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Date: Fri, 19 May 2017 16:29:13 -0500 From: Josh Poimboeuf <jpoimboe@...hat.com> To: "H. Peter Anvin" <hpa@...or.com> Cc: 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>, Andy Lutomirski <luto@...nel.org>, Jiri Kosina <jikos@...nel.org>, Linus Torvalds <torvalds@...ux-foundation.org> Subject: Re: [PATCH 7/7] DWARF: add the config option > How are you handling control flow? Control flow of what? > > Here's the struct in its current state: > > > > #define UNDWARF_REG_UNDEFINED 0 > > #define UNDWARF_REG_CFA 1 > > #define UNDWARF_REG_SP 2 > > #define UNDWARF_REG_FP 3 > > #define UNDWARF_REG_SP_INDIRECT 4 > > #define UNDWARF_REG_FP_INDIRECT 5 > > #define UNDWARF_REG_R10 6 > > #define UNDWARF_REG_DI 7 > > #define UNDWARF_REG_DX 8 > > > > Why only those registers? Also, if you have the option I would really > suggest using the actual x86 register numbers (ax, ex, dx, bx, sp, bp, > si, di, r8-r15 in that order.) Those are the only registers which are ever needed as the base for finding the previous stack frame. 99% of the time it's sp or bp, the other registers are needed for aligned stacks and entry code. Using the actual register numbers isn't an option because I don't need them all and they need to fit in a small number of bits. This construct might be useful for other arches, which is why I called it "FP" instead of "BP". But then I ruined that with the last 3 :-) -- Josh
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