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authorSong Liu <songliubraving@fb.com>2021-09-10 11:33:51 -0700
committerAlexei Starovoitov <ast@kernel.org>2021-09-13 10:53:50 -0700
commit856c02dbce4f8d6a5644083db22c11750aa11481 (patch)
tree3c3230ddfc3a5e7a03b30614b3da5aa2cc6cfe86 /tools/include/uapi
parentc22ac2a3d4bd83411ebf0b1726e9e5fc4f5e7ebf (diff)
downloadlinux-856c02dbce4f8d6a5644083db22c11750aa11481.tar.bz2
bpf: Introduce helper bpf_get_branch_snapshot
Introduce bpf_get_branch_snapshot(), which allows tracing pogram to get branch trace from hardware (e.g. Intel LBR). To use the feature, the user need to create perf_event with proper branch_record filtering on each cpu, and then calls bpf_get_branch_snapshot in the bpf function. On Intel CPUs, VLBR event (raw event 0x1b00) can be use for this. Signed-off-by: Song Liu <songliubraving@fb.com> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Acked-by: John Fastabend <john.fastabend@gmail.com> Acked-by: Andrii Nakryiko <andrii@kernel.org> Link: https://lore.kernel.org/bpf/20210910183352.3151445-3-songliubraving@fb.com
Diffstat (limited to 'tools/include/uapi')
-rw-r--r--tools/include/uapi/linux/bpf.h22
1 files changed, 22 insertions, 0 deletions
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index 51cfd91cc387..d21326558d42 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -4877,6 +4877,27 @@ union bpf_attr {
* Get the struct pt_regs associated with **task**.
* Return
* A pointer to struct pt_regs.
+ *
+ * long bpf_get_branch_snapshot(void *entries, u32 size, u64 flags)
+ * Description
+ * Get branch trace from hardware engines like Intel LBR. The
+ * hardware engine is stopped shortly after the helper is
+ * called. Therefore, the user need to filter branch entries
+ * based on the actual use case. To capture branch trace
+ * before the trigger point of the BPF program, the helper
+ * should be called at the beginning of the BPF program.
+ *
+ * The data is stored as struct perf_branch_entry into output
+ * buffer *entries*. *size* is the size of *entries* in bytes.
+ * *flags* is reserved for now and must be zero.
+ *
+ * Return
+ * On success, number of bytes written to *buf*. On error, a
+ * negative value.
+ *
+ * **-EINVAL** if *flags* is not zero.
+ *
+ * **-ENOENT** if architecture does not support branch records.
*/
#define __BPF_FUNC_MAPPER(FN) \
FN(unspec), \
@@ -5055,6 +5076,7 @@ union bpf_attr {
FN(get_func_ip), \
FN(get_attach_cookie), \
FN(task_pt_regs), \
+ FN(get_branch_snapshot), \
/* */
/* integer value in 'imm' field of BPF_CALL instruction selects which helper