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sys.c
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/*
* linux/kernel/sys.c
*
* Copyright (C) 1991, 1992 Linus Torvalds
*/
#include <linux/config.h>
#include <linux/module.h>
#include <linux/mm.h>
#include <linux/utsname.h>
#include <linux/mman.h>
#include <linux/smp_lock.h>
#include <linux/notifier.h>
#include <linux/reboot.h>
#include <linux/prctl.h>
#include <linux/init.h>
#include <linux/highuid.h>
#include <linux/fs.h>
#include <linux/kernel.h>
#include <linux/kexec.h>
#include <linux/workqueue.h>
#include <linux/device.h>
#include <linux/key.h>
#include <linux/times.h>
#include <linux/posix-timers.h>
#include <linux/security.h>
#include <linux/dcookies.h>
#include <linux/suspend.h>
#include <linux/tty.h>
#include <linux/signal.h>
#include <linux/compat.h>
#include <linux/syscalls.h>
#include <asm/uaccess.h>
#include <asm/io.h>
#include <asm/unistd.h>
#ifndef SET_UNALIGN_CTL
# define SET_UNALIGN_CTL(a,b) (-EINVAL)
#endif
#ifndef GET_UNALIGN_CTL
# define GET_UNALIGN_CTL(a,b) (-EINVAL)
#endif
#ifndef SET_FPEMU_CTL
# define SET_FPEMU_CTL(a,b) (-EINVAL)
#endif
#ifndef GET_FPEMU_CTL
# define GET_FPEMU_CTL(a,b) (-EINVAL)
#endif
#ifndef SET_FPEXC_CTL
# define SET_FPEXC_CTL(a,b) (-EINVAL)
#endif
#ifndef GET_FPEXC_CTL
# define GET_FPEXC_CTL(a,b) (-EINVAL)
#endif
/*
* this is where the system-wide overflow UID and GID are defined, for
* architectures that now have 32-bit UID/GID but didn't in the past
*/
int overflowuid = DEFAULT_OVERFLOWUID;
int overflowgid = DEFAULT_OVERFLOWGID;
#ifdef CONFIG_UID16
EXPORT_SYMBOL(overflowuid);
EXPORT_SYMBOL(overflowgid);
#endif
/*
* the same as above, but for filesystems which can only store a 16-bit
* UID and GID. as such, this is needed on all architectures
*/
int fs_overflowuid = DEFAULT_FS_OVERFLOWUID;
int fs_overflowgid = DEFAULT_FS_OVERFLOWUID;
EXPORT_SYMBOL(fs_overflowuid);
EXPORT_SYMBOL(fs_overflowgid);
/*
* this indicates whether you can reboot with ctrl-alt-del: the default is yes
*/
int C_A_D = 1;
int cad_pid = 1;
/*
* Notifier list for kernel code which wants to be called
* at shutdown. This is used to stop any idling DMA operations
* and the like.
*/
static struct notifier_block *reboot_notifier_list;
static DEFINE_RWLOCK(notifier_lock);
/**
* notifier_chain_register - Add notifier to a notifier chain
* @list: Pointer to root list pointer
* @n: New entry in notifier chain
*
* Adds a notifier to a notifier chain.
*
* Currently always returns zero.
*/
int notifier_chain_register(struct notifier_block **list, struct notifier_block *n)
{
write_lock(¬ifier_lock);
while(*list)
{
if(n->priority > (*list)->priority)
break;
list= &((*list)->next);
}
n->next = *list;
*list=n;
write_unlock(¬ifier_lock);
return 0;
}
EXPORT_SYMBOL(notifier_chain_register);
/**
* notifier_chain_unregister - Remove notifier from a notifier chain
* @nl: Pointer to root list pointer
* @n: New entry in notifier chain
*
* Removes a notifier from a notifier chain.
*
* Returns zero on success, or %-ENOENT on failure.
*/
int notifier_chain_unregister(struct notifier_block **nl, struct notifier_block *n)
{
write_lock(¬ifier_lock);
while((*nl)!=NULL)
{
if((*nl)==n)
{
*nl=n->next;
write_unlock(¬ifier_lock);
return 0;
}
nl=&((*nl)->next);
}
write_unlock(¬ifier_lock);
return -ENOENT;
}
EXPORT_SYMBOL(notifier_chain_unregister);
/**
* notifier_call_chain - Call functions in a notifier chain
* @n: Pointer to root pointer of notifier chain
* @val: Value passed unmodified to notifier function
* @v: Pointer passed unmodified to notifier function
*
* Calls each function in a notifier chain in turn.
