[PATCH v2 0/3] uaccess: unify inline vs outline copy_{from,to}_user() selection

[PATCH v2 0/3] uaccess: unify inline vs outline copy_{from,to}_user() selection

[Yury Norov]

The kernel allows arches to select between inline and outline
implementations of the copy_{from,to}_user() by defining individual
INLINE_COPY_FROM_USER and INLINE_COPY_TO_USER, correspondingly.
However, all arches enable or disable them always together.

Without the real use-case for one helper being inlined while the other
outlined, having independent controls is excessive and error prone.

The first patch of the series fixes rust/uaccess coppy_to_user() wrapper
guarded with INLINE_COPY_FROM_USER. The 2nd patch switches codebase to
the unified INLINE_COPY_USER. And the last patch cleans up ifdefery in
the include/linux/uaccess.h

---
v1: https://lore.kernel.org/all/20260325163313.749336-1-ynorov@nvidia.com/
v2:
 - reword cover letter (Andrew);
 - add v2#1 to fix rust/uaccess explicitly (Alice);

Yury Norov (3):
  rust: uaccess: use INLINE_COPY_TO_USER to guard copy_to_user()
  uaccess: unify inline vs outline copy_{from,to}_user() selection
  uaccess: minimize INLINE_COPY_USER-related ifdefery

 arch/arc/include/asm/uaccess.h        |  3 +--
 arch/arm/include/asm/uaccess.h        |  3 +--
 arch/arm64/include/asm/uaccess.h      |  3 +--
 arch/hexagon/include/asm/uaccess.h    |  3 +--
 arch/loongarch/include/asm/uaccess.h  |  3 +--
 arch/m68k/include/asm/uaccess.h       |  3 +--
 arch/microblaze/include/asm/uaccess.h |  3 +--
 arch/mips/include/asm/uaccess.h       |  3 +--
 arch/nios2/include/asm/uaccess.h      |  3 +--
 arch/openrisc/include/asm/uaccess.h   |  3 +--
 arch/parisc/include/asm/uaccess.h     |  3 +--
 arch/s390/include/asm/uaccess.h       |  3 +--
 arch/sh/include/asm/uaccess.h         |  3 +--
 arch/sparc/include/asm/uaccess_32.h   |  3 +--
 arch/sparc/include/asm/uaccess_64.h   |  3 +--
 arch/um/include/asm/uaccess.h         |  3 +--
 arch/xtensa/include/asm/uaccess.h     |  3 +--
 include/asm-generic/uaccess.h         |  3 +--
 include/linux/uaccess.h               | 25 +++++++++----------------
 lib/usercopy.c                        |  4 +---
 rust/helpers/uaccess.c                |  2 +-
 21 files changed, 29 insertions(+), 56 deletions(-)

-- 
2.51.0

[PATCH v2 1/3] rust: uaccess: use INLINE_COPY_TO_USER to guard copy_to_user()

[Yury Norov]

The copy_to_user() rust helper is only needed when the main kernel inlines
the function. It is controlled by INLINE_COPY_TO_USER, but the rust helper
is protected with INLINE_COPY_FROM_USER.

Fix that.

Reported-by: Christophe Leroy (CS GROUP) <chleroy@kernel.org>
Closes: https://lore.kernel.org/all/746c9c50-20c4-4dc9-a539-bf1310ff9414@kernel.org/
Fixes: d99dc586ca7c7 ("uaccess: decouple INLINE_COPY_FROM_USER and CONFIG_RUST")
Signed-off-by: Yury Norov <ynorov@nvidia.com>
---
 rust/helpers/uaccess.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/rust/helpers/uaccess.c b/rust/helpers/uaccess.c
index d9625b9ee046..aff22f16ab38 100644
--- a/rust/helpers/uaccess.c
+++ b/rust/helpers/uaccess.c
@@ -20,7 +20,9 @@ unsigned long rust_helper__copy_from_user(void *to, const void __user *from, uns
 {
 	return _inline_copy_from_user(to, from, n);
 }
+#endif
 
+#ifdef INLINE_COPY_TO_USER
 __rust_helper
 unsigned long rust_helper__copy_to_user(void __user *to, const void *from, unsigned long n)
 {
-- 
2.51.0

[PATCH v2 2/3] uaccess: unify inline vs outline copy_{from,to}_user() selection

[Yury Norov]

The kernel allows arches to select between inline and outline
implementations of the copy_{from,to}_user() by defining individual
INLINE_COPY_FROM_USER and INLINE_COPY_TO_USER, correspondingly.
However, all arches enable or disable them always together.

