From: Sedat Dilek <sedat.dilek@xxxxxxxxx>
It turns out that if your config tickles __builtin_constant_p via
differences in choices to inline or not, this now produces invalid
assembly:
$ cat foo.c
long a(long b, long c) {
asm("orb\t%1, %0" : "+q"(c): "r"(b));
return c;
}
$ gcc foo.c
foo.c: Assembler messages:
foo.c:2: Error: `%rax' not allowed with `orb'
The "q" constraint only has meanting on -m32 otherwise is treated as
"r".
This is easily reproducible via Clang+CONFIG_STAGING=y+CONFIG_VT6656=m,
or Clang+allyesconfig.
Keep the masking operation to appease sparse (`make C=1`), add back the
cast in order to properly select the proper 8b register alias.
[Nick: reworded]
Cc: stable@xxxxxxxxxxxxxxx
Cc: Jesse Brandeburg <jesse.brandeburg@xxxxxxxxx>
Link: https://github.com/ClangBuiltLinux/linux/issues/961
Link: https://lore.kernel.org/lkml/20200504193524.GA221287@xxxxxxxxxx/
Fixes: 1651e700664b4 ("x86: Fix bitops.h warning with a moved cast")
Reported-by: Sedat Dilek <sedat.dilek@xxxxxxxxx>
Reported-by: kernelci.org bot <bot@xxxxxxxxxxxx>
Suggested-by: Andy Shevchenko <andriy.shevchenko@xxxxxxxxx>
Suggested-by: Ilie Halip <ilie.halip@xxxxxxxxx>
Tested-by: Sedat Dilek <sedat.dilek@xxxxxxxxx>
Signed-off-by: Sedat Dilek <sedat.dilek@xxxxxxxxx>
Signed-off-by: Nick Desaulniers <ndesaulniers@xxxxxxxxxx>
---
arch/x86/include/asm/bitops.h | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/arch/x86/include/asm/bitops.h b/arch/x86/include/asm/bitops.h
index b392571c1f1d..139122e5b25b 100644
--- a/arch/x86/include/asm/bitops.h
+++ b/arch/x86/include/asm/bitops.h
@@ -54,7 +54,7 @@ arch_set_bit(long nr, volatile unsigned long *addr)
if (__builtin_constant_p(nr)) {
asm volatile(LOCK_PREFIX "orb %1,%0"
: CONST_MASK_ADDR(nr, addr)
- : "iq" (CONST_MASK(nr) & 0xff)
+ : "iq" ((u8)(CONST_MASK(nr) & 0xff))
: "memory");
} else {
asm volatile(LOCK_PREFIX __ASM_SIZE(bts) " %1,%0"
@@ -74,7 +74,7 @@ arch_clear_bit(long nr, volatile unsigned long *addr)
if (__builtin_constant_p(nr)) {
asm volatile(LOCK_PREFIX "andb %1,%0"
: CONST_MASK_ADDR(nr, addr)
- : "iq" (CONST_MASK(nr) ^ 0xff));
+ : "iq" ((u8)(CONST_MASK(nr) ^ 0xff)));
} else {
asm volatile(LOCK_PREFIX __ASM_SIZE(btr) " %1,%0"
: : RLONG_ADDR(addr), "Ir" (nr) : "memory");
--
2.26.2.526.g744177e7f7-goog
