[PATCH] D110869: [X86] Implement -fzero-call-used-regs option

[Nathan Chancellor via Phabricator via cfe-commits]

nathanchance added a comment.

It looks like `_paravirt_ident_64()` is the problematic function. This diff on top of v5.17-rc2 allows me to boot:

  diff --git a/arch/x86/kernel/paravirt.c b/arch/x86/kernel/paravirt.c
  index 4420499f7bb4..c1b68504136c 100644
  --- a/arch/x86/kernel/paravirt.c
  +++ b/arch/x86/kernel/paravirt.c
  @@ -96,7 +96,7 @@ static unsigned paravirt_patch_call(void *insn_buff, const void *target,
  
   #ifdef CONFIG_PARAVIRT_XXL
   /* identity function, which can be inlined */
  -u64 notrace _paravirt_ident_64(u64 x)
  +u64 notrace __attribute__((zero_call_used_regs("skip"))) _paravirt_ident_64(u64 x)
   {
          return x;
   }

Rather interesting function to have problems with as a result of this patch but it seems like this function is being used in a very specific way further down the file with the `__PV_IS_CALLEE_SAVE` macro.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D110869/new/

https://reviews.llvm.org/D110869