Without the real use-case for one helper being inlined while the other
outlined, having independent controls is excessive and error prone.

Switch the codebase to the single unified INLINE_COPY_USER control.

Tested-by: Alice Ryhl <aliceryhl@google.com>
Signed-off-by: Yury Norov <ynorov@nvidia.com>
---
 arch/arc/include/asm/uaccess.h        |  3 +--
 arch/arm/include/asm/uaccess.h        |  3 +--
 arch/arm64/include/asm/uaccess.h      |  3 +--
 arch/hexagon/include/asm/uaccess.h    |  3 +--
 arch/loongarch/include/asm/uaccess.h  |  3 +--
 arch/m68k/include/asm/uaccess.h       |  3 +--
 arch/microblaze/include/asm/uaccess.h |  3 +--
 arch/mips/include/asm/uaccess.h       |  3 +--
 arch/nios2/include/asm/uaccess.h      |  3 +--
 arch/openrisc/include/asm/uaccess.h   |  3 +--
 arch/parisc/include/asm/uaccess.h     |  3 +--
 arch/s390/include/asm/uaccess.h       |  3 +--
 arch/sh/include/asm/uaccess.h         |  3 +--
 arch/sparc/include/asm/uaccess_32.h   |  3 +--
 arch/sparc/include/asm/uaccess_64.h   |  3 +--
 arch/um/include/asm/uaccess.h         |  3 +--
 arch/xtensa/include/asm/uaccess.h     |  3 +--
 include/asm-generic/uaccess.h         |  3 +--
 include/linux/uaccess.h               | 12 ++++++------
 lib/usercopy.c                        |  4 +---
 rust/helpers/uaccess.c                |  4 +---
 21 files changed, 26 insertions(+), 48 deletions(-)

diff --git a/arch/arc/include/asm/uaccess.h b/arch/arc/include/asm/uaccess.h
index 1e8809ea000a..6df2209541ac 100644
--- a/arch/arc/include/asm/uaccess.h
+++ b/arch/arc/include/asm/uaccess.h
@@ -628,8 +628,7 @@ static inline unsigned long __clear_user(void __user *to, unsigned long n)
 	return res;
 }
 
-#define INLINE_COPY_TO_USER
-#define INLINE_COPY_FROM_USER
+#define INLINE_COPY_USER
 
 #define __clear_user			__clear_user
 
diff --git a/arch/arm/include/asm/uaccess.h b/arch/arm/include/asm/uaccess.h
index d6ae80b5df36..1593cf3b9800 100644
--- a/arch/arm/include/asm/uaccess.h
+++ b/arch/arm/include/asm/uaccess.h
@@ -616,8 +616,7 @@ raw_copy_to_user(void __user *to, const void *from, unsigned long n)
 }
 #define __clear_user(addr, n)		(memset((void __force *)addr, 0, n), 0)
 #endif
-#define INLINE_COPY_TO_USER
-#define INLINE_COPY_FROM_USER
+#define INLINE_COPY_USER
 
 static inline unsigned long __must_check clear_user(void __user *to, unsigned long n)
 {
diff --git a/arch/arm64/include/asm/uaccess.h b/arch/arm64/include/asm/uaccess.h
index b0c83a08dda9..9f5bd9c69c24 100644
--- a/arch/arm64/include/asm/uaccess.h
+++ b/arch/arm64/include/asm/uaccess.h
@@ -456,8 +456,7 @@ do {									\
 	unsafe_copy_loop(__ucu_dst, __ucu_src, __ucu_len, u8, label);	\
 } while (0)
 
