Messages in this thread | | | Date | Mon, 28 Nov 2022 15:49:05 -0500 | From | Steven Rostedt <> | Subject | Re: [PATCH -tip] x86/kprobes: Drop removed INT3 handling code |
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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.
Anyway, looks good.
Reviewed-by: Steven Rostedt (Google) <rostedt@goodmis.org>
-- 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;
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