[PATCH 3/5] perf, tools, script: Add support for printing assembler

Andi Kleen
2016-03-28T17:46:04Z

When dumping PT traces with perf script it is very useful to see the
assembler for each sample, so that it is easily possible to follow
the control flow.

As using objdump is difficult and inefficient from perf script this
patch uses the udis86 library to implement assembler output.
The library can be downloaded from http://udis86.sourceforge.net/

The library is probed as an external dependency in the usual way. Then perf
script calls into it when needed, and handles callbacks to resolve
symbols.

% perf record -e intel_pt//u true
% perf script -F sym,symoff,ip,asm --itrace=i0ns | head
7fc7188b4190 _start+0x0 mov %rsp, %rdi
7fc7188b4193 _start+0x3 call _dl_start
7fc7188b7710 _dl_start+0x0 push %rbp
7fc7188b7711 _dl_start+0x1 mov %rsp, %rbp
7fc7188b7714 _dl_start+0x4 push %r15
7fc7188b7716 _dl_start+0x6 push %r14
7fc7188b7718 _dl_start+0x8 push %r13
7fc7188b771a _dl_start+0xa push %r12
7fc7188b771c _dl_start+0xc mov %rdi, %r12
7fc7188b771f _dl_start+0xf push %rbx

Current issues:
- Some jump references do not get resolved to symbols.
- udis86 release does not support STAC/CLAC, which are used in the kernel,
but there is a pending patch for it.

Cc: adrian.hunter@intel.com
v2: Fix address resolution. Port to latest acme/perf/core
Signed-off-by: Andi Kleen <ak@linux.intel.com>
---
tools/perf/Documentation/perf-script.txt | 4 +-
tools/perf/builtin-script.c | 107 +++++++++++++++++++++++++++++--
2 files changed, 105 insertions(+), 6 deletions(-)

diff --git a/tools/perf/Documentation/perf-script.txt b/tools/perf/Documentation/perf-script.txt
index 22ef393..f2b81d8 100644
--- a/tools/perf/Documentation/perf-script.txt
+++ b/tools/perf/Documentation/perf-script.txt
@@ -116,7 +116,7 @@ OPTIONS
--fields::
Comma separated list of fields to print. Options are:
comm, tid, pid, time, cpu, event, trace, ip, sym, dso, addr, symoff,
- srcline, period, iregs, brstack, brstacksym, flags.
+ srcline, period, iregs, brstack, brstacksym, flags, asm.
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
@@ -185,6 +185,8 @@ OPTIONS

The brstacksym is identical to brstack, except that the FROM and TO addresses are printed in a symbolic form if possible.

+ When asm is specified the assembler instruction of each sample is printed in disassembled form.
+
-k::
--vmlinux=<file>::
vmlinux pathname
diff --git a/tools/perf/builtin-script.c b/tools/perf/builtin-script.c
index 3770c3d..323572e 100644
--- a/tools/perf/builtin-script.c
+++ b/tools/perf/builtin-script.c
@@ -25,6 +25,10 @@
#include "asm/bug.h"
#include "util/mem-events.h"

+#ifdef HAVE_UDIS86
+#include <udis86.h>
+#endif
+
static char const *script_name;
static char const *generate_script_lang;
static bool debug_mode;
@@ -62,6 +66,7 @@ enum perf_output_field {
PERF_OUTPUT_DATA_SRC = 1U << 17,
PERF_OUTPUT_WEIGHT = 1U << 18,
PERF_OUTPUT_BPF_OUTPUT = 1U << 19,
+ PERF_OUTPUT_ASM = 1U << 20,
};

struct output_option {
@@ -88,6 +93,7 @@ struct output_option {
{.str = "data_src", .field = PERF_OUTPUT_DATA_SRC},
{.str = "weight", .field = PERF_OUTPUT_WEIGHT},
{.str = "bpf-output", .field = PERF_OUTPUT_BPF_OUTPUT},
+ {.str = "asm", .field = PERF_OUTPUT_ASM},
};

/* default set to maintain compatibility with current format */
@@ -282,7 +288,11 @@ static int perf_evsel__check_attr(struct perf_evsel *evsel,
"selected. Hence, no address to lookup the source line number.\n");
return -EINVAL;
}
-
+ if (PRINT_FIELD(ASM) && !PRINT_FIELD(IP)) {
+ pr_err("Display of assembler requested but sample IP is not\n"
+ "selected.\n");
+ return -EINVAL;
+ }
if ((PRINT_FIELD(PID) || PRINT_FIELD(TID)) &&
perf_evsel__check_stype(evsel, PERF_SAMPLE_TID, "TID",
PERF_OUTPUT_TID|PERF_OUTPUT_PID))
@@ -421,6 +431,88 @@ static void print_sample_iregs(struct perf_sample *sample,
}
}

