[PATCH 01/10] drivers/char: Support compiling out memory-access char devices
From: Tom Zanussi
Date: Fri Jan 23 2015 - 13:37:42 EST
Many embedded systems can get by without the complete set of
memory-access char devices: /dev/mem, /dev/kmem, /dev/zero, /dev/null,
/dev/full, /dev/random, /dev/urandom, /dev/port, and /dev/kmsg.
Omitting them all can be accomplished by disabling DEVMEM_BASE, a new
EMBEDDED config option.
If DEVMEM_BASE is enabled, each of those devices can still be enabled
individually.
bloat-o-meter (based on tinyconfig):
add/remove: 0/51 grow/shrink: 2/1 up/down: 313/-5820 (-5507)
function old new delta
sys_getrandom 211 432 +221
do_syslog 1027 1119 +92
write_null 3 - -3
read_null 3 - -3
aio_read_null 3 - -3
pipe_to_null 4 - -4
mem_class 4 - -4
write_full 6 - -6
devkmsg_release 15 - -15
random_fasync 16 - -16
mmap_zero 16 - -16
aio_write_null 18 - -18
open_port 19 - -19
random_read 20 - -20
splice_write_null 24 - -24
null_lseek 25 - -25
mmap_mem_ops 32 - -32
mem_devnode 35 - -35
mmap_kmem 37 - -37
random_write 42 - -42
write_pool 82 - -82
random_poll 83 - -83
read_iter_zero 95 - -95
urandom_read 96 - -96
memory_open 96 - -96
devkmsg_poll 97 - -97
read_port 98 - -98
mmap_mem 103 - -103
devkmsg_open 112 - -112
check_syslog_permissions 114 - -114
zero_fops 116 - -116
write_port 116 - -116
urandom_fops 116 - -116
random_fops 116 - -116
port_fops 116 - -116
null_fops 116 - -116
memory_fops 116 - -116
mem_fops 116 - -116
kmsg_fops 116 - -116
kmem_fops 116 - -116
full_fops 116 - -116
memory_lseek 122 - -122
devkmsg_llseek 144 - -144
chr_dev_init 162 3 -159
read_mem 162 - -162
_random_read.part 173 - -173
write_mem 184 - -184
devlist 192 - -192
devkmsg_write 209 - -209
zero_bdi 244 - -244
read_kmem 290 - -290
random_ioctl 319 - -319
write_kmem 349 - -349
devkmsg_read 699 - -699
Signed-off-by: Tom Zanussi <tom.zanussi@xxxxxxxxxxxxxxx>
---
arch/x86/Kconfig.debug | 1 +
drivers/char/Kconfig | 12 ++++++++++++
drivers/char/mem.c | 7 +++++++
3 files changed, 20 insertions(+)
diff --git a/arch/x86/Kconfig.debug b/arch/x86/Kconfig.debug
index 61bd2ad..34a781a 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_BASE
---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 efefd12..7a8204a 100644
--- a/drivers/char/Kconfig
+++ b/drivers/char/Kconfig
@@ -6,8 +6,19 @@ menu "Character devices"
source "drivers/tty/Kconfig"
+config DEVMEM_BASE
+ bool "Base support for memory-access char devices" if EMBEDDED
+ default y
+ help
+ Say Y here if you want to support the various character
+ devices used to access memory, such as /dev/mem, /dev/null,
+ /dev/zero, /dev/random, etc. Many embedded systems can get
+ by without these devices; doing so will save memory. When
+ in doubt, say "Y".
+
config DEVKMEM
bool "/dev/kmem virtual device support"
+ depends on DEVMEM_BASE
default y
help
Say Y here if you want to support the /dev/kmem device. The
@@ -577,6 +588,7 @@ config DEVPORT
bool
depends on !M68K
depends on ISA || PCI
+ depends on DEVMEM_BASE
default y
source "drivers/s390/char/Kconfig"
diff --git a/drivers/char/mem.c b/drivers/char/mem.c
index 4c58333..c141c0f 100644
--- a/drivers/char/mem.c
+++ b/drivers/char/mem.c
@@ -34,6 +34,7 @@
# include <linux/efi.h>
#endif
+#ifdef CONFIG_DEVMEM_BASE
#define DEVPORT_MINOR 4
static inline unsigned long size_inside_page(unsigned long start,
@@ -876,5 +877,11 @@ static int __init chr_dev_init(void)
return tty_init();
}
+#else
+static int __init chr_dev_init(void)
+{
+ return tty_init();
+}
+#endif /* CONFIG_DEVMEM_BASE */
fs_initcall(chr_dev_init);
--
1.9.3
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/