[PATCH V4 13/13] perf intel-pt: Add support for text poke events

Adrian Hunter
2020-03-04T09:08:17Z

Select text poke events when available and the kernel is being traced.
Process text poke events to invalidate entries in Intel PT's instruction
cache.

Example:

The example requires kernel config:
CONFIG_PROC_SYSCTL=y
CONFIG_SCHED_DEBUG=y
CONFIG_SCHEDSTATS=y

Before:

# perf record -o perf.data.before --kcore -a -e intel_pt//k -m,64M &
# cat /proc/sys/kernel/sched_schedstats
0
# echo 1 > /proc/sys/kernel/sched_schedstats
# cat /proc/sys/kernel/sched_schedstats
1
# echo 0 > /proc/sys/kernel/sched_schedstats
# cat /proc/sys/kernel/sched_schedstats
0
# kill %1
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 3.341 MB perf.data.before ]
[1]+ Terminated perf record -o perf.data.before --kcore -a -e intel_pt//k -m,64M
# perf script -i perf.data.before --itrace=e >/dev/null
Warning:
474 instruction trace errors

After:

# perf record -o perf.data.after --kcore -a -e intel_pt//k -m,64M &
# cat /proc/sys/kernel/sched_schedstats
0
# echo 1 > /proc/sys/kernel/sched_schedstats
# cat /proc/sys/kernel/sched_schedstats
1
# echo 0 > /proc/sys/kernel/sched_schedstats
# cat /proc/sys/kernel/sched_schedstats
0
# kill %1
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 2.646 MB perf.data.after ]
[1]+ Terminated perf record -o perf.data.after --kcore -a -e intel_pt//k -m,64M
# perf script -i perf.data.after --itrace=e >/dev/null

Example:

The example requires kernel config:
# CONFIG_FUNCTION_TRACER is not set

Before:
# perf record --kcore -m,64M -o t1 -a -e intel_pt//k &
# perf probe __schedule
Added new event:
probe:__schedule (on __schedule)

You can now use it in all perf tools, such as:

perf record -e probe:__schedule -aR sleep 1

# perf record -e probe:__schedule -aR sleep 1
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 0.026 MB perf.data (68 samples) ]
# perf probe -d probe:__schedule
Removed event: probe:__schedule
# kill %1
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 41.268 MB t1 ]
[1]+ Terminated perf record --kcore -m,64M -o t1 -a -e intel_pt//k
# perf script -i t1 --itrace=e >/dev/null
Warning:
207 instruction trace errors

After:
# perf record --kcore -m,64M -o t1 -a -e intel_pt//k &
# perf probe __schedule
Added new event:
probe:__schedule (on __schedule)

You can now use it in all perf tools, such as:

perf record -e probe:__schedule -aR sleep 1

# perf record -e probe:__schedule -aR sleep 1
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 0.028 MB perf.data (107 samples) ]
# perf probe -d probe:__schedule
Removed event: probe:__schedule
# kill %1
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 39.978 MB t1 ]
[1]+ Terminated perf record --kcore -m,64M -o t1 -a -e intel_pt//k
# perf script -i t1 --itrace=e >/dev/null
# perf script -i t1 --no-itrace -D | grep 'POKE\|KSYMBOL'
6 565303693547 0x291f18 [0x50]: PERF_RECORD_KSYMBOL addr ffffffffc027a000 len 4096 type 2 flags 0x0 name kprobe_insn_page
6 565303697010 0x291f68 [0x40]: PERF_RECORD_TEXT_POKE addr 0xffffffffc027a000 old len 0 new len 6
6 565303838278 0x291fa8 [0x50]: PERF_RECORD_KSYMBOL addr ffffffffc027c000 len 4096 type 2 flags 0x0 name kprobe_optinsn_page
6 565303848286 0x291ff8 [0xa0]: PERF_RECORD_TEXT_POKE addr 0xffffffffc027c000 old len 0 new len 106
6 565369336743 0x292af8 [0x40]: PERF_RECORD_TEXT_POKE addr 0xffffffff88ab8890 old len 5 new len 5
7 566434327704 0x217c208 [0x40]: PERF_RECORD_TEXT_POKE addr 0xffffffff88ab8890 old len 5 new len 5
6 566456313475 0x293198 [0xa0]: PERF_RECORD_TEXT_POKE addr 0xffffffffc027c000 old len 106 new len 0
6 566456314935 0x293238 [0x40]: PERF_RECORD_TEXT_POKE addr 0xffffffffc027a000 old len 6 new len 0

