Hi, Here are the 2nd version for generic kretprobe and kretprobe on x86 for replacing the kretprobe trampoline with rethook. The previous version is here[1] [1] https://lore.kernel.org/all/164818251899.2252200.7306353689206167903.stgit@devnote2/T/#u In this version I added completing pt_regs by saving regs->ss register for rethook (from Peter) and optprobe. Background: This rethook came from Jiri's request of multiple kprobe for bpf[1]. He tried to solve an issue that starting bpf with multiple kprobe will take a long time because bpf-kprobe will wait for RCU grace period for sync rcu events. Jiri wanted to attach a single bpf handler to multiple kprobes and he tried to introduce multiple-probe interface to kprobe. So I asked him to use ftrace and kretprobe-like hook if it is only for the function entry and exit, instead of adding ad-hoc interface to kprobes. For this purpose, I introduced the fprobe (kprobe like interface for ftrace) with the rethook (this is a generic return hook feature for fprobe exit handler)[2]. [1] https://lore.kernel.org/all/20220104080943.113249-1-jolsa@xxxxxxxxxx/T/#u [2] https://lore.kernel.org/all/164191321766.806991.7930388561276940676.stgit@devnote2/T/#u The rethook is basically same as the kretprobe trampoline. I just made it decoupled from kprobes. Eventually, the all arch dependent kretprobe trampolines will be replaced with the rethook trampoline instead of cloning and set HAVE_RETHOOK=y. When I port the rethook for all arch which supports kretprobe, the legacy kretprobe specific code (which is for CONFIG_KRETPROBE_ON_RETHOOK=n) will be removed eventually. Worktree notice: BTW, this patch can be applied to next-20220324, not the bpf-next tree directly, because this depends on ANNOTATE_NOENDBR macro. However, since the fprobe is merged in the bpf-next, I marked this for bpf-next. So until merging the both of fprobes and ENDBR series, to compile this you need below 2 lines in arch/x86/kernel/rethook.c. #ifndef ANNOTATE_NOENDBR #define ANNOTATE_NOENDBR But after those are merged, these lines will be unneeded. How should I handle this issue? (Just remove ANNOTATE_NOENDBR line in bpf-next?) Thank you, --- Masami Hiramatsu (3): kprobes: Use rethook for kretprobe if possible rethook: kprobes: x86: Replace kretprobe with rethook on x86 x86,kprobes: Fix optprobe trampoline to generate complete pt_regs Peter Zijlstra (1): Subject: x86,rethook: Fix arch_rethook_trampoline() to generate a complete pt_regs arch/Kconfig | 7 ++ arch/x86/Kconfig | 1 arch/x86/include/asm/unwind.h | 23 +++---- arch/x86/kernel/Makefile | 1 arch/x86/kernel/kprobes/common.h | 1 arch/x86/kernel/kprobes/core.c | 107 --------------------------------- arch/x86/kernel/kprobes/opt.c | 25 +++++--- arch/x86/kernel/rethook.c | 123 ++++++++++++++++++++++++++++++++++++++ arch/x86/kernel/unwind_orc.c | 10 ++- include/linux/kprobes.h | 51 +++++++++++++++- kernel/kprobes.c | 124 ++++++++++++++++++++++++++++++++------ kernel/trace/trace_kprobe.c | 4 + 12 files changed, 319 insertions(+), 158 deletions(-) create mode 100644 arch/x86/kernel/rethook.c -- Masami Hiramatsu (Linaro) <mhiramat@xxxxxxxxxx>
