Re: [PATCH v3 27/37] x86/shstk: Introduce routines modifying shstk

Peter Zijlstra
2022-11-15T19:43:58Z

On Fri, Nov 04, 2022 at 03:35:54PM -0700, Rick Edgecombe wrote:

> +#ifdef CONFIG_X86_USER_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);
> + return 0;
> +fail:
> + return -EFAULT;
> +}
> +#endif /* CONFIG_X86_USER_SHADOW_STACK */

Why isn't this modelled after put_user() ?

Should you write a 64bit value even if the task receiving a signal is
32bit ?