On Tue, Oct 12, 2021 at 4:25 PM Peter Oskolkov [off-list ref] 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.

[...]