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| author | Peter Zijlstra <peterz@infradead.org> | 2021-03-26 18:12:01 +0300 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2021-04-02 13:41:17 +0300 |
| commit | 23c1ad538f4f371bdb67d8a112314842d5db7e5a (patch) | |
| tree | a057eba5ff709afba56b16586bc990340ec562c6 /tools/objtool | |
| parent | b1f480bc0686e65d5413c035bd13af2ea4888784 (diff) | |
| download | linux-23c1ad538f4f371bdb67d8a112314842d5db7e5a.tar.xz | |
x86/alternatives: Optimize optimize_nops()
Currently, optimize_nops() scans to see if the alternative starts with
NOPs. However, the emit pattern is:
141: \oldinstr
142: .skip (len-(142b-141b)), 0x90
That is, when 'oldinstr' is short, the tail is padded with NOPs. This case
never gets optimized.
Rewrite optimize_nops() to replace any trailing string of NOPs inside
the alternative to larger NOPs. Also run it irrespective of patching,
replacing NOPs in both the original and replaced code.
A direct consequence is that 'padlen' becomes superfluous, so remove it.
[ bp:
- Adjust commit message
- remove a stale comment about needing to pad
- add a comment in optimize_nops()
- exit early if the NOP verif. loop catches a mismatch - function
should not not add NOPs in that case
- fix the "optimized NOPs" offsets output ]
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lkml.kernel.org/r/20210326151259.442992235@infradead.org
Diffstat (limited to 'tools/objtool')
| -rw-r--r-- | tools/objtool/arch/x86/include/arch/special.h | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/tools/objtool/arch/x86/include/arch/special.h b/tools/objtool/arch/x86/include/arch/special.h index d818b2bffa02..14271cca0c74 100644 --- a/tools/objtool/arch/x86/include/arch/special.h +++ b/tools/objtool/arch/x86/include/arch/special.h @@ -10,7 +10,7 @@ #define JUMP_ORIG_OFFSET 0 #define JUMP_NEW_OFFSET 4 -#define ALT_ENTRY_SIZE 13 +#define ALT_ENTRY_SIZE 12 #define ALT_ORIG_OFFSET 0 #define ALT_NEW_OFFSET 4 #define ALT_FEATURE_OFFSET 8 |