| Message ID | 20200929084750.419168-2-songliubraving@fb.com |
|---|---|
| State | New |
| Headers | show |
| Series | introduce BPF_F_SHARE_PE | expand |
On 9/29/20 10:47 AM, Song Liu wrote: > Currently, perf event in perf event array is removed from the array when > the map fd used to add the event is closed. This behavior makes it > difficult to the share perf events with perf event array. > > Introduce perf event map that keeps the perf event open with a new flag > BPF_F_SHARE_PE. With this flag set, perf events in the array are not > removed when the original map fd is closed. Instead, the perf event will > stay in the map until 1) it is explicitly removed from the array; or 2) > the array is freed. > > Signed-off-by: Song Liu <songliubraving@fb.com> > --- > include/uapi/linux/bpf.h | 3 +++ > kernel/bpf/arraymap.c | 31 +++++++++++++++++++++++++++++-- > tools/include/uapi/linux/bpf.h | 3 +++ > 3 files changed, 35 insertions(+), 2 deletions(-) > > diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h > index 82522f05c0213..74f7a09e9d1e3 100644 > --- a/include/uapi/linux/bpf.h > +++ b/include/uapi/linux/bpf.h > @@ -414,6 +414,9 @@ enum { > > /* Enable memory-mapping BPF map */ > BPF_F_MMAPABLE = (1U << 10), > + > +/* Share perf_event among processes */ > + BPF_F_SHARE_PE = (1U << 11), nit but given UAPI: maybe name into something more self-descriptive like BPF_F_SHAREABLE_EVENT ? > }; > > /* Flags for BPF_PROG_QUERY. */ > diff --git a/kernel/bpf/arraymap.c b/kernel/bpf/arraymap.c > index e5fd31268ae02..4938ff183d846 100644 > --- a/kernel/bpf/arraymap.c > +++ b/kernel/bpf/arraymap.c > @@ -15,7 +15,7 @@ > #include "map_in_map.h" > > #define ARRAY_CREATE_FLAG_MASK \ > - (BPF_F_NUMA_NODE | BPF_F_MMAPABLE | BPF_F_ACCESS_MASK) > + (BPF_F_NUMA_NODE | BPF_F_MMAPABLE | BPF_F_ACCESS_MASK | BPF_F_SHARE_PE) > > static void bpf_array_free_percpu(struct bpf_array *array) > { > @@ -64,6 +64,10 @@ int array_map_alloc_check(union bpf_attr *attr) > attr->map_flags & BPF_F_MMAPABLE) > return -EINVAL; > > + if (attr->map_type != BPF_MAP_TYPE_PERF_EVENT_ARRAY && > + attr->map_flags & BPF_F_SHARE_PE) > + return -EINVAL; > + > if (attr->value_size > KMALLOC_MAX_SIZE) > /* if value_size is bigger, the user space won't be able to > * access the elements. > @@ -778,6 +782,26 @@ static int fd_array_map_delete_elem(struct bpf_map *map, void *key) > } > } > > +static void perf_event_fd_array_map_free(struct bpf_map *map) > +{ > + struct bpf_event_entry *ee; > + struct bpf_array *array; > + int i; > + > + if ((map->map_flags & BPF_F_SHARE_PE) == 0) { > + fd_array_map_free(map); > + return; > + } > + > + array = container_of(map, struct bpf_array, map); > + for (i = 0; i < array->map.max_entries; i++) { > + ee = READ_ONCE(array->ptrs[i]); > + if (ee) > + fd_array_map_delete_elem(map, &i); > + } > + bpf_map_area_free(array); Why not simplify into: if (map->map_flags & BPF_F_SHAREABLE_EVENT) bpf_fd_array_map_clear(map); fd_array_map_free(map); > +} > + > static void *prog_fd_array_get_ptr(struct bpf_map *map, > struct file *map_file, int fd) > { > @@ -1134,6 +1158,9 @@ static void perf_event_fd_array_release(struct bpf_map *map, > struct bpf_event_entry *ee; > int i; > > + if (map->map_flags & BPF_F_SHARE_PE) > + return; > + > rcu_read_lock(); > for (i = 