Re: [PATCH] x86/entry: add compatibility with IAS

[Arvind Sankar <nivedita@alum.mit.edu>]

On Mon, Jul 13, 2020 at 02:38:01PM -0700, Jian Cai wrote:
> Clang's integrated assembler does not allow symbols with non-absolute
> values to be reassigned. This patch allows the affected code to be
> compatible with IAS.
> 
> Link: https://github.com/ClangBuiltLinux/linux/issues/1043
> Reported-by: Nick Desaulniers <ndesaulniers@google.com>
> Reported-by: Sedat Dilek <sedat.dilek@gmail.com>
> Suggested-by: Nick Desaulniers <ndesaulniers@google.com>
> Suggested-by: Brian Gerst <brgerst@gmail.com>
> Suggested-by: Arvind Sankar <nivedita@alum.mit.edu>
> Tested-by: Sedat Dilek <sedat.dilek@gmail.com>
> Signed-off-by: Jian Cai <caij2003@gmail.com>
> ---
>  arch/x86/include/asm/idtentry.h | 16 +++++++---------
>  1 file changed, 7 insertions(+), 9 deletions(-)
> 
> diff --git a/arch/x86/include/asm/idtentry.h b/arch/x86/include/asm/idtentry.h
> index f3d70830bf2a..7d22684eafdf 100644
> --- a/arch/x86/include/asm/idtentry.h
> +++ b/arch/x86/include/asm/idtentry.h
> @@ -469,16 +469,15 @@ __visible noinstr void func(struct pt_regs *regs,			\
>  	.align 8
>  SYM_CODE_START(irq_entries_start)
>      vector=FIRST_EXTERNAL_VECTOR
> -    pos = .
>      .rept (FIRST_SYSTEM_VECTOR - FIRST_EXTERNAL_VECTOR)
> +0 :
>  	UNWIND_HINT_IRET_REGS

I know I had it this way, but I think it may be slightly safer to put
the label immediately after UNWIND_HINT_IRET_REGS instead of before,
just in case anyone adds a 0: inside that macro.