-#define INLINE_COPY_TO_USER
-#define INLINE_COPY_FROM_USER
+#define INLINE_COPY_USER
 
 extern unsigned long __must_check __arch_clear_user(void __user *to, unsigned long n);
 static inline unsigned long __must_check __clear_user(void __user *to, unsigned long n)
diff --git a/arch/hexagon/include/asm/uaccess.h b/arch/hexagon/include/asm/uaccess.h
index bff77efc0d9a..1aecf60ec4f5 100644
--- a/arch/hexagon/include/asm/uaccess.h
+++ b/arch/hexagon/include/asm/uaccess.h
@@ -26,8 +26,7 @@ unsigned long raw_copy_from_user(void *to, const void __user *from,
 				     unsigned long n);
 unsigned long raw_copy_to_user(void __user *to, const void *from,
 				   unsigned long n);
-#define INLINE_COPY_FROM_USER
-#define INLINE_COPY_TO_USER
+#define INLINE_COPY_USER
 
 __kernel_size_t __clear_user_hexagon(void __user *dest, unsigned long count);
 #define __clear_user(a, s) __clear_user_hexagon((a), (s))
diff --git a/arch/loongarch/include/asm/uaccess.h b/arch/loongarch/include/asm/uaccess.h
index 438269313e78..428f373feabf 100644
--- a/arch/loongarch/include/asm/uaccess.h
+++ b/arch/loongarch/include/asm/uaccess.h
@@ -292,8 +292,7 @@ raw_copy_to_user(void __user *to, const void *from, unsigned long n)
 	return __copy_user((__force void *)to, from, n);
 }
 
-#define INLINE_COPY_FROM_USER
-#define INLINE_COPY_TO_USER
+#define INLINE_COPY_USER
 
 /*
  * __clear_user: - Zero a block of memory in user space, with less checking.
diff --git a/arch/m68k/include/asm/uaccess.h b/arch/m68k/include/asm/uaccess.h
index 64914872a5c9..31d133faa45e 100644
--- a/arch/m68k/include/asm/uaccess.h
+++ b/arch/m68k/include/asm/uaccess.h
@@ -377,8 +377,7 @@ raw_copy_to_user(void __user *to, const void *from, unsigned long n)
 		return __constant_copy_to_user(to, from, n);
 	return __generic_copy_to_user(to, from, n);
 }
-#define INLINE_COPY_FROM_USER
-#define INLINE_COPY_TO_USER
+#define INLINE_COPY_USER
 
 #define __get_kernel_nofault(dst, src, type, err_label)			\
 do {									\
diff --git a/arch/microblaze/include/asm/uaccess.h b/arch/microblaze/include/asm/uaccess.h
index 3aab2f17e046..afa0dd8d013f 100644
--- a/arch/microblaze/include/asm/uaccess.h
+++ b/arch/microblaze/include/asm/uaccess.h
@@ -250,8 +250,7 @@ raw_copy_to_user(void __user *to, const void *from, unsigned long n)
 {
 	return __copy_tofrom_user(to, (__force const void __user *)from, n);
 }
-#define INLINE_COPY_FROM_USER
-#define INLINE_COPY_TO_USER
+#define INLINE_COPY_USER
 
 /*
  * Copy a null terminated string from userspace.
diff --git a/arch/mips/include/asm/uaccess.h b/arch/mips/include/asm/uaccess.h
index c0cede273c7c..f00c36676b73 100644
--- a/arch/mips/include/asm/uaccess.h
+++ b/arch/mips/include/asm/uaccess.h
@@ -433,8 +433,7 @@ raw_copy_to_user(void __user *to, const void *from, unsigned long n)
 	return __cu_len_r;
 }
 
-#define INLINE_COPY_FROM_USER
-#define INLINE_COPY_TO_USER
+#define INLINE_COPY_USER
 
 extern __kernel_size_t __bzero(void __user *addr, __kernel_size_t size);
 
diff --git a/arch/nios2/include/asm/uaccess.h b/arch/nios2/include/asm/uaccess.h
index 6ccc9a232c23..5e6e05cc6efc 100644
--- a/arch/nios2/include/asm/uaccess.h
+++ b/arch/nios2/include/asm/uaccess.h
@@ -57,8 +57,7 @@ extern unsigned long
 raw_copy_from_user(void *to, const void __user *from, unsigned long n);
 extern unsigned long
 raw_copy_to_user(void __user *to, const void *from, unsigned long n);
-#define INLINE_COPY_FROM_USER
-#define INLINE_COPY_TO_USER
+#define INLINE_COPY_USER
 
