From: akpm@linux-foundation.org (Andrew Morton) Date: Thu, 15 Jul 2010 13:02:14 -0700 Subject: [PATCH] Stop ARM boards crashing when CUPS is loaded - 2.6.35-rc5 In-Reply-To: <4C3C72C6.4000005@canonical.com> References: <4C3C72C6.4000005@canonical.com> Message-ID: <20100715130214.4c9303b2.akpm@linux-foundation.org> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org (cc linux-arm-kernel) On Tue, 13 Jul 2010 15:05:58 +0100 Lee Jones wrote: > >From 219005d9522043bc42ddb51d59688959eed0d443 Mon Sep 17 00:00:00 2001 > From: Lee Jones > Date: Tue, 13 Jul 2010 15:02:17 +0100 > Subject: [PATCH] UBUNTU: [Upstream] Stop ARM boards crashing when CUPS is loaded > > BugLink: http://bugs.launchpad.net/bugs/601226 > > When CUPS loads, it tries to load several drivers that it may need. > When one of these drivers, specifically parport_pc is loaded on ARM > based systems, it causes a segmentation fault as the ISA addresses > which are attempted are not writable on non-PC based architectures. > This code prevents ISA addresses from being attempted except on x86. > That sounds like a pretty serious problem. But presumably it isn't - otherwise it would have been fixed earlier! So what actions are required to trigger this bug and why aren't others seeing it? > arch/arm/include/asm/parport.h | 7 +++++-- This should probably go via the arm tree. > > diff --git a/arch/arm/include/asm/parport.h b/arch/arm/include/asm/parport.h > index 26e94b0..a1874f8 100644 > --- a/arch/arm/include/asm/parport.h > +++ b/arch/arm/include/asm/parport.h > @@ -9,10 +9,13 @@ > #ifndef __ASMARM_PARPORT_H > #define __ASMARM_PARPORT_H > > -static int __devinit parport_pc_find_isa_ports (int autoirq, int autodma); > static int __devinit parport_pc_find_nonpci_ports (int autoirq, int autodma) It's strange that this function isn't marked inline. It's in a .h file. But many arch/*/include/asm/parport.h's do it this way. They're probably broken. It adds a risk that unneeded code will be generated into each compilation unit which includes these headers, although gcc can probably fix that, depending on the version. Plus it's plain odd. > { > - return parport_pc_find_isa_ports (autoirq, autodma); > +/* parport_pc_find_isa_ports uses direct register addresses which are > + * only correct on x86 architectures. This may have undesirable > + * consequences (including segfaults) when used on other architectures. > + */ > + return 0; > } That comment layout is whacky. I did this: --- a/arch/arm/include/asm/parport.h~parport-prevent-arm-boards-frmo-crashing-when-cups-is-loaded-fix +++ a/arch/arm/include/asm/parport.h @@ -9,12 +9,13 @@ #ifndef __ASMARM_PARPORT_H #define __ASMARM_PARPORT_H -static int __devinit parport_pc_find_nonpci_ports (int autoirq, int autodma) +static int __devinit parport_pc_find_nonpci_ports(int autoirq, int autodma) { -/* parport_pc_find_isa_ports uses direct register addresses which are - * only correct on x86 architectures. This may have undesirable - * consequences (including segfaults) when used on other architectures. - */ + /* + * parport_pc_find_isa_ports() uses direct register addresses which are + * only correct on x86 architectures. This may have undesirable + * consequences (including segfaults) when used on other architectures. + */ return 0; } _