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

[Adrian Hunter]

On 5/02/24 14:19, Changbin Du wrote:
> 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.

It could be validated in advance, perhaps in parse_output_fields().

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