[PATCH 5.15 098/570] powerpc/uaccess: Fix inline assembly for clang build on PPC32

Greg Kroah-Hartman
2026-04-13T16:22:17Z

From: Christophe Leroy (CS GROUP) <chleroy@kernel.org>

[ Upstream commit 0ee95a1d458630272d0415d0ffa9424fcb606c90 ]

Test robot reports the following error with clang-16.0.6:

In file included from kernel/rseq.c:75:
include/linux/rseq_entry.h:141:3: error: invalid operand for instruction
unsafe_get_user(offset, &ucs->post_commit_offset, efault);
^
include/linux/uaccess.h:608:2: note: expanded from macro 'unsafe_get_user'
arch_unsafe_get_user(x, ptr, local_label); \
^
arch/powerpc/include/asm/uaccess.h:518:2: note: expanded from macro 'arch_unsafe_get_user'
__get_user_size_goto(__gu_val, __gu_addr, sizeof(*(p)), e); \
^
arch/powerpc/include/asm/uaccess.h:284:2: note: expanded from macro '__get_user_size_goto'
__get_user_size_allowed(x, ptr, size, __gus_retval); \
^
arch/powerpc/include/asm/uaccess.h:275:10: note: expanded from macro '__get_user_size_allowed'
case 8: __get_user_asm2(x, (u64 __user *)ptr, retval); break; \
^
arch/powerpc/include/asm/uaccess.h:258:4: note: expanded from macro '__get_user_asm2'
" li %1+1,0\n" \
^
<inline asm>:7:5: note: instantiated into assembly here
li 31+1,0
^
1 error generated.

On PPC32, for 64 bits vars a pair of registers is used. Usually the
lower register in the pair is the high part and the higher register is
the low part. GCC uses r3/r4 ... r11/r12 ... r14/r15 ... r30/r31

In older kernel code inline assembly was using %1 and %1+1 to represent
64 bits values. However here it looks like clang uses r31 as high part,
allthough r32 doesn't exist hence the error.

Allthoug %1+1 should work, most places now use %L1 instead of %1+1, so
let's do the same here.

With that change, the build doesn't fail anymore and a disassembly shows
clang uses r17/r18 and r31/r14 pair when GCC would have used r16/r17 and
r30/r31:

Disassembly of section .fixup:

00000000 <.fixup>:
0: 38 a0 ff f2 li r5,-14
4: 3a 20 00 00 li r17,0
8: 3a 40 00 00 li r18,0
c: 48 00 00 00 b c <.fixup+0xc>
c: R_PPC_REL24 .text+0xbc
10: 38 a0 ff f2 li r5,-14
14: 3b e0 00 00 li r31,0
18: 39 c0 00 00 li r14,0
1c: 48 00 00 00 b 1c <.fixup+0x1c>
1c: R_PPC_REL24 .text+0x144

Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202602021825.otcItxGi-lkp@intel.com/
Fixes: c20beffeec3c ("powerpc/uaccess: Use flexible addressing with __put_user()/__get_user()")
Signed-off-by: Christophe Leroy (CS GROUP) <chleroy@kernel.org>
Acked-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Madhavan Srinivasan <maddy@linux.ibm.com>
Link: https://patch.msgid.link/8ca3a657a650e497a96bfe7acde2f637dadab344.1770103646.git.chleroy@kernel.org
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
arch/powerpc/include/asm/uaccess.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/powerpc/include/asm/uaccess.h b/arch/powerpc/include/asm/uaccess.h
index 7781f6dd51390..62c07deb995c1 100644
--- a/arch/powerpc/include/asm/uaccess.h
+++ b/arch/powerpc/include/asm/uaccess.h
@@ -228,7 +228,7 @@ __gus_failed: \
".section .fixup,\"ax\"\n" \
"4: li %0,%3\n" \
" li %1,0\n" \
- " li %1+1,0\n" \
+ " li %L1,0\n" \
" b 3b\n" \
".previous\n" \
EX_TABLE(1b, 4b) \
--
2.51.0