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. v4 changes: - added acks [Oleg,Andrii,Masami] - reworded the man page and adding more info to NOTE section [Masami] - rewrote bpf tests not to use trace_pipe [Andrii] - cc-ed linux-man list 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 | 7 +- tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c | 123 ++++++++++++++++++++++++++++- tools/testing/selftests/bpf/prog_tests/uprobe_syscall.c | 382 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ tools/testing/selftests/bpf/progs/uprobe_syscall.c | 15 ++++ tools/testing/selftests/bpf/progs/uprobe_syscall_executed.c | 17 +++++ 14 files changed, 691 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 | 45 +++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 45 insertions(+) create mode 100644 man2/uretprobe.2
