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Subject[PATCH 4/4] perf tools: Add support for breakpoint events in perf tools
Date
Add the breakpoint events support with this new sysnopsis:

mem:addr[:access]

Where addr is a raw addr value in the kernel and access can be
either [r][w][x]

Example to profile tasklist_lock:

$ grep tasklist_lock /proc/kallsyms
ffffffff8189c000 D tasklist_lock
$ perf record -e mem:0xffffffff8189c000:rw -a -f -c 1
$ perf report
# Samples: 62
#
# Overhead Command Shared Object Symbol
# ........ ............... ............. ......
#
29.03% swapper [kernel] [k] _raw_read_trylock
29.03% swapper [kernel] [k] _raw_read_unlock
19.35% init [kernel] [k] _raw_read_trylock
19.35% init [kernel] [k] _raw_read_unlock
1.61% events/0 [kernel] [k] _raw_read_trylock
1.61% events/0 [kernel] [k] _raw_read_unlock
Coming soon:

- support for symbols in the event definition.
- default period to 1 for breakpoint events because these are not
high frequency events. The same thing is needed for trace events.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Prasad <prasad@linux.vnet.ibm.com>
---
tools/perf/Documentation/perf-record.txt | 16 ++++--
tools/perf/util/parse-events.c | 84 +++++++++++++++++++++++++++++-
2 files changed, 95 insertions(+), 5 deletions(-)
diff --git a/tools/perf/Documentation/perf-record.txt b/tools/perf/Documentation/perf-record.txt
index 0ff23de..fc46c0b 100644
--- a/tools/perf/Documentation/perf-record.txt
+++ b/tools/perf/Documentation/perf-record.txt
@@ -26,11 +26,19 @@ OPTIONS

-e::
--event=::
- Select the PMU event. Selection can be a symbolic event name
- (use 'perf list' to list all events) or a raw PMU
- event (eventsel+umask) in the form of rNNN where NNN is a
- hexadecimal event descriptor.
+ Select the PMU event. Selection can be:

+ - a symbolic event name (use 'perf list' to list all events)
+
+ - a raw PMU event (eventsel+umask) in the form of rNNN where NNN is a
+ hexadecimal event descriptor.
+
+ - a hardware breakpoint event in the form of '\mem:addr[:access]'
+ where addr is the address in memory you want to break in.
+ Access is the memory access type (read, write, execute) it can
+ be passed as follows: '\mem:addr[:[r][w][x]]'.
+ If you want to profile read-write accesses in 0x1000, just set
+ 'mem:0x1000:rw'.
-a::
System-wide collection.

diff --git a/tools/perf/util/parse-events.c b/tools/perf/util/parse-events.c
index 0faf4f2..0700274 100644
--- a/tools/perf/util/parse-events.c
+++ b/tools/perf/util/parse-events.c
@@ -1,4 +1,4 @@
-
+#include "../../../include/linux/hw_breakpoint.h"
#include "util.h"
#include "../perf.h"
#include "parse-options.h"
@@ -540,6 +540,81 @@ static enum event_result parse_tracepoint_event(const char **strp,
attr, strp);
}

+static enum event_result
+parse_breakpoint_type(const char *type, const char **strp,
+ struct perf_event_attr *attr)
+{
+ int i;
+
+ for (i = 0; i < 3; i++) {
+ if (!type[i])
+ break;
+
+ switch (type[i]) {
+ case 'r':
+ attr->bp_type |= HW_BREAKPOINT_R;
+ break;
+ case 'w':
+ attr->bp_type |= HW_BREAKPOINT_W;
+ break;
+ case 'x':
+ attr->bp_type |= HW_BREAKPOINT_X;
+ break;
+ default:
+ return EVT_FAILED;
+ }
+ }
+ if (!attr->bp_type) /* Default */
+ attr->bp_type = HW_BREAKPOINT_R | HW_BREAKPOINT_W;
+
+ *strp = type + i;
+
+ return EVT_HANDLED;
+}
+
+static enum event_result
+parse_breakpoint_event(const char **strp, struct perf_event_attr *attr)
+{
+ const char *target;
+ const char *type;
+ char *endaddr;
+ u64 addr;
+ enum event_result err;
+
+ target = strchr(*strp, ':');
+ if (!target)
+ return EVT_FAILED;
+
+ if (strncmp(*strp, "mem", target - *strp) != 0)
+ return EVT_FAILED;
+
+ target++;
+
+ addr = strtoull(target, &endaddr, 0);
+ if (target == endaddr)
+ return EVT_FAILED;
+
+ attr->bp_addr = addr;
+ *strp = endaddr;
+
+ type = strchr(target, ':');
+
+ /* If no type is defined, just rw as default */
+ if (!type) {
+ attr->bp_type = HW_BREAKPOINT_R | HW_BREAKPOINT_W;
+ } else {
+ err = parse_breakpoint_type(++type, strp, attr);
+ if (err == EVT_FAILED)
+ return EVT_FAILED;
+ }
+
+ /* We should find a nice way to override the access type */
+ attr->bp_len = HW_BREAKPOINT_LEN_4;
+ attr->type = PERF_TYPE_BREAKPOINT;
+
+ return EVT_HANDLED;
+}
+
static int check_events(const char *str, unsigned int i)
{
int n;
@@ -673,6 +748,10 @@ parse_event_symbols(const char **str, struct perf_event_attr *attr)
if (ret != EVT_FAILED)
goto modifier;

+ ret = parse_breakpoint_event(str, attr);
+ if (ret != EVT_FAILED)
+ goto modifier;
+
fprintf(stderr, "invalid or unsupported event: '%s'\n", *str);
fprintf(stderr, "Run 'perf list' for a list of valid events\n");
return EVT_FAILED;
@@ -859,6 +938,9 @@ void print_events(void)
"rNNN");
printf("\n");

+ printf(" %-42s [hardware breakpoint]\n", "mem:<addr>[:access]");
+ printf("\n");
+
print_tracepoint_events();

exit(129);
--
1.6.2.3


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