On Tue, Jul 26, 2022, Paolo Bonzini wrote:
> The "BIT" macro cannot be used in top-level assembly statements
> (it can be used in functions through the "i" constraint). To
> avoid having to hard-code EFLAGS.AC being bit 18, define the
> constants for CR0, CR4 and EFLAGS bits in terms of new macros
> for just the bit number.
>
> Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
> ---
...
> diff --git a/x86/smap.c b/x86/smap.c
> index 0994c29..3f63ee1 100644
> --- a/x86/smap.c
> +++ b/x86/smap.c
> @@ -39,7 +39,7 @@ asm ("pf_tss:\n"
> #endif
> "add $"S", %"R "sp\n"
> #ifdef __x86_64__
> - "orl $" xstr(X86_EFLAGS_AC) ", 2*"S"(%"R "sp)\n" // set EFLAGS.AC and retry
I don't understand, this compiles cleanly on both gcc and clang, and generates the
correct code. What am I missing?
> + "orl $(1<<" xstr(X86_EFLAGS_AC_BIT) "), 2*"S"(%"R "sp)\n" // set EFLAGS.AC and retry
> #endif
> "iret"W" \n\t"
> "jmp pf_tss\n\t");
> --
> 2.36.1
>
