From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751493AbcFRU4y (ORCPT ); Sat, 18 Jun 2016 16:56:54 -0400 Received: from mail-yw0-f194.google.com ([209.85.161.194]:34117 "EHLO mail-yw0-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751293AbcFRU4g (ORCPT ); Sat, 18 Jun 2016 16:56:36 -0400 From: Brian Gerst To: x86@kernel.org, linux-kernel@vger.kernel.org Cc: Ingo Molnar , "H. Peter Anvin" , Denys Vlasenko , Andy Lutomirski , Borislav Petkov , Thomas Gleixner Subject: [PATCH v2 6/6] x86: Fix thread_saved_pc() Date: Sat, 18 Jun 2016 16:56:18 -0400 Message-Id: <1466283378-17062-7-git-send-email-brgerst@gmail.com> X-Mailer: git-send-email 2.5.5 In-Reply-To: <1466283378-17062-1-git-send-email-brgerst@gmail.com> References: <1466283378-17062-1-git-send-email-brgerst@gmail.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org thread_saved_pc() was using a completely bogus method to get the return address. Since switch_to() was previously inlined, there was no sane way to know where on the stack the return address was stored. Now with the frame of a sleeping thread well defined, this can be implemented correctly. Signed-off-by: Brian Gerst --- arch/x86/include/asm/processor.h | 10 ++-------- arch/x86/kernel/process.c | 10 ++++++++++ arch/x86/kernel/process_32.c | 8 -------- 3 files changed, 12 insertions(+), 16 deletions(-) diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h index 1e7d634..413f4f1 100644 --- a/arch/x86/include/asm/processor.h +++ b/arch/x86/include/asm/processor.h @@ -716,8 +716,6 @@ static inline void spin_lock_prefetch(const void *x) .io_bitmap_ptr = NULL, \ } -extern unsigned long thread_saved_pc(struct task_struct *tsk); - /* * TOP_OF_KERNEL_STACK_PADDING reserves 8 bytes on top of the ring0 stack. * This is necessary to guarantee that the entire "struct pt_regs" @@ -767,17 +765,13 @@ extern unsigned long thread_saved_pc(struct task_struct *tsk); .sp0 = TOP_OF_INIT_STACK \ } -/* - * Return saved PC of a blocked thread. - * What is this good for? it will be always the scheduler or ret_from_fork. - */ -#define thread_saved_pc(t) READ_ONCE_NOCHECK(*(unsigned long *)((t)->thread.sp - 8)) - #define task_pt_regs(tsk) ((struct pt_regs *)(tsk)->thread.sp0 - 1) extern unsigned long KSTK_ESP(struct task_struct *task); #endif /* CONFIG_X86_64 */ +extern unsigned long thread_saved_pc(struct task_struct *tsk); + extern void start_thread(struct pt_regs *regs, unsigned long new_ip, unsigned long new_sp); diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c index 00ebab0..db458c4 100644 --- a/arch/x86/kernel/process.c +++ b/arch/x86/kernel/process.c @@ -513,6 +513,16 @@ unsigned long arch_randomize_brk(struct mm_struct *mm) } /* + * Return saved PC of a blocked thread. + */ +unsigned long thread_saved_pc(struct task_struct *tsk) +{ + struct inactive_task_frame *frame = + (struct inactive_task_frame *) READ_ONCE(tsk->thread.sp); + return READ_ONCE_NOCHECK(frame->ret_addr); +} + +/* * Called from fs/proc with a reference on @p to find the function * which called into schedule(). This needs to be done carefully * because the task might wake up and we might look at a stack diff --git a/arch/x86/kernel/process_32.c b/arch/x86/kernel/process_32.c index acee6ca..bcf0a38 100644 --- a/arch/x86/kernel/process_32.c +++ b/arch/x86/kernel/process_32.c @@ -58,14 +58,6 @@ asmlinkage void ret_from_fork(void) __asm__("ret_from_fork"); asmlinkage void ret_from_kernel_thread(void) __asm__("ret_from_kernel_thread"); -/* - * Return saved PC of a blocked thread. - */ -unsigned long thread_saved_pc(struct task_struct *tsk) -{ - return ((unsigned long *)tsk->thread.sp)[3]; -} - void __show_regs(struct pt_regs *regs, int all) { unsigned long cr0 = 0L, cr2 = 0L, cr3 = 0L, cr4 = 0L; -- 2.5.5