[PATCH] lib/xor: use r10 rather than r7 in xor_arm4regs_{2|3}

[Nick Desaulniers]

kbuild test robot reports:
In file included from crypto/xor.c:17:
./arch/arm/include/asm/xor.h:61:3: error: write to reserved register 'R7'
                GET_BLOCK_4(p1);
                ^
./arch/arm/include/asm/xor.h:20:10: note: expanded from macro 'GET_BLOCK_4'
        __asm__("ldmia  %0, {%1, %2, %3, %4}" \
                ^
./arch/arm/include/asm/xor.h:63:3: error: write to reserved register 'R7'
                PUT_BLOCK_4(p1);
                ^
./arch/arm/include/asm/xor.h:42:23: note: expanded from macro 'PUT_BLOCK_4'
        __asm__ __volatile__("stmia     %0!, {%2, %3, %4, %5}" \
                             ^
./arch/arm/include/asm/xor.h:83:3: error: write to reserved register 'R7'
                GET_BLOCK_4(p1);
                ^
./arch/arm/include/asm/xor.h:20:10: note: expanded from macro 'GET_BLOCK_4'
        __asm__("ldmia  %0, {%1, %2, %3, %4}" \
                ^
./arch/arm/include/asm/xor.h:86:3: error: write to reserved register 'R7'
                PUT_BLOCK_4(p1);
                ^
./arch/arm/include/asm/xor.h:42:23: note: expanded from macro 'PUT_BLOCK_4'
        __asm__ __volatile__("stmia     %0!, {%2, %3, %4, %5}" \
                             ^
Thumb2 uses r7 rather than r11 as the frame pointer. Let's use r10
rather than r7 for these temporaries.

Link: https://github.com/ClangBuiltLinux/linux/issues/1732
Link: https://lore.kernel.org/llvm/202210072120.V1O2SuKY-lkp@intel.com/
Reported-by: kernel test robot <lkp at intel.com>
Suggested-by: Ard Biesheuvel <ardb at kernel.org>
Signed-off-by: Nick Desaulniers <ndesaulniers at google.com>
---
 arch/arm/include/asm/xor.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/arm/include/asm/xor.h b/arch/arm/include/asm/xor.h
index 669cad5194d3..934b549905f5 100644
--- a/arch/arm/include/asm/xor.h
+++ b/arch/arm/include/asm/xor.h
@@ -51,7 +51,7 @@ xor_arm4regs_2(unsigned long bytes, unsigned long * __restrict p1,
 	register unsigned int a1 __asm__("r4");
 	register unsigned int a2 __asm__("r5");
 	register unsigned int a3 __asm__("r6");
-	register unsigned int a4 __asm__("r7");
+	register unsigned int a4 __asm__("r10");
 	register unsigned int b1 __asm__("r8");
 	register unsigned int b2 __asm__("r9");
 	register unsigned int b3 __asm__("ip");
@@ -73,7 +73,7 @@ xor_arm4regs_3(unsigned long bytes, unsigned long * __restrict p1,
 	register unsigned int a1 __asm__("r4");
 	register unsigned int a2 __asm__("r5");
 	register unsigned int a3 __asm__("r6");
-	register unsigned int a4 __asm__("r7");
+	register unsigned int a4 __asm__("r10");
 	register unsigned int b1 __asm__("r8");
 	register unsigned int b2 __asm__("r9");
 	register unsigned int b3 __asm__("ip");
-- 
2.38.0.rc2.412.g84df46c1b4-goog