| Message ID | 1496180392-98718-3-git-send-email-keescook@chromium.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Tue, May 30, 2017 at 02:39:51PM -0700, Kees Cook wrote: > The coming x86 refcount protection needs to be able to add trailing > instructions to the GEN_*_RMWcc() operations. This extracts the > difference between the goto/non-goto cases so the helper macros > can be defined outside the #ifdef cases. Additionally adds argument > naming to the resulting asm for referencing from suffixed > instructions, and adds clobbers for "cc", and "cx" to let suffixes > use _ASM_CX, and retain any set flags. Another option is to simply require __GCC_ASM_FLAG_OUTPUT__ for the fast refcount stuff. That would result in simpler and more readable code.
On Wed, May 31, 2017 at 4:13 AM, Peter Zijlstra <peterz@infradead.org> wrote: > On Tue, May 30, 2017 at 02:39:51PM -0700, Kees Cook wrote: >> The coming x86 refcount protection needs to be able to add trailing >> instructions to the GEN_*_RMWcc() operations. This extracts the >> difference between the goto/non-goto cases so the helper macros >> can be defined outside the #ifdef cases. Additionally adds argument >> naming to the resulting asm for referencing from suffixed >> instructions, and adds clobbers for "cc", and "cx" to let suffixes >> use _ASM_CX, and retain any set flags. > > Another option is to simply require __GCC_ASM_FLAG_OUTPUT__ for the fast > refcount stuff. That would result in simpler and more readable code. What versions of GCC support that? -Kees
On Wed, May 31, 2017 at 06:17:16AM -0700, Kees Cook wrote: > On Wed, May 31, 2017 at 4:13 AM, Peter Zijlstra <peterz@infradead.org> wrote: > > On Tue, May 30, 2017 at 02:39:51PM -0700, Kees Cook wrote: > >> The coming x86 refcount protection needs to be able to add trailing > >> instructions to the GEN_*_RMWcc() operations. This extracts the > >> difference between the goto/non-goto cases so the helper macros > >> can be defined outside the #ifdef cases. Additionally adds argument > >> naming to the resulting asm for referencing from suffixed > >> instructions, and adds clobbers for "cc", and "cx" to let suffixes > >> use _ASM_CX, and retain any set flags. > > > > Another option is to simply require __GCC_ASM_FLAG_OUTPUT__ for the fast > > refcount stuff. That would result in simpler and more readable code. > > What versions of GCC support that? IIRC 6+
On Wed, May 31, 2017 at 7:03 AM, Peter Zijlstra <peterz@infradead.org> wrote: > On Wed, May 31, 2017 at 06:17:16AM -0700, Kees Cook wrote: >> On Wed, May 31, 2017 at 4:13 AM, Peter Zijlstra <peterz@infradead.org> wrote: >> > On Tue, May 30, 2017 at 02:39:51PM -0700, Kees Cook wrote: >> >> The coming x86 refcount protection needs to be able to add trailing >> >> instructions to the GEN_*_RMWcc() operations. This extracts the >> >> difference between the goto/non-goto cases so the helper macros >> >> can be defined outside the #ifdef cases. Additionally adds argument >> >> naming to the resulting asm for referencing from suffixed >> >> instructions, and adds clobbers for "cc", and "cx" to let suffixes >> >> use _ASM_CX, and retain any set flags. >> > >> > Another option is to simply require __GCC_ASM_FLAG_OUTPUT__ for the fast >> > refcount stuff. That would result in simpler and more readable code. >> >> What versions of GCC support that? > > IIRC 6+ Given how many folks are still using 4.9 (and lower, see the thread with Arnd[1]), I'd like to just keep this as I have it. It's not much less readable, IMO (It was already pretty complex). I cleaned it up a little before making it more ugly, so I think on sum, it's only a little more weird. I think that's better than making this compiler-specific or copy/pasting. -Kees [1] https://lkml.org/lkml/2017/4/25/66
