Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759400AbaD3Qfm (ORCPT ); Wed, 30 Apr 2014 12:35:42 -0400 Received: from relay1.mentorg.com ([192.94.38.131]:61884 "EHLO relay1.mentorg.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759365AbaD3Qfa (ORCPT ); Wed, 30 Apr 2014 12:35:30 -0400 Message-ID: <53612647.1040604@mentor.com> Date: Thu, 1 May 2014 00:35:19 +0800 From: Hui Zhu User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.4.0 MIME-Version: 1.0 To: Hui Zhu , Mark Kettenis CC: "H. Peter Anvin" , , Thomas Gleixner , Ingo Molnar , , , , "linux-kernel@vger.kernel.org" , "gdb@sourceware.org" , Pedro Alves Subject: Re: [PATCH] Fix get ERESTARTSYS with m32 in x86_64 when debug by GDB References: <53554846.3070608@zytor.com> <53608125.2020103@zytor.com> <536085B7.5070002@zytor.com> <201404301335.s3UDZX4J017978@glazunov.sibelius.xs4all.nl> In-Reply-To: Content-Type: text/plain; charset="ISO-8859-1"; format=flowed Content-Transfer-Encoding: 7bit X-OriginalArrivalTime: 30 Apr 2014 16:35:25.0025 (UTC) FILETIME=[2FFE9510:01CF6492] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 05/01/14 00:28, Hui Zhu wrote: > On Wed, Apr 30, 2014 at 9:35 PM, Mark Kettenis wrote: >>> Date: Tue, 29 Apr 2014 22:10:15 -0700 >>> From: "H. Peter Anvin" >>> >>> On 04/29/2014 10:08 PM, Andrew Pinski wrote: >>>> >>>> restoring the values is hard since even the ptrace interface does not >>>> allow for that. >>>> >>> >>> So that begs the ultimate question, which is: given the fact that there >>> is *state missing* from the state vector (this is the core of the >>> problem), is there a way we can add that state so that gdb will be able >>> to save and restore it? >> >> Carrying around additional state in GDB is complicated; I'd rather >> avoid it. >> >> arch/x86/kernel/ptrace.c:putreg32() has this bit of code: >> >> case offsetof(struct user32, regs.orig_eax): >> /* >> * A 32-bit debugger setting orig_eax means to restore >> * the state of the task restarting a 32-bit syscall. >> * Make sure we interpret the -ERESTART* codes correctly >> * in case the task is not actually still sitting at the >> * exit from a 32-bit syscall with TS_COMPAT still set. >> */ >> regs->orig_ax = value; >> if (syscall_get_nr(child, regs) >= 0) >> task_thread_info(child)->status |= TS_COMPAT; >> break; >> >> which gets used for 32-bit compat ptrace(2). Perhaps the same logic >> should be added to putreg() if the child is a 32-bit process? > > Make a new patch that add following code to putreg(): > case offsetof(struct user_regs_struct, orig_ax): > /* > * A 64-bit debugger setting orig_ax of a 32-bit inferior > * means to restore the state of the task restarting a > * 32-bit syscall. > * Make sure we interpret the -ERESTART* codes correctly > * in case the task is not actually still sitting at the > * exit from a 32-bit syscall with TS_COMPAT still set. > */ > if (test_ti_thread_flag(task_thread_info(child), TIF_IA32)) { > struct pt_regs *regs = task_pt_regs(child); > regs->orig_ax = value; > if (syscall_get_nr(child, regs) >= 0) > task_thread_info(child)->status |= TS_COMPAT; > return 0; > } > >> >> If (and only if) the goal of that TS_COMPAT flag solely is to trigger >> the error code sign-extension in arch/x86/asm/syscall.h:syscall_get_error(), >> we could work around to problem in GDB by checking "orig_ax" to see if >> we're continuing an interrupted system call and sign extend the error >> code in the real "eax" register if we are. > > I will update patch in > https://sourceware.org/ml/gdb-patches/2014-04/msg00429.html > according to this comments. > > Thanks, > Hui > I sorry that previous patch has some format issue, post a new one. Signed-off-by: Hui Zhu --- --- a/arch/x86/kernel/ptrace.c +++ b/arch/x86/kernel/ptrace.c @@ -452,6 +452,23 @@ static int putreg(struct task_struct *ch if (child->thread.gs != value) return do_arch_prctl(child, ARCH_SET_GS, value); return 0; + case offsetof(struct user_regs_struct, orig_ax): + /* + * A 64-bit debugger setting orig_ax of a 32-bit inferior + * means to restore the state of the task restarting a + * 32-bit syscall. + * Make sure we interpret the -ERESTART* codes correctly + * in case the task is not actually still sitting at the + * exit from a 32-bit syscall with TS_COMPAT still set. + */ + if (test_ti_thread_flag(task_thread_info(child), TIF_IA32)) { + struct pt_regs *regs = task_pt_regs(child); + regs->orig_ax = value; + if (syscall_get_nr(child, regs) >= 0) + task_thread_info(child)->status |= TS_COMPAT; + return 0; + } + break; #endif } -- 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/