Messages in this thread | | | From | Nick Desaulniers <> | Date | Fri, 25 May 2018 10:49:28 -0700 | Subject | Re: [clang] stack protector and f1f029c7bf |
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On Fri, May 25, 2018 at 10:35 AM Tom Stellard <tstellar@redhat.com> wrote: > On 05/25/2018 10:31 AM, Nick Desaulniers wrote: > > On Fri, May 25, 2018 at 9:53 AM <hpa@zytor.com> wrote: > >> On May 25, 2018 9:46:42 AM PDT, Nick Desaulniers < ndesaulniers@google.com> > > wrote: > >>> On Fri, May 25, 2018 at 9:33 AM <hpa@zytor.com> wrote: > >>>> On May 25, 2018 9:27:40 AM PDT, Nick Desaulniers > >>> <ndesaulniers@google.com> wrote: > >>> When you say > >>> > >>>> It still should be available as as inline, however, but now "extern > >>> inline". > >>> > >>> Am I understanding correctly that native_save_fl should be inlined into > >>> all > >>> call sites (modulo the problematic pv_irq_ops.save_fl case)? Because > >>> for > >>> these two assembly implementations, it's not, but maybe there's > >>> something > >>> missing in my implementation? > > > >> Yes, that's what "extern inline" means. Maybe it needs a must inline > > annotation, but that's really messed up. > >
> What about doing something like suggested here: > https://bugs.llvm.org/show_bug.cgi?id=37512#c17
> This would keep the definition in C and make it easier for compilers > to inline.
The GCC docs for __attribute__((naked)) seem to imply this is a machine specific constraint (of which x86 is not listed): https://gcc.gnu.org/onlinedocs/gcc-4.7.2/gcc/Function-Attributes.html
But let's try with source: https://godbolt.org/g/aJ4gZB
Clang errors: <source>:3:3: error: non-ASM statement in naked function is not supported unsigned long flags; ^
Is it valid to use assembly to place the results in %rax and mark the c function somehow?
gcc doesn't support this attribute until 4.9 (but we can add a feature test for attributes with gcc (unlike builtins)), but warns that:
warning: ‘naked’ attribute directive ignored [-Wattributes]
gcc 8.1 and trunk inserts a `ud2` instruction (what?!) (let me see if I can repro outside of godbolt, and will file a bug report). -- Thanks, ~Nick Desaulniers
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