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From 4003b9a2c05f4d0d37535c3dffbf4a7b47d5c36c Mon Sep 17 00:00:00 2001
From: Maarten ter Huurne <maarten@treewalker.org>
Date: Wed, 8 Sep 2010 02:31:19 +0200
Subject: [PATCH 09/21] /dev/mem: Add kernel config option to omit this
device.
Omitting this device prevents software from accessing the hardware directly, which can cause trouble if the kernel accesses the same hardware.
It also saves some space on embedded systems.
---
arch/x86/Kconfig.debug | 1 +
drivers/char/Kconfig | 10 ++++++++++
drivers/char/mem.c | 17 +++++++++++++++++
3 files changed, 28 insertions(+), 0 deletions(-)
diff --git a/arch/x86/Kconfig.debug b/arch/x86/Kconfig.debug
index bf56e17..0c97d51 100644
--- a/arch/x86/Kconfig.debug
+++ b/arch/x86/Kconfig.debug
@@ -7,6 +7,7 @@ source "lib/Kconfig.debug"
config STRICT_DEVMEM
bool "Filter access to /dev/mem"
+ depends on DEVMEM
---help---
If this option is disabled, you allow userspace (root) access to all
of memory, including kernel and userspace memory. Accidental
diff --git a/drivers/char/Kconfig b/drivers/char/Kconfig
index 4364303..a2e462e 100644
--- a/drivers/char/Kconfig
+++ b/drivers/char/Kconfig
@@ -6,6 +6,16 @@ menu "Character devices"
source "drivers/tty/Kconfig"
+config DEVMEM
+ bool "/dev/mem virtual device support"
+ default y
+ help
+ Say Y here if you want to support the /dev/mem device.
+ Some X server drivers access the video hardware using this device.
+ Accessing hardware directly from user space can be useful in some
+ cases, but it is not without risks.
+ When in doubt, say "N".
+
config DEVKMEM
bool "/dev/kmem virtual device support"
default y
diff --git a/drivers/char/mem.c b/drivers/char/mem.c
index 1451790..a6020ca 100644
--- a/drivers/char/mem.c
+++ b/drivers/char/mem.c
@@ -87,6 +87,8 @@ void __weak unxlate_dev_mem_ptr(unsigned long phys, void *addr)
{
}
+#ifdef CONFIG_DEVMEM
+
/*
* This funcion reads the *physical* memory. The f_pos points directly to the
* memory location.
@@ -210,6 +212,10 @@ static ssize_t write_mem(struct file *file, const char __user *buf,
return written;
}
+#endif
+
+#if defined(CONFIG_DEVMEM) || defined(CONFIG_DEVKMEM)
+
int __weak phys_mem_access_prot_allowed(struct file *file,
unsigned long pfn, unsigned long size, pgprot_t *vma_prot)
{
@@ -331,6 +337,8 @@ static int mmap_mem(struct file *file, struct vm_area_struct *vma)
return 0;
}
+#endif
+
#ifdef CONFIG_DEVKMEM
static int mmap_kmem(struct file *file, struct vm_area_struct *vma)
{
@@ -694,6 +702,7 @@ static loff_t null_lseek(struct file *file, loff_t offset, int orig)
return file->f_pos = 0;
}
+#if defined(CONFIG_DEVMEM) || defined(CONFIG_DEVKMEM) || defined(CONFIG_DEVPORT)
/*
* The memory devices use the full 32/64 bits of the offset, and so we cannot
* check against negative addresses: they are ok. The return value is weird,
@@ -726,11 +735,15 @@ static loff_t memory_lseek(struct file *file, loff_t offset, int orig)
mutex_unlock(&file->f_path.dentry->d_inode->i_mutex);
return ret;
}
+#endif
+#if defined(CONFIG_DEVMEM) || defined(CONFIG_DEVKMEM) || \
+ defined(CONFIG_DEVPORT) || defined(CONFIG_CRASH_DUMP)
static int open_port(struct inode * inode, struct file * filp)
{
return capable(CAP_SYS_RAWIO) ? 0 : -EPERM;
}
+#endif
#define zero_lseek null_lseek
#define full_lseek null_lseek
@@ -740,6 +753,7 @@ static int open_port(struct inode * inode, struct file * filp)
#define open_kmem open_mem
#define open_oldmem open_mem
+#ifdef CONFIG_DEVMEM
static const struct file_operations mem_fops = {
.llseek = memory_lseek,
.read = read_mem,
@@ -748,6 +762,7 @@ static const struct file_operations mem_fops = {
.open = open_mem,
.get_unmapped_area = get_unmapped_area_mem,
};
+#endif
#ifdef CONFIG_DEVKMEM
static const struct file_operations kmem_fops = {
@@ -851,7 +866,9 @@ static const struct memdev {
const struct file_operations *fops;
struct backing_dev_info *dev_info;
} devlist[] = {
+#ifdef CONFIG_DEVMEM
[1] = { "mem", 0, &mem_fops, &directly_mappable_cdev_bdi },
+#endif
#ifdef CONFIG_DEVKMEM
[2] = { "kmem", 0, &kmem_fops, &directly_mappable_cdev_bdi },
#endif
--
1.7.5.4
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