This is a repost to LKML of the patches I sent to the linux-perf-users mailing list.
I am reposting it to lkml per Arnaldo Carvalho's request.
The following patch was submitted to the mailing list but
is currently not accepted. I have forward ported it to the latest
kernel version. The following patches are dependent on this patch.
Carl Love
-----------------------------------------------------------------------
This patch adds a PR_TASK_PERF_UEVENT prctl call which can be used by
any process to inject custom data into perf data stream as a new
PERF_RECORD_UEVENT record, if such process is being observed or if it
is running on a CPU being observed by the perf framework.
The prctl call takes the following arguments:
prctl(PR_TASK_PERF_UEVENT, type, size, data, flags);
- type: a number meaning to describe content of the following data.
Kernel does not pay attention to it and merely passes it further in
the perf data, therefore its use must be agreed between the events
producer (the process being observed) and the consumer (performance
analysis tool). The perf userspace tool will contain a repository of
"well known" types and reference implementation of their decoders.
- size: Length in bytes of the data.
- data: Pointer to the data.
- flags: Reserved for future use. Always pass zero.
Perf context that are supposed to receive events generated with the
prctl above must be opened with perf_event_attr.uevent set to 1. The
PERF_RECORD_UEVENT records consist of a standard perf event header,
32-bit type value, 32-bit data size and the data itself, followed by
padding to align the overall record size to 8 bytes and optional,
standard sample_id field.
Example use cases:
- "perf_printf" like mechanism to add logging messages to perf data;
in the simplest case it can be just
prctl(PR_TASK_PERF_UEVENT, 0, 8, "Message", 0);
- synchronisation of performance data generated in user space with the
perf stream coming from the kernel. For example, the marker can be
inserted by a JIT engine after it generated portion of the code, but
before the code is executed for the first time, allowing the
post-processor to pick the correct debugging information.
Signed-off-by: Pawel Moll <[email protected]>
---
include/linux/perf_event.h | 4 +++
include/uapi/linux/perf_event.h | 22 ++++++++++++-
include/uapi/linux/prctl.h | 9 ++++++
kernel/events/core.c | 72 +++++++++++++++++++++++++++++++++++++++++
kernel/sys.c | 5 +++
5 files changed, 111 insertions(+), 1 deletion(-)
diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index 4f7a61c..b6ff319 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -726,6 +726,8 @@ extern int perf_unregister_guest_info_callbacks(struct perf_guest_info_callbacks
extern void perf_event_exec(void);
extern void perf_event_comm(struct task_struct *tsk, bool exec);
extern void perf_event_fork(struct task_struct *tsk);
+extern int perf_uevent(struct task_struct *tsk, u32 type, u32 size,
+ const char __user *data);
/* Callchains */
DECLARE_PER_CPU(struct perf_callchain_entry, perf_callchain_entry);
@@ -834,6 +836,8 @@ static inline void perf_event_mmap(struct vm_area_struct *vma) { }
static inline void perf_event_exec(void) { }
static inline void perf_event_comm(struct task_struct *tsk, bool exec) { }
static inline void perf_event_fork(struct task_struct *tsk) { }
+static inline int perf_uevent(struct task_struct *tsk, u32 type, u32 size,
+ const char __user *data) { return -1; };
static inline void perf_event_init(void) { }
static inline int perf_swevent_get_recursion_context(void) { return -1; }
static inline void perf_swevent_put_recursion_context(int rctx) { }
diff --git a/include/uapi/linux/perf_event.h b/include/uapi/linux/perf_event.h
index 9b79abb..c0cf2b5 100644
--- a/include/uapi/linux/perf_event.h
+++ b/include/uapi/linux/perf_event.h
@@ -305,7 +305,8 @@ struct perf_event_attr {
exclude_callchain_user : 1, /* exclude user callchains */
mmap2 : 1, /* include mmap with inode data */
comm_exec : 1, /* flag comm events that are due to an exec */
- __reserved_1 : 39;
+ uevents : 1, /* allow uevents into the buffer */
+ __reserved_1 : 38;
union {
__u32 wakeup_events; /* wakeup every n events */
@@ -724,6 +725,25 @@ enum perf_event_type {
* };
*/
PERF_RECORD_MMAP2 = 10,
+ /*
+ * Data in userspace event record is transparent for the kernel
+
+ * Userspace perf tool code maintains a list of known types with
+ * reference implementations of parsers for the data field.
