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Date: Fri, 23 Jan 2015 12:37:08 -0600
From: Tom Zanussi <tom.zanussi@...ux.intel.com>
To: josh@...htriplett.org
Cc: linux-kernel@...r.kernel.org,
Tom Zanussi <tom.zanussi@...ux.intel.com>
Subject: [PATCH 02/10] drivers/char: Support compiling out /dev/mem
Most embedded systems have no use for /dev/mem, and omitting it saves
space. Add a new EMBEDDED config option to disable it.
mmap_mem() is shared between /dev/mem and /dev/kmem; making it
__maybe_unused prevents it from emitting warnings if both devices are
compiled out, while avoiding ugly compound ifdefs.
Also, STRICT_DEVMEM can now be refined to depend on DEVMEM rather than
the big hammer, DEVMEM_BASE.
bloat-o-meter (based on tinyconfig):
add/remove: 0/4 grow/shrink: 1/0 up/down: 96/-565 (-469)
function old new delta
mmap_kmem 37 133 +96
mmap_mem 103 - -103
mem_fops 116 - -116
read_mem 162 - -162
write_mem 184 - -184
Here we see mmap_mem inlined in mmap_kmem and mmap_mem going away.
bloat-o-meter showing only CONFIG_DEVKMEM off:
add/remove: 0/4 grow/shrink: 0/0 up/down: 0/-792 (-792)
function old new delta
mmap_kmem 37 - -37
kmem_fops 116 - -116
read_kmem 290 - -290
write_kmem 349 - -349
bloat-o-meter showing the difference between only CONFIG_DEVKMEM off
and both CONFIG_DEVKMEM and CONFIG_DEVMEM off:
add/remove: 0/5 grow/shrink: 0/0 up/down: 0/-597 (-597)
function old new delta
mmap_mem_ops 32 - -32
mmap_mem 103 - -103
mem_fops 116 - -116
read_mem 162 - -162
write_mem 184 - -184
Here we see mmap_mem going away as before, but also not being inlined
by mmap_kmem because that's gone, and mmap_mem_ops goes away as well,
because it's not being used by even an inlined mmap_mem.
Signed-off-by: Tom Zanussi <tom.zanussi@...ux.intel.com>
---
arch/x86/Kconfig.debug | 2 +-
drivers/char/Kconfig | 10 ++++++++++
drivers/char/mem.c | 9 ++++++++-
3 files changed, 19 insertions(+), 2 deletions(-)
diff --git a/arch/x86/Kconfig.debug b/arch/x86/Kconfig.debug
index 34a781a..39afd1c 100644
--- a/arch/x86/Kconfig.debug
+++ b/arch/x86/Kconfig.debug
@@ -7,7 +7,7 @@ source "lib/Kconfig.debug"
config STRICT_DEVMEM
bool "Filter access to /dev/mem"
- depends on DEVMEM_BASE
+ 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 7a8204a..73e2bb8 100644
--- a/drivers/char/Kconfig
+++ b/drivers/char/Kconfig
@@ -26,6 +26,16 @@ config DEVKMEM
kind of kernel debugging operations.
When in doubt, say "N".
+config DEVMEM
+ bool "/dev/mem virtual device support" if EMBEDDED
+ depends on DEVMEM_BASE
+ default y
+ help
+ Say Y here if you want to support the /dev/mem device. The
+ /dev/mem device is used mainly by X and dosemu, and can be
+ disabled on systems that will never use either, such as many
+ embedded systems. When in doubt, say "Y".
+
config SGI_SNSC
bool "SGI Altix system controller communication support"
depends on (IA64_SGI_SN2 || IA64_GENERIC)
diff --git a/drivers/char/mem.c b/drivers/char/mem.c
index c141c0f..9b7b04e 100644
--- a/drivers/char/mem.c
+++ b/drivers/char/mem.c
@@ -92,6 +92,7 @@ void __weak unxlate_dev_mem_ptr(phys_addr_t phys, void *addr)
}
#endif
+#ifdef CONFIG_DEVMEM
/*
* This funcion reads the *physical* memory. The f_pos points directly to the
* memory location.
@@ -220,6 +221,7 @@ static ssize_t write_mem(struct file *file, const char __user *buf,
*ppos += written;
return written;
}
+#endif
int __weak phys_mem_access_prot_allowed(struct file *file,
unsigned long pfn, unsigned long size, pgprot_t *vma_prot)
@@ -308,7 +310,8 @@ static const struct vm_operations_struct mmap_mem_ops = {
#endif
};
-static int mmap_mem(struct file *file, struct vm_area_struct *vma)
+static int __maybe_unused mmap_mem(struct file *file,
+ struct vm_area_struct *vma)
{
size_t size = vma->vm_end - vma->vm_start;
@@ -716,6 +719,7 @@ static int open_port(struct inode *inode, struct file *filp)
#define open_mem open_port
#define open_kmem open_mem
+#ifdef CONFIG_DEVMEM
static const struct file_operations mem_fops = {
.llseek = memory_lseek,
.read = read_mem,
@@ -724,6 +728,7 @@ 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 = {
@@ -786,7 +791,9 @@ 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
--
1.9.3
--
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