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

[Changbin Du]

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.

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:'.

> > +		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
		 * 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.

> > +	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?

> > +
> > +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 */
> 

-- 
Cheers,
Changbin Du