Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1763537AbYCGW5V (ORCPT ); Fri, 7 Mar 2008 17:57:21 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754196AbYCGW44 (ORCPT ); Fri, 7 Mar 2008 17:56:56 -0500 Received: from mx1.redhat.com ([66.187.233.31]:51839 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1760995AbYCGW4p (ORCPT ); Fri, 7 Mar 2008 17:56:45 -0500 MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit From: Roland McGrath To: Andrew Morton , Linus Torvalds , Ingo Molnar , Thomas Gleixner Cc: linux-kernel@vger.kernel.org Subject: [PATCH] x86_64 ptrace orig_ax on ia32 task In-Reply-To: Roland McGrath's message of Thursday, 28 February 2008 19:57:07 -0800 <20080229035707.EAE862700FD@magilla.localdomain> X-Fcc: ~/Mail/linus References: <20080229035707.EAE862700FD@magilla.localdomain> Emacs: more than just a Lisp interpreter, a text editor as well! Message-Id: <20080307225602.6491B26F990@magilla.localdomain> Date: Fri, 7 Mar 2008 14:56:02 -0800 (PST) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2195 Lines: 55 This makes 64-bit ptrace calls setting the 64-bit orig_ax field for a 32-bit task sign-extend the low 32 bits up to 64. This matches what a 64-bit debugger expects when tracing a 32-bit task. This follows on my "x86_64 ia32 syscall restart fix". This didn't matter until that was fixed. The debugger ignores or zeros the high half of every register slot it sets (including the orig_rax pseudo-register) uniformly. It expects that the setting of the low 32 bits always has the same meaning as a 32-bit debugger setting those same 32 bits with native 32-bit facilities. This never arose before because the syscall restart check never matched any -ERESTART* values due to lack of sign extension. Before that fix, even 32-bit ptrace setting orig_eax to -1 failed to trigger the restart check anyway. So this was never noticed as a regression of 64-bit debuggers vs 32-bit debuggers on the same 64-bit kernel. Signed-off-by: Roland McGrath --- arch/x86/kernel/ptrace.c | 14 ++++++++++++++ 1 files changed, 14 insertions(+), 0 deletions(-) diff --git a/arch/x86/kernel/ptrace.c b/arch/x86/kernel/ptrace.c index f8eed1b..92b44e1 100644 --- a/arch/x86/kernel/ptrace.c +++ b/arch/x86/kernel/ptrace.c @@ -322,6 +322,20 @@ static int putreg(struct task_struct *child, case offsetof(struct user_regs_struct, flags): return set_flags(child, value); +#ifdef CONFIG_IA32_EMULATION + case offsetof(struct user_regs_struct, orig_ax): + /* + * For a 32-bit task, setting only the low 32 bits and + * leaving the high bits untouched (all 0) has the same + * effect as setting those bits via 32-bit ptrace would. + * This means sign-extending an orig_eax of -1, which + * here is an orig_rax of (u32)-1. + */ + if (test_tsk_thread_flag(child, TIF_IA32)) + value = (long) (s32) value; + break; +#endif + #ifdef CONFIG_X86_64 case offsetof(struct user_regs_struct,fs_base): if (value >= TASK_SIZE_OF(child)) -- 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/