From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753809Ab3A1HnO (ORCPT ); Mon, 28 Jan 2013 02:43:14 -0500 Received: from us01smtp3.synopsys.com ([198.182.44.81]:58545 "EHLO hermes.synopsys.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753418Ab3A1HnM (ORCPT ); Mon, 28 Jan 2013 02:43:12 -0500 Message-ID: <51062C01.6010502@synopsys.com> Date: Mon, 28 Jan 2013 13:12:57 +0530 From: Vineet Gupta User-Agent: Mozilla/5.0 (X11; Linux i686; rv:16.0) Gecko/20121011 Thunderbird/16.0.1 MIME-Version: 1.0 Newsgroups: gmane.linux.kernel.cross-arch,gmane.linux.kernel To: Al Viro CC: , , Subject: Re: [PATCH v3 22/71] ARC: [Review] Prevent incorrect syscall restarts References: <1359024639-21915-1-git-send-email-vgupta@synopsys.com> <1359024639-21915-11-git-send-email-vgupta@synopsys.com> In-Reply-To: <1359024639-21915-11-git-send-email-vgupta@synopsys.com> Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.12.197.164] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Al, On Thursday 24 January 2013 04:20 PM, Vineet Gupta wrote: > Per Al Viro's "signals for dummies" https://lkml.org/lkml/2012/12/6/366 > there are 3 golden rules for (not) restarting syscalls: > > " What we need to guarantee is > * restarts do not happen on signals caught in interrupts or exceptions > * restarts do not happen on signals caught in sigreturn() > * restart should happen only once, even if we get through do_signal() > many times." > > ARC Port already handled #1, this patch fixes #2 and #3. > > We use the additional state in pt_regs->orig_r8 to ckh if restarting > has already been done once. > > Thanks to Al Viro for spotting this. > > Signed-off-by: Vineet Gupta > Cc: Al Viro > --- > arch/arc/include/asm/ptrace.h | 3 +++ > arch/arc/kernel/signal.c | 12 ++++++++---- > 2 files changed, 11 insertions(+), 4 deletions(-) > > diff --git a/arch/arc/include/asm/ptrace.h b/arch/arc/include/asm/ptrace.h > index 1711d56..8bf7ff4 100644 > --- a/arch/arc/include/asm/ptrace.h > +++ b/arch/arc/include/asm/ptrace.h > @@ -135,6 +135,9 @@ struct user_regs_struct { > #define in_syscall(regs) (regs->event & orig_r8_IS_SCALL) > #define in_brkpt_trap(regs) (regs->event & orig_r8_IS_BRKPT) > > +#define syscall_wont_restart(regs) (regs->event |= orig_r8_IS_SCALL_RESTARTED) > +#define syscall_restartable(regs) !(regs->event & orig_r8_IS_SCALL_RESTARTED) > + > #define current_pt_regs() \ > ({ \ > /* open-coded current_thread_info() */ \ > diff --git a/arch/arc/kernel/signal.c b/arch/arc/kernel/signal.c > index 887a383..9a1ea2b 100644 > --- a/arch/arc/kernel/signal.c > +++ b/arch/arc/kernel/signal.c > @@ -131,6 +131,9 @@ SYSCALL_DEFINE0(rt_sigreturn) > if (restore_altstack(&sf->uc.uc_stack)) > goto badframe; > > + /* Don't restart from sigreturn */ > + syscall_wont_restart(regs); > + > return regs->r0; > > badframe: > @@ -321,13 +324,13 @@ void do_signal(struct pt_regs *regs) > > signr = get_signal_to_deliver(&info, &ka, regs, NULL); > > - /* Are we from a system call? */ > - restart_scall = in_syscall(regs); > + restart_scall = in_syscall(regs) && syscall_restartable(regs); > > if (signr > 0) { > - if (restart_scall) > + if (restart_scall) { > arc_restart_syscall(&ka, regs); > - > + syscall_wont_restart(regs); /* No more restarts */ > + } > handle_signal(signr, &ka, &info, regs); > return; > } > @@ -342,6 +345,7 @@ void do_signal(struct pt_regs *regs) > regs->r8 = __NR_restart_syscall; > regs->ret -= 4; > } > + syscall_wont_restart(regs); /* No more restarts */ > } > > /* If there's no signal to deliver, restore the saved sigmask back */ > If this looks OK, can I get your ACK on this. Thx, -Vineet