[PATCHv5 bpf-next 0/8] uprobe: uretprobe speed up

Jiri Olsa
2024-05-07T10:53:29Z

hi,
as part of the effort on speeding up the uprobes [0] coming with
return uprobe optimization by using syscall instead of the trap
on the uretprobe trampoline.

The speed up depends on instruction type that uprobe is installed
and depends on specific HW type, please check patch 1 for details.

Patches 1-7 are based on bpf-next/master, but path 1 and 2 are
apply-able on linux-trace.git tree probes/for-next branch.
Patch 8 is based on man-pages master.

v5 changes:
- added shadow stack support for uretprobe [peterz]
- reworded man page + typos [Alejandro Colom]
- added pipe ASSERT_OK [Andrii]
- added acks [Andrii]
- removed compat test for now before ci is fixed

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

thanks,
jirka

Notes to check list items in Documentation/process/adding-syscalls.rst:

- System Call Alternatives
New syscall seems like the best way in here, because we need
just to quickly enter kernel with no extra arguments processing,
which we'd need to do if we decided to use another syscall.

- Designing the API: Planning for Extension
The uretprobe syscall is very specific and most likely won't be
extended in the future.

At the moment it does not take any arguments and even if it does
in future, it's allowed to be called only from trampoline prepared
by kernel, so there'll be no broken user.

- Designing the API: Other Considerations
N/A because uretprobe syscall does not return reference to kernel
object.

- Proposing the API
Wiring up of the uretprobe system call is in separate change,
selftests and man page changes are part of the patchset.

- Generic System Call Implementation
There's no CONFIG option for the new functionality because it
keeps the same behaviour from the user POV.

- x86 System Call Implementation
It's 64-bit syscall only.

- Compatibility System Calls (Generic)
N/A uretprobe syscall has no arguments and is not supported
for compat processes.

- Compatibility System Calls (x86)
N/A uretprobe syscall is not supported for compat processes.

- System Calls Returning Elsewhere
N/A.

- Other Details
N/A.

- Testing
Adding new bpf selftests and ran ltp on top of this change.

- Man Page
Attached.

- Do not call System Calls in the Kernel
N/A.

[0] https://lore.kernel.org/bpf/ZeCXHKJ--iYYbmLj@krava/
---
Jiri Olsa (7):
uprobe: Wire up uretprobe system call
uprobe: Add uretprobe syscall to speed up return probe
selftests/bpf: Add uretprobe syscall test for regs integrity
selftests/bpf: Add uretprobe syscall test for regs changes
selftests/bpf: Add uretprobe syscall call from user space test
x86/shstk: Add return uprobe support
selftests/x86: Add return uprobe shadow stack test

arch/x86/entry/syscalls/syscall_64.tbl | 1 +
arch/x86/include/asm/shstk.h | 4 ++
arch/x86/kernel/shstk.c | 29 +++++++++
arch/x86/kernel/uprobes.c | 127 +++++++++++++++++++++++++++++++++++-
include/linux/syscalls.h | 2 +
include/linux/uprobes.h | 3 +
include/uapi/asm-generic/unistd.h | 5 +-
kernel/events/uprobes.c | 24 +++++--
kernel/sys_ni.c | 2 +
tools/include/linux/compiler.h | 4 ++
tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c | 123 ++++++++++++++++++++++++++++++++++-
tools/testing/selftests/bpf/prog_tests/uprobe_syscall.c | 325 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
tools/testing/selftests/bpf/progs/uprobe_syscall.c | 15 +++++
tools/testing/selftests/bpf/progs/uprobe_syscall_executed.c | 17 +++++
tools/testing/selftests/x86/test_shadow_stack.c | 142 ++++++++++++++++++++++++++++++++++++++++
15 files changed, 813 insertions(+), 10 deletions(-)
create mode 100644 tools/testing/selftests/bpf/prog_tests/uprobe_syscall.c
create mode 100644 tools/testing/selftests/bpf/progs/uprobe_syscall.c
create mode 100644 tools/testing/selftests/bpf/progs/uprobe_syscall_executed.c

Jiri Olsa (1):
man2: Add uretprobe syscall page

man2/uretprobe.2 | 50 ++++++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 50 insertions(+)
create mode 100644 man2/uretprobe.2