Re: [PATCHv3 bpf-next 0/7] uprobe: uretprobe speed up

[Jiri Olsa <olsajiri@gmail.com>]

On Tue, Apr 23, 2024 at 12:09:43AM +0900, Masami Hiramatsu wrote:
> Hi Jiri,
> 
> On Sun, 21 Apr 2024 21:41:59 +0200
> Jiri Olsa <jolsa@kernel.org> wrote:
> 
> > 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 1-6 are based on bpf-next/master, but path 1 and 2 are
> > apply-able on linux-trace.git tree probes/for-next branch.
> > Patch 7 is based on man-pages master.
> 
> Thanks for updated! I reviewed the series and just except for the
> manpage, it looks good to me.
> 
> Reviewed-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
> 
> for the series.
> If Linux API maintainers are OK, I can pick this in probes/for-next.

great, thanks

> (BTW, who will pick the manpage patch?)

ugh, I cc-ed linux-api but not linux-man@vger.kernel.org
I'll add that for new version

jirka

> 
> Thank you,
> 
> > 
> > v3 changes:
> >   - added source ip check if the uretprobe syscall is called from
> >     trampoline and sending SIGILL to process if it's not
> >   - keep x86 compat process to use standard breakpoint
> >   - split syscall wiring into separate change
> >   - ran ltp and syzkaller locally, no issues found [Masami]
> >   - building uprobe_compat binary in selftests which breaks
> >     CI atm because of missing 32-bit delve packages, I will
> >     need to fix that in separate changes once this is acked
> >   - added man page change
> >   - there were several changes so I removed acks [Oleg Andrii]
> > 
> > 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, becase 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 si 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 (6):
> >       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
> >       selftests/bpf: Add uretprobe compat test
> > 
> >  arch/x86/entry/syscalls/syscall_64.tbl                    |   1 +
> >  arch/x86/kernel/uprobes.c                                 | 115 ++++++++++++++++++++++++++++++
> >  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/.gitignore                    |   1 +
> >  tools/testing/selftests/bpf/Makefile                      |   6 +-
> >  tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c     | 123 +++++++++++++++++++++++++++++++-
> >  tools/testing/selftests/bpf/prog_tests/uprobe_syscall.c   | 362 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
> >  tools/testing/selftests/bpf/progs/uprobe_syscall.c        |  15 ++++
> >  tools/testing/selftests/bpf/progs/uprobe_syscall_call.c   |  15 ++++
> >  tools/testing/selftests/bpf/progs/uprobe_syscall_compat.c |  13 ++++
> >  15 files changed, 681 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_call.c
> >  create mode 100644 tools/testing/selftests/bpf/progs/uprobe_syscall_compat.c
> > 
> > 
> > Jiri Olsa (1):
> >       man2: Add uretprobe syscall page
> > 
> >  man2/uretprobe.2 | 40 ++++++++++++++++++++++++++++++++++++++++
> >  1 file changed, 40 insertions(+)
> >  create mode 100644 man2/uretprobe.2
> 
> 
> -- 
> Masami Hiramatsu (Google) <mhiramat@kernel.org>