A-Team_Digital_Solutions/android_kernel_motorola_sm6375
Watch
2
0
Fork
You've already forked android_kernel_motorola_sm6375
 0
mirror of https://github.com/BobTheBlinker/android_kernel_motorola_sm6375.git synced 2026-10-07 12:25:00 -04:00
Code Issues Projects Releases Packages Wiki Activity

BACKPORT: bpf: Add bpf_read_branch_records() helper

Browse source 
Branch records are a CPU feature that can be configured to record
certain branches that are taken during code execution. This data is
particularly interesting for profile guided optimizations. perf has had
branch record support for a while but the data collection can be a bit
coarse grained.

We (Facebook) have seen in experiments that associating metadata with
branch records can improve results (after postprocessing). We generally
use bpf_probe_read_*() to get metadata out of userspace. That's why bpf
support for branch records is useful.

Aside from this particular use case, having branch data available to bpf
progs can be useful to get stack traces out of userspace applications
that omit frame pointers.

Change-Id: I6475b600df60571d1b0daa985eff1ee01c8886eb
Signed-off-by: Daniel Xu <dxu@dxuuu.xyz>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Link: https://lore.kernel.org/bpf/20200218030432.4600-2-dxu@dxuuu.xyz
This commit is contained in:
Daniel Xu 2020-02-17 19:04:31 -08:00 • committed by basamaryan
commit 9abe700c5b
No known key found for this signature in database
GPG key ID: 210D5384FB2A5885
2 changed files with 63 additions and 0 deletions
Download patch file Download diff file Expand all files Collapse all files

22
include/uapi/linux/bpf.h
View file

@ -2902,6 +2902,25 @@ union bpf_attr {
* Obtain the 64bit jiffies
* Return
* The 64 bit jiffies
*
* int bpf_read_branch_records(struct bpf_perf_event_data *ctx, void *buf, u32 size, u64 flags)
* Description
* For an eBPF program attached to a perf event, retrieve the
* branch records (struct perf_branch_entry) associated to *ctx*
* and store it in the buffer pointed by *buf* up to size
* *size* bytes.
* Return
* On success, number of bytes written to *buf*. On error, a
* negative value.
*
* The *flags* can be set to **BPF_F_GET_BRANCH_RECORDS_SIZE** to
* instead return the number of bytes required to store all the
* branch entries. If this flag is set, *buf* may be NULL.
*
* **-EINVAL** if arguments invalid or **size** not a multiple
* of sizeof(struct perf_branch_entry).
*
* **-ENOENT** if architecture does not support branch records.
*/
#define __BPF_FUNC_MAPPER(FN) \
FN(unspec), \
@ -3108,6 +3127,9 @@ enum bpf_func_id {
/* BPF_FUNC_sk_storage_get flags */
#define BPF_SK_STORAGE_GET_F_CREATE (1ULL << 0)
/* BPF_FUNC_read_branch_records flags. */
#define BPF_F_GET_BRANCH_RECORDS_SIZE (1ULL << 0)
/* Mode for BPF_FUNC_skb_adjust_room helper. */
enum bpf_adj_room_mode {
BPF_ADJ_ROOM_NET,