This is a note to let you know that I've just added the patch titled
x86/percpu: Use __force to cast from __percpu address space
to the 6.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
x86-percpu-use-__force-to-cast-from-__percpu-address-space.patch
and it can be found in the queue-6.9 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From a55c1fdad5f61b4bfe42319694b23671a758cb28 Mon Sep 17 00:00:00 2001
From: Uros Bizjak <ubizjak@xxxxxxxxx>
Date: Tue, 2 Apr 2024 19:50:38 +0200
Subject: x86/percpu: Use __force to cast from __percpu address space
From: Uros Bizjak <ubizjak@xxxxxxxxx>
commit a55c1fdad5f61b4bfe42319694b23671a758cb28 upstream.
Fix Sparse warning when casting from __percpu address space by using
__force in the cast. x86 named address spaces are not considered to
be subspaces of the generic (flat) address space, so explicit casts
are required to convert pointers between these address spaces and the
generic address space (the application should cast to uintptr_t and
apply the segment base offset). The cast to uintptr_t removes
__percpu address space tag and Sparse reports:
warning: cast removes address space '__percpu' of expression
Use __force to inform Sparse that the cast is intentional.
Fixes: 9a462b9eafa6 ("x86/percpu: Use compiler segment prefix qualifier")
Reported-by: Charlemagne Lasse <charlemagnelasse@xxxxxxxxx>
Signed-off-by: Uros Bizjak <ubizjak@xxxxxxxxx>
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/20240402175058.52649-1-ubizjak@xxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Closes: https://lore.kernel.org/lkml/CAFGhKbzev7W4aHwhFPWwMZQEHenVgZUj7=aunFieVqZg3mt14A@xxxxxxxxxxxxxx/
---
arch/x86/include/asm/percpu.h | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
--- a/arch/x86/include/asm/percpu.h
+++ b/arch/x86/include/asm/percpu.h
@@ -70,7 +70,7 @@
unsigned long tcp_ptr__; \
tcp_ptr__ = __raw_cpu_read(, this_cpu_off); \
\
- tcp_ptr__ += (unsigned long)(ptr); \
+ tcp_ptr__ += (__force unsigned long)(ptr); \
(typeof(*(ptr)) __kernel __force *)tcp_ptr__; \
})
#else /* CONFIG_USE_X86_SEG_SUPPORT */
@@ -102,8 +102,8 @@
#endif /* CONFIG_SMP */
#define __my_cpu_type(var) typeof(var) __percpu_seg_override
-#define __my_cpu_ptr(ptr) (__my_cpu_type(*ptr) *)(uintptr_t)(ptr)
-#define __my_cpu_var(var) (*__my_cpu_ptr(&var))
+#define __my_cpu_ptr(ptr) (__my_cpu_type(*ptr)*)(__force uintptr_t)(ptr)
+#define __my_cpu_var(var) (*__my_cpu_ptr(&(var)))
#define __percpu_arg(x) __percpu_prefix "%" #x
#define __force_percpu_arg(x) __force_percpu_prefix "%" #x
Patches currently in stable-queue which might be from ubizjak@xxxxxxxxx are
queue-6.9/x86-percpu-use-__force-to-cast-from-__percpu-address-space.patch
