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authorJan Beulich <JBeulich@suse.com>2018-02-19 07:49:12 -0700
committerIngo Molnar <mingo@kernel.org>2018-02-20 09:33:39 +0100
commit700b7c5409c3e9da279fbea78cf28a78fbc176cd (patch)
tree005f64cec96d3ff3b7b05f2c26c5903f5a9c004b /arch/x86
parent3b3a9268bba62b35a29bafe0931715b1725fdf26 (diff)
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x86/asm: Improve how GEN_*_SUFFIXED_RMWcc() specify clobbers
Commit: df3405245a ("x86/asm: Add suffix macro for GEN_*_RMWcc()") ... introduced "suffix" RMWcc operations, adding bogus clobber specifiers: For one, on x86 there's no point explicitly clobbering "cc". In fact, with GCC properly fixed, this results in an overlap being detected by the compiler between outputs and clobbers. Furthermore it seems bad practice to me to have clobber specification and use of the clobbered register(s) disconnected - it should rather be at the invocation place of that GEN_{UN,BIN}ARY_SUFFIXED_RMWcc() macros that the clobber is specified which this particular invocation needs. Drop the "cc" clobber altogether and move the "cx" one to refcount.h. Signed-off-by: Jan Beulich <jbeulich@suse.com> Acked-by: Thomas Gleixner <tglx@linutronix.de> Cc: Andy Lutomirski <luto@kernel.org> Cc: Borislav Petkov <bp@alien8.de> Cc: Brian Gerst <brgerst@gmail.com> Cc: Denys Vlasenko <dvlasenk@redhat.com> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Josh Poimboeuf <jpoimboe@redhat.com> Cc: Kees Cook <keescook@chromium.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/5A8AF1F802000078001A91E1@prv-mh.provo.novell.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'arch/x86')
-rw-r--r--arch/x86/include/asm/refcount.h4
-rw-r--r--arch/x86/include/asm/rmwcc.h16
2 files changed, 10 insertions, 10 deletions
diff --git a/arch/x86/include/asm/refcount.h b/arch/x86/include/asm/refcount.h
index 4e44250e7d0d..d65171120e90 100644
--- a/arch/x86/include/asm/refcount.h
+++ b/arch/x86/include/asm/refcount.h
@@ -67,13 +67,13 @@ static __always_inline __must_check
bool refcount_sub_and_test(unsigned int i, refcount_t *r)
{
GEN_BINARY_SUFFIXED_RMWcc(LOCK_PREFIX "subl", REFCOUNT_CHECK_LT_ZERO,
- r->refs.counter, "er", i, "%0", e);
+ r->refs.counter, "er", i, "%0", e, "cx");
}
static __always_inline __must_check bool refcount_dec_and_test(refcount_t *r)
{
GEN_UNARY_SUFFIXED_RMWcc(LOCK_PREFIX "decl", REFCOUNT_CHECK_LT_ZERO,
- r->refs.counter, "%0", e);
+ r->refs.counter, "%0", e, "cx");
}
static __always_inline __must_check
diff --git a/arch/x86/include/asm/rmwcc.h b/arch/x86/include/asm/rmwcc.h
index f91c365e57c3..4914a3e7c803 100644
--- a/arch/x86/include/asm/rmwcc.h
+++ b/arch/x86/include/asm/rmwcc.h
@@ -2,8 +2,7 @@
#ifndef _ASM_X86_RMWcc
#define _ASM_X86_RMWcc
-#define __CLOBBERS_MEM "memory"
-#define __CLOBBERS_MEM_CC_CX "memory", "cc", "cx"
+#define __CLOBBERS_MEM(clb...) "memory", ## clb
#if !defined(__GCC_ASM_FLAG_OUTPUTS__) && defined(CC_HAVE_ASM_GOTO)
@@ -40,18 +39,19 @@ do { \
#endif /* defined(__GCC_ASM_FLAG_OUTPUTS__) || !defined(CC_HAVE_ASM_GOTO) */
#define GEN_UNARY_RMWcc(op, var, arg0, cc) \
- __GEN_RMWcc(op " " arg0, var, cc, __CLOBBERS_MEM)
+ __GEN_RMWcc(op " " arg0, var, cc, __CLOBBERS_MEM())
-#define GEN_UNARY_SUFFIXED_RMWcc(op, suffix, var, arg0, cc) \
+#define GEN_UNARY_SUFFIXED_RMWcc(op, suffix, var, arg0, cc, clobbers...)\
__GEN_RMWcc(op " " arg0 "\n\t" suffix, var, cc, \
- __CLOBBERS_MEM_CC_CX)
+ __CLOBBERS_MEM(clobbers))
#define GEN_BINARY_RMWcc(op, var, vcon, val, arg0, cc) \
__GEN_RMWcc(op __BINARY_RMWcc_ARG arg0, var, cc, \
- __CLOBBERS_MEM, vcon (val))
+ __CLOBBERS_MEM(), vcon (val))
-#define GEN_BINARY_SUFFIXED_RMWcc(op, suffix, var, vcon, val, arg0, cc) \
+#define GEN_BINARY_SUFFIXED_RMWcc(op, suffix, var, vcon, val, arg0, cc, \
+ clobbers...) \
__GEN_RMWcc(op __BINARY_RMWcc_ARG arg0 "\n\t" suffix, var, cc, \
- __CLOBBERS_MEM_CC_CX, vcon (val))
+ __CLOBBERS_MEM(clobbers), vcon (val))
#endif /* _ASM_X86_RMWcc */