[RFC PATCH v3 0/9] fprobe: Introduce fprobe function entry/exit probe

Masami Hiramatsu
2022-01-19T14:56:46Z

Hello Jiri,

Here is the 3rd version of fprobe. I added some comments and
fixed some issues. But I still saw some problems when I add
your selftest patches.

This series introduces the fprobe, the function entry/exit probe
with multiple probe point support. This also introduces the rethook
for hooking function return as same as kretprobe does. This
abstraction will help us to generalize the fgraph tracer,
because we can just switch it from rethook in fprobe, depending
on the kernel configuration.

The patch [1/9] and [7/9] are from Jiri's series[1]. Other libbpf
patches will not be affected by this change.

[1] https://lore.kernel.org/all/20220104080943.113249-1-jolsa@kernel.org/T/#u

However, when I applied all other patches on top of this series,
I saw the "#8 bpf_cookie" test case has been stacked (maybe related
to the bpf_cookie issue which Andrii and Jiri talked?) And when I
remove the last selftest patch[2], the selftest stopped at "#112
raw_tp_test_run".

[2] https://lore.kernel.org/all/20220104080943.113249-1-jolsa@kernel.org/T/#m242d2b3a3775eeb5baba322424b15901e5e78483

Note that I used tools/testing/selftests/bpf/vmtest.sh to check it.

This added 2 more out-of-tree patches. [8/9] is for adding wildcard
support to the sample program, [9/9] is a testing patch for replacing
kretprobe trampoline with rethook.
According to this work, I noticed that using rethook in kretprobe
needs 2 steps.
1. port the rethook on all architectures which supports kretprobes.
(some arch requires CONFIG_KPROBES for rethook)
2. replace kretprobe trampoline with rethook for all archs, at once.
This must be done by one treewide patch.

Anyway, I'll do the kretprobe update in the next step as another series.
(This testing patch is just for confirming the rethook is correctly
implemented.)

BTW, on the x86, ftrace (with fentry) location address is same as
symbol address. But on other archs, it will be different (e.g. arm64
will need 2 instructions to save link-register and call ftrace, the
2nd instruction will be the ftrace location.)
Does libbpf correctly handle it?

Thank you,

---

Jiri Olsa (2):
ftrace: Add ftrace_set_filter_ips function
bpf: Add kprobe link for attaching raw kprobes

Masami Hiramatsu (7):
fprobe: Add ftrace based probe APIs
rethook: Add a generic return hook
rethook: x86: Add rethook x86 implementation
fprobe: Add exit_handler support
fprobe: Add sample program for fprobe
[DO NOT MERGE] Out-of-tree: Support wildcard symbol option to sample
[DO NOT MERGE] out-of-tree: kprobes: Use rethook for kretprobe

arch/x86/Kconfig | 1
arch/x86/include/asm/unwind.h | 8 +
arch/x86/kernel/Makefile | 1
arch/x86/kernel/kprobes/core.c | 106 --------------
arch/x86/kernel/rethook.c | 115 +++++++++++++++
include/linux/bpf_types.h | 1
include/linux/fprobe.h | 84 +++++++++++
include/linux/ftrace.h | 3
include/linux/kprobes.h | 85 +----------
include/linux/rethook.h | 99 +++++++++++++
include/linux/sched.h | 4 -
include/uapi/linux/bpf.h | 12 ++
kernel/bpf/syscall.c | 195 +++++++++++++++++++++++++-
kernel/exit.c | 3
kernel/fork.c | 4 -
kernel/kallsyms.c | 1
kernel/kprobes.c | 265 +++++------------------------------
kernel/trace/Kconfig | 22 +++
kernel/trace/Makefile | 2
kernel/trace/fprobe.c | 179 ++++++++++++++++++++++++
kernel/trace/ftrace.c | 54 ++++++-
kernel/trace/rethook.c | 295 +++++++++++++++++++++++++++++++++++++++
kernel/trace/trace_kprobe.c | 4 -
kernel/trace/trace_output.c | 2
samples/Kconfig | 7 +
samples/Makefile | 1
samples/fprobe/Makefile | 3
samples/fprobe/fprobe_example.c | 154 ++++++++++++++++++++
tools/include/uapi/linux/bpf.h | 12 ++
29 files changed, 1283 insertions(+), 439 deletions(-)
create mode 100644 arch/x86/kernel/rethook.c
create mode 100644 include/linux/fprobe.h
create mode 100644 include/linux/rethook.h
create mode 100644 kernel/trace/fprobe.c
create mode 100644 kernel/trace/rethook.c
create mode 100644 samples/fprobe/Makefile
create mode 100644 samples/fprobe/fprobe_example.c

--
Masami Hiramatsu (Linaro) <mhiramat@kernel.org>