Example:

The example requires kernel config:
CONFIG_FUNCTION_TRACER=y

Before:
# perf record --kcore -m,64M -o t1 -a -e intel_pt//k &
# perf probe __kmalloc
Added new event:
probe:__kmalloc (on __kmalloc)

You can now use it in all perf tools, such as:

perf record -e probe:__kmalloc -aR sleep 1

# perf record -e probe:__kmalloc -aR sleep 1
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 0.022 MB perf.data (6 samples) ]
# perf probe -d probe:__kmalloc
Removed event: probe:__kmalloc
# kill %1
[ perf record: Woken up 2 times to write data ]
[ perf record: Captured and wrote 43.850 MB t1 ]
[1]+ Terminated perf record --kcore -m,64M -o t1 -a -e intel_pt//k
# perf script -i t1 --itrace=e >/dev/null
Warning:
8 instruction trace errors

After:
# perf record --kcore -m,64M -o t1 -a -e intel_pt//k &
# perf probe __kmalloc
Added new event:
probe:__kmalloc (on __kmalloc)

You can now use it in all perf tools, such as:

perf record -e probe:__kmalloc -aR sleep 1

# perf record -e probe:__kmalloc -aR sleep 1
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 0.037 MB perf.data (206 samples) ]
# perf probe -d probe:__kmalloc
Removed event: probe:__kmalloc
# kill %1
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 41.442 MB t1 ]
[1]+ Terminated perf record --kcore -m,64M -o t1 -a -e intel_pt//k
# perf script -i t1 --itrace=e >/dev/null
# perf script -i t1 --no-itrace -D | grep 'POKE\|KSYMBOL'
5 312216133258 0x8bafe0 [0x50]: PERF_RECORD_KSYMBOL addr ffffffffc0360000 len 415 type 2 flags 0x0 name ftrace_trampoline
5 312216133494 0x8bb030 [0x1d8]: PERF_RECORD_TEXT_POKE addr 0xffffffffc0360000 old len 0 new len 415
5 312216229563 0x8bb208 [0x40]: PERF_RECORD_TEXT_POKE addr 0xffffffffac6016f5 old len 5 new len 5
5 312216239063 0x8bb248 [0x40]: PERF_RECORD_TEXT_POKE addr 0xffffffffac601803 old len 5 new len 5
5 312216727230 0x8bb288 [0x40]: PERF_RECORD_TEXT_POKE addr 0xffffffffabbea190 old len 5 new len 5
5 312216739322 0x8bb2c8 [0x40]: PERF_RECORD_TEXT_POKE addr 0xffffffffac6016f5 old len 5 new len 5
5 312216748321 0x8bb308 [0x40]: PERF_RECORD_TEXT_POKE addr 0xffffffffac601803 old len 5 new len 5
7 313287163462 0x2817430 [0x40]: PERF_RECORD_TEXT_POKE addr 0xffffffffac6016f5 old len 5 new len 5
7 313287174890 0x2817470 [0x40]: PERF_RECORD_TEXT_POKE addr 0xffffffffac601803 old len 5 new len 5
7 313287818979 0x28174b0 [0x40]: PERF_RECORD_TEXT_POKE addr 0xffffffffabbea190 old len 5 new len 5
7 313287829357 0x28174f0 [0x40]: PERF_RECORD_TEXT_POKE addr 0xffffffffac6016f5 old len 5 new len 5
7 313287841246 0x2817530 [0x40]: PERF_RECORD_TEXT_POKE addr 0xffffffffac601803 old len 5 new len 5

Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
---
tools/perf/arch/x86/util/intel-pt.c | 4 ++
tools/perf/util/intel-pt.c | 75 +++++++++++++++++++++++++++++
2 files changed, 79 insertions(+)

diff --git a/tools/perf/arch/x86/util/intel-pt.c b/tools/perf/arch/x86/util/intel-pt.c
index 20df442fdf36..ec75445ef7cf 100644
--- a/tools/perf/arch/x86/util/intel-pt.c
+++ b/tools/perf/arch/x86/util/intel-pt.c
@@ -827,6 +827,10 @@ static int intel_pt_recording_options(struct auxtrace_record *itr,
}
}

