Messages in this thread | | | Date | Wed, 30 Nov 2022 01:28:17 +0900 | From | Masami Hiramatsu (Google) <> | Subject | Re: [PATCH -tip] x86/kprobes: Drop removed INT3 handling code |
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On Mon, 28 Nov 2022 15:49:05 -0500 Steven Rostedt <rostedt@goodmis.org> wrote:
> On Fri, 25 Nov 2022 23:44:47 +0900 > "Masami Hiramatsu (Google)" <mhiramat@kernel.org> wrote: > > > From: Masami Hiramatsu (Google) <mhiramat@kernel.org> > > > > Drop removed INT3 handling code from kprobe_int3_handler() because this > > case (get_kprobe() doesn't return corresponding kprobe AND the INT3 is > > removed) must not happen with the kprobe managed INT3, but can happen > > with the non-kprobe INT3, which should be handled by other callbacks. > > > > For the kprobe managed INT3, the arch_disarm_kprobe() removes the INT3 > > and then calls text_poke_sync(). Since this text_poke_sync() uses IPI > > to call sync_core() on all online cpus, that ensures that all running > > INT3 exception handlers have done. > > And, the unregister_kprobe() will remove the kprobe from the hash table > > after arch_disarm_kprobe(). > > > > Thus, when the kprobe managed INT3 hits, kprobe_int3_handler() should > > be able to find corresponding kprobe always by get_kprobe(). If it can > > not find any kprobe, this means that is NOT a kprobe managed INT3. > > > > I believe this was fixed by: > > 5c02ece81848d ("x86/kprobes: Fix ordering while text-patching") > > That should be mentioned in the commit log.
Thanks for pointing! Yes, it ensures since it add text_poke_sync() in arch_arm/disarm_kprobe(). So this is the last part of the commit 5c02ece81848d.
> > Anyway, looks good. > > Reviewed-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Thank you!
> > -- Steve > > > > > Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org> > > --- > > arch/x86/kernel/kprobes/core.c | 14 -------------- > > 1 file changed, 14 deletions(-) > > > > diff --git a/arch/x86/kernel/kprobes/core.c b/arch/x86/kernel/kprobes/core.c > > index 66299682b6b7..33390ed4dcf3 100644 > > --- a/arch/x86/kernel/kprobes/core.c > > +++ b/arch/x86/kernel/kprobes/core.c > > @@ -986,20 +986,6 @@ int kprobe_int3_handler(struct pt_regs *regs) > > kprobe_post_process(p, regs, kcb); > > return 1; > > } > > - } > > - > > - if (*addr != INT3_INSN_OPCODE) { > > - /* > > - * The breakpoint instruction was removed right > > - * after we hit it. Another cpu has removed > > - * either a probepoint or a debugger breakpoint > > - * at this address. In either case, no further > > - * handling of this interrupt is appropriate. > > - * Back up over the (now missing) int3 and run > > - * the original instruction. > > - */ > > - regs->ip = (unsigned long)addr; > > - return 1; > > } /* else: not a kprobe fault; let the kernel handle it */ > > > > return 0; >
-- Masami Hiramatsu (Google) <mhiramat@kernel.org>
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