[PATCH] Reduce stack usage in sys.c
From: Yum Rayan (yum.rayan_at_gmail.com)
Date: 03/31/05
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Date: Wed, 30 Mar 2005 23:44:38 -0800 To: linux-kernel@vger.kernel.org
Attempt to reduce stack usage in sys.c (linux-2.6.12-rc1-mm3). Stack
usage was noted using checkstack.pl. Specifically
Before patch
------------
sys_reboot - 256
After patch
-----------
sys_reboot - none (register usage only)
Along the way, wrap code to 80 column width and cleanup lock usage.
Signed-off-by: Yum Rayan <yum.rayan@gmail.com>
--- a/kernel/sys.c 2005-03-25 22:11:06.000000000 -0800
+++ b/kernel/sys.c 2005-03-30 22:34:03.000000000 -0800
@@ -369,9 +369,9 @@
*
* reboot doesn't sync: do that yourself before calling this.
*/
-asmlinkage long sys_reboot(int magic1, int magic2, unsigned int cmd,
void __user * arg)
+asmlinkage long sys_reboot(int magic1, int magic2,
+ unsigned int cmd, void __user * arg)
{
- char buffer[256];
/* We only trust the superuser with rebooting the system. */
if (!capable(CAP_SYS_BOOT))
@@ -385,14 +385,15 @@
magic2 != LINUX_REBOOT_MAGIC2C))
return -EINVAL;
- lock_kernel();
switch (cmd) {
case LINUX_REBOOT_CMD_RESTART:
+ lock_kernel();
notifier_call_chain(&reboot_notifier_list, SYS_RESTART, NULL);
system_state = SYSTEM_RESTART;
device_shutdown();
printk(KERN_EMERG "Restarting system.\n");
machine_restart(NULL);
+ unlock_kernel();
break;
case LINUX_REBOOT_CMD_CAD_ON:
@@ -404,6 +405,7 @@
break;
case LINUX_REBOOT_CMD_HALT:
+ lock_kernel();
notifier_call_chain(&reboot_notifier_list, SYS_HALT, NULL);
system_state = SYSTEM_HALT;
device_shutdown();
@@ -414,6 +416,7 @@
break;
case LINUX_REBOOT_CMD_POWER_OFF:
+ lock_kernel();
notifier_call_chain(&reboot_notifier_list, SYS_POWER_OFF, NULL);
system_state = SYSTEM_POWER_OFF;
device_shutdown();
@@ -424,51 +427,60 @@
break;
case LINUX_REBOOT_CMD_RESTART2:
- if (strncpy_from_user(&buffer[0], arg, sizeof(buffer) - 1) < 0) {
- unlock_kernel();
+ {
+ char *buffer;
+ buffer = kmalloc(256, GFP_KERNEL);
+ if (!buffer)
+ return -ENOMEM;
+ if (strncpy_from_user(buffer, arg, 255) < 0) {
+ kfree(buffer);
return -EFAULT;
}
- buffer[sizeof(buffer) - 1] = '\0';
-
+ buffer[255] = '\0';
+ lock_kernel();
notifier_call_chain(&reboot_notifier_list, SYS_RESTART, buffer);
system_state = SYSTEM_RESTART;
device_shutdown();
- printk(KERN_EMERG "Restarting system with command '%s'.\n", buffer);
+ printk(KERN_EMERG "Restarting system with command '%s'.\n",
+ buffer);
machine_restart(buffer);
+ unlock_kernel();
+ kfree(buffer);
break;
-
+ }
#ifdef CONFIG_KEXEC
case LINUX_REBOOT_CMD_KEXEC:
{
struct kimage *image;
image = xchg(&kexec_image, 0);
if (!image) {
- unlock_kernel();
return -EINVAL;
}
+ lock_kernel();
notifier_call_chain(&reboot_notifier_list, SYS_RESTART, NULL);
system_state = SYSTEM_RESTART;
device_shutdown();
printk(KERN_EMERG "Starting new kernel\n");
machine_shutdown();
machine_kexec(image);
+ unlock_kernel();
break;
}
#endif
#ifdef CONFIG_SOFTWARE_SUSPEND
case LINUX_REBOOT_CMD_SW_SUSPEND:
- {
- int ret = software_suspend();
- unlock_kernel();
- return ret;
- }
+ {
+ int ret;
+ lock_kernel();
+ ret = software_suspend();
+ unlock_kernel();
+ return ret;
+ }
#endif
default:
- unlock_kernel();
return -EINVAL;
}
- unlock_kernel();
return 0;
}
-
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