Re: [PATCH] Disable /dev/port interface on powerpc systems
flat view
From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Date: 2012-03-21 07:23:40
On Tue, 2012-03-20 at 22:37 -0700, Haren Myneni wrote:
Some power systems do not have legacy ISA devices. So, /dev/port is not a valid interface on these systems. User level tools such as kbdrate is trying to access the device using this interface which is causing the system crash. This patch will fix this issue by not creating this interface on these powerpc systems.
Doesn't fix 32-bit... not a big deal for now I suppose... But I'd rather you change the patch a tiny bit to change legacy_isa_device_found() to arch_has_dev_port() instead. There may be other reason than legacy ISA to enable dev/port or not so let's make the arch hook more generic. Another approach which might be even better is to filter per-access, ie for each read/write to /dev/port, have a hook to check if that specific port is valid, but that may be overkill for what is essentially a legacy interface that should have died a long time ago :) Cheers, Ben.
quoted hunk ↗ jump to hunk
Signed-off-by: Haren Myneni <haren@us.ibm.com> diff -Naurp linux.orig/arch/powerpc/kernel/isa-bridge.c linux/arch/powerpc/kernel/isa-bridge.c--- linux.orig/arch/powerpc/kernel/isa-bridge.c 2012-02-1102:08:08.780005293 -0800+++ linux/arch/powerpc/kernel/isa-bridge.c 2012-02-11 02:16:25.080003386 -0800@@ -255,6 +255,14 @@ static struct notifier_block isa_bridge_ .notifier_call = isa_bridge_notify }; +int __init legacy_isa_device_found(void) +{ + if (isa_bridge_pcidev) + return 1; + + return 0; +} + /** * isa_bridge_init - register to be notified of ISA bridgeaddition/removal * diff -Naurp linux.orig/drivers/char/mem.c linux/drivers/char/mem.c--- linux.orig/drivers/char/mem.c 2012-02-11 02:08:42.710002440 -0800 +++ linux/drivers/char/mem.c 2012-03-20 20:40:43.650000003 -0700@@ -35,6 +35,8 @@ # include <linux/efi.h> #endif +#define DEVPORT_MINOR 4 + static inline unsigned long size_inside_page(unsigned long start, unsigned long size) {@@ -910,6 +912,11 @@ static char *mem_devnode(struct device * static struct class *mem_class; +int __init __weak legacy_isa_device_found(void) +{ + return 1; +} + static int __init chr_dev_init(void) { int minor;@@ -930,6 +937,13 @@ static int __init chr_dev_init(void) for (minor = 1; minor < ARRAY_SIZE(devlist); minor++) { if (!devlist[minor].name) continue; + + /* + * Create /dev/port? + */ + if ((minor == DEVPORT_MINOR) && !legacy_isa_device_found()) + continue; + device_create(mem_class, NULL, MKDEV(MEM_MAJOR, minor), NULL, devlist[minor].name); }diff -Naurp linux.orig/include/linux/isa.h linux/include/linux/isa.h--- linux.orig/include/linux/isa.h 2012-02-11 02:07:52.030019810 -0800 +++ linux/include/linux/isa.h 2012-02-11 02:16:49.810002296 -0800@@ -36,4 +36,5 @@ static inline void isa_unregister_driver } #endif +extern int __init legacy_isa_device_found(void); #endif /* __LINUX_ISA_H */