 extern long strncpy_from_user(char *__to, const char __user *__from,
 			      long __len);
diff --git a/arch/openrisc/include/asm/uaccess.h b/arch/openrisc/include/asm/uaccess.h
index d6500a374e18..db934ebc0069 100644
--- a/arch/openrisc/include/asm/uaccess.h
+++ b/arch/openrisc/include/asm/uaccess.h
@@ -218,8 +218,7 @@ raw_copy_to_user(void __user *to, const void *from, unsigned long size)
 {
 	return __copy_tofrom_user((__force void *)to, from, size);
 }
-#define INLINE_COPY_FROM_USER
-#define INLINE_COPY_TO_USER
+#define INLINE_COPY_USER
 
 extern unsigned long __clear_user(void __user *addr, unsigned long size);
 
diff --git a/arch/parisc/include/asm/uaccess.h b/arch/parisc/include/asm/uaccess.h
index 6c531d2c847e..0d17f81c8b27 100644
--- a/arch/parisc/include/asm/uaccess.h
+++ b/arch/parisc/include/asm/uaccess.h
@@ -197,7 +197,6 @@ unsigned long __must_check raw_copy_to_user(void __user *dst, const void *src,
 					    unsigned long len);
 unsigned long __must_check raw_copy_from_user(void *dst, const void __user *src,
 					    unsigned long len);
-#define INLINE_COPY_TO_USER
-#define INLINE_COPY_FROM_USER
+#define INLINE_COPY_USER
 
 #endif /* __PARISC_UACCESS_H */
diff --git a/arch/s390/include/asm/uaccess.h b/arch/s390/include/asm/uaccess.h
index dff035372601..a9f32c53f699 100644
--- a/arch/s390/include/asm/uaccess.h
+++ b/arch/s390/include/asm/uaccess.h
@@ -30,8 +30,7 @@ void debug_user_asce(int exit);
 #define uaccess_kmsan_or_inline __always_inline
 #endif
 
-#define INLINE_COPY_FROM_USER
-#define INLINE_COPY_TO_USER
+#define INLINE_COPY_USER
 
 static uaccess_kmsan_or_inline __must_check unsigned long
 raw_copy_from_user(void *to, const void __user *from, unsigned long size)
diff --git a/arch/sh/include/asm/uaccess.h b/arch/sh/include/asm/uaccess.h
index a79609eb14be..02e7a066538e 100644
--- a/arch/sh/include/asm/uaccess.h
+++ b/arch/sh/include/asm/uaccess.h
@@ -95,8 +95,7 @@ raw_copy_to_user(void __user *to, const void *from, unsigned long n)
 {
 	return __copy_user((__force void *)to, from, n);
 }
-#define INLINE_COPY_FROM_USER
-#define INLINE_COPY_TO_USER
+#define INLINE_COPY_USER
 
 /*
  * Clear the area and return remaining number of bytes
diff --git a/arch/sparc/include/asm/uaccess_32.h b/arch/sparc/include/asm/uaccess_32.h
index 43284b6ec46a..5542d5b32994 100644
--- a/arch/sparc/include/asm/uaccess_32.h
+++ b/arch/sparc/include/asm/uaccess_32.h
@@ -190,8 +190,7 @@ static inline unsigned long raw_copy_from_user(void *to, const void __user *from
 	return __copy_user((__force void __user *) to, from, n);
 }
 
-#define INLINE_COPY_FROM_USER
-#define INLINE_COPY_TO_USER
+#define INLINE_COPY_USER
 
 static inline unsigned long __clear_user(void __user *addr, unsigned long size)
 {
diff --git a/arch/sparc/include/asm/uaccess_64.h b/arch/sparc/include/asm/uaccess_64.h
index b825a5dd0210..e2989cfba626 100644
--- a/arch/sparc/include/asm/uaccess_64.h
+++ b/arch/sparc/include/asm/uaccess_64.h
@@ -231,8 +231,7 @@ unsigned long __must_check raw_copy_from_user(void *to,
 unsigned long __must_check raw_copy_to_user(void __user *to,
 					   const void *from,
 					   unsigned long size);
-#define INLINE_COPY_FROM_USER
-#define INLINE_COPY_TO_USER
+#define INLINE_COPY_USER
 
 unsigned long __must_check raw_copy_in_user(void __user *to,
 					   const void __user *from,
diff --git a/arch/um/include/asm/uaccess.h b/arch/um/include/asm/uaccess.h
index 0df9ea4abda8..4417c8b1d37a 100644
--- a/arch/um/include/asm/uaccess.h
+++ b/arch/um/include/asm/uaccess.h
@@ -27,8 +27,7 @@ static inline int __access_ok(const void __user *ptr, unsigned long size);
 #define __access_ok __access_ok
 #define __clear_user __clear_user
 
