linux-kernel - [PATCH v2 07/10] powerpc/uaccess: Refactor user_{read/write/}_access

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Message-ID: <cd88a8e7b9af97c0cab84fc4b9dec74f10932568.1755854833.git.christophe.leroy@csgroup.eu>
Date: Fri, 22 Aug 2025 11:58:03 +0200
From: Christophe Leroy <christophe.leroy@...roup.eu>
To: Michael Ellerman <mpe@...erman.id.au>,
	Nicholas Piggin <npiggin@...il.com>,
	Madhavan Srinivasan <maddy@...ux.ibm.com>,
	Alexander Viro <viro@...iv.linux.org.uk>,
	Christian Brauner <brauner@...nel.org>,
	Jan Kara <jack@...e.cz>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Darren Hart <dvhart@...radead.org>,
	Davidlohr Bueso <dave@...olabs.net>,
	"Andre Almeida" <andrealmeid@...lia.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	David Laight <david.laight.linux@...il.com>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Daniel Borkmann <daniel@...earbox.net>
Cc: Christophe Leroy <christophe.leroy@...roup.eu>,
	linux-kernel@...r.kernel.org,
	linuxppc-dev@...ts.ozlabs.org,
	linux-fsdevel@...r.kernel.org,
	linux-mm@...ck.org,
	linux-block@...r.kernel.org
Subject: [PATCH v2 07/10] powerpc/uaccess: Refactor user_{read/write/}_access_begin()

user_read_access_begin() and user_write_access_begin() and
user_access_begin() are now very similar. Create a common
__user_access_begin() that take direction as parameter.

In order to avoid a warning with the conditional call of
barrier_nospec() which is sometimes an empty macro, change it to a
do {} while (0).

Signed-off-by: Christophe Leroy <christophe.leroy@...roup.eu>
---
v2: New
---
 arch/powerpc/include/asm/barrier.h |  2 +-
 arch/powerpc/include/asm/uaccess.h | 46 +++++++++---------------------
 2 files changed, 14 insertions(+), 34 deletions(-)

diff --git a/arch/powerpc/include/asm/barrier.h b/arch/powerpc/include/asm/barrier.h
index b95b666f0374..7acbf27cac6c 100644
--- a/arch/powerpc/include/asm/barrier.h
+++ b/arch/powerpc/include/asm/barrier.h
@@ -102,7 +102,7 @@ do {									\
 
 #else /* !CONFIG_PPC_BARRIER_NOSPEC */
 #define barrier_nospec_asm
-#define barrier_nospec()
+#define barrier_nospec()	do {} while (0)
 #endif /* CONFIG_PPC_BARRIER_NOSPEC */
 
 /*
diff --git a/arch/powerpc/include/asm/uaccess.h b/arch/powerpc/include/asm/uaccess.h
index 698996f34891..49254f7d9069 100644
--- a/arch/powerpc/include/asm/uaccess.h
+++ b/arch/powerpc/include/asm/uaccess.h
@@ -410,50 +410,30 @@ copy_mc_to_user(void __user *to, const void *from, unsigned long n)
 extern long __copy_from_user_flushcache(void *dst, const void __user *src,
 		unsigned size);
 
-static __must_check __always_inline bool user_access_begin(const void __user *ptr, size_t len)
+static __must_check __always_inline bool __user_access_begin(const void __user *ptr, size_t len,
+							     unsigned long dir)
 {
 	if (unlikely(!access_ok(ptr, len)))
 		return false;
 
 	might_fault();
 
-	barrier_nospec();
-	allow_read_write_user((void __user *)ptr, ptr, len);
+	if (dir & KUAP_READ)
+		barrier_nospec();
+	allow_user_access((void __user *)ptr, dir);
 	return true;
 }
-#define user_access_begin	user_access_begin
-#define user_access_end		prevent_current_access_user
-#define user_access_save	prevent_user_access_return
-#define user_access_restore	restore_user_access
 
-static __must_check __always_inline bool
-user_read_access_begin(const void __user *ptr, size_t len)
-{
-	if (unlikely(!access_ok(ptr, len)))
-		return false;
+#define user_access_begin(p, l)		__user_access_begin(p, l, KUAP_READ_WRITE)
+#define user_read_access_begin(p, l)	__user_access_begin(p, l, KUAP_READ)
+#define user_write_access_begin(p, l)	__user_access_begin(p, l, KUAP_WRITE)
 
-	might_fault();
-
-	barrier_nospec();
-	allow_read_from_user(ptr, len);
-	return true;
-}
-#define user_read_access_begin	user_read_access_begin
-#define user_read_access_end		prevent_current_read_from_user
+#define user_access_end()		prevent_user_access(KUAP_READ_WRITE)
+#define user_read_access_end()		prevent_user_access(KUAP_READ)
+#define user_write_access_end()		prevent_user_access(KUAP_WRITE)
 
-static __must_check __always_inline bool
-user_write_access_begin(const void __user *ptr, size_t len)
-{
-	if (unlikely(!access_ok(ptr, len)))
-		return false;
-
-	might_fault();
-
-	allow_write_to_user((void __user *)ptr, len);
-	return true;
-}
-#define user_write_access_begin	user_write_access_begin
-#define user_write_access_end		prevent_current_write_to_user
+#define user_access_save	prevent_user_access_return
+#define user_access_restore	restore_user_access
 
 #define unsafe_get_user(x, p, e) do {					\
 	__long_type(*(p)) __gu_val;				\
-- 
2.49.0