Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752104Ab2BZQR2 (ORCPT ); Sun, 26 Feb 2012 11:17:28 -0500 Received: from mail-pw0-f46.google.com ([209.85.160.46]:52352 "EHLO mail-pw0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751411Ab2BZQR1 (ORCPT ); Sun, 26 Feb 2012 11:17:27 -0500 Authentication-Results: mr.google.com; spf=pass (google.com: domain of siddhesh.poyarekar@gmail.com designates 10.68.135.71 as permitted sender) smtp.mail=siddhesh.poyarekar@gmail.com; dkim=pass header.i=siddhesh.poyarekar@gmail.com From: Siddhesh Poyarekar To: x86@kernel.org Cc: KOSAKI Motohiro , linux-kernel@vger.kernel.org, Jamie Lokier , Mike Frysinger , Andrew Morton , Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , Siddhesh Poyarekar Subject: [PATCH] x86_64: Record stack pointer before task execution begins Date: Sun, 26 Feb 2012 21:47:55 +0530 Message-Id: <1330273075-2949-1-git-send-email-siddhesh.poyarekar@gmail.com> X-Mailer: git-send-email 1.7.7.4 In-Reply-To: References: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1319 Lines: 34 task->thread.usersp is unusable immediately after a binary is exec()'d until it undergoes a context switch cycle. The start_thread() function called during execve() saves the stack pointer into pt_regs and into old_rsp, but fails to record it into task->thread.usersp. Because of this, KSTK_ESP(task) returns an incorrect value for a 64-bit program until the task is switched out and back in since switch_to swaps %rsp values in and out into task->thread.usersp. Signed-off-by: Siddhesh Poyarekar --- arch/x86/kernel/process_64.c | 1 + 1 files changed, 1 insertions(+), 0 deletions(-) diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c index 9b9fe4a..702a3b9 100644 --- a/arch/x86/kernel/process_64.c +++ b/arch/x86/kernel/process_64.c @@ -341,6 +341,7 @@ start_thread_common(struct pt_regs *regs, unsigned long new_ip, loadsegment(es, _ds); loadsegment(ds, _ds); load_gs_index(0); + current->thread.usersp = new_sp; regs->ip = new_ip; regs->sp = new_sp; percpu_write(old_rsp, new_sp); -- 1.7.7.4 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/