0; i < array->map.max_entries; i++) { > ee = READ_ONCE(array->ptrs[i]); > @@ -1148,7 +1175,7 @@ const struct bpf_map_ops perf_event_array_map_ops = { > .map_meta_equal = bpf_map_meta_equal, > .map_alloc_check = fd_array_map_alloc_check, > .map_alloc = array_map_alloc, > - .map_free = fd_array_map_free, > + .map_free = perf_event_fd_array_map_free, > .map_get_next_key = array_map_get_next_key, > .map_lookup_elem = fd_array_map_lookup_elem, > .map_delete_elem = fd_array_map_delete_elem, > diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h > index 82522f05c0213..74f7a09e9d1e3 100644 > --- a/tools/include/uapi/linux/bpf.h > +++ b/tools/include/uapi/linux/bpf.h > @@ -414,6 +414,9 @@ enum { > > /* Enable memory-mapping BPF map */ > BPF_F_MMAPABLE = (1U << 10), > + > +/* Share perf_event among processes */ > + BPF_F_SHARE_PE = (1U << 11), > }; > > /* Flags for BPF_PROG_QUERY. */ >
On Tue, Sep 29, 2020 at 04:02:10PM +0200, Daniel Borkmann wrote: > > + > > +/* Share perf_event among processes */ > > + BPF_F_SHARE_PE = (1U << 11), > > nit but given UAPI: maybe name into something more self-descriptive > like BPF_F_SHAREABLE_EVENT ? I'm not happy with either name. It's not about sharing and not really about perf event. I think the current behavior of perf_event_array is unusual and surprising. Sadly we cannot fix it without breaking user space, so flag is needed. How about BPF_F_STICKY_OBJECTS or BPF_F_PRESERVE_OBJECTS or the same with s/OBJECTS/FILES/ ? > > +static void perf_event_fd_array_map_free(struct bpf_map *map) > > +{ > > + struct bpf_event_entry *ee; > > + struct bpf_array *array; > > + int i; > > + > > + if ((map->map_flags & BPF_F_SHARE_PE) == 0) { > > + fd_array_map_free(map); > > + return; > > + } > > + > > + array = container_of(map, struct bpf_array, map); > > + for (i = 0; i < array->map.max_entries; i++) { > > + ee = READ_ONCE(array->ptrs[i]); > > + if (ee) > > + fd_array_map_delete_elem(map, &i); > > + } > > + bpf_map_area_free(array); > > Why not simplify into: > > if (map->map_flags & BPF_F_SHAREABLE_EVENT) > bpf_fd_array_map_clear(map); > fd_array_map_free(map); +1 > > +} > > + > > static void *prog_fd_array_get_ptr(struct bpf_map *map, > > struct file *map_file, int fd) > > { > > @@ -1134,6 +1158,9 @@ static void perf_event_fd_array_release(struct bpf_map *map, > > struct bpf_event_entry *ee; > > int i; add empty line pls. > > + if (map->map_flags & BPF_F_SHARE_PE) > > + return; > > +
On 9/29/20 9:00 PM, Alexei Starovoitov wrote: > On Tue, Sep 29, 2020 at 04:02:10PM +0200, Daniel Borkmann wrote: >>> + >>> +/* Share perf_event among processes */ >>> + BPF_F_SHARE_PE = (1U << 11), >> >> nit but given UAPI: maybe name into something more self-descriptive >> like BPF_F_SHAREABLE_EVENT ? > > I'm not happy with either name. > It's not about sharing and not really about perf event. > I think the current behavior of perf_event_array is unusual and surprising. > Sadly we cannot fix it without breaking user space, so flag is needed. > How about BPF_F_STICKY_OBJECTS or BPF_F_PRESERVE_OBJECTS > or the same with s/OBJECTS/FILES/ ? Sounds good to me, BPF_F_PRESERVE_OBJECTS or _ENTRIES seems reasonable. >>> +static void perf_event_fd_array_map_free(struct bpf_map *map) >>> +{ >>> + struct bpf_event_entry *ee; >>> + struct