+ *
+ * Overall size of the record (including type and size fields)
+ * is always aligned to 8 bytes by adding padding after the data.
+ *
+ * struct {
+ * struct perf_event_header header;
+ * u32 type;
+ * u32 size;
+ * char data[size];
+ * char __padding[-size & 7];
+ * struct sample_id sample_id;
+ * };
+ */
+ PERF_RECORD_UEVENT = 11,
PERF_RECORD_MAX, /* non-ABI */
};
diff --git a/include/uapi/linux/prctl.h b/include/uapi/linux/prctl.h
index 89f6350..fca8940 100644
--- a/include/uapi/linux/prctl.h
+++ b/include/uapi/linux/prctl.h
@@ -184,5 +184,14 @@ struct prctl_mm_map {
*/
#define PR_MPX_ENABLE_MANAGEMENT 43
#define PR_MPX_DISABLE_MANAGEMENT 44
+/*
+ * Perf userspace event generation
+ *
+ * second argument: event type
+ * third argument: data size
+ * fourth argument: pointer to data
+ * fifth argument: flags (currently unused, pass 0)
+ */
+#define PR_TASK_PERF_UEVENT 45
#endif /* _LINUX_PRCTL_H */
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 882f835..a801653 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -5602,6 +5602,78 @@ static void perf_log_throttle(struct perf_event *event, int enable)
}
/*
+ * Userspace-generated event
+ */
+
+struct perf_uevent {
+ struct perf_event_header header;
+ u32 type;
+ u32 size;
+ u8 data[0];
+};
+
+static void perf_uevent_output(struct perf_event *event, void *data)
+{
+ struct perf_uevent *uevent = data;
+ struct perf_output_handle handle;
+ struct perf_sample_data sample;
+ int size = uevent->header.size;
+
+ if (!event->attr.uevents)
+ return;
+
+ perf_event_header__init_id(&uevent->header, &sample, event);
+
+ if (perf_output_begin(&handle, event, uevent->header.size) != 0)
+ goto out;
+ perf_output_put(&handle, uevent->header);
+ perf_output_put(&handle, uevent->type);
+ perf_output_put(&handle, uevent->size);
+ __output_copy(&handle, uevent->data, uevent->size);
+
+ /* Padding to align overall data size to 8 bytes */
+ perf_output_skip(&handle, -uevent->size & (sizeof(u64) - 1));
+
+ perf_event__output_id_sample(event, &handle, &sample);
+
+ perf_output_end(&handle);
+out:
+ uevent->header.size = size;
+}
+
+
+int perf_uevent(struct task_struct *tsk, u32 type, u32 size,
+ const char __user *data)
+{
+ struct perf_uevent *uevent;
+
+ /* Need some reasonable limit */
+ if (size > PAGE_SIZE)
+ return -E2BIG;
+
+ uevent = kmalloc(sizeof(*uevent) + size, GFP_KERNEL);
+ if (!uevent)
+ return -ENOMEM;
+
+ uevent->header.type = PERF_RECORD_UEVENT;
+ uevent->header.size = sizeof(*uevent) + ALIGN(size, sizeof(u64));
+
+ uevent->type = type;
+ uevent->size = size;
+ if (copy_from_user(uevent->data, data, size)) {
+ kfree(uevent);
+ return -EFAULT;
+ }
+
+ perf_event_aux(perf_uevent_output, uevent, NULL);
+
+ kfree(uevent);
+
+ return 0;
+}
+
+
+/*
* Generic event overflow handling, sampling.
*/
diff --git a/kernel/sys.c b/kernel/sys.c
index a8c9f5a..db395ae 100644
--- a/kernel/sys.c
+++ b/kernel/sys.c
@@ -2127,6 +2127,11 @@ SYSCALL_DEFINE5(prctl, int, option, unsigned long, arg2, unsigned long, arg3,
case PR_TASK_PERF_EVENTS_ENABLE:
error = perf_event_task_enable();
break;
+ case PR_TASK_PERF_UEVENT:
+ if (arg5 != 0)
+ return -EINVAL;
+ error = perf_uevent(me, arg2, arg3, (char __user *)arg4);
+ break;
case PR_GET_TIMERSLACK:
error = current->timer_slack_ns;
break;
--
1.8.3.1