From 2657983b4c0d81632c6a73bae469951b0d341251 Mon Sep 17 00:00:00 2001 From: Steve MacLean Date: Sat, 28 Sep 2019 01:53:08 +0000 Subject: 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 Acked-by: Stephane Eranian Cc: Alexander Shishkin Cc: Andi Kleen Cc: Brian Robbins Cc: Davidlohr Bueso Cc: Eric Saint-Etienne Cc: Jiri Olsa Cc: John Keeping Cc: John Salem Cc: Leo Yan Cc: Mark Rutland Cc: Namhyung Kim Cc: Peter Zijlstra Cc: Song Liu Cc: Tom McDonald Link: http://lore.kernel.org/lkml/BN8PR21MB1362F63CDE7AC69736FC7F9EF7800@BN8PR21MB1362.namprd21.prod.outlook.com Signed-off-by: Arnaldo Carvalho de Melo --- tools/perf/Documentation/jitdump-specification.txt | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'tools/perf/Documentation/jitdump-specification.txt') 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 -- cgit