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Merge tag 'x86_alternatives_for_v6.5' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

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Pull x86 instruction alternatives updates from Borislav Petkov:

 - Up until now the Fast Short Rep Mov optimizations implied the
   presence of the ERMS CPUID flag. AMD decoupled them with a BIOS
   setting so decouple that dependency in the kernel code too

 - Teach the alternatives machinery to handle relocations

 - Make debug_alternative accept flags in order to see only that set of
   patching done one is interested in

 - Other fixes, cleanups and optimizations to the patching code

* tag 'x86_alternatives_for_v6.5' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/alternative: PAUSE is not a NOP
  x86/alternatives: Add cond_resched() to text_poke_bp_batch()
  x86/nospec: Shorten RESET_CALL_DEPTH
  x86/alternatives: Add longer 64-bit NOPs
  x86/alternatives: Fix section mismatch warnings
  x86/alternative: Optimize returns patching
  x86/alternative: Complicate optimize_nops() some more
  x86/alternative: Rewrite optimize_nops() some
  x86/lib/memmove: Decouple ERMS from FSRM
  x86/alternative: Support relocations in alternatives
  x86/alternative: Make debug-alternative selective
This commit is contained in:
Linus Torvalds
2023-06-26 15:14:55 -07:00
parent aa35a4835e 2bd4aa9325
commit 8c69e7afe9
6 changed files with 365 additions and 172 deletions
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13
arch/x86/lib/memmove_64.S
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@@ -38,10 +38,12 @@ SYM_FUNC_START(__memmove)
cmp %rdi, %r8
jg 2f
/* FSRM implies ERMS => no length checks, do the copy directly */
#define CHECK_LEN cmp $0x20, %rdx; jb 1f
#define MEMMOVE_BYTES movq %rdx, %rcx; rep movsb; RET
.Lmemmove_begin_forward:
ALTERNATIVE "cmp $0x20, %rdx; jb 1f", "", X86_FEATURE_FSRM
ALTERNATIVE "", "jmp .Lmemmove_erms", X86_FEATURE_ERMS
ALTERNATIVE_2 __stringify(CHECK_LEN), \
__stringify(CHECK_LEN; MEMMOVE_BYTES), X86_FEATURE_ERMS, \
__stringify(MEMMOVE_BYTES), X86_FEATURE_FSRM
/*
* movsq instruction have many startup latency
@@ -207,11 +209,6 @@ SYM_FUNC_START(__memmove)
movb %r11b, (%rdi)
13:
RET
.Lmemmove_erms:
movq %rdx, %rcx
rep movsb
RET
SYM_FUNC_END(__memmove)
EXPORT_SYMBOL(__memmove)