On Thu, Feb 13, 2014 at 2:02 PM, Jiri Olsa <jo...@redhat.com> wrote: > On Tue, Feb 11, 2014 at 08:50:13AM -0300, Arnaldo Carvalho de Melo wrote: >> Em Tue, Feb 11, 2014 at 12:14:21PM +0100, Peter Zijlstra escreveu: >> > On Tue, Feb 11, 2014 at 12:08:56PM +0100, Stephane Eranian wrote: >> > > Assuming you can decode and get the info about the base registers used, >> > > you'd have to do this for each arch with load/store sampling >> > > capabilities. >> > > this is painful compared to getting the portable info from dwarf >> > > directly. >> >> > But its useful now, as compared to whenever GCC gets around to >> > implementing more dwarves and that GCC getting used widely enough to >> > actually rely on it. >> >> > All you need for the decode is a disassembler, and every arch should >> > already have multiple of those. Should be easy to reuse one, right? >> >> Yeah, I never got around to actually try to implement this, but my >> feeling was that all the bits and pieces were there already: >> >> 1) the precise IP for the instruction, that disassembled would tell >> which registers were being operated on, or memory that we would "reverse >> map" to a register >> >> 2) DWARF expression locations that allows us to go from registers to a >> variable/parameter and thus to a type >> >> 3) PERF_SAMPLE_REGS_USER (from a quick look, why do we have "USER" in >> it? Jiri?) > > well, it was meant for store user registers only > to assists user DWARF unwind > But it does captures the user state regardless of the stack snapshotting.
> we can add PERF_SAMPLE_REGS_KERNEL > I have a patch series to do this and more. It will be ready next month hopefully. >> >> 4) libunwind have register maps for various arches, so probably >> something there could be reused here as well (Jiri?) > > not sure what you mean by 'something' here.. but yep, > libunwind does have register maps for various arches > > jirka -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