*
* If the return value of the notifier can be and'd
* with %NOTIFY_STOP_MASK, then notifier_call_chain
* will return immediately, with the return value of
* the notifier function which halted execution.
* Otherwise, the return value is the return value
* of the last notifier function called.
*/
int notifier_call_chain(struct notifier_block **n, unsigned long val, void *v)
{
int ret=NOTIFY_DONE;
struct notifier_block *nb = *n;
while(nb)
{
ret=nb->notifier_call(nb,val,v);
if(ret&NOTIFY_STOP_MASK)
{
return ret;
}
nb=nb->next;
}
return ret;
}
EXPORT_SYMBOL(notifier_call_chain);
/**
* register_reboot_notifier - Register function to be called at reboot time
* @nb: Info about notifier function to be called
*
* Registers a function with the list of functions
* to be called at reboot time.
*
* Currently always returns zero, as notifier_chain_register
* always returns zero.
*/
int register_reboot_notifier(struct notifier_block * nb)
{
return notifier_chain_register(&reboot_notifier_list, nb);
}
EXPORT_SYMBOL(register_reboot_notifier);
/**
* unregister_reboot_notifier - Unregister previously registered reboot notifier
* @nb: Hook to be unregistered
*
* Unregisters a previously registered reboot
* notifier function.
*
* Returns zero on success, or %-ENOENT on failure.
*/
int unregister_reboot_notifier(struct notifier_block * nb)
{
return notifier_chain_unregister(&reboot_notifier_list, nb);
}
EXPORT_SYMBOL(unregister_reboot_notifier);
static int set_one_prio(struct task_struct *p, int niceval, int error)
{
int no_nice;
if (p->uid != current->euid &&
p->euid != current->euid && !capable(CAP_SYS_NICE)) {
error = -EPERM;
goto out;
}
if (niceval < task_nice(p) && !can_nice(p, niceval)) {
error = -EACCES;
goto out;
}
no_nice = security_task_setnice(p, niceval);
if (no_nice) {
error = no_nice;
goto out;
}
if (error == -ESRCH)
error = 0;
set_user_nice(p, niceval);
out:
return error;
}
asmlinkage long sys_setpriority(int which, int who, int niceval)
{
struct task_struct *g, *p;
struct user_struct *user;
int error = -EINVAL;
if (which > 2 || which < 0)
goto out;
/* normalize: avoid signed division (rounding problems) */
error = -ESRCH;
if (niceval < -20)
niceval = -20;
if (niceval > 19)
niceval = 19;
read_lock(&tasklist_lock);
switch (which) {
case PRIO_PROCESS:
if (!who)
who = current->pid;
p = find_task_by_pid(who);
if (p)
error = set_one_prio(p, niceval, error);
break;
case PRIO_PGRP:
if (!who)
who = process_group(current);
do_each_task_pid(who, PIDTYPE_PGID, p) {
error = set_one_prio(p, niceval, error);
} while_each_task_pid(who, PIDTYPE_PGID, p);
break;
case PRIO_USER:
user = current->user;
if (!who)
who = current->uid;
else
if ((who != current->uid) && !(user = find_user(who)))
goto out_unlock; /* No processes for this user */
do_each_thread(g, p)
if (p->uid == who)
error = set_one_prio(p, niceval, error);
while_each_thread(g, p);
if (who != current->uid)
free_uid(user); /* For find_user() */
break;
}
out_unlock:
read_unlock(&tasklist_lock);
out:
return error;
}
/*
* Ugh. To avoid negative return values, "getpriority()" will
* not return the normal nice-value, but a negated value that
* has been offset by 20 (ie it returns 40..1 instead of -20..19)
* to stay compatible.
*/
asmlinkage long sys_getpriority(int which, int who)
{
struct task_struct *g, *p;
struct user_struct *user;
long niceval, retval = -ESRCH;
if (which > 2 || which < 0)
return -EINVAL;
read_lock(&tasklist_lock);
switch (which) {
case PRIO_PROCESS:
if (!who)
who = current->pid;
p = find_task_by_pid(who);
if (p) {
niceval = 20 - task_nice(p);
if (niceval > retval)
retval = niceval;
}
break;
case PRIO_PGRP:
if (!who)
who = process_group(current);
do_each_task_pid(who, PIDTYPE_PGID, p) {
niceval = 20 - task_nice(p);
if (niceval > retval)
retval = niceval;
} while_each_task_pid(who, PIDTYPE_PGID, p);
break;
case PRIO_USER:
user = current->user;
if (!who)
who = current->uid;
else
if ((who != current->uid) && !(user = find_user(who)))
goto out_unlock; /* No processes for this user */
do_each_thread(g, p)
if (p->uid == who) {
niceval = 20 - task_nice(p);
if (niceval > retval)
retval = niceval;
}
while_each_thread(g, p);
if (who != current->uid)
free_uid(user); /* for find_user() */
break;
}
out_unlock:
read_unlock(&tasklist_lock);
return retval;
}
/*
* Reboot system call: for obvious reasons only root may call it,
* and even root needs to set up some magic numbers in the registers
* so that some mistake won't make this reboot the whole machine.
