[patch V4 05/12] riscv/uaccess: Use unsafe wrappers for ASM GOTO

Thomas Gleixner
2025-10-22T12:49:18Z

ASM GOTO is miscompiled by GCC when it is used inside a auto cleanup scope:

bool foo(u32 __user *p, u32 val)
{
scoped_guard(pagefault)
unsafe_put_user(val, p, efault);
return true;
efault:
return false;
}

It ends up leaking the pagefault disable counter in the fault path. clang
at least fails the build.

Rename unsafe_*_user() to arch_unsafe_*_user() which makes the generic
uaccess header wrap it with a local label that makes both compilers emit
correct code. Same for the kernel_nofault() variants.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Paul Walmsley <pjw@kernel.org>
Cc: Palmer Dabbelt <palmer@dabbelt.com>
Cc: linux-riscv@lists.infradead.org
---
arch/riscv/include/asm/uaccess.h | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)

--- a/arch/riscv/include/asm/uaccess.h
+++ b/arch/riscv/include/asm/uaccess.h
@@ -437,10 +437,10 @@ unsigned long __must_check clear_user(vo
__clear_user(untagged_addr(to), n) : n;
}

-#define __get_kernel_nofault(dst, src, type, err_label) \
+#define arch_get_kernel_nofault(dst, src, type, err_label) \
__get_user_nocheck(*((type *)(dst)), (__force __user type *)(src), err_label)

-#define __put_kernel_nofault(dst, src, type, err_label) \
+#define arch_put_kernel_nofault(dst, src, type, err_label) \
__put_user_nocheck(*((type *)(src)), (__force __user type *)(dst), err_label)

static __must_check __always_inline bool user_access_begin(const void __user *ptr, size_t len)
@@ -460,10 +460,10 @@ static inline void user_access_restore(u
* We want the unsafe accessors to always be inlined and use
* the error labels - thus the macro games.
*/
-#define unsafe_put_user(x, ptr, label) \
+#define arch_unsafe_put_user(x, ptr, label) \
__put_user_nocheck(x, (ptr), label)

-#define unsafe_get_user(x, ptr, label) do { \
+#define arch_unsafe_get_user(x, ptr, label) do { \
__inttype(*(ptr)) __gu_val; \
__get_user_nocheck(__gu_val, (ptr), label); \
(x) = (__force __typeof__(*(ptr)))__gu_val; \