From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753170AbcHLOel (ORCPT ); Fri, 12 Aug 2016 10:34:41 -0400 Received: from mx1.redhat.com ([209.132.183.28]:50274 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753083AbcHLOcj (ORCPT ); Fri, 12 Aug 2016 10:32:39 -0400 From: Josh Poimboeuf To: Thomas Gleixner , Ingo Molnar , "H . Peter Anvin" Cc: x86@kernel.org, linux-kernel@vger.kernel.org, Andy Lutomirski , Linus Torvalds , Steven Rostedt , Brian Gerst , Kees Cook , Peter Zijlstra , Frederic Weisbecker , Byungchul Park , Nilay Vaish Subject: [PATCH v3 42/51] x86/unwind: create stack frames for saved syscall registers Date: Fri, 12 Aug 2016 09:29:01 -0500 Message-Id: In-Reply-To: References: X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.38]); Fri, 12 Aug 2016 14:32:39 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The entry code doesn't encode pt_regs for syscalls. But they're always at the same location, so we can add a manual check for them. Signed-off-by: Josh Poimboeuf --- arch/x86/kernel/unwind_frame.c | 35 +++++++++++++++++++++++++++++++++++ 1 file changed, 35 insertions(+) diff --git a/arch/x86/kernel/unwind_frame.c b/arch/x86/kernel/unwind_frame.c index e02acec..d2480a3 100644 --- a/arch/x86/kernel/unwind_frame.c +++ b/arch/x86/kernel/unwind_frame.c @@ -24,6 +24,14 @@ unsigned long unwind_get_return_address(struct unwind_state *state) } EXPORT_SYMBOL_GPL(unwind_get_return_address); +static bool is_last_task_frame(struct unwind_state *state) +{ + unsigned long bp = (unsigned long)state->bp; + unsigned long regs = (unsigned long)task_pt_regs(state->task); + + return bp == regs - FRAME_HEADER_SIZE; +} + /* * This determines if the frame pointer actually contains an encoded pointer to * pt_regs on the stack. See ENCODE_FRAME_POINTER. @@ -77,6 +85,33 @@ bool unwind_next_frame(struct unwind_state *state) if (state->regs && user_mode(state->regs)) goto the_end; + if (is_last_task_frame(state)) { + regs = task_pt_regs(state->task); + + /* + * kthreads (other than the boot CPU's idle thread) have some + * partial regs at the end of their stack which were placed + * there by copy_thread_tls(). But the regs don't have any + * useful information, so we can skip them. + * + * This user_mode() check is slightly broader than a PF_KTHREAD + * check because it also catches the awkward situation where a + * newly forked kthread transitions into a user task by calling + * do_execve(), which eventually clears PF_KTHREAD. + */ + if (!user_mode(regs)) + goto the_end; + + /* + * We're almost at the end, but not quite: there's still the + * syscall regs frame. Entry code doesn't encode the regs + * pointer for syscalls, so we have to set it manually. + */ + state->regs = regs; + state->bp = NULL; + return true; + } + /* get the next frame pointer */ if (state->regs) next_bp = (unsigned long *)state->regs->bp; -- 2.7.4