Re: [PATCH v0.7 2/5] mm, x86/uaccess: add userspace atomic helpers

[Peter Oskolkov <posk@posk.io>]

On Tue, Oct 12, 2021 at 4:25 PM Peter Oskolkov <posk@posk.io> wrote:

[...]

> +static inline int __try_xchg_user_32(u32 *oval, u32 __user *uaddr, u32 newval)
> +{
> +       u32 oldval = 0;
> +       int ret = 0;
> +
> +       asm volatile("\n"
> +               "1:\txchgl %0, %2\n"
> +               "2:\n"
> +               "\t.section .fixup, \"ax\"\n"
> +               "3:\tmov     %3, %0\n"

I believe the line above should be "mov %3, %1", not "mov %3, %0".
I'll fix this in the next patchset mailing.

> +               "\tjmp     2b\n"
> +               "\t.previous\n"
> +               _ASM_EXTABLE_UA(1b, 3b)
> +               : "=r" (oldval), "=r" (ret), "+m" (*uaddr)
> +               : "i" (-EFAULT), "0" (newval), "1" (0)
> +       );
> +
> +       if (ret)
> +               return ret;
> +
> +       *oval = oldval;
> +       return 0;
> +}
> +
> +static inline int __try_xchg_user_64(u64 *oval, u64 __user *uaddr, u64 newval)
> +{> +> +
> +       u64 oldval = 0;
> +       int ret = 0;
> +
> +       asm volatile("\n"
> +               "1:\txchgq %0, %2\n"
> +               "2:\n"
> +               "\t.section .fixup, \"ax\"\n"
> +               "3:\tmov     %3, %0\n"

Same here.

[...]