diff --git a/arch/x86/include/asm/rmwcc.h b/arch/x86/include/asm/rmwcc.h index 661dd305694a..045f99211a99 100644 --- a/arch/x86/include/asm/rmwcc.h +++ b/arch/x86/include/asm/rmwcc.h @@ -1,45 +1,56 @@ #ifndef _ASM_X86_RMWcc #define _ASM_X86_RMWcc +#define __CLOBBERS_MEM "memory" +#define __CLOBBERS_MEM_CC_CX "memory", "cc", "cx" + #if !defined(__GCC_ASM_FLAG_OUTPUTS__) && defined(CC_HAVE_ASM_GOTO) /* Use asm goto */ -#define __GEN_RMWcc(fullop, var, cc, ...) \ +#define __GEN_RMWcc(fullop, var, cc, clobbers, ...) \ do { \ asm_volatile_goto (fullop "; j" #cc " %l[cc_label]" \ - : : "m" (var), ## __VA_ARGS__ \ - : "memory" : cc_label); \ + : : [counter] "m" (var), ## __VA_ARGS__ \ + : clobbers : cc_label); \ return 0; \ cc_label: \ return 1; \ } while (0) -#define GEN_UNARY_RMWcc(op, var, arg0, cc) \ - __GEN_RMWcc(op " " arg0, var, cc) +#define __BINARY_RMWcc_ARG " %1, " -#define GEN_BINARY_RMWcc(op, var, vcon, val, arg0, cc) \ - __GEN_RMWcc(op " %1, " arg0, var, cc, vcon (val)) #else /* defined(__GCC_ASM_FLAG_OUTPUTS__) || !defined(CC_HAVE_ASM_GOTO) */ /* Use flags output or a set instruction */ -#define __GEN_RMWcc(fullop, var, cc, ...) \ +#define __GEN_RMWcc(fullop, var, cc, clobbers, ...) \ do { \ bool c; \ asm volatile (fullop ";" CC_SET(cc) \ - : "+m" (var), CC_OUT(cc) (c) \ - : __VA_ARGS__ : "memory"); \ + : [counter] "+m" (var), CC_OUT(cc) (c) \ + : __VA_ARGS__ : clobbers); \ return c; \ } while (0) +#define __BINARY_RMWcc_ARG " %2, " + +#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) + __GEN_RMWcc(op " " arg0, var, cc, __CLOBBERS_MEM) + +#define GEN_UNARY_SUFFIXED_RMWcc(op, suffix, var, arg0, cc) \ + __GEN_RMWcc(op " " arg0 "\n\t" suffix, var, cc, \ + __CLOBBERS_MEM_CC_CX) #define GEN_BINARY_RMWcc(op, var, vcon, val, arg0, cc) \ - __GEN_RMWcc(op " %2, " arg0, var, cc, vcon (val)) + __GEN_RMWcc(op __BINARY_RMWcc_ARG arg0, var, cc, \ + __CLOBBERS_MEM, vcon (val)) -#endif /* defined(__GCC_ASM_FLAG_OUTPUTS__) || !defined(CC_HAVE_ASM_GOTO) */ +#define GEN_BINARY_SUFFIXED_RMWcc(op, suffix, var, vcon, val, arg0, cc) \ + __GEN_RMWcc(op __BINARY_RMWcc_ARG arg0 "\n\t" suffix, var, cc, \ + __CLOBBERS_MEM_CC_CX, vcon (val)) #endif /* _ASM_X86_RMWcc */
The coming x86 refcount protection needs to be able to add trailing instructions to the GEN_*_RMWcc() operations. This extracts the difference between the goto/non-goto cases so the helper macros can be defined outside the #ifdef cases. Additionally adds argument naming to the resulting asm for referencing from suffixed instructions, and adds clobbers for "cc", and "cx" to let suffixes use _ASM_CX, and retain any set flags. Signed-off-by: Kees Cook <keescook@chromium.org> --- arch/x86/include/asm/rmwcc.h | 37 ++++++++++++++++++++++++------------- 1 file changed, 24 insertions(+), 13 deletions(-)