From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-0.6 required=3.0 tests=DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS,T_DKIM_INVALID autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id A4BF5C433EF for ; Tue, 19 Jun 2018 09:26:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5CCC82083A for ; Tue, 19 Jun 2018 09:26:22 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="FY7UV3fR" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 5CCC82083A Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: mail.kernel.org; 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Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=hirez.programming.kicks-ass.net) by bombadil.infradead.org with esmtpsa (Exim 4.90_1 #2 (Red Hat Linux)) id 1fVCu0-0002CC-KY; Tue, 19 Jun 2018 09:26:16 +0000 Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 528452011CEBD; Tue, 19 Jun 2018 11:26:14 +0200 (CEST) Date: Tue, 19 Jun 2018 11:26:14 +0200 From: Peter Zijlstra To: Alexey Brodkin Cc: linux-snps-arc@lists.infradead.org, linux-kernel@vger.kernel.org, Vineet Gupta , Max Filippov , linux-arch@vger.kernel.org Subject: Re: [PATCH] ARC: Improve cmpxchng syscall implementation Message-ID: <20180619092614.GD2494@hirez.programming.kicks-ass.net> References: <20180319110002.27419-1-abrodkin@synopsys.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180319110002.27419-1-abrodkin@synopsys.com> User-Agent: Mutt/1.10.0 (2018-05-17) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Mar 19, 2018 at 02:00:02PM +0300, Alexey Brodkin wrote: > diff --git a/arch/arc/kernel/process.c b/arch/arc/kernel/process.c > index 5ac3b547453f..d7d3e16133d6 100644 > --- a/arch/arc/kernel/process.c > +++ b/arch/arc/kernel/process.c > @@ -47,7 +47,9 @@ SYSCALL_DEFINE0(arc_gettls) > SYSCALL_DEFINE3(arc_usr_cmpxchg, int *, uaddr, int, expected, int, new) > { > struct pt_regs *regs = current_pt_regs(); > + struct page *page; > + u32 val; > + int ret; > > /* > * This is only for old cores lacking LLOCK/SCOND, which by defintion > @@ -60,23 +62,48 @@ SYSCALL_DEFINE3(arc_usr_cmpxchg, int *, uaddr, int, expected, int, new) > /* Z indicates to userspace if operation succeded */ > regs->status32 &= ~STATUS_Z_MASK; > > + ret = access_ok(VERIFY_WRITE, uaddr, sizeof(*uaddr)); > + if (!ret) > + goto fail; > > +again: > preempt_disable(); > > + ret = __get_user(val, uaddr); > + if (ret == -EFAULT) { > + preempt_enable(); > + ret = get_user_pages_fast((unsigned long)uaddr, 1, 1, &page); > + if (ret < 0) > + goto fail; > + > + put_page(page); > + goto again; > + } else if (ret) > + goto fail; goto fail with preempt disabled. > + > + if (val == expected) { > + ret = __put_user(new, uaddr); > + if (!ret) > regs->status32 |= STATUS_Z_MASK; > } > > -done: > preempt_enable(); > > - return uval; > + if (ret == -EFAULT) { > + ret = get_user_pages_fast((unsigned long)uaddr, 1, 1, &page); > + if (ret < 0) > + goto fail; > + > + put_page(page); > + goto again; > + } else if (ret) > + goto fail; > + > + return val; > + > +fail: > + force_sig(SIGSEGV, current); > + return ret; > } Sorry for the delay, but I would write it like: --- a/arch/arc/kernel/process.c +++ b/arch/arc/kernel/process.c @@ -47,7 +47,9 @@ SYSCALL_DEFINE0(arc_gettls) SYSCALL_DEFINE3(arc_usr_cmpxchg, int *, uaddr, int, expected, int, new) { struct pt_regs *regs = current_pt_regs(); - int uval = -EFAULT; + struct page *page; + u32 val; + int ret; /* * This is only for old cores lacking LLOCK/SCOND, which by defintion @@ -60,23 +62,46 @@ SYSCALL_DEFINE3(arc_usr_cmpxchg, int *, /* Z indicates to userspace if operation succeded */ regs->status32 &= ~STATUS_Z_MASK; - if (!access_ok(VERIFY_WRITE, uaddr, sizeof(int))) - return -EFAULT; + ret = access_ok(VERIFY_WRITE, uaddr, sizeof(*uaddr)); + if (!ret) + goto fail; +again: preempt_disable(); - if (__get_user(uval, uaddr)) - goto done; + ret = __get_user(val, uaddr); + if (ret) + goto fault; - if (uval == expected) { - if (!__put_user(new, uaddr)) - regs->status32 |= STATUS_Z_MASK; - } + if (val != expected) + goto out; -done: + ret = __put_user(new, uaddr); + if (ret) + goto fault; + + regs->status32 |= STATUS_Z_MASK; + +out: preempt_enable(); + return val; + +fault: + preempt_enable(); + + if (unlikely(ret != -EFAULT)) + goto fail; - return uval; + down_read(¤t->mm->mmap_sem); + ret = fixup_user_fault(current, current->mm, uaddr, FAULT_FLAG_WRITE, NULL); + up_read(¤t->mm->mmap_sem); + + if (likely(!ret)) + goto again; + +fail: + force_sig(SIGSEGV, current); + return ret; } #ifdef CONFIG_ISA_ARCV2