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Date: Fri, 23 Jan 2015 12:37:13 -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 07/10] drivers/char: Support compiling out /dev/random
Some embedded systems with tightly controlled userspace have no use
for /dev/random, and could benefit from the size savings gained by
omitting it. Add a new EMBEDDED config option to disable it.
The newly marked __maybe_unused functions, random_write, random_ioctl,
and random_fasync are shared between /dev/random and /dev/urandom, and
will be compiled out if both devices are disabled.
bloat-o-meter (based on tinyconfig):
add/remove: 0/4 grow/shrink: 1/0 up/down: 139/-392 (-253)
function old new delta
sys_getrandom 211 350 +139
random_read 20 - -20
random_poll 83 - -83
random_fops 116 - -116
_random_read.part 173 - -173
bloat-o-meter showing the difference between only CONFIG_DEVURANDOM
off and both CONFIG_DEVURANDOM and CONFIG_DEVRANDOM off:
add/remove: 0/8 grow/shrink: 1/0 up/down: 144/-851 (-707)
function old new delta
sys_getrandom 288 432 +144
random_fasync 16 - -16
random_read 20 - -20
random_write 42 - -42
write_pool 82 - -82
random_poll 83 - -83
random_fops 116 - -116
_random_read.part 173 - -173
random_ioctl 319 - -319
So we see the extra symbols drop, while _random_read is inlined into
sys_getrandom.
Signed-off-by: Tom Zanussi <tom.zanussi@...ux.intel.com>
---
drivers/char/Kconfig | 11 +++++++++++
drivers/char/mem.c | 2 ++
drivers/char/random.c | 16 ++++++++++++----
3 files changed, 25 insertions(+), 4 deletions(-)
diff --git a/drivers/char/Kconfig b/drivers/char/Kconfig
index 62290e0..9416b7e 100644
--- a/drivers/char/Kconfig
+++ b/drivers/char/Kconfig
@@ -67,6 +67,17 @@ config DEVFULL
never use it in production, such as many embedded systems.
When in doubt, say "Y".
+config DEVRANDOM
+ bool "/dev/random virtual device support" if EMBEDDED
+ depends on DEVMEM_BASE
+ default y
+ help
+ Say Y here if you want to support the /dev/random
+ device. The /dev/random device is the blocking userspace
+ interface to the kernel random number generator, and can be
+ disabled on systems that will never use it in production,
+ 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 5b60003..f226714 100644
--- a/drivers/char/mem.c
+++ b/drivers/char/mem.c
@@ -826,7 +826,9 @@ static const struct memdev {
#ifdef CONFIG_DEVFULL
[7] = { "full", 0666, &full_fops, NULL },
#endif
+#ifdef CONFIG_DEVRANDOM
[8] = { "random", 0666, &random_fops, NULL },
+#endif
[9] = { "urandom", 0666, &urandom_fops, NULL },
#ifdef CONFIG_PRINTK
[11] = { "kmsg", 0644, &kmsg_fops, NULL },
diff --git a/drivers/char/random.c b/drivers/char/random.c
index 04645c0..8547056 100644
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -1370,11 +1370,13 @@ _random_read(int nonblock, char __user *buf, size_t nbytes)
}
}
+#ifdef CONFIG_DEVRANDOM
static ssize_t
random_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
{
return _random_read(file->f_flags & O_NONBLOCK, buf, nbytes);
}
+#endif
static ssize_t
urandom_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
@@ -1394,6 +1396,7 @@ urandom_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
return ret;
}
+#ifdef CONFIG_DEVRANDOM
static unsigned int
random_poll(struct file *file, poll_table * wait)
{
@@ -1408,6 +1411,7 @@ random_poll(struct file *file, poll_table * wait)
mask |= POLLOUT | POLLWRNORM;
return mask;
}
+#endif
static int
write_pool(struct entropy_store *r, const char __user *buffer, size_t count)
@@ -1431,8 +1435,9 @@ write_pool(struct entropy_store *r, const char __user *buffer, size_t count)
return 0;
}
-static ssize_t random_write(struct file *file, const char __user *buffer,
- size_t count, loff_t *ppos)
+static ssize_t __maybe_unused random_write(struct file *file,
+ const char __user *buffer,
+ size_t count, loff_t *ppos)
{
size_t ret;
@@ -1446,7 +1451,8 @@ static ssize_t random_write(struct file *file, const char __user *buffer,
return (ssize_t)count;
}
-static long random_ioctl(struct file *f, unsigned int cmd, unsigned long arg)
+static long __maybe_unused random_ioctl(struct file *f, unsigned int cmd,
+ unsigned long arg)
{
int size, ent_count;
int __user *p = (int __user *)arg;
@@ -1498,11 +1504,12 @@ static long random_ioctl(struct file *f, unsigned int cmd, unsigned long arg)
}
}
-static int random_fasync(int fd, struct file *filp, int on)
+static int __maybe_unused random_fasync(int fd, struct file *filp, int on)
{
return fasync_helper(fd, filp, on, &fasync);
}
+#ifdef CONFIG_DEVRANDOM
const struct file_operations random_fops = {
.read = random_read,
.write = random_write,
@@ -1511,6 +1518,7 @@ const struct file_operations random_fops = {
.fasync = random_fasync,
.llseek = noop_llseek,
};
+#endif
const struct file_operations urandom_fops = {
.read = urandom_read,
--
1.9.3
--
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