From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S968668AbdAISBq (ORCPT ); Mon, 9 Jan 2017 13:01:46 -0500 Received: from mx1.redhat.com ([209.132.183.28]:35354 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756663AbdAISAh (ORCPT ); Mon, 9 Jan 2017 13:00:37 -0500 From: Josh Poimboeuf To: x86@kernel.org Cc: Dave Jones , Dmitry Vyukov , Miroslav Benes , Andy Lutomirski , Brian Gerst , linux-kernel@vger.kernel.org Subject: [PATCH 3/4] x86/unwind: include __schedule() in stack traces Date: Mon, 9 Jan 2017 12:00:24 -0600 Message-Id: <598e9f7505ed0aba86e8b9590aa528c6c7ae8dcd.1483978430.git.jpoimboe@redhat.com> In-Reply-To: References: X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.31]); Mon, 09 Jan 2017 18:00:37 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org In the following commit: 0100301bfdf5 ("sched/x86: Rewrite the switch_to() code") ... the layout of the 'inactive_task_frame' struct was designed to have a frame pointer header embedded in it, so that the unwinder could use the 'bp' and 'ret_addr' fields to report __schedule() on the stack (or ret_from_fork() for newly forked tasks which haven't actually run yet). Finish the job by changing get_frame_pointer() to return a pointer to inactive_task_frame's 'bp' field rather than 'bp' itself. This allows the unwinder to start one frame higher on the stack, so that it properly reports __schedule(). Reported-by: Miroslav Benes Signed-off-by: Josh Poimboeuf --- arch/x86/include/asm/stacktrace.h | 5 +---- arch/x86/include/asm/switch_to.h | 10 +++++++++- 2 files changed, 10 insertions(+), 5 deletions(-) diff --git a/arch/x86/include/asm/stacktrace.h b/arch/x86/include/asm/stacktrace.h index 20ce3db..2e41c50 100644 --- a/arch/x86/include/asm/stacktrace.h +++ b/arch/x86/include/asm/stacktrace.h @@ -52,16 +52,13 @@ static inline bool on_stack(struct stack_info *info, void *addr, size_t len) static inline unsigned long * get_frame_pointer(struct task_struct *task, struct pt_regs *regs) { - struct inactive_task_frame *frame; - if (regs) return (unsigned long *)regs->bp; if (task == current) return __builtin_frame_address(0); - frame = (struct inactive_task_frame *)task->thread.sp; - return (unsigned long *)READ_ONCE_NOCHECK(frame->bp); + return &((struct inactive_task_frame *)task->thread.sp)->bp; } #else static inline unsigned long * diff --git a/arch/x86/include/asm/switch_to.h b/arch/x86/include/asm/switch_to.h index 5cb436a..fcc5cd3 100644 --- a/arch/x86/include/asm/switch_to.h +++ b/arch/x86/include/asm/switch_to.h @@ -36,7 +36,10 @@ static inline void prepare_switch_to(struct task_struct *prev, asmlinkage void ret_from_fork(void); -/* data that is pointed to by thread.sp */ +/* + * This is the structure pointed to by thread.sp for an inactive task. The + * order of the fields must match the code in __switch_to_asm(). + */ struct inactive_task_frame { #ifdef CONFIG_X86_64 unsigned long r15; @@ -48,6 +51,11 @@ struct inactive_task_frame { unsigned long di; #endif unsigned long bx; + + /* + * These two fields must be together. They form a stack frame header, + * needed by get_frame_pointer(). + */ unsigned long bp; unsigned long ret_addr; }; -- 2.7.4