bpf_array *array; >>> + int i; >>> + >>> + if ((map->map_flags & BPF_F_SHARE_PE) == 0) { >>> + fd_array_map_free(map); >>> + return; >>> + } >>> + >>> + array = container_of(map, struct bpf_array, map); >>> + for (i = 0; i < array->map.max_entries; i++) { >>> + ee = READ_ONCE(array->ptrs[i]); >>> + if (ee) >>> + fd_array_map_delete_elem(map, &i); >>> + } >>> + bpf_map_area_free(array); >> >> Why not simplify into: >> >> if (map->map_flags & BPF_F_SHAREABLE_EVENT) >> bpf_fd_array_map_clear(map); >> fd_array_map_free(map); > > +1 > >>> +} >>> + >>> static void *prog_fd_array_get_ptr(struct bpf_map *map, >>> struct file *map_file, int fd) >>> { >>> @@ -1134,6 +1158,9 @@ static void perf_event_fd_array_release(struct bpf_map *map, >>> struct bpf_event_entry *ee; >>> int i; > > add empty line pls. > >>> + if (map->map_flags & BPF_F_SHARE_PE) >>> + return; >>> +
On Tue, Sep 29, 2020 at 12:18 PM Daniel Borkmann <daniel@iogearbox.net> wrote: > > On 9/29/20 9:00 PM, Alexei Starovoitov wrote: > > On Tue, Sep 29, 2020 at 04:02:10PM +0200, Daniel Borkmann wrote: > >>> + > >>> +/* Share perf_event among processes */ > >>> + BPF_F_SHARE_PE = (1U << 11), > >> > >> nit but given UAPI: maybe name into something more self-descriptive > >> like BPF_F_SHAREABLE_EVENT ? > > > > I'm not happy with either name. > > It's not about sharing and not really about perf event. > > I think the current behavior of perf_event_array is unusual and surprising. > > Sadly we cannot fix it without breaking user space, so flag is needed. > > How about BPF_F_STICKY_OBJECTS or BPF_F_PRESERVE_OBJECTS > > or the same with s/OBJECTS/FILES/ ? > > Sounds good to me, BPF_F_PRESERVE_OBJECTS or _ENTRIES seems reasonable. May be BPF_F_PRESERVE_ELEMENTS? or _ELEMS ? I think we refer to map elements more often as elements instead of entries. But both _entries and _elems work for me.
> On Sep 29, 2020, at 12:28 PM, Alexei Starovoitov <alexei.starovoitov@gmail.com> wrote: > > On Tue, Sep 29, 2020 at 12:18 PM Daniel Borkmann <daniel@iogearbox.net> wrote: >> >> On 9/29/20 9:00 PM, Alexei Starovoitov wrote: >>> On Tue, Sep 29, 2020 at 04:02:10PM +0200, Daniel Borkmann wrote: >>>>> + >>>>> +/* Share perf_event among processes */ >>>>> + BPF_F_SHARE_PE = (1U << 11), >>>> >>>> nit but given UAPI: maybe name into something more self-descriptive >>>> like BPF_F_SHAREABLE_EVENT ? >>> >>> I'm not happy with either name. >>> It's not about sharing and not really about perf event. >>> I think the current behavior of perf_event_array is unusual and surprising. >>> Sadly we cannot fix it without breaking user space, so flag is needed. >>> How about BPF_F_STICKY_OBJECTS or BPF_F_PRESERVE_OBJECTS >>> or the same with s/OBJECTS/FILES/ ? >> >> Sounds good to me, BPF_F_PRESERVE_OBJECTS or _ENTRIES seems reasonable. > > May be BPF_F_PRESERVE_ELEMENTS? > or _ELEMS ? > I think we refer to map elements more often as elements instead of entries. > But both _entries and _elems work for me. BPF_F_PRESERVE_ELEMS sounds best to me. I will go ahead with it. Thanks, Song
