Re: [PATCH v4 2/5] perf: util: use capstone disasm engine to show assembly instructions

[Adrian Hunter]

On 20/01/24 11:13, Changbin Du wrote:
> On Fri, Jan 19, 2024 at 08:39:19PM +0200, Adrian Hunter wrote:
>> On 19/01/24 12:48, 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@xxxxxxxxxx>
>>> ---
>>>  tools/perf/builtin-script.c  |   8 +--
>>>  tools/perf/util/Build        |   1 +
>>>  tools/perf/util/print_insn.c | 122 +++++++++++++++++++++++++++++++++++
>>>  tools/perf/util/print_insn.h |  14 ++++
>>>  4 files changed, 140 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/builtin-script.c b/tools/perf/builtin-script.c
>>> index b1f57401ff23..4817a37f16e2 100644
>>> --- a/tools/perf/builtin-script.c
>>> +++ b/tools/perf/builtin-script.c
>>> @@ -34,6 +34,7 @@
>>>  #include "util/event.h"
>>>  #include "ui/ui.h"
>>>  #include "print_binary.h"
>>> +#include "print_insn.h"
>>>  #include "archinsn.h"
>>>  #include <linux/bitmap.h>
>>>  #include <linux/kernel.h>
>>> @@ -1511,11 +1512,8 @@ static int perf_sample__fprintf_insn(struct perf_sample *sample,
>>>  	if (PRINT_FIELD(INSNLEN))
>>>  		printed += fprintf(fp, " ilen: %d", sample->insn_len);
>>>  	if (PRINT_FIELD(INSN) && sample->insn_len) {
>>> -		int i;
>>> -
>>> -		printed += fprintf(fp, " insn:");
>>> -		for (i = 0; i < sample->insn_len; i++)
>>> -			printed += fprintf(fp, " %02x", (unsigned char)sample->insn[i]);
>>> +		printed += fprintf(fp, " insn: ");
>>
>> "insn:" seems unnecessary.  Also xed prints 2 tabs, which
>> helps line up the output.  Perhaps 1 tab and 2 spaces is
>> enough.
>>
> The "insn:" is used by xed. So it can not be removed if we preserve xed
> function.

I got mixed up - it is patch 3 that the comment is meant for.

> 
> For 'insn' field, I keep the original output format.
> For 'disasm' field, we can line up the output. I changed to 2 tabs and removed
> 'insn:'.

That is better, thanks!

> 
>>> +		printed += sample__fprintf_insn_raw(sample, fp);
>>>  	}
>>>  	if (PRINT_FIELD(BRSTACKINSN) || PRINT_FIELD(BRSTACKINSNLEN))
>>>  		printed += perf_sample__fprintf_brstackinsn(sample, thread, attr, machine, fp);
>>> diff --git a/tools/perf/util/Build b/tools/perf/util/Build
>>> index 988473bf907a..c33aab53d8dd 100644
>>> --- a/tools/perf/util/Build
>>> +++ b/tools/perf/util/Build
>>> @@ -32,6 +32,7 @@ perf-y += perf_regs.o
>>>  perf-y += perf-regs-arch/
>>>  perf-y += path.o
>>>  perf-y += print_binary.o
>>> +perf-y += print_insn.o
>>>  perf-y += rlimit.o
>>>  perf-y += argv_split.o
>>>  perf-y += rbtree.o
>>> diff --git a/tools/perf/util/print_insn.c b/tools/perf/util/print_insn.c
>>> new file mode 100644
>>> index 000000000000..162be4856f79
>>> --- /dev/null
>>> +++ b/tools/perf/util/print_insn.c
>>> @@ -0,0 +1,122 @@
>>> +// SPDX-License-Identifier: GPL-2.0
>>> +/*
>>> + * Instruction binary disassembler based on capstone.
>>> + *
>>> + * Author(s): Changbin Du <changbin.du@xxxxxxxxxx>
>>> + */
>>> +#include "print_insn.h"
>>
>> Please put with the other non-system includes
>>
> done.
> 
>>> +#include <stdlib.h>
>>> +#include <string.h>
>>> +#include <stdbool.h>
>>> +#include "util/debug.h"
>>
>> util/ not needed
>>
> done.
> 
>>> +#include "util/symbol.h"
>>
>> util/ not needed
>>
> done.
> 
>>> +#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]);
>>
>> Why change this to put a space on the end?
>>
> Removed the tailing space.
> 
>>> +	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, "s390")) {
>>> +		arch = CS_ARCH_SYSZ;
>>> +		mode = CS_MODE_BIG_ENDIAN;
>>> +	} else {
>>> +		return -1;
>>> +	}
>>> +
>>> +	if (cs_open(arch, mode, cs_handle) != CS_ERR_OK) {
>>> +		pr_warning_once("cs_open failed\n");
>>> +		return -1;
>>> +	}
>>> +
>>> +	cs_option(*cs_handle, CS_OPT_SYNTAX, CS_OPT_SYNTAX_ATT);
>>
>> That's only needed for x86 isn't it
>>
> Moved into below branch.
> 
>>> +	if (machine__normalized_is(machine, "x86"))
>>> +		cs_option(*cs_handle, CS_OPT_DETAIL, CS_OPT_ON);
>>
>> Why? Could use a comment.
>>
> 		/*
> 		 * Resolving address oprands to symbols is implemented

