[PATCHv3 bpf-next 00/13] bpf: Add kprobe multi link

Jiri Olsa
2022-03-16T12:24:33Z

hi,
this patchset adds new link type BPF_TRACE_KPROBE_MULTI that attaches
kprobe program through fprobe API [1] instroduced by Masami.

The fprobe API allows to attach probe on multiple functions at once very
fast, because it works on top of ftrace. On the other hand this limits
the probe point to the function entry or return.

With bpftrace support I see following attach speed:

# perf stat --null -r 5 ./src/bpftrace -e 'kprobe:x* { } i:ms:1 { exit(); } '
Attaching 2 probes...
Attaching 3342 functions
...

1.4960 +- 0.0285 seconds time elapsed ( +- 1.91% )

v3 changes:
- based on latest fprobe post from Masami [2]
- add acks
- add extra comment to kprobe_multi_link_handler wrt entry ip setup [Masami]
- keep swap_words_64 static and swap values directly in
bpf_kprobe_multi_cookie_swap [Andrii]
- rearrange locking/migrate setup in kprobe_multi_link_prog_run [Andrii]
- move uapi fields [Andrii]
- add bpf_program__attach_kprobe_multi_opts function [Andrii]
- many small test changes [Andrii]
- added tests for bpf_program__attach_kprobe_multi_opts
- make kallsyms_lookup_name check for empty string [Andrii]

v2 changes:
- based on latest fprobe changes [1]
- renaming the uapi interface to kprobe multi
- adding support for sort_r to pass user pointer for swap functions
and using that in cookie support to keep just single functions array
- moving new link to kernel/trace/bpf_trace.c file
- using single fprobe callback function for entry and exit
- using kvzalloc, libbpf_ensure_mem functions
- adding new k[ret]probe.multi sections instead of using current kprobe
- used glob_match from test_progs.c, added '?' matching
- move bpf_get_func_ip verifier inline change to seprate change
- couple of other minor fixes

Also available at:
https://git.kernel.org/pub/scm/linux/kernel/git/jolsa/perf.git
bpf/kprobe_multi

thanks,
jirka

[1] https://lore.kernel.org/bpf/164458044634.586276.3261555265565111183.stgit@devnote2/
[2] https://lore.kernel.org/bpf/164735281449.1084943.12438881786173547153.stgit@devnote2/
---
Jiri Olsa (13):
lib/sort: Add priv pointer to swap function
kallsyms: Skip the name search for empty string
bpf: Add multi kprobe link
bpf: Add bpf_get_func_ip kprobe helper for multi kprobe link
bpf: Add support to inline bpf_get_func_ip helper on x86
bpf: Add cookie support to programs attached with kprobe multi link
libbpf: Add libbpf_kallsyms_parse function
libbpf: Add bpf_link_create support for multi kprobes
libbpf: Add bpf_program__attach_kprobe_multi_opts function
selftests/bpf: Add kprobe_multi attach test
selftests/bpf: Add kprobe_multi bpf_cookie test
selftests/bpf: Add attach test for bpf_program__attach_kprobe_multi_opts
selftests/bpf: Add cookie test for bpf_program__attach_kprobe_multi_opts

include/linux/bpf_types.h | 1 +
include/linux/sort.h | 2 +-
include/linux/trace_events.h | 7 ++
include/linux/types.h | 1 +
include/uapi/linux/bpf.h | 14 ++++
kernel/bpf/syscall.c | 26 +++++--
kernel/bpf/verifier.c | 21 +++++-
kernel/kallsyms.c | 4 ++
kernel/trace/bpf_trace.c | 342 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++-
lib/sort.c | 40 ++++++++---
tools/include/uapi/linux/bpf.h | 14 ++++
tools/lib/bpf/bpf.c | 9 +++
tools/lib/bpf/bpf.h | 9 ++-
tools/lib/bpf/libbpf.c | 222 +++++++++++++++++++++++++++++++++++++++++++++++++++++-------
tools/lib/bpf/libbpf.h | 23 +++++++
tools/lib/bpf/libbpf.map | 1 +
tools/lib/bpf/libbpf_internal.h | 5 ++
tools/testing/selftests/bpf/prog_tests/bpf_cookie.c | 177 ++++++++++++++++++++++++++++++++++++++++++++++++
tools/testing/selftests/bpf/prog_tests/kprobe_multi_test.c | 323 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
tools/testing/selftests/bpf/progs/kprobe_multi.c | 98 +++++++++++++++++++++++++++
tools/testing/selftests/bpf/trace_helpers.c | 7 ++
21 files changed, 1302 insertions(+), 44 deletions(-)
create mode 100644 tools/testing/selftests/bpf/prog_tests/kprobe_multi_test.c
create mode 100644 tools/testing/selftests/bpf/progs/kprobe_multi.c