On Wed, May 06, 2020 at 05:32:56PM +0530, Amit Kachhap wrote: > On 5/4/20 10:47 PM, Will Deacon wrote: > > On Mon, Apr 27, 2020 at 11:55:01AM +0530, Amit Daniel Kachhap wrote: > > > diff --git a/arch/arm64/include/asm/compiler.h > > > b/arch/arm64/include/asm/compiler.h > > > index eece20d..32d5900 100644 > > > --- a/arch/arm64/include/asm/compiler.h > > > +++ b/arch/arm64/include/asm/compiler.h > > > @@ -19,6 +19,9 @@ > > > #define __builtin_return_address(val) > > > \ > > > (void *)(ptrauth_clear_pac((unsigned > > > long)__builtin_return_address(val))) > > > +#else /* !CONFIG_ARM64_PTR_AUTH */ > > > +#define ptrauth_user_pac_mask() 0ULL > > > +#define ptrauth_kernel_pac_mask() 0ULL > > > > This doesn't look quite right to me, since you still have to take into > > account the case where CONFIG_ARM64_PTR_AUTH=y but the feature is not > > available at runtime: > > Yes agree with you here. However the config gaurd is saving some extra > computation for __builtin_return_address. There are some compiler > support being added in __builtin_extract_return_address to mask the PAC. > Hopefully that will improve this code. In the meantime let it be like this.
Does the extra computation matter? Isn't it just a couple of instructions? Will
