On 5/18/26 4:49 PM, Ruidong Tian wrote:
From: Tong Tiangen <[email protected]>
x86/powerpc has it's implementation of copy_mc_to_user(), we add generic
fallback in include/linux/uaccess.h prepare for other architechures to
enable CONFIG_ARCH_HAS_COPY_MC.
Signed-off-by: Tong Tiangen <[email protected]>
Acked-by: Michael Ellerman <[email protected]>
Reviewed-by: Mauro Carvalho Chehab <[email protected]>
Reviewed-by: Jonathan Cameron <[email protected]>
---
arch/powerpc/include/asm/uaccess.h | 1 +
arch/x86/include/asm/uaccess.h | 1 +
include/linux/uaccess.h | 8 ++++++++
3 files changed, 10 insertions(+)
diff --git a/arch/powerpc/include/asm/uaccess.h
b/arch/powerpc/include/asm/uaccess.h
index e98c628e3899..073de098d45a 100644
--- a/arch/powerpc/include/asm/uaccess.h
+++ b/arch/powerpc/include/asm/uaccess.h
@@ -432,6 +432,7 @@ copy_mc_to_user(void __user *to, const void *from, unsigned
long n)
return n;
}
+#define copy_mc_to_user copy_mc_to_user
#endif
extern size_t copy_from_user_flushcache(void *dst, const void __user *src, size_t size);
diff --git a/arch/x86/include/asm/uaccess.h b/arch/x86/include/asm/uaccess.h
index 3a0dd3c2b233..308b0854d1d5 100644
--- a/arch/x86/include/asm/uaccess.h
+++ b/arch/x86/include/asm/uaccess.h
@@ -496,6 +496,7 @@ copy_mc_to_kernel(void *to, const void *from, unsigned len);
unsigned long __must_check
copy_mc_to_user(void __user *to, const void *from, unsigned len);
+#define copy_mc_to_user copy_mc_to_user
#endif
/*
diff --git a/include/linux/uaccess.h b/include/linux/uaccess.h
index 56328601218c..c53a65394f80 100644
--- a/include/linux/uaccess.h
+++ b/include/linux/uaccess.h
@@ -250,6 +250,14 @@ copy_mc_to_kernel(void *dst, const void *src, size_t cnt)
}
#endif
+#ifndef copy_mc_to_user
+static inline unsigned long __must_check
+copy_mc_to_user(void *dst, const void *src, size_t cnt)
+{
The prototype of this generic fallback diverges from both copy_to_user()
and the existing arch implementations of copy_mc_to_user() in two
non-trivial ways:
1. The destination pointer drops the __user annotation.
copy_to_user() is declared as:
unsigned long copy_to_user(void __user *to,
const void *from,
unsigned long n);
and arch/x86/include/asm/uaccess.h declares the arch version as:
unsigned long copy_mc_to_user(void __user *to,
const void *from,
unsigned long len);
With this fallback typed as 'void *dst', sparse will silently
accept a kernel pointer being passed in, and the address-space
check is effectively lost for any architecture that ends up using
the fallback. The annotation is the whole point of __user; please
keep it.
2. The size parameter is 'size_t cnt' instead of 'unsigned long n'.
copy_to_user() and the x86/ppc copy_mc_to_user() implementations
all use 'unsigned long'. On all supported arches this happens to
be the same width as size_t, so it is not a functional bug, but
the inconsistent signature is a foot-gun: when an arch later
switches from the fallback to its own implementation, every
caller signature has to be re-checked.
Please align the fallback prototype exactly with the arch versions:
#ifndef copy_mc_to_user
static inline unsigned long __must_check
copy_mc_to_user(void __user *dst, const void *src, unsigned long cnt)
{
return copy_to_user(dst, src, cnt);
}
#endif
With that fixed:
Reviewed-by: Shuai Xue <[email protected]>
Thanks.
Shuai
