Messages in this thread | | | From | Andrew Cooper <> | Subject | Re: [PATCH v2 26/39] x86/cet/shstk: Introduce routines modifying shstk | Date | Wed, 5 Oct 2022 02:43:14 +0000 |
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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
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