linux-kernel - Re: [PATCH v2 2/5] perf: util: use capstone disasm engine to show assembly instructions

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Date: Thu, 18 Jan 2024 12:00:42 +0800
From: Changbin Du <changbin.du@...wei.com>
To: Thomas Richter <tmricht@...ux.ibm.com>
CC: Changbin Du <changbin.du@...wei.com>, 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@...nel.org>,
	Namhyung Kim <namhyung@...nel.org>, Ian Rogers <irogers@...gle.com>, Adrian
 Hunter <adrian.hunter@...el.com>, <linux-kernel@...r.kernel.org>,
	<linux-perf-users@...r.kernel.org>, Andi Kleen <ak@...ux.intel.com>,
	<changbin.du@...il.com>
Subject: Re: [PATCH v2 2/5] perf: util: use capstone disasm engine to show
 assembly instructions

On Wed, Jan 17, 2024 at 09:54:59AM +0100, Thomas Richter wrote:
> On 1/17/24 06:11, Changbin Du wrote:
> > Currently, the instructions of samples are shown as raw hex strings
> > which are hard to read. x86 has a special option '--xed' to disassemble
> > the hex string via intel XED tool.
> > 
> > Here we use capstone as our disassembler engine to give more friendly
> > instructions. We select libcapstone because capstone can provide more
> > insn details. Perf will fallback to raw instructions if libcapstone is
> > not available.
> > 
> > The advantages compared to XED tool:
> >  * Support arm, arm64, x86-32, x86_64 (more could be supported),
> >    xed only for x86_64.
> >  * Immediate address operands are shown as symbol+offs.
> > 
> > Signed-off-by: Changbin Du <changbin.du@...wei.com>
> > ---
> >  tools/perf/builtin-script.c  |   8 +--
> >  tools/perf/util/Build        |   1 +
> >  tools/perf/util/print_insn.c | 123 +++++++++++++++++++++++++++++++++++
> >  tools/perf/util/print_insn.h |  14 ++++
> >  4 files changed, 141 insertions(+), 5 deletions(-)
> >  create mode 100644 tools/perf/util/print_insn.c
> >  create mode 100644 tools/perf/util/print_insn.h> 
> ...
> 
> > diff --git a/tools/perf/util/print_insn.c b/tools/perf/util/print_insn.c
> > new file mode 100644
> > index 000000000000..fe035efe8cf6
> > --- /dev/null
> > +++ b/tools/perf/util/print_insn.c
> > @@ -0,0 +1,123 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +/*
> > + * Instruction binary disassembler based on capstone.
> > + *
> > + * Author(s): Changbin Du <changbin.du@...wei.com>
> > + */
> > +#include "print_insn.h"
> > +#include <stdlib.h>
> > +#include <string.h>
> > +#include <stdbool.h>
> > +#include "util/debug.h"
> > +#include "util/symbol.h"
> > +#include "machine.h"
> > +
> > +size_t sample__fprintf_insn_raw(struct perf_sample *sample, FILE *fp)
> > +{
> > +	int printed = 0;
> > +
> > +	for (int i = 0; i < sample->insn_len; i++)
> > +		printed += fprintf(fp, "%02x ", (unsigned char)sample->insn[i]);
> > +	return printed;
> > +}
> > +
> > +#ifdef HAVE_LIBCAPSTONE_SUPPORT
> > +#include <capstone/capstone.h>
> > +
> > +static int capstone_init(struct machine *machine, csh *cs_handle)
> > +{
> > +	cs_arch arch;
> > +	cs_mode mode;
> > +
> > +	if (machine__is(machine, "x86_64")) {
> > +		arch = CS_ARCH_X86;
> > +		mode = CS_MODE_64;
> > +	} else if (machine__normalized_is(machine, "x86")) {
> > +		arch = CS_ARCH_X86;
> > +		mode = CS_MODE_32;
> > +	} else if (machine__normalized_is(machine, "arm64")) {
> > +		arch = CS_ARCH_ARM64;
> > +		mode = CS_MODE_ARM;
> > +	} else if (machine__normalized_is(machine, "arm")) {
> > +		arch = CS_ARCH_ARM;
> > +		mode = CS_MODE_ARM + CS_MODE_V8;
> > +	} else if (machine__normalized_is(machine, "s390x")) {
> 
>         } else if (machine__normalized_is(machine, "s390")) {                 
> 
> > +		arch = CS_ARCH_SYSZ;
> > +		mode = CS_MODE_BIG_ENDIAN;
> > +	} else {
> > +		return -1;
> > +	}
> 
> I have debugged your reworked patch this morning and discovered that
> it was not working. The issue turned out to be function machine__normalized_is().
> The first parameter is passed to several functions before the comparison.
> The calls executed are
> 
>    machine__normhalized_is()
>    +--> perf_env__arch() --> called for first parameter.
>         +--> normalize_arch() --> always returns "s390"
> 
> We need to change the second parameter to "s390" without the trailing x
> as indicated above. Sorry for the confusion.
>
ok, will fix it later. Thanks.

> Thanks a lot.
> Thomas Richter, Dept 3303, IBM s390 Linux Development, Boeblingen, Germany
> --
> IBM Deutschland Research & Development GmbH
> 
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> 
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> 
> Sitz der Gesellschaft: Böblingen / Registergericht: Amtsgericht Stuttgart, HRB 243294
> 

-- 
Cheers,
Changbin Du