Re: [PATCH v2 26/39] x86/cet/shstk: Introduce routines modifying shstk
From: Andrew Cooper <hidden>
Date: 2022-10-05 02:45:02
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linux-arch, linux-doc, linux-mm, lkml
On 29/09/2022 23:29, Rick Edgecombe wrote:
quoted hunk ↗ jump to hunk
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