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| author | Peter Zijlstra <peterz@infradead.org> | 2022-06-14 23:15:48 +0200 |
|---|---|---|
| committer | Borislav Petkov <bp@suse.de> | 2022-06-27 10:33:59 +0200 |
| commit | a149180fbcf336e97ce4eb2cdc13672727feb94d (patch) | |
| tree | 465e0b2ebf7a147d686abed224a732907c475c1b /arch/x86/include/asm/cpufeatures.h | |
| parent | 951ddecf435659553ed15a9214e153a3af43a9a1 (diff) | |
| download | linux-stable-a149180fbcf336e97ce4eb2cdc13672727feb94d.tar.gz linux-stable-a149180fbcf336e97ce4eb2cdc13672727feb94d.tar.bz2 linux-stable-a149180fbcf336e97ce4eb2cdc13672727feb94d.zip | |
x86: Add magic AMD return-thunk
Note: needs to be in a section distinct from Retpolines such that the
Retpoline RET substitution cannot possibly use immediate jumps.
ORC unwinding for zen_untrain_ret() and __x86_return_thunk() is a
little tricky but works due to the fact that zen_untrain_ret() doesn't
have any stack ops and as such will emit a single ORC entry at the
start (+0x3f).
Meanwhile, unwinding an IP, including the __x86_return_thunk() one
(+0x40) will search for the largest ORC entry smaller or equal to the
IP, these will find the one ORC entry (+0x3f) and all works.
[ Alexandre: SVM part. ]
[ bp: Build fix, massages. ]
Suggested-by: Andrew Cooper <Andrew.Cooper3@citrix.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
Diffstat (limited to 'arch/x86/include/asm/cpufeatures.h')
| -rw-r--r-- | arch/x86/include/asm/cpufeatures.h | 1 |
1 files changed, 1 insertions, 0 deletions
diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h index 295e69090fb8..fa3d0db1470e 100644 --- a/arch/x86/include/asm/cpufeatures.h +++ b/arch/x86/include/asm/cpufeatures.h @@ -301,6 +301,7 @@ #define X86_FEATURE_RETPOLINE (11*32+12) /* "" Generic Retpoline mitigation for Spectre variant 2 */ #define X86_FEATURE_RETPOLINE_LFENCE (11*32+13) /* "" Use LFENCE for Spectre variant 2 */ #define X86_FEATURE_RETHUNK (11*32+14) /* "" Use REturn THUNK */ +#define X86_FEATURE_UNRET (11*32+15) /* "" AMD BTB untrain return */ /* Intel-defined CPU features, CPUID level 0x00000007:1 (EAX), word 12 */ #define X86_FEATURE_AVX_VNNI (12*32+ 4) /* AVX VNNI instructions */ |