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h index 82522f05c0213..74f7a09e9d1e3 100644 --- a/include/uapi/linux/bpf.h +++ b/include/uapi/linux/bpf.h @@ -414,6 +414,9 @@ enum { /* Enable memory-mapping BPF map */ BPF_F_MMAPABLE = (1U << 10), + +/* Share perf_event among processes */ + BPF_F_SHARE_PE = (1U << 11), }; /* Flags for BPF_PROG_QUERY. */ diff --git a/kernel/bpf/arraymap.c b/kernel/bpf/arraymap.c index e5fd31268ae02..4938ff183d846 100644 --- a/kernel/bpf/arraymap.c +++ b/kernel/bpf/arraymap.c @@ -15,7 +15,7 @@ #include "map_in_map.h" #define ARRAY_CREATE_FLAG_MASK \ - (BPF_F_NUMA_NODE | BPF_F_MMAPABLE | BPF_F_ACCESS_MASK) + (BPF_F_NUMA_NODE | BPF_F_MMAPABLE | BPF_F_ACCESS_MASK | BPF_F_SHARE_PE) static void bpf_array_free_percpu(struct bpf_array *array) { @@ -64,6 +64,10 @@ int array_map_alloc_check(union bpf_attr *attr) attr->map_flags & BPF_F_MMAPABLE) return -EINVAL; + if (attr->map_type != BPF_MAP_TYPE_PERF_EVENT_ARRAY && + attr->map_flags & BPF_F_SHARE_PE) + return -EINVAL; + if (attr->value_size > KMALLOC_MAX_SIZE) /* if value_size is bigger, the user space won't be able to * access the elements. @@ -778,6 +782,26 @@ static int fd_array_map_delete_elem(struct bpf_map *map, void *key) } } +static void perf_event_fd_array_map_free(struct bpf_map *map) +{ + struct bpf_event_entry *ee; + struct bpf_array *array; + int i; + + if ((map->map_flags & BPF_F_SHARE_PE) == 0) { + fd_array_map_free(map); + return; + } + + array = container_of(map, struct bpf_array, map); + for (i = 0; i < array->map.max_entries; i++) { + ee = READ_ONCE(array->ptrs[i]); + if (ee) + fd_array_map_delete_elem(map, &i); + } + bpf_map_area_free(array); +} + static void *prog_fd_array_get_ptr(struct bpf_map *map, struct file *map_file, int fd) { @@ -1134,6 +1158,9 @@ static void perf_event_fd_array_release(struct bpf_map *map, struct bpf_event_entry *ee; int i; + if (map->map_flags & BPF_F_SHARE_PE) + return; + rcu_read_lock(); for (i = 0; i < array->map.max_entries; i++) { ee = READ_ONCE(array->ptrs[i]); @@ -1148,7 +1175,7 @@ const struct bpf_map_ops perf_event_array_map_ops = { .map_meta_equal = bpf_map_meta_equal, .map_alloc_check = fd_array_map_alloc_check, .map_alloc = array_map_alloc, - .map_free = fd_array_map_free, + .map_free = perf_event_fd_array_map_free, .map_get_next_key = array_map_get_next_key, .map_lookup_elem = fd_array_map_lookup_elem, .map_delete_elem = fd_array_map_delete_elem, diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h index 82522f05c0213..74f7a09e9d1e3 100644 --- a/tools/include/uapi/linux/bpf.h +++ b/tools/include/uapi/linux/bpf.h @@ -414,6 +414,9 @@ enum { /* Enable memory-mapping BPF map */ BPF_F_MMAPABLE = (1U << 10), + +/* Share perf_event among processes */ + BPF_F_SHARE_PE = (1U << 11), }; /* Flags for BPF_PROG_QUERY. */
Currently, perf event in perf event array is removed from the array when the map fd used to add the event is closed. This behavior makes it difficult to the share perf events with perf event array. Introduce perf event map that keeps the perf event open with a new flag BPF_F_SHARE_PE. With this flag set, perf events in the array are not removed when the original map fd is closed. Instead, the perf event will stay in the map until 1) it is explicitly removed from the array; or 2) the array is freed. Signed-off-by: Song Liu <songliubraving@fb.com> --- include/uapi/linux/bpf.h | 3 +++ kernel/bpf/arraymap.c | 31 +++++++++++++++++++++++++++++-- tools/include/uapi/linux/bpf.h | 3 +++ 3 files changed, 35 insertions(+), 2 deletions(-)