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Date: Fri, 3 Apr 2020 14:43:04 +0900 From: Masami Hiramatsu <mhiramat@...nel.org> To: Daniel Shaulov <daniel.shaulov@...il.com> Cc: Daniel Shaulov <daniel.shaulov@...nulate.io>, Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>, Arnaldo Carvalho de Melo <acme@...nel.org>, Mark Rutland <mark.rutland@....com>, Alexander Shishkin <alexander.shishkin@...ux.intel.com>, Jiri Olsa <jolsa@...hat.com>, Namhyung Kim <namhyung@...nel.org>, Masami Hiramatsu <mhiramat@...nel.org>, Thomas Gleixner <tglx@...utronix.de>, Greg Kroah-Hartman <gregkh@...uxfoundation.org>, Thomas Richter <tmricht@...ux.ibm.com>, linux-kernel@...r.kernel.org Subject: Re: [PATCH] perf probe: Add support for DW_OP_call_frame_cfa vars Hi Daniel, On Wed, 1 Apr 2020 19:19:52 +0300 Daniel Shaulov <daniel.shaulov@...il.com> wrote: > Add support for probes on variables with DW_OP_call_frame_cfa > as the dwarf operation in the debug info. > > Some compilers (specifically Golang compiler) output > DW_OP_call_frame_cfa instead of DW_OP_fbreg for variables > on the stack. If DW_OP_call_frame_cfa is the only expression > than it is the same as DW_OP_fbreg with an offset of zero. > In the case of the Golang compiler, DW_OP_call_frame_cfa may > be followed by DW_OP_consts, with a number and than DW_OP_plus. > This trio is the same as DW_OP_fbreg with the number from > DW_OP_consts as the offset. > > With this change, probing on functions in Golang with variables works. > This looks good to me:) Acked-by: Masami Hiramatsu <mhiramat@...nel.org> Thanks! > Signed-off-by: Daniel Shaulov <daniel.shaulov@...nulate.io> > --- > tools/perf/util/probe-finder.c | 16 ++++++++++++++-- > 1 file changed, 14 insertions(+), 2 deletions(-) > > diff --git a/tools/perf/util/probe-finder.c b/tools/perf/util/probe-finder.c > index e4cff49384f4..866b17aea263 100644 > --- a/tools/perf/util/probe-finder.c > +++ b/tools/perf/util/probe-finder.c > @@ -240,11 +240,23 @@ static int convert_variable_location(Dwarf_Die *vr_die, Dwarf_Addr addr, > } > > /* If this is based on frame buffer, set the offset */ > - if (op->atom == DW_OP_fbreg) { > + if (op->atom == DW_OP_fbreg || op->atom == DW_OP_call_frame_cfa) { > if (fb_ops == NULL) > return -ENOTSUP; > ref = true; > - offs = op->number; > + if (op->atom == DW_OP_fbreg) { > + offs = op->number; > + } else if (nops == 3) { > + /* > + * In the case of DW_OP_call_frame_cfa, we either have > + * an offset of 0 or we have two more expressions that > + * add a const > + */ > + if ((op + 1)->atom != DW_OP_consts || > + (op + 2)->atom != DW_OP_plus) > + return -ENOTSUP; > + offs = (op + 1)->number; > + } > op = &fb_ops[0]; > } > > -- > 2.22.0 > -- Masami Hiramatsu <mhiramat@...nel.org>
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