From mboxrd@z Thu Jan 1 00:00:00 1970 From: Peter Zijlstra Date: Mon, 05 Jul 2021 11:36:14 +0000 Subject: Re: [PATCH -tip v8 11/13] x86/unwind: Recover kretprobe trampoline entry Message-Id: List-Id: References: <162399992186.506599.8457763707951687195.stgit@devnote2> <162400002631.506599.2413605639666466945.stgit@devnote2> In-Reply-To: <162400002631.506599.2413605639666466945.stgit@devnote2> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Masami Hiramatsu Cc: Steven Rostedt , Josh Poimboeuf , Ingo Molnar , X86 ML , Daniel Xu , linux-kernel@vger.kernel.org, bpf@vger.kernel.org, kuba@kernel.org, mingo@redhat.com, ast@kernel.org, Thomas Gleixner , Borislav Petkov , kernel-team@fb.com, yhs@fb.com, linux-ia64@vger.kernel.org, Abhishek Sagar , Andrii Nakryiko On Fri, Jun 18, 2021 at 04:07:06PM +0900, Masami Hiramatsu wrote: > @@ -549,7 +548,15 @@ bool unwind_next_frame(struct unwind_state *state) > (void *)orig_ip); > goto err; > } > - > + /* > + * There is a small chance to interrupt at the entry of > + * kretprobe_trampoline where the ORC info doesn't exist. > + * That point is right after the RET to kretprobe_trampoline > + * which was modified return address. So the @addr_p must > + * be right before the regs->sp. > + */ > + state->ip = unwind_recover_kretprobe(state, state->ip, > + (unsigned long *)(state->sp - sizeof(long))); > state->regs = (struct pt_regs *)sp; > state->prev_regs = NULL; > state->full_regs = true; > @@ -562,6 +569,9 @@ bool unwind_next_frame(struct unwind_state *state) > (void *)orig_ip); > goto err; > } > + /* See UNWIND_HINT_TYPE_REGS case comment. */ > + state->ip = unwind_recover_kretprobe(state, state->ip, > + (unsigned long *)(state->sp - sizeof(long))); > > if (state->full_regs) > state->prev_regs = state->regs; Why doesn't the ftrace case have this? That is, why aren't both return trampolines having the same general shape?