From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932270AbcJUHub (ORCPT ); Fri, 21 Oct 2016 03:50:31 -0400 Received: from terminus.zytor.com ([198.137.202.10]:35266 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751441AbcJUHu2 (ORCPT ); Fri, 21 Oct 2016 03:50:28 -0400 Date: Fri, 21 Oct 2016 00:49:37 -0700 From: tip-bot for Josh Poimboeuf Message-ID: Cc: tglx@linutronix.de, brgerst@gmail.com, hpa@zytor.com, luto@kernel.org, mingo@kernel.org, peterz@infradead.org, linux-kernel@vger.kernel.org, jpoimboe@redhat.com, torvalds@linux-foundation.org, dvlasenk@redhat.com, bp@alien8.de Reply-To: torvalds@linux-foundation.org, dvlasenk@redhat.com, bp@alien8.de, hpa@zytor.com, tglx@linutronix.de, brgerst@gmail.com, luto@kernel.org, linux-kernel@vger.kernel.org, peterz@infradead.org, jpoimboe@redhat.com, mingo@kernel.org In-Reply-To: References: To: linux-tip-commits@vger.kernel.org Subject: [tip:x86/asm] x86/unwind: Create stack frames for saved syscall registers Git-Commit-ID: acb4608ad1865a42af8e0a2db332a7c3a381e1f5 X-Mailer: tip-git-log-daemon Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit-ID: acb4608ad1865a42af8e0a2db332a7c3a381e1f5 Gitweb: http://git.kernel.org/tip/acb4608ad1865a42af8e0a2db332a7c3a381e1f5 Author: Josh Poimboeuf AuthorDate: Thu, 20 Oct 2016 11:34:41 -0500 Committer: Ingo Molnar CommitDate: Fri, 21 Oct 2016 09:26:04 +0200 x86/unwind: Create stack frames for saved syscall registers The entry code doesn't encode the pt_regs pointer for syscalls. But the pt_regs are always at the same location, so we can add a manual check for them. A later patch prints them as part of the oops stack dump. They could be useful, for example, to determine the arguments to a system call. Signed-off-by: Josh Poimboeuf Cc: Andy Lutomirski Cc: Borislav Petkov Cc: Brian Gerst Cc: Denys Vlasenko Cc: H. Peter Anvin Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/e176aa9272930cd3f51fda0b94e2eae356677da4.1476973742.git.jpoimboe@redhat.com Signed-off-by: Ingo Molnar --- 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 2221ab1..5795427 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. @@ -71,6 +79,33 @@ 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;