[PATCH] random: vDSO: Fix shadow declarations

From: shao.mingyin
Date: Mon Mar 24 2025 - 07:14:54 EST


From: Peng Jiang <jiang.peng9@xxxxxxxxxx>

Compiling the kernel with gcc12.3 W=2 produces a warning:
In file included from linux-next/lib/vdso/getrandom.c:10,
from <command-line>:
linux-next/lib/vdso/getrandom.c: In function 'memcpy_and_zero_src':
./include/vdso/unaligned.h:6:44:
warning: declaration of '__pptr' shadows a previous local [-Wshadow]
6 | const struct { type x; } __packed *__pptr = (typeof(__pptr))(ptr);
| ^~~~~~
./include/vdso/unaligned.h:12:22:
note: in definition of macro '__put_unaligned_t'
12 | __pptr->x = (val);
| ^~~
linux-next/lib/vdso/getrandom.c:25:41:
note: in expansion of macro '__get_unaligned_t'
25 | __put_unaligned_t(type, __get_unaligned_t(type, src), dst);
| ^~~~~~~~~~~~~~~~~
linux-next/lib/vdso/getrandom.c:37:25:
note: in expansion of macro 'MEMCPY_AND_ZERO_SRC'
37 | MEMCPY_AND_ZERO_SRC(u64, dst, src, len);

To reproduce the issue before applying the patch:
make defconfig ARCH=arm64 CROSS_COMPILE=aarch64-linux-
make vmlinux ARCH=arm64 CROSS_COMPILE=aarch64-linux- W=2

The existing implementation of the __get_unaligned_t and __put_unaligned_t
macros in include/vdso/unaligned.h uses a local variable named '__pptr'
which can lead to variable shadowing when these macros are used in
the same scope. This results in a -Wshadow warning during compilation.

To address this issue, we have renamed the local variables within
the macros to ensure uniqueness:
- In __get_unaligned_t, '__pptr' has been renamed to '__get_pptr'.
- In __put_unaligned_t, '__pptr' has been renamed to '__put_pptr'.

These changes prevent variable shadowing and eliminate the
-Wshadow warning, improving code readability and maintainability.

Signed-off-by: Peng Jiang <jiang.peng9@xxxxxxxxxx>
Signed-off-by: Shao Mingyin <shao.mingyin@xxxxxxxxxx>
---
include/vdso/unaligned.h | 12 ++++++------
1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/include/vdso/unaligned.h b/include/vdso/unaligned.h
index eee3d2a4dbe4..ff0c06b6513e 100644
--- a/include/vdso/unaligned.h
+++ b/include/vdso/unaligned.h
@@ -2,14 +2,14 @@
#ifndef __VDSO_UNALIGNED_H
#define __VDSO_UNALIGNED_H

-#define __get_unaligned_t(type, ptr) ({ \
- const struct { type x; } __packed *__pptr = (typeof(__pptr))(ptr); \
- __pptr->x; \
+#define __get_unaligned_t(type, ptr) ({ \
+ const struct { type x; } __packed * __get_pptr = (typeof(__get_pptr))(ptr); \
+ __get_pptr->x; \
})

-#define __put_unaligned_t(type, val, ptr) do { \
- struct { type x; } __packed *__pptr = (typeof(__pptr))(ptr); \
- __pptr->x = (val); \
+#define __put_unaligned_t(type, val, ptr) do { \
+ struct { type x; } __packed * __put_pptr = (typeof(__put_pptr))(ptr); \
+ __put_pptr->x = (val); \
} while (0)

#endif /* __VDSO_UNALIGNED_H */
--
2.25.1