Re: [PATCH v5 3/5] perf: script: add field 'disasm' to display mnemonic instructions

[Changbin Du]

On Mon, Feb 05, 2024 at 11:23:21AM +0200, Adrian Hunter wrote:
> On 22/01/24 13:20, Changbin Du wrote:
> > In addition to the 'insn' field, this adds a new field 'disasm' to
> > display mnemonic instructions instead of the raw code.
> > 
> > $ sudo perf script -F +disasm
> >        perf-exec 1443864 [006] 2275506.209848:          psb:  psb offs: 0                                      0 [unknown] ([unknown])
> >        perf-exec 1443864 [006] 2275506.209848:          cbr:  cbr: 41 freq: 4100 MHz (114%)                    0 [unknown] ([unknown])
> >               ls 1443864 [006] 2275506.209905:          1  branches:uH:      7f216b426100 _start+0x0 (/usr/lib/x86_64-linux-gnu/ld-2.31.so)	movq %rsp, %rdi
> >               ls 1443864 [006] 2275506.209908:          1  branches:uH:      7f216b426103 _start+0x3 (/usr/lib/x86_64-linux-gnu/ld-2.31.so)	callq _dl_start+0x0
> > 
> > Signed-off-by: Changbin Du <changbin.du@xxxxxxxxxx>
> > 
> > ---
> > v2:
> >   - update Documentation.
> > ---
> >  tools/perf/Documentation/perf-script.txt | 13 +++++++------
> >  tools/perf/builtin-script.c              |  8 +++++++-
> >  2 files changed, 14 insertions(+), 7 deletions(-)
> > 
> > diff --git a/tools/perf/Documentation/perf-script.txt b/tools/perf/Documentation/perf-script.txt
> > index ff9a52e44688..578fa59f51a5 100644
> > --- a/tools/perf/Documentation/perf-script.txt
> > +++ b/tools/perf/Documentation/perf-script.txt
> > @@ -132,9 +132,10 @@ OPTIONS
> >          Comma separated list of fields to print. Options are:
> >          comm, tid, pid, time, cpu, event, trace, ip, sym, dso, dsoff, addr, symoff,
> >          srcline, period, iregs, uregs, brstack, brstacksym, flags, bpf-output,
> > -        brstackinsn, brstackinsnlen, brstackoff, callindent, insn, insnlen, synth,
> > -        phys_addr, metric, misc, srccode, ipc, data_page_size, code_page_size, ins_lat,
> > -        machine_pid, vcpu, cgroup, retire_lat.
> > +        brstackinsn, brstackinsnlen, brstackoff, callindent, insn, disasm,
> > +        insnlen, synth, phys_addr, metric, misc, srccode, ipc, data_page_size,
> > +        code_page_size, ins_lat, machine_pid, vcpu, cgroup, retire_lat.
> > +
> >          Field list can be prepended with the type, trace, sw or hw,
> >          to indicate to which event type the field list applies.
> >          e.g., -F sw:comm,tid,time,ip,sym  and -F trace:time,cpu,trace
> > @@ -217,9 +218,9 @@ OPTIONS
> >  	Instruction Trace decoding. For calls and returns, it will display the
> >  	name of the symbol indented with spaces to reflect the stack depth.
> >  
> > -	When doing instruction trace decoding insn and insnlen give the
> > -	instruction bytes and the instruction length of the current
> > -	instruction.
> > +	When doing instruction trace decoding, insn, disasm and insnlen give the
> > +	instruction bytes, disassembled instructions (requires libcapstone support)
> > +	and the instruction length of the current instruction respectively.
> >  
> >  	The synth field is used by synthesized events which may be created when
> >  	Instruction Trace decoding.
> > diff --git a/tools/perf/builtin-script.c b/tools/perf/builtin-script.c
> > index 4817a37f16e2..4ac9670704ff 100644
> > --- a/tools/perf/builtin-script.c
> > +++ b/tools/perf/builtin-script.c
> > @@ -135,6 +135,7 @@ enum perf_output_field {
> >  	PERF_OUTPUT_CGROUP          = 1ULL << 39,
> >  	PERF_OUTPUT_RETIRE_LAT      = 1ULL << 40,
> >  	PERF_OUTPUT_DSOFF           = 1ULL << 41,
> > +	PERF_OUTPUT_DISASM          = 1ULL << 42,
> >  };
> >  
> >  struct perf_script {
> > @@ -190,6 +191,7 @@ struct output_option {
> >  	{.str = "bpf-output",   .field = PERF_OUTPUT_BPF_OUTPUT},
> >  	{.str = "callindent", .field = PERF_OUTPUT_CALLINDENT},
> >  	{.str = "insn", .field = PERF_OUTPUT_INSN},
> > +	{.str = "disasm", .field = PERF_OUTPUT_DISASM},
> >  	{.str = "insnlen", .field = PERF_OUTPUT_INSNLEN},
> >  	{.str = "brstackinsn", .field = PERF_OUTPUT_BRSTACKINSN},
> >  	{.str = "brstackoff", .field = PERF_OUTPUT_BRSTACKOFF},
> > @@ -1515,6 +1517,10 @@ static int perf_sample__fprintf_insn(struct perf_sample *sample,
> >  		printed += fprintf(fp, " insn: ");
> >  		printed += sample__fprintf_insn_raw(sample, fp);
> >  	}
> > +	if (PRINT_FIELD(DISASM) && sample->insn_len) {
> > +		printed += fprintf(fp, "\t\t");
> 
> This is good, except if both 'insn' and 'disasm' are used together.
> It either:
>  a) without libcapstone, prints insn bytes twice
> 
> 	Probably simpler to make 'disasm' without libcapstone
> 	a fatal error explaining that perf needs to be built
> 	with libcapstone support for 'disasm' to work.
>
Instead of fatal error, I print a warning message for this. Because
perf_sample__fprintf_insn() cannot return negtive error number.

>  b) with libcapstone, disassembly does not line up nicely
> 
 

-- 
Cheers,
Changbin Du