lkml.org 
[lkml]   [2022]   [Oct]   [4]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
SubjectRe: [PATCH v2 26/39] x86/cet/shstk: Introduce routines modifying shstk
Date
On 29/09/2022 23:29, Rick Edgecombe wrote:
> diff --git a/arch/x86/include/asm/special_insns.h b/arch/x86/include/asm/special_insns.h
> index 35f709f619fb..f096f52bd059 100644
> --- a/arch/x86/include/asm/special_insns.h
> +++ b/arch/x86/include/asm/special_insns.h
> @@ -223,6 +223,19 @@ static inline void clwb(volatile void *__p)
> : [pax] "a" (p));
> }
>
> +#ifdef CONFIG_X86_SHADOW_STACK
> +static inline int write_user_shstk_64(u64 __user *addr, u64 val)
> +{
> + asm_volatile_goto("1: wrussq %[val], (%[addr])\n"
> + _ASM_EXTABLE(1b, %l[fail])
> + :: [addr] "r" (addr), [val] "r" (val)
> + :: fail);

"1: wrssq %[val], %[addr]\n"
_ASM_EXTABLE(1b, %l[fail])
: [addr] "+m" (*addr)
: [val] "r" (val)
:: fail

Otherwise you've failed to tell the compiler that you wrote to *addr.

With that fixed, it's not volatile because there are no unexpressed side
effects.

~Andrew
\
 
 \ /
  Last update: 2022-10-05 04:45    [W:0.856 / U:0.028 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site