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Date: Wed, 28 May 2014 11:45:04 +0300
From: Adrian Hunter <adrian.hunter@...el.com>
To: Peter Zijlstra <peterz@...radead.org>
Cc: Ingo Molnar <mingo@...hat.com>, Dave Jones <davej@...hat.com>,
Arnaldo Carvalho de Melo <acme@...nel.org>,
linux-kernel@...r.kernel.org, David Ahern <dsahern@...il.com>,
Jiri Olsa <jolsa@...hat.com>, Paul Mackerras <paulus@...ba.org>
Subject: [PATCH] perf: Differentiate exec() and non-exec() comm events
perf tools like 'perf report' can aggregate samples by comm
strings, which generally works. However, there are other
potential use-cases. For example, to pair up 'calls'
with 'returns' accurately (from branch events like Intel BTS)
it is necessary to identify whether the process has exec'd.
Although a comm event is generated when an 'exec' happens
it is also generated whenever the comm string is changed
on a whim (e.g. by prctl PR_SET_NAME). This patch adds a
flag to the comm event to differentiate one case from the
other.
In order to determine whether the kernel supports the new
flag, a selection bit named 'exec' is added to struct
perf_event_attr. The bit does nothing but will cause
perf_event_open() to fail if the bit is set on kernels
that do not have it defined.
Cc: Dave Jones <davej@...hat.com>
Link: http://lkml.kernel.org/r/537D9EBE.7030806@intel.com
Signed-off-by: Adrian Hunter <adrian.hunter@...el.com>
---
fs/exec.c | 6 +++---
include/linux/perf_event.h | 4 ++--
include/linux/sched.h | 6 +++++-
include/uapi/linux/perf_event.h | 9 +++++++--
kernel/events/core.c | 4 ++--
5 files changed, 19 insertions(+), 10 deletions(-)
diff --git a/fs/exec.c b/fs/exec.c
index eb83064..a9a9591 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -1046,13 +1046,13 @@ EXPORT_SYMBOL_GPL(get_task_comm);
* so that a new one can be started
*/
-void set_task_comm(struct task_struct *tsk, const char *buf)
+void __set_task_comm(struct task_struct *tsk, const char *buf, bool exec)
{
task_lock(tsk);
trace_task_rename(tsk, buf);
strlcpy(tsk->comm, buf, sizeof(tsk->comm));
task_unlock(tsk);
- perf_event_comm(tsk);
+ perf_event_comm(tsk, exec);
}
int flush_old_exec(struct linux_binprm * bprm)
@@ -1111,7 +1111,7 @@ void setup_new_exec(struct linux_binprm * bprm)
set_dumpable(current->mm, suid_dumpable);
perf_event_exec();
- set_task_comm(current, kbasename(bprm->filename));
+ __set_task_comm(current, kbasename(bprm->filename), true);
/* Set the new mm task size. We have to do that late because it may
* depend on TIF_32BIT which is only updated in flush_thread() on
diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index ec2e29f..3f736a5 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -707,7 +707,7 @@ extern int perf_register_guest_info_callbacks(struct perf_guest_info_callbacks *
extern int perf_unregister_guest_info_callbacks(struct perf_guest_info_callbacks *callbacks);
extern void perf_event_exec(void);
-extern void perf_event_comm(struct task_struct *tsk);
+extern void perf_event_comm(struct task_struct *tsk, bool exec);
extern void perf_event_fork(struct task_struct *tsk);
/* Callchains */
@@ -814,7 +814,7 @@ static inline int perf_unregister_guest_info_callbacks
(struct perf_guest_info_callbacks *callbacks) { return 0; }
static inline void perf_event_mmap(struct vm_area_struct *vma) { }
-static inline void perf_event_comm(struct task_struct *tsk) { }
+static inline void perf_event_comm(struct task_struct *tsk, bool exec) { }
static inline void perf_event_fork(struct task_struct *tsk) { }
static inline void perf_event_init(void) { }
static inline int perf_swevent_get_recursion_context(void) { return -1; }
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 25f54c7..cadcf38 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -2376,7 +2376,11 @@ extern long do_fork(unsigned long, unsigned long, unsigned long, int __user *, i
struct task_struct *fork_idle(int);
extern pid_t kernel_thread(int (*fn)(void *), void *arg, unsigned long flags);
-extern void set_task_comm(struct task_struct *tsk, const char *from);
+extern void __set_task_comm(struct task_struct *tsk, const char *from, bool exec);
+static inline void set_task_comm(struct task_struct *tsk, const char *from)
+{
+ __set_task_comm(tsk, from, false);
+}
extern char *get_task_comm(char *to, struct task_struct *tsk);
#ifdef CONFIG_SMP
diff --git a/include/uapi/linux/perf_event.h b/include/uapi/linux/perf_event.h
index d9cd853..7e55160 100644
--- a/include/uapi/linux/perf_event.h
+++ b/include/uapi/linux/perf_event.h
@@ -302,8 +302,8 @@ struct perf_event_attr {
exclude_callchain_kernel : 1, /* exclude kernel callchains */
exclude_callchain_user : 1, /* exclude user callchains */
mmap2 : 1, /* include mmap with inode data */
-
- __reserved_1 : 40;
+ exec : 1, /* flag comm events that are due to an exec */
+ __reserved_1 : 39;
union {
__u32 wakeup_events; /* wakeup every n events */
@@ -502,7 +502,12 @@ struct perf_event_mmap_page {
#define PERF_RECORD_MISC_GUEST_KERNEL (4 << 0)
#define PERF_RECORD_MISC_GUEST_USER (5 << 0)
+/*
+ * PERF_RECORD_MISC_MMAP_DATA and PERF_RECORD_MISC_COMM_EXEC are used on
+ * different events so can reuse the same bit position.
+ */
#define PERF_RECORD_MISC_MMAP_DATA (1 << 13)
+#define PERF_RECORD_MISC_COMM_EXEC (1 << 13)
/*
* Indicates that the content of PERF_SAMPLE_IP points to
* the actual instruction that triggered the event. See also
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 6a5e064..9efb1e7 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -5090,7 +5090,7 @@ static void perf_event_comm_event(struct perf_comm_event *comm_event)
NULL);
}
-void perf_event_comm(struct task_struct *task)
+void perf_event_comm(struct task_struct *task, bool exec)
{
struct perf_comm_event comm_event;
@@ -5104,7 +5104,7 @@ void perf_event_comm(struct task_struct *task)
.event_id = {
.header = {
.type = PERF_RECORD_COMM,
- .misc = 0,
+ .misc = exec ? PERF_RECORD_MISC_COMM_EXEC : 0,
/* .size */
},
/* .pid */
--
1.8.3.2
--
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