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write to reserved register 'R7' #1732

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nickdesaulniers opened this issue Oct 10, 2022 · 5 comments
Closed

write to reserved register 'R7' #1732

nickdesaulniers opened this issue Oct 10, 2022 · 5 comments
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@nickdesaulniers
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[ARCH] arm32 This bug impacts ARCH=arm [BUG] linux A bug that should be fixed in the mainline kernel. [FIXED][LINUX] 6.2 This bug was fixed in Linux 6.2 [Reported-by] kbuild test robot Reported-by: kbuild test robot <lkp@intel.com>

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@nickdesaulniers
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From this 0day report:

$ wget https://lore.kernel.org/llvm/202210072120.V1O2SuKY-lkp@intel.com/2-config -O .config
$ make ARCH=arm LLVM=1 -j128 crypto/xor.o
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}" \
                             ^

cc @ardbiesheuvel
Looks like CONFIG_THUMB2 was not set in the .config. Reminds me of #701.
CONFIG_FTRACE=y is set, this patch references -pg w/ clang.
@nickdesaulniers nickdesaulniers added [BUG] Untriaged Something isn't working [ARCH] arm32 This bug impacts ARCH=arm [Reported-by] kbuild test robot Reported-by: kbuild test robot <lkp@intel.com> labels Oct 10, 2022
@ardbiesheuvel
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CONFIG_THUMB2_KERNEL is set, which makes R7 a reserved register when using -pg. In this case, we could just switch to R10 instead.

@nickdesaulniers
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Oops, I grepped something other than .config...

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");

?

@nickdesaulniers nickdesaulniers added [PATCH] Exists There is a patch that fixes this issue [BUG] linux A bug that should be fixed in the mainline kernel. and removed [BUG] Untriaged Something isn't working labels Oct 10, 2022
@nickdesaulniers nickdesaulniers self-assigned this Oct 10, 2022
@nickdesaulniers
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submitted: https://lore.kernel.org/lkml/20221010175134.2671410-1-ndesaulniers@google.com/

@nickdesaulniers nickdesaulniers added [PATCH] Submitted A patch has been submitted for review and removed [PATCH] Exists There is a patch that fixes this issue labels Oct 10, 2022
@nickdesaulniers
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submitted to RMK's queue: https://www.arm.linux.org.uk/developer/patches/viewpatch.php?id=9260/1.

@nickdesaulniers nickdesaulniers added [PATCH] Accepted A submitted patch has been accepted upstream and removed [PATCH] Submitted A patch has been submitted for review labels Nov 7, 2022
jonhunter pushed a commit to jonhunter/linux that referenced this issue Nov 8, 2022
@nickdesaulniers
ARM: 9260/1: lib/xor: use r10 rather than r7 in xor_arm4regs_{2|3}
527d086 
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: ClangBuiltLinux#1732
Link: https://lore.kernel.org/llvm/202210072120.V1O2SuKY-lkp@intel.com/

Reported-by: kernel test robot <lkp@intel.com>
Suggested-by: Ard Biesheuvel <ardb@kernel.org>
Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
@nathanchance
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Merged into mainline: https://git.kernel.org/linus/527d08631b30fb99721274eab8ebabd9c54b0b25

@nathanchance nathanchance added [FIXED][LINUX] 6.2 This bug was fixed in Linux 6.2 and removed [PATCH] Accepted A submitted patch has been accepted upstream labels Dec 14, 2022
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@nickdesaulniers nickdesaulniers

Labels
[ARCH] arm32 This bug impacts ARCH=arm [BUG] linux A bug that should be fixed in the mainline kernel. [FIXED][LINUX] 6.2 This bug was fixed in Linux 6.2 [Reported-by] kbuild test robot Reported-by: kbuild test robot <lkp@intel.com>
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