On Sun, 1 Mar 2026 20:33:58 +0100
"Christophe Leroy (CS GROUP)" <[email protected]> wrote:
> After converting powerpc checksum wrappers to scoped user access,
> following build failure happens:
>
> CC arch/powerpc/lib/checksum_wrappers.o
> In file included from arch/powerpc/lib/checksum_wrappers.c:12:
> arch/powerpc/lib/checksum_wrappers.c: In function
> 'csum_and_copy_from_user':
> ./include/linux/uaccess.h:691:1: error: initialization discards 'const'
> qualifier from pointer target type [-Werror=discarded-qualifiers]
> 691 | ({
> \
> | ^
> ./include/linux/uaccess.h:755:37: note: in expansion of macro
> '__scoped_user_access_begin'
> 755 | for (void __user *_tmpptr =
> __scoped_user_access_begin(mode, uptr, size, elbl); \
> | ^~~~~~~~~~~~~~~~~~~~~~~~~~
> ./include/linux/uaccess.h:770:9: note: in expansion of macro
> '__scoped_user_access'
> 770 | __scoped_user_access(read, usrc, size, elbl)
> | ^~~~~~~~~~~~~~~~~~~~
> arch/powerpc/lib/checksum_wrappers.c:17:9: note: in expansion of macro
> 'scoped_user_read_access_size'
> 17 | scoped_user_read_access_size(src, len, efault)
> | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
>
> Cast __scoped_user_access_begin() to (void __user *) to fix it.
I posted a patch to fix this in december, I'll find it and resend it.
David
>
> Fixes: e497310b4ffb ("uaccess: Provide scoped user access regions")
> Signed-off-by: Christophe Leroy (CS GROUP) <[email protected]>
> ---
> Thomas, I encountered this problem while preparing some patches to start using
> scope user access widely on powerpc in order to benefit more from masked user
> access. Can you make this patch go into 7.0 as a fix in order avoid dependency
> on this change when we start using scoped user access ?
>
> include/linux/uaccess.h | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/include/linux/uaccess.h b/include/linux/uaccess.h
> index 1f3804245c06..5d9f6d45d301 100644
> --- a/include/linux/uaccess.h
> +++ b/include/linux/uaccess.h
> @@ -752,7 +752,8 @@ USER_ACCESS_GUARD(rw)
> */
> #define __scoped_user_access(mode, uptr, size, elbl)
> \
> for (bool done = false; !done; done = true)
> \
> - for (void __user *_tmpptr = __scoped_user_access_begin(mode, uptr,
> size, elbl); \
> + for (void __user *_tmpptr = (void __user *)
> \
> + __scoped_user_access_begin(mode, uptr,
> size, elbl); \
> !done; done = true)
> \
> for (CLASS(user_##mode##_access, scope)(_tmpptr); !done; done =
> true) \
> /* Force modified pointer usage within the scope */
> \