* You can also set the meaning of the ctrl-alt-del-key here.
*
* reboot doesn't sync: do that yourself before calling this.
*/
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))
return -EPERM;
/* For safety, we require "magic" arguments. */
if (magic1 != LINUX_REBOOT_MAGIC1 ||
(magic2 != LINUX_REBOOT_MAGIC2 &&
magic2 != LINUX_REBOOT_MAGIC2A &&
magic2 != LINUX_REBOOT_MAGIC2B &&
magic2 != LINUX_REBOOT_MAGIC2C))
return -EINVAL;
lock_kernel();
switch (cmd) {
case LINUX_REBOOT_CMD_RESTART:
notifier_call_chain(&reboot_notifier_list, SYS_RESTART, NULL);
system_state = SYSTEM_RESTART;
device_shutdown();
printk(KERN_EMERG "Restarting system.\n");
machine_restart(NULL);
break;
case LINUX_REBOOT_CMD_CAD_ON:
C_A_D = 1;
break;
case LINUX_REBOOT_CMD_CAD_OFF:
C_A_D = 0;
break;
case LINUX_REBOOT_CMD_HALT:
notifier_call_chain(&reboot_notifier_list, SYS_HALT, NULL);
system_state = SYSTEM_HALT;
device_suspend(PMSG_SUSPEND);
device_shutdown();
printk(KERN_EMERG "System halted.\n");
machine_halt();
unlock_kernel();
do_exit(0);
break;
case LINUX_REBOOT_CMD_POWER_OFF:
notifier_call_chain(&reboot_notifier_list, SYS_POWER_OFF, NULL);
system_state = SYSTEM_POWER_OFF;
device_suspend(PMSG_SUSPEND);
device_shutdown();
printk(KERN_EMERG "Power down.\n");
machine_power_off();
unlock_kernel();
do_exit(0);
break;
case LINUX_REBOOT_CMD_RESTART2:
if (strncpy_from_user(&buffer[0], arg, sizeof(buffer) - 1) < 0) {
unlock_kernel();
return -EFAULT;
}
buffer[sizeof(buffer) - 1] = '\0';
notifier_call_chain(&reboot_notifier_list, SYS_RESTART, buffer);
system_state = SYSTEM_RESTART;
device_suspend(PMSG_FREEZE);
device_shutdown();
printk(KERN_EMERG "Restarting system with command '%s'.\n", buffer);
machine_restart(buffer);
break;
#ifdef CONFIG_KEXEC
case LINUX_REBOOT_CMD_KEXEC:
{
struct kimage *image;
image = xchg(&kexec_image, 0);
if (!image) {
unlock_kernel();
return -EINVAL;
}
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);
break;
}
#endif
#ifdef CONFIG_SOFTWARE_SUSPEND
case LINUX_REBOOT_CMD_SW_SUSPEND:
{
int ret = software_suspend();
unlock_kernel();
return ret;
}
#endif
default:
unlock_kernel();
return -EINVAL;
}
unlock_kernel();
return 0;
}
static void deferred_cad(void *dummy)
{
notifier_call_chain(&reboot_notifier_list, SYS_RESTART, NULL);
machine_restart(NULL);
}
/*
* This function gets called by ctrl-alt-del - ie the keyboard interrupt.
* As it's called within an interrupt, it may NOT sync: the only choice
* is whether to reboot at once, or just ignore the ctrl-alt-del.
*/
void ctrl_alt_del(void)
{
static DECLARE_WORK(cad_work, deferred_cad, NULL);
if (C_A_D)
schedule_work(&cad_work);
else
kill_proc(cad_pid, SIGINT, 1);
}
/*
* Unprivileged users may change the real gid to the effective gid
* or vice versa. (BSD-style)
*
* If you set the real gid at all, or set the effective gid to a value not
* equal to the real gid, then the saved gid is set to the new effective gid.
*
* This makes it possible for a