From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 17773 invoked by alias); 30 Apr 2014 16:35:35 -0000 Mailing-List: contact gdb-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: gdb-owner@sourceware.org Received: (qmail 17733 invoked by uid 89); 30 Apr 2014 16:35:34 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-1.9 required=5.0 tests=AWL,BAYES_00 autolearn=ham version=3.3.2 X-HELO: relay1.mentorg.com Received: from relay1.mentorg.com (HELO relay1.mentorg.com) (192.94.38.131) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with ESMTP; Wed, 30 Apr 2014 16:35:32 +0000 Received: from svr-orw-fem-01.mgc.mentorg.com ([147.34.98.93]) by relay1.mentorg.com with esmtp id 1WfXTh-0004Fy-DY from Hui_Zhu@mentor.com ; Wed, 30 Apr 2014 09:35:25 -0700 Received: from SVR-ORW-FEM-05.mgc.mentorg.com ([147.34.97.43]) by svr-orw-fem-01.mgc.mentorg.com over TLS secured channel with Microsoft SMTPSVC(6.0.3790.4675); Wed, 30 Apr 2014 09:35:25 -0700 Received: from localhost.localdomain (147.34.91.1) by svr-orw-fem-05.mgc.mentorg.com (147.34.97.43) with Microsoft SMTP Server id 14.2.247.3; Wed, 30 Apr 2014 09:34:00 -0700 Message-ID: <53612647.1040604@mentor.com> Date: Wed, 30 Apr 2014 17:49:00 -0000 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-IsSubscribed: yes X-SW-Source: 2014-04/txt/msg00099.txt.bz2 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 }