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Date: Wed, 27 Feb 2019 13:20:59 +0100 From: Peter Zijlstra <peterz@...radead.org> To: Josh Poimboeuf <jpoimboe@...hat.com> Cc: torvalds@...ux-foundation.org, tglx@...utronix.de, hpa@...or.com, julien.thierry@....com, will.deacon@....com, luto@...capital.net, mingo@...nel.org, catalin.marinas@....com, james.morse@....com, valentin.schneider@....com, brgerst@...il.com, luto@...nel.org, bp@...en8.de, dvlasenk@...hat.com, linux-kernel@...r.kernel.org Subject: Re: [PATCH 4/6] objtool: Replace STACK_FRAME_NON_STANDARD annotation On Mon, Feb 25, 2019 at 10:11:24AM -0600, Josh Poimboeuf wrote: > On Mon, Feb 25, 2019 at 01:43:34PM +0100, Peter Zijlstra wrote: > > -#define STACK_FRAME_NON_STANDARD(func) \ > > - static void __used __section(.discard.func_stack_frame_non_standard) \ > > - *__func_stack_frame_non_standard_##func = func > > +#define STACK_FRAME_NON_STANDARD(func) \ > > + asm (".pushsection .discard.nonstd_frame_strtab, \"S\", @3\n\t" \ > > + "999: .ascii \"" #func "\"\n\t" \ > > + " .byte 0\n\t" \ > > + ".popsection\n\t" \ > > + ".pushsection .discard.nonstd_frame\n\t" \ > > + ".long 999b - .\n\t" \ > > + ".popsection\n\t") > > + > > I don't think this will work in the case where GCC does an IPA > optimization and renames the function (e.g., renames func to > func.isra.1234), right? That might be a deal breaker... Or; as has been found by 0day; the whole function gets inlined and the symbol no longer exists at all. That's curable with a noinline, but all things considered, I think we should go back to the old horrible scheme. Andy?
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