+#ifdef HAVE_UDIS86
+
+struct perf_ud {
+ ud_t ud_obj;
+ struct thread *thread;
+ u8 cpumode;
+ int cpu;
+};
+
+static const char *dis_resolve(struct ud *u, uint64_t addr, int64_t *off)
+{
+ struct perf_ud *ud = container_of(u, struct perf_ud, ud_obj);
+ struct addr_location al;
+
+ memset(&al, 0, sizeof(struct addr_location));
+
+ thread__find_addr_map(ud->thread, ud->cpumode, MAP__FUNCTION, addr, &al);
+ if (!al.map)
+ thread__find_addr_map(ud->thread, ud->cpumode, MAP__VARIABLE,
+ addr, &al);
+ al.cpu = ud->cpu;
+ al.sym = NULL;
+
+ if (al.map)
+ al.sym = map__find_symbol(al.map, al.addr, NULL);
+
+ if (!al.sym)
+ return NULL;
+
+ if (al.addr < al.sym->end)
+ *off = al.addr - al.sym->start;
+ else
+ *off = al.addr - al.map->start - al.sym->start;
+ return al.sym->name;
+}
+#endif
+
+static void print_sample_asm(struct perf_sample *sample __maybe_unused,
+ struct thread *thread __maybe_unused,
+ struct perf_event_attr *attr __maybe_unused,
+ struct addr_location *al __maybe_unused,
+ struct machine *machine __maybe_unused)
+{
+#ifdef HAVE_UDIS86
+ static bool ud_initialized = false;
+ static struct perf_ud ud;
+ u8 buffer[32];
+ int len;
+ u64 offset;
+
+ if (!ud_initialized) {
+ ud_initialized = true;
+ ud_init(&ud.ud_obj);
+ ud_set_syntax(&ud.ud_obj, UD_SYN_ATT);
+ ud_set_sym_resolver(&ud.ud_obj, dis_resolve);
+ }
+ ud.thread = thread;
+ ud.cpumode = sample->cpumode;
+ ud.cpu = sample->cpu;
+
+ if (!al->map || !al->map->dso)
+ return;
+ if (al->map->dso->data.status == DSO_DATA_STATUS_ERROR)
+ return;
+
+ /* Load maps to ensure dso->is_64_bit has been updated */
+ map__load(al->map, machine->symbol_filter);
+
+ offset = al->map->map_ip(al->map, sample->ip);
+ len = dso__data_read_offset(al->map->dso, machine,
+ offset, buffer, 32);
+ if (len <= 0)
+ return;
+
+ ud_set_mode(&ud.ud_obj, al->map->dso->is_64_bit ? 64 : 32);
+ ud_set_pc(&ud.ud_obj, sample->ip);
+ ud_set_input_buffer(&ud.ud_obj, buffer, len);
+ ud_disassemble(&ud.ud_obj);
+ printf("\t%s", ud_insn_asm(&ud.ud_obj));
+#endif
+}
+
static void print_sample_start(struct perf_sample *sample,
struct thread *thread,
struct perf_evsel *evsel)
@@ -739,7 +831,8 @@ static size_t data_src__printf(u64 data_src)

static void process_event(struct perf_script *script,
struct perf_sample *sample, struct perf_evsel *evsel,
- struct addr_location *al)
+ struct addr_location *al,
+ struct machine *machine)
{
struct thread *thread = al->thread;
struct perf_event_attr *attr = &evsel->attr;
@@ -767,7 +860,7 @@ static void process_event(struct perf_script *script,

if (is_bts_event(attr)) {
print_sample_bts(sample, evsel, thread, al);
- return;
+ goto print_rest;
}

if (PRINT_FIELD(TRACE))
@@ -796,6 +889,7 @@ static void process_event(struct perf_script *script,
if (PRINT_FIELD(IREGS))
print_sample_iregs(sample, attr);

+print_rest:
if (PRINT_FIELD(BRSTACK))
print_sample_brstack(sample);
else if (PRINT_FIELD(BRSTACKSYM))
@@ -804,6 +898,9 @@ static void process_event(struct perf_script *script,
if (perf_evsel__is_bpf_output(evsel) && PRINT_FIELD(BPF_OUTPUT))
print_sample_bpf_output(sample);

+ if (PRINT_FIELD(ASM))
+ print_sample_asm(sample, thread, attr, al, machine);
+
printf("\n");
}

@@ -910,7 +1007,7 @@ static int process_sample_event(struct perf_tool *tool,
if (scripting_ops)
scripting_ops->process_event(event, sample, evsel, &al);
else
- process_event(scr, sample, evsel, &al);
+ process_event(scr, sample, evsel, &al, machine);

out_put:
addr_location__put(&al);
@@ -2010,7 +2107,7 @@ int cmd_script(int argc, const char **argv, const char *prefix __maybe_unused)
"comma separated output fields prepend with 'type:'. "
"Valid types: hw,sw,trace,raw. "
"Fields: comm,tid,pid,time,cpu,event,trace,ip,sym,dso,"
- "addr,symoff,period,iregs,brstack,brstacksym,flags", parse_output_fields),
+ "addr,symoff,period,iregs,brstack,brstacksym,flags,asm", parse_output_fields),
OPT_BOOLEAN('a', "all-cpus", &system_wide,
"system-wide collection from all CPUs"),
OPT_STRING('S', "symbols", &symbol_conf.sym_list_str, "symbol[,symbol...]",
--
2.5.5