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Date: Mon, 22 May 2017 07:39:57 -0700 From: "H.J. Lu" <hjl.tools@...il.com> To: Jiri Kosina <jikos@...nel.org> Cc: Andy Lutomirski <luto@...nel.org>, Josh Poimboeuf <jpoimboe@...hat.com>, "H. Peter Anvin" <hpa@...or.com>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, Jiri Slaby <jslaby@...e.cz>, Andrew Morton <akpm@...ux-foundation.org>, live-patching@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>, "the arch/x86 maintainers" <x86@...nel.org>, Linus Torvalds <torvalds@...ux-foundation.org> Subject: Re: [PATCH 7/7] DWARF: add the config option On Mon, May 22, 2017 at 4:34 AM, Jiri Kosina <jikos@...nel.org> wrote: > On Sat, 20 May 2017, H.J. Lu wrote: > >> >>>> pushq %whatever >> >>>> .cfi_adjust_sp -8 >> >>>> ... >> >>>> popq %whatever >> >>>> .cfi_adjust_sp 8 >> >>>> >> >> >> >> Np. Compiler needs to generate this. >> >> >> > >> > How would the compiler generate this when inline asm is involved? For >> > the kernel, objtool could get around the need to have these >> > annotations, but not so much for user code? Is the compiler supposed >> > to parse the inline asm? Would the compiler provide some magic % code >> > to represent the current CFA base register? >> >> Here is one example of inline asm with call frame info: >> >> https://sourceware.org/git/?p=glibc.git;a=blob;f=sysdeps/unix/sysv/linux/x86_64/sigaction.c;h=be058bac436d1cc9794b2b03107676ed99f6b872;hb=HEAD > > That brings us basically pretty close to square one though; having to > maintain "manual" anotations. Something we're pretty much trying to avoid > through this excercise. Assembler only encodes instructions. You need to a different tool to figure out what an instruction does. -- H.J.
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