On Fri, May 19, 2017 at 04:29:13PM -0500, Josh Poimboeuf wrote: > > 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 :-)
BTW, here's the link to the unwinder code if you're interested: https://github.com/jpoimboe/linux/blob/undwarf/arch/x86/kernel/unwind_undwarf.c -- Josh