+ if (have_timing_info && !intel_pt_evsel->core.attr.exclude_kernel &&
+ perf_can_record_text_poke_events() && perf_can_record_cpu_wide())
+ opts->text_poke = true;
+
if (intel_pt_evsel) {
/*
* To obtain the auxtrace buffer file descriptor, the auxtrace
diff --git a/tools/perf/util/intel-pt.c b/tools/perf/util/intel-pt.c
index 33cf8928cf05..64768312c994 100644
--- a/tools/perf/util/intel-pt.c
+++ b/tools/perf/util/intel-pt.c
@@ -514,6 +514,17 @@ intel_pt_cache_lookup(struct dso *dso, struct machine *machine, u64 offset)
return auxtrace_cache__lookup(dso->auxtrace_cache, offset);
}

+static void intel_pt_cache_invalidate(struct dso *dso, struct machine *machine,
+ u64 offset)
+{
+ struct auxtrace_cache *c = intel_pt_cache(dso, machine);
+
+ if (!c)
+ return;
+
+ auxtrace_cache__remove(dso->auxtrace_cache, offset);
+}
+
static inline u8 intel_pt_cpumode(struct intel_pt *pt, uint64_t ip)
{
return ip >= pt->kernel_start ?
@@ -2592,6 +2603,67 @@ static int intel_pt_process_itrace_start(struct intel_pt *pt,
event->itrace_start.tid);
}

+static int intel_pt_find_map(struct thread *thread, u8 cpumode, u64 addr,
+ struct addr_location *al)
+{
+ if (!al->map || addr < al->map->start || addr >= al->map->end) {
+ if (!thread__find_map(thread, cpumode, addr, al))
+ return -1;
+ }
+
+ return 0;
+}
+
+/* Invalidate all instruction cache entries that overlap the text poke */
+static int intel_pt_text_poke(struct intel_pt *pt, union perf_event *event)
+{
+ u8 cpumode = event->header.misc & PERF_RECORD_MISC_CPUMODE_MASK;
+ u64 addr = event->text_poke.addr + event->text_poke.new_len - 1;
+ /* Assume text poke begins in a basic block no more than 4096 bytes */
+ int cnt = 4096 + event->text_poke.new_len;
+ struct thread *thread = pt->unknown_thread;
+ struct addr_location al = { .map = NULL };
+ struct machine *machine = pt->machine;
+ struct intel_pt_cache_entry *e;
+ u64 offset;
+
+ if (!event->text_poke.new_len)
+ return 0;
+
+ for (; cnt; cnt--, addr--) {
+ if (intel_pt_find_map(thread, cpumode, addr, &al)) {
+ if (addr < event->text_poke.addr)
+ return 0;
+ continue;
+ }
+
+ if (!al.map->dso || !al.map->dso->auxtrace_cache)
+ continue;
+
+ offset = al.map->map_ip(al.map, addr);
+
+ e = intel_pt_cache_lookup(al.map->dso, machine, offset);
+ if (!e)
+ continue;
+
+ if (addr + e->byte_cnt + e->length <= event->text_poke.addr) {
+ /*
+ * No overlap. Working backwards there cannot be another
+ * basic block that overlaps the text poke if there is a
+ * branch instruction before the text poke address.
+ */
+ if (e->branch != INTEL_PT_BR_NO_BRANCH)
+ return 0;
+ } else {
+ intel_pt_cache_invalidate(al.map->dso, machine, offset);
+ intel_pt_log("Invalidated instruction cache for %s at %#"PRIx64"\n",
+ al.map->dso->long_name, addr);
+ }
+ }
+
+ return 0;
+}
+
static int intel_pt_process_event(struct perf_session *session,
union perf_event *event,
struct perf_sample *sample,
@@ -2653,6 +2725,9 @@ static int intel_pt_process_event(struct perf_session *session,
event->header.type == PERF_RECORD_SWITCH_CPU_WIDE)
err = intel_pt_context_switch(pt, event, sample);

+ if (!err && event->header.type == PERF_RECORD_TEXT_POKE)
+ err = intel_pt_text_poke(pt, event);
+
intel_pt_log("event %u: cpu %d time %"PRIu64" tsc %#"PRIx64" ",
event->header.type, sample->cpu, sample->time, timestamp);
intel_pt_log_event(event);
--
2.17.1