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Date: Fri, 17 Feb 2017 08:07:17 -0600 From: Josh Poimboeuf <jpoimboe@...hat.com> To: Jiri Slaby <jslaby@...e.cz> Cc: mingo@...hat.com, tglx@...utronix.de, hpa@...or.com, x86@...nel.org, linux-kernel@...r.kernel.org Subject: Re: [PREVIEW 10/10] linkage: add .cfi_{start/end}proc to ENTRY/ENDPROC On Fri, Feb 17, 2017 at 02:36:15PM +0100, Jiri Slaby wrote: > On 02/17/2017, 02:16 PM, Josh Poimboeuf wrote: > > On Fri, Feb 17, 2017 at 11:47:57AM +0100, Jiri Slaby wrote: > >> This is just a preview, not to merged now, only later with DWARF > >> unwinder series. This is what the series will serve for (aside from > >> cleanup and unification). > >> > >> I am aware of CFI_STARTPROC and CFI_ENDPROC left defined in other archs > >> in spite of cfi annotations removal ages ago. For simplicity. I am using > >> DW_ prefix here. > > > > If objtool is going to be generating CFI instructions, why not have it > > generate .cfi_startproc and .cfi_endproc too? > > I tried that, but in many places it is very hard to recognize start > and/or end of a function. How so? objtool already knows where the start and end of every function is due to ENDPROC's use of the .type and .size macros. > Having .cfi_startproc and .cfi_endproc in place makes it rather easy, > actually reduced to "emit dwarf instructions for this code between > here and there". Plus pre-prepared .eh_frame only to be extended. > (.eh_frame_hdr has to be rehashed of course.) Hm, but now objtool has to read *and* write CFI instead of just writing. It would help to see the generation code. Have you written it? -- Josh
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