oprands -> operands

> 		 * on x86 by investigating instruction details.
> 		 */
> 
>>> +
>>> +	return 0;
>>> +}
>>> +
>>> +static size_t print_insn_x86(struct perf_sample *sample, struct thread *thread,
>>> +			     cs_insn *insn, FILE *fp)
>>> +{
>>> +	struct addr_location al;
>>> +	size_t printed = 0;
>>> +
>>> +	if (insn->detail && insn->detail->x86.op_count == 1) {
>>> +		cs_x86_op *op = &insn->detail->x86.operands[0];
>>> +
>>> +		addr_location__init(&al);
>>
>> Missing addr_location__exit()
>>
> Fixed.
> 
>>> +
>>> +		if (op->type == X86_OP_IMM &&
>>> +		    thread__find_symbol(thread, sample->cpumode, op->imm, &al)) {
>>> +			printed += fprintf(fp, "%s ", insn[0].mnemonic);
>>> +			printed += symbol__fprintf_symname_offs(al.sym, &al, fp);
>>> +			return printed;
>>> +		}
>>> +	}
>>> +
>>> +	printed += fprintf(fp, "%s %s", insn[0].mnemonic, insn[0].op_str);
>>> +	return printed;
>>> +}
>>> +
>>> +size_t sample__fprintf_insn(struct perf_sample *sample, struct thread *thread,
>>> +			    struct machine *machine, FILE *fp)
>>> +{
>>> +	static csh cs_handle;
>>
>> Why static?
>>
> Removed. See below.
> 
>>> +	cs_insn *insn;
>>> +	size_t count;
>>> +	size_t printed = 0;
>>> +	int ret;
>>> +
>>> +	ret = capstone_init(machine, &cs_handle);
>>
>> Does this really need to be done every time?
>>
> Only need to init once exactly. The problem is I cannot find a appropriate
> place to do the initiation.
> 
> I tried to initiate on first call but we still need a global mutex to be
> initiated.
> 
> So finally I fallback to initiate every time. The redundant initiation is
> acceptable per my test.

OK, could add a FIXME

> 
>>> +	if (ret < 0) {
>>> +		/* fallback */
>>> +		return sample__fprintf_insn_raw(sample, fp);
>>> +	}
>>> +
>>> +	count = cs_disasm(cs_handle, (uint8_t *)sample->insn, sample->insn_len,
>>> +			  sample->ip, 1, &insn);
>>> +	if (count > 0) {
>>> +		if (machine__normalized_is(machine, "x86"))
>>> +			printed += print_insn_x86(sample, thread, &insn[0], fp);
>>> +		else
>>> +			printed += fprintf(fp, "%s %s", insn[0].mnemonic, insn[0].op_str);
>>> +		cs_free(insn, count);
>>> +	} else {
>>> +		printed += fprintf(fp, "illegal instruction");
>>> +	}
>>> +
>>> +	cs_close(&cs_handle);
>>> +	return printed;
>>> +}
>>> +#else
>>> +size_t sample__fprintf_insn(struct perf_sample *sample, struct thread *thread __maybe_unused,
>>> +			    struct machine *machine __maybe_unused, FILE *fp)
>>> +{
>>> +	return sample__fprintf_insn_raw(sample, fp);
>>> +}
>>> +#endif
>>> diff --git a/tools/perf/util/print_insn.h b/tools/perf/util/print_insn.h
>>> new file mode 100644
>>> index 000000000000..af8fa5d01fb7
>>> --- /dev/null
>>> +++ b/tools/perf/util/print_insn.h
>>> @@ -0,0 +1,14 @@
>>> +/* SPDX-License-Identifier: GPL-2.0 */
>>> +#ifndef PERF_PRINT_ISNS_H
>>
>> Here and elsewhere
>>
>> ISNS -> INSN
>>
> fixed.
> 
>>> +#define PERF_PRINT_ISNS_H
>>> +
>>> +#include <stddef.h>
>>> +#include <stdio.h>
>>> +#include "event.h"
>>> +#include "util/thread.h"
>>
>> Instead of including event.h and thread.h, just forward declare:
>>
>> struct perf_sample;
>> struct thread;
>> struct machine;
>>
> Why forward declaration?

That is how it is done in perf tools.  It avoids unnecessary dependency
among headers.

> 
>>> +
>>> +size_t sample__fprintf_insn(struct perf_sample *sample, struct thread *thread,
>>> +			    struct machine *machine, FILE *fp);
>>> +size_t sample__fprintf_insn_raw(struct perf_sample *sample, FILE *fp);
>>> +
>>> +#endif /* PERF_PRINT_ISNS_H */
>>
>