| Message ID | 20180518053253.2908444-1-yhs@fb.com |
|---|---|
| State | RFC, archived |
| Delegated to: | BPF Maintainers |
| Headers | show |
| Series | [bpf-next,v2,1/7] perf/core: add perf_get_event() to return perf_event given a struct file | expand |
On Thu, May 17, 2018 at 10:32:53PM -0700, Yonghong Song wrote: > A new extern function, perf_get_event(), is added to return a perf event > given a struct file. This function will be used in later patches. Can't you do a narrower interface? Like return the prog. I'm not too keen on random !perf code frobbing around inside the event.
On 5/18/18 12:18 AM, Peter Zijlstra wrote: > On Thu, May 17, 2018 at 10:32:53PM -0700, Yonghong Song wrote: >> A new extern function, perf_get_event(), is added to return a perf event >> given a struct file. This function will be used in later patches. > > Can't you do a narrower interface? Like return the prog. I'm not too > keen on random !perf code frobbing around inside the event. Hi, Peter, My initial implementation (not upstreamed) actually have the whole function bpf_get_perf_event_info() in the events/core.c. In that case, the "struct file *" pointer is passed. This way, the event pointer does not need to go to kernel/bpf/syscall.c or kernel/trace/bpf_trace.c. I dropped this mechanism since it added more codes in the events/core.c file, and I felt that such query code might clutter events/core.c. The function bpf_get_perf_event_info() is now placed in kernel/trace/bpf_trace.c. Just getting bpf prog pointer is not enough as it does not provide enough attachment information. Getting such information requires poking into event/tp_event etc. Currently we have this extern function exposed by events/core.c: extern struct perf_event *perf_get_event(struct file *file); We could make the result value "const" like extern const struct perf_event *perf_get_event(struct file *file); This will make it clear that we do not change "event" fields, and merely poking at it. Please let me know your preference. Thanks! Yonghong
diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h index e71e99e..b5c1ad3 100644 --- a/include/linux/perf_event.h +++ b/include/linux/perf_event.h @@ -868,6 +868,7 @@ extern void perf_event_exit_task(struct task_struct *child); extern void perf_event_free_task(struct task_struct *task); extern void perf_event_delayed_put(struct task_struct *task); extern struct file *perf_event_get(unsigned int fd); +extern struct perf_event *perf_get_event(struct file *file); extern const struct perf_event_attr *perf_event_attrs(struct perf_event *event); extern void perf_event_print_debug(void); extern void perf_pmu_disable(struct pmu *pmu); @@ -1289,6 +1290,10 @@ static inline void perf_event_exit_task(struct task_struct *child) { } static inline void perf_event_free_task(struct task_struct *task) { } static inline void perf_event_delayed_put(struct task_struct *task) { } static inline struct file *perf_event_get(unsigned int fd) { return ERR_PTR(-EINVAL); } +static inline struct perf_event *perf_get_event(struct file *file) +{ + return ERR_PTR(-EINVAL); +} static inline const struct perf_event_attr *perf_event_attrs(struct perf_event *event) { return ERR_PTR(-EINVAL); diff --git a/kernel/events/core.c b/kernel/events/core.c index 67612ce..1e3cddb 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -11212,6 +11212,14 @@ struct file *perf_event_get(unsigned int fd) return file; } +struct perf_event *perf_get_event(struct file *file) +{ + if (file->f_op != &perf_fops) + return ERR_PTR(-EINVAL); + + return file->private_data; +} + const struct perf_event_attr *perf_event_attrs(struct perf_event *event) { if (!event)
A new extern function, perf_get_event(), is added to return a perf event given a struct file. This function will be used in later patches. Signed-off-by: Yonghong Song <yhs@fb.com> --- include/linux/perf_event.h | 5 +++++ kernel/events/core.c | 8 ++++++++ 2 files changed, 13 insertions(+)