linux-kernel - [patch V3 05/12] riscv/uaccess: Use unsafe wrappers for ASM GOTO

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Message-ID: <20251017093030.128245987@linutronix.de>
Date: Fri, 17 Oct 2025 12:09:04 +0200 (CEST)
From: Thomas Gleixner <tglx@...utronix.de>
To: LKML <linux-kernel@...r.kernel.org>
Cc: Paul Walmsley <pjw@...nel.org>,
 Palmer Dabbelt <palmer@...belt.com>,
 linux-riscv@...ts.infradead.org,
 kernel test robot <lkp@...el.com>,
 Russell King <linux@...linux.org.uk>,
 linux-arm-kernel@...ts.infradead.org,
 Linus Torvalds <torvalds@...ux-foundation.org>,
 x86@...nel.org,
 Madhavan Srinivasan <maddy@...ux.ibm.com>,
 Michael Ellerman <mpe@...erman.id.au>,
 Nicholas Piggin <npiggin@...il.com>,
 Christophe Leroy <christophe.leroy@...roup.eu>,
 linuxppc-dev@...ts.ozlabs.org,
 Heiko Carstens <hca@...ux.ibm.com>,
 Christian Borntraeger <borntraeger@...ux.ibm.com>,
 Sven Schnelle <svens@...ux.ibm.com>,
 linux-s390@...r.kernel.org,
 Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
 Andrew Cooper <andrew.cooper3@...rix.com>,
 Julia Lawall <Julia.Lawall@...ia.fr>,
 Nicolas Palix <nicolas.palix@...g.fr>,
 Peter Zijlstra <peterz@...radead.org>,
 Darren Hart <dvhart@...radead.org>,
 Davidlohr Bueso <dave@...olabs.net>,
 André Almeida <andrealmeid@...lia.com>,
 Alexander Viro <viro@...iv.linux.org.uk>,
 Christian Brauner <brauner@...nel.org>,
 Jan Kara <jack@...e.cz>,
 linux-fsdevel@...r.kernel.org
Subject: [patch V3 05/12] riscv/uaccess: Use unsafe wrappers for ASM GOTO

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@...utronix.de>
Cc: Paul Walmsley <pjw@...nel.org>
Cc: Palmer Dabbelt <palmer@...belt.com>
Cc: linux-riscv@...ts.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;			\