-#define INLINE_COPY_FROM_USER
-#define INLINE_COPY_TO_USER
+#define INLINE_COPY_USER
 
 #include <asm-generic/uaccess.h>
 
diff --git a/arch/xtensa/include/asm/uaccess.h b/arch/xtensa/include/asm/uaccess.h
index 56aec6d504fe..6538a29a2bbd 100644
--- a/arch/xtensa/include/asm/uaccess.h
+++ b/arch/xtensa/include/asm/uaccess.h
@@ -237,8 +237,7 @@ raw_copy_to_user(void __user *to, const void *from, unsigned long n)
 	prefetch(from);
 	return __xtensa_copy_user((__force void *)to, from, n);
 }
-#define INLINE_COPY_FROM_USER
-#define INLINE_COPY_TO_USER
+#define INLINE_COPY_USER
 
 /*
  * We need to return the number of bytes not cleared.  Our memset()
diff --git a/include/asm-generic/uaccess.h b/include/asm-generic/uaccess.h
index b276f783494c..4569045e7139 100644
--- a/include/asm-generic/uaccess.h
+++ b/include/asm-generic/uaccess.h
@@ -91,8 +91,7 @@ raw_copy_to_user(void __user *to, const void *from, unsigned long n)
 	memcpy((void __force *)to, from, n);
 	return 0;
 }
-#define INLINE_COPY_FROM_USER
-#define INLINE_COPY_TO_USER
+#define INLINE_COPY_USER
 #endif /* CONFIG_UACCESS_MEMCPY */
 
 /*
diff --git a/include/linux/uaccess.h b/include/linux/uaccess.h
index 56328601218c..6100f1046546 100644
--- a/include/linux/uaccess.h
+++ b/include/linux/uaccess.h
@@ -84,7 +84,7 @@
  * the 6 functions (copy_{to,from}_user(), __copy_{to,from}_user_inatomic())
  * that are used instead.  Out of those, __... ones are inlined.  Plain
  * copy_{to,from}_user() might or might not be inlined.  If you want them
- * inlined, have asm/uaccess.h define INLINE_COPY_{TO,FROM}_USER.
+ * inlined, have asm/uaccess.h define INLINE_COPY_USER.
  *
  * NOTE: only copy_from_user() zero-pads the destination in case of short copy.
  * Neither __copy_from_user() nor __copy_from_user_inatomic() zero anything
@@ -157,7 +157,7 @@ __copy_to_user(void __user *to, const void *from, unsigned long n)
 }
 
 /*
- * Architectures that #define INLINE_COPY_TO_USER use this function
+ * Architectures that #define INLINE_COPY_USER use this function
  * directly in the normal copy_to/from_user(), the other ones go
  * through an extern _copy_to/from_user(), which expands the same code
  * here.
@@ -190,7 +190,7 @@ _inline_copy_from_user(void *to, const void __user *from, unsigned long n)
 	memset(to + (n - res), 0, res);
 	return res;
 }
-#ifndef INLINE_COPY_FROM_USER
+#ifndef INLINE_COPY_USER
 extern __must_check unsigned long
 _copy_from_user(void *, const void __user *, unsigned long);
 #endif
@@ -207,7 +207,7 @@ _inline_copy_to_user(void __user *to, const void *from, unsigned long n)
 	}
 	return n;
 }
-#ifndef INLINE_COPY_TO_USER
+#ifndef INLINE_COPY_USER
 extern __must_check unsigned long
 _copy_to_user(void __user *, const void *, unsigned long);
 #endif
@@ -217,7 +217,7 @@ copy_from_user(void *to, const void __user *from, unsigned long n)
 {
 	if (!check_copy_size(to, n, false))
 		return n;
-#ifdef INLINE_COPY_FROM_USER
+#ifdef INLINE_COPY_USER
 	return _inline_copy_from_user(to, from, n);
 #else
 	return _copy_from_user(to, from, n);
@@ -230,7 +230,7 @@ copy_to_user(void __user *to, const void *from, unsigned long n)
 	if (!check_copy_size(from, n, true))
 		return n;
 
