https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86673
Arnd Bergmann <arnd at linaro dot org> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |mkuvyrkov at gcc dot gnu.org
--- Comment #2 from Arnd Bergmann <arnd at linaro dot org> ---
Forcing constant inputs for put_user to be read from a volatile variable avoids
this problem and lets me cleanly build all files that showed it.
diff --git a/arch/arm/include/asm/uaccess.h b/arch/arm/include/asm/uaccess.h
index 35c9db857ebe..23e92a9a5ef4 100644
--- a/arch/arm/include/asm/uaccess.h
+++ b/arch/arm/include/asm/uaccess.h
@@ -251,7 +251,8 @@ extern int __put_user_8(void *, unsigned long long);
({ \
unsigned long __limit = current_thread_info()->addr_limit - 1;
\
const typeof(*(p)) __user *__tmp_p = (p); \
- register const typeof(*(p)) __r2 asm("r2") = (x); \
+ const typeof(*(p)) __x = (x); \
+ register const typeof(*(p)) __r2 asm("r2") = READ_ONCE(__x);
\
register const typeof(*(p)) __user *__p asm("r0") = __tmp_p; \
register unsigned long __l asm("r1") = __limit; \
register int __e asm("r0"); \
This confirms that constant inputs are what leads to the problem.
