[RFC,bpf-next,0/3] uprobe: uretprobe speed up

Message

Jiri Olsa March 18, 2024, 9:31 a.m. UTC

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.

I added extra bpf selftest to check on registers values before and
after uretprobe to make sure the syscall saves all the needed regs.

reasons for this being RFC:

 - I'm not sure we want specific uretprobe syscall and not generic
   uprobe syscall to extend in future.. when I added extra code to
   read registers from stack I did not see any notable performance
   degradation, so I think we could survive restoring another register
   for argument

 - I'm not sure how we want to handle assembly code in bpf selftests

thanks,
jirka


[0] https://lore.kernel.org/bpf/ZeCXHKJ--iYYbmLj@krava/
---
Jiri Olsa (3):
      uprobe: Add uretprobe syscall to speed up return probe
      selftests/bpf: Add uretprobe syscall test
      selftests/bpf: Mark uprobe trigger functions with nocf_check attribute

 arch/x86/entry/syscalls/syscall_64.tbl                           |  1 +
 arch/x86/kernel/uprobes.c                                        | 48 ++++++++++++++++++++++++++++++++++++++++++++++++
 include/linux/syscalls.h                                         |  2 ++
 include/linux/uprobes.h                                          |  2 ++
 include/uapi/asm-generic/unistd.h                                |  5 ++++-
 kernel/events/uprobes.c                                          | 18 ++++++++++++++----
 kernel/sys_ni.c                                                  |  2 ++
 tools/include/linux/compiler.h                                   |  4 ++++
 tools/testing/selftests/bpf/Makefile                             | 15 +++++++++++++--
 tools/testing/selftests/bpf/benchs/bench_trigger.c               |  6 +++---
 tools/testing/selftests/bpf/prog_tests/arch/x86/uprobe_syscall.S | 89 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 tools/testing/selftests/bpf/prog_tests/uprobe_syscall.c          | 84 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 tools/testing/selftests/bpf/progs/uprobe_syscall.c               | 15 +++++++++++++++
 13 files changed, 281 insertions(+), 10 deletions(-)
 create mode 100644 tools/testing/selftests/bpf/prog_tests/arch/x86/uprobe_syscall.S
 create mode 100644 tools/testing/selftests/bpf/prog_tests/uprobe_syscall.c
 create mode 100644 tools/testing/selftests/bpf/progs/uprobe_syscall.c