-#ifdef INLINE_COPY_TO_USER
+#ifdef INLINE_COPY_USER
 	return _inline_copy_to_user(to, from, n);
 #else
 	return _copy_to_user(to, from, n);
diff --git a/lib/usercopy.c b/lib/usercopy.c
index b00a3a957de6..e2f0bf104a59 100644
--- a/lib/usercopy.c
+++ b/lib/usercopy.c
@@ -12,15 +12,13 @@
 
 /* out-of-line parts */
 
-#if !defined(INLINE_COPY_FROM_USER)
+#if !defined(INLINE_COPY_USER)
 unsigned long _copy_from_user(void *to, const void __user *from, unsigned long n)
 {
 	return _inline_copy_from_user(to, from, n);
 }
 EXPORT_SYMBOL(_copy_from_user);
-#endif
 
-#if !defined(INLINE_COPY_TO_USER)
 unsigned long _copy_to_user(void __user *to, const void *from, unsigned long n)
 {
 	return _inline_copy_to_user(to, from, n);
diff --git a/rust/helpers/uaccess.c b/rust/helpers/uaccess.c
index aff22f16ab38..6e59cc9c665c 100644
--- a/rust/helpers/uaccess.c
+++ b/rust/helpers/uaccess.c
@@ -14,15 +14,13 @@ rust_helper_copy_to_user(void __user *to, const void *from, unsigned long n)
 	return copy_to_user(to, from, n);
 }
 
-#ifdef INLINE_COPY_FROM_USER
+#ifdef INLINE_COPY_USER
 __rust_helper
 unsigned long rust_helper__copy_from_user(void *to, const void __user *from, unsigned long n)
 {
 	return _inline_copy_from_user(to, from, n);
 }
-#endif
 
-#ifdef INLINE_COPY_TO_USER
 __rust_helper
 unsigned long rust_helper__copy_to_user(void __user *to, const void *from, unsigned long n)
 {
-- 
2.51.0

[PATCH v2 3/3] uaccess: minimize INLINE_COPY_USER-related ifdefery

[Yury Norov]

Now that we've got the same config selecting inline vs outline
copy_to_user() and copy_from_user(), we can simplify the corresponding
logic in the uaccess.h.

Fixes: 1f9a8286bc0c ("uaccess: always export _copy_[from|to]_user with CONFIG_RUST")
Tested-by: Alice Ryhl <aliceryhl@google.com>
Signed-off-by: Yury Norov <ynorov@nvidia.com>
---
 include/linux/uaccess.h | 21 +++++++--------------
 1 file changed, 7 insertions(+), 14 deletions(-)

diff --git a/include/linux/uaccess.h b/include/linux/uaccess.h
index 6100f1046546..e0c3d6e29301 100644
--- a/include/linux/uaccess.h
+++ b/include/linux/uaccess.h
@@ -190,10 +190,6 @@ _inline_copy_from_user(void *to, const void __user *from, unsigned long n)
 	memset(to + (n - res), 0, res);
 	return res;
 }
-#ifndef INLINE_COPY_USER
-extern __must_check unsigned long
-_copy_from_user(void *, const void __user *, unsigned long);
-#endif
 
 static inline __must_check unsigned long
 _inline_copy_to_user(void __user *to, const void *from, unsigned long n)
@@ -207,7 +203,13 @@ _inline_copy_to_user(void __user *to, const void *from, unsigned long n)
 	}
 	return n;
 }
-#ifndef INLINE_COPY_USER
+#ifdef INLINE_COPY_USER
+# define _copy_to_user _inline_copy_to_user
+# define _copy_from_user _inline_copy_from_user
+#else
+extern __must_check unsigned long
+_copy_from_user(void *, const void __user *, unsigned long);
+
 extern __must_check unsigned long
 _copy_to_user(void __user *, const void *, unsigned long);
 #endif
@@ -217,11 +219,7 @@ copy_from_user(void *to, const void __user *from, unsigned long n)
 {
 	if (!check_copy_size(to, n, false))
 		return n;
-#ifdef INLINE_COPY_USER
-	return _inline_copy_from_user(to, from, n);
-#else
 	return _copy_from_user(to, from, n);
-#endif
 }
 
