII form. It written is as 0x4A695444. The reader will detect an endian mismatch when it reads 0x4454694a.
+* uint32_t version : a 4-byte value representing the format version. It is currently set to 1
* 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