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authorNick Desaulniers <ndesaulniers@google.com>2020-05-22 22:22:45 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2020-05-23 10:26:31 -0700
commitc071b0f11e7fb944525b12c80e728af69648d967 (patch)
treeadd23517de24537d3c81f75a37a2b49eec60a7f1
parent60858c00e5f018eda711a3aa84cf62214ef62d61 (diff)
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x86: bitops: fix build regression
This is easily reproducible via CC=clang + CONFIG_STAGING=y + CONFIG_VT6656=m. It turns out that if your config tickles __builtin_constant_p via differences in choices to inline or not, these statements produce invalid assembly: $ cat foo.c long a(long b, long c) { asm("orb %1, %0" : "+q"(c): "r"(b)); return c; } $ gcc foo.c foo.c: Assembler messages: foo.c:2: Error: `%rax' not allowed with `orb' Use the `%b` "x86 Operand Modifier" to instead force register allocation to select a lower-8-bit GPR operand. The "q" constraint only has meaning on -m32 otherwise is treated as "r". Not all GPRs have low-8-bit aliases for -m32. Fixes: 1651e700664b4 ("x86: Fix bitops.h warning with a moved cast") Reported-by: kernelci.org bot <bot@kernelci.org> Suggested-by: Andy Shevchenko <andriy.shevchenko@intel.com> Suggested-by: Brian Gerst <brgerst@gmail.com> Suggested-by: H. Peter Anvin <hpa@zytor.com> Suggested-by: Ilie Halip <ilie.halip@gmail.com> Signed-off-by: Nick Desaulniers <ndesaulniers@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Tested-by: Sedat Dilek <sedat.dilek@gmail.com> Tested-by: Nathan Chancellor <natechancellor@gmail.com> [build, clang-11] Reviewed-by: Nathan Chancellor <natechancellor@gmail.com> Reviewed-By: Brian Gerst <brgerst@gmail.com> Reviewed-by: Jesse Brandeburg <jesse.brandeburg@intel.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@redhat.com> Cc: Borislav Petkov <bp@alien8.de> Cc: Marco Elver <elver@google.com> Cc: "Paul E. McKenney" <paulmck@kernel.org> Cc: Andrey Ryabinin <aryabinin@virtuozzo.com> Cc: Luc Van Oostenryck <luc.vanoostenryck@gmail.com> Cc: Masahiro Yamada <yamada.masahiro@socionext.com> Cc: Daniel Axtens <dja@axtens.net> Cc: "Peter Zijlstra (Intel)" <peterz@infradead.org> Link: http://lkml.kernel.org/r/20200508183230.229464-1-ndesaulniers@google.com Link: https://github.com/ClangBuiltLinux/linux/issues/961 Link: https://lore.kernel.org/lkml/20200504193524.GA221287@google.com/ Link: https://gcc.gnu.org/onlinedocs/gcc/Extended-Asm.html#x86Operandmodifiers Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--arch/x86/include/asm/bitops.h12
1 files changed, 6 insertions, 6 deletions
diff --git a/arch/x86/include/asm/bitops.h b/arch/x86/include/asm/bitops.h
index 53f246e9df5a..0367efdc5b7a 100644
--- a/arch/x86/include/asm/bitops.h
+++ b/arch/x86/include/asm/bitops.h
@@ -52,9 +52,9 @@ static __always_inline void
arch_set_bit(long nr, volatile unsigned long *addr)
{
if (__builtin_constant_p(nr)) {
- asm volatile(LOCK_PREFIX "orb %1,%0"
+ asm volatile(LOCK_PREFIX "orb %b1,%0"
: CONST_MASK_ADDR(nr, addr)
- : "iq" (CONST_MASK(nr) & 0xff)
+ : "iq" (CONST_MASK(nr))
: "memory");
} else {
asm volatile(LOCK_PREFIX __ASM_SIZE(bts) " %1,%0"
@@ -72,9 +72,9 @@ static __always_inline void
arch_clear_bit(long nr, volatile unsigned long *addr)
{
if (__builtin_constant_p(nr)) {
- asm volatile(LOCK_PREFIX "andb %1,%0"
+ asm volatile(LOCK_PREFIX "andb %b1,%0"
: CONST_MASK_ADDR(nr, addr)
- : "iq" (CONST_MASK(nr) ^ 0xff));
+ : "iq" (~CONST_MASK(nr)));
} else {
asm volatile(LOCK_PREFIX __ASM_SIZE(btr) " %1,%0"
: : RLONG_ADDR(addr), "Ir" (nr) : "memory");
@@ -123,9 +123,9 @@ static __always_inline void
arch_change_bit(long nr, volatile unsigned long *addr)
{
if (__builtin_constant_p(nr)) {
- asm volatile(LOCK_PREFIX "xorb %1,%0"
+ asm volatile(LOCK_PREFIX "xorb %b1,%0"
: CONST_MASK_ADDR(nr, addr)
- : "iq" ((u8)CONST_MASK(nr)));
+ : "iq" (CONST_MASK(nr)));
} else {
asm volatile(LOCK_PREFIX __ASM_SIZE(btc) " %1,%0"
: : RLONG_ADDR(addr), "Ir" (nr) : "memory");