 static __always_inline unsigned long __must_check
@@ -229,12 +227,7 @@ copy_to_user(void __user *to, const void *from, unsigned long n)
 {
 	if (!check_copy_size(from, n, true))
 		return n;
-
-#ifdef INLINE_COPY_USER
-	return _inline_copy_to_user(to, from, n);
-#else
 	return _copy_to_user(to, from, n);
-#endif
 }
 
 #ifndef copy_mc_to_kernel
-- 
2.51.0

Re: [PATCH v2 1/3] rust: uaccess: use INLINE_COPY_TO_USER to guard copy_to_user()\

[Alice Ryhl]

On Fri, Apr 24, 2026 at 10:08:55PM -0400, Yury Norov wrote:
> The copy_to_user() rust helper is only needed when the main kernel inlines
> the function. It is controlled by INLINE_COPY_TO_USER, but the rust helper
> is protected with INLINE_COPY_FROM_USER.
> 
> Fix that.
> 
> Reported-by: Christophe Leroy (CS GROUP) <chleroy@kernel.org>
> Closes: https://lore.kernel.org/all/746c9c50-20c4-4dc9-a539-bf1310ff9414@kernel.org/
> Fixes: d99dc586ca7c7 ("uaccess: decouple INLINE_COPY_FROM_USER and CONFIG_RUST")
> Signed-off-by: Yury Norov <ynorov@nvidia.com>

Reviewed-by: Alice Ryhl <aliceryhl@google.com>

Re: [PATCH v2 0/3] uaccess: unify inline vs outline copy_{from,to}_user() selection

[Andrew Morton]

On Fri, 24 Apr 2026 22:08:54 -0400 Yury Norov <ynorov@nvidia.com> wrote:

> The kernel allows arches to select between inline and outline
> implementations of the copy_{from,to}_user() by defining individual
> INLINE_COPY_FROM_USER and INLINE_COPY_TO_USER, correspondingly.
> However, all arches enable or disable them always together.
> 
> Without the real use-case for one helper being inlined while the other
> outlined, having independent controls is excessive and error prone.
> 
> The first patch of the series fixes rust/uaccess coppy_to_user() wrapper
> guarded with INLINE_COPY_FROM_USER. The 2nd patch switches codebase to
> the unified INLINE_COPY_USER. And the last patch cleans up ifdefery in
> the include/linux/uaccess.h

Seems sensible, thanks.  I'll queue these up for test-n-review.

Arnd was involved in some of the Fixes: commits and might be interested
in these changes, so Cc:.

Re: [PATCH v2 0/3] uaccess: unify inline vs outline copy_{from,to}_user() selection

[Christophe Leroy (CS GROUP)]

Le 27/04/2026 à 17:58, Andrew Morton a écrit :
> On Fri, 24 Apr 2026 22:08:54 -0400 Yury Norov <ynorov@nvidia.com> wrote:
> 
>> The kernel allows arches to select between inline and outline
>> implementations of the copy_{from,to}_user() by defining individual
>> INLINE_COPY_FROM_USER and INLINE_COPY_TO_USER, correspondingly.
>> However, all arches enable or disable them always together.
>>
>> Without the real use-case for one helper being inlined while the other
>> outlined, having independent controls is excessive and error prone.
>>
>> The first patch of the series fixes rust/uaccess coppy_to_user() wrapper
>> guarded with INLINE_COPY_FROM_USER. The 2nd patch switches codebase to
>> the unified INLINE_COPY_USER. And the last patch cleans up ifdefery in
>> the include/linux/uaccess.h
> 
> Seems sensible, thanks.  I'll queue these up for test-n-review.
> 
> Arnd was involved in some of the Fixes: commits and might be interested
> in these changes, so Cc:.
> 

I have an alternative as patch 2 in this series : 
https://lore.kernel.org/all/cover.1777306795.git.chleroy@kernel.org/

Christophe