On Thu, Jan 26, 2017 at 11:40:57AM +0200, Alexander Shishkin wrote:
> While supporting file-based address filters for cpu events requires some
> extra context switch handling, kernel address filters are easy, since the
> kernel mapping is preserved across address spaces. It is also useful as
> it permits tracing scheduling paths of the kernel.
>
> This patch allows setting up kernel filters for cpu events.
>
> Signed-off-by: Alexander Shishkin <[email protected]>
> Cc: Mathieu Poirier <[email protected]>
> ---
> include/linux/perf_event.h | 2 ++
> kernel/events/core.c | 42 ++++++++++++++++++++++++++++--------------
> 2 files changed, 30 insertions(+), 14 deletions(-)
>
> diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
> index fcb37c81ca..f4ea0600b2 100644
> --- a/include/linux/perf_event.h
> +++ b/include/linux/perf_event.h
> @@ -486,6 +486,7 @@ struct perf_addr_filter {
> * @list: list of filters for this event
> * @lock: spinlock that serializes accesses to the @list and event's
> * (and its children's) filter generations.
> + * @nr_file_filters: number of file-based filters
> *
> * A child event will use parent's @list (and therefore @lock), so they are
> * bundled together; see perf_event_addr_filters().
> @@ -493,6 +494,7 @@ struct perf_addr_filter {
> struct perf_addr_filters_head {
> struct list_head list;
> raw_spinlock_t lock;
> + unsigned int nr_file_filters;
> };
>
> /**
> diff --git a/kernel/events/core.c b/kernel/events/core.c
> index 36770a13ef..2eeb8fec2f 100644
> --- a/kernel/events/core.c
> +++ b/kernel/events/core.c
> @@ -8093,6 +8093,9 @@ static void perf_event_addr_filters_apply(struct
> perf_event *event)
> if (task == TASK_TOMBSTONE)
> return;
>
> + if (!ifh->nr_file_filters)
> + return;
Is this mandatory or an optimisation to avoid circling through a list of filters
that don't included user space files?
> +
> mm = get_task_mm(event->ctx->task);
> if (!mm)
> goto restart;
> @@ -8269,6 +8272,18 @@ perf_event_parse_addr_filter(struct perf_event *event,
> char *fstr,
> if (!filename)
> goto fail;
>
> + /*
> + * For now, we only support file-based filters
> + * in per-task events; doing so for CPU-wide
> + * events requires additional context switching
> + * trickery, since same object code will be
> + * mapped at different virtual addresses in
> + * different processes.
> + */
> + ret = -EOPNOTSUPP;
> + if (!event->ctx->task)
> + goto fail_free_name;
> +
> /* look up the path and grab its inode */
> ret = kern_path(filename, LOOKUP_FOLLOW, &path);
> if (ret)
> @@ -8284,6 +8299,8 @@ perf_event_parse_addr_filter(struct perf_event *event,
> char *fstr,
> !S_ISREG(filter->inode->i_mode))
> /* free_filters_list() will iput() */
> goto fail;
> +
> + event->addr_filters.nr_file_filters++;
> }
>
> /* ready to consume more filters */
> @@ -8323,24 +8340,13 @@ perf_event_set_addr_filter(struct perf_event *event,
> char *filter_str)
> if (WARN_ON_ONCE(event->parent))
> return -EINVAL;
>
> - /*
> - * For now, we only support filtering in per-task events; doing so
> - * for CPU-wide events requires additional context switching trickery,
> - * since same object code will be mapped at different virtual
> - * addresses in different processes.
> - */
> - if (!event->ctx->task)
> - return -EOPNOTSUPP;
> -
> ret = perf_event_parse_addr_filter(event, filter_str, &filters);
> if (ret)
> - return ret;
> + goto fail_clear_files;
>
> ret = event->pmu->addr_filters_validate(&filters);
> - if (ret) {
> - free_filters_list(&filters);
> - return ret;
> - }
> + if (ret)
> + goto fail_free_filters;
>
> /* remove existing filters, if any */
> perf_addr_filters_splice(event, &filters);
> @@ -8349,6 +8355,14 @@ perf_event_set_addr_filter(struct perf_event *event,
> char *filter_str)
> perf_event_for_each_child(event, perf_event_addr_filters_apply);
>
> return ret;
> +
> +fail_free_filters:
> + free_filters_list(&filters);
> +
> +fail_clear_files:
> + event->addr_filters.nr_file_filters = 0;
> +
> + return ret;
> }
>
> static int perf_event_set_filter(struct perf_event *event, void __user *arg)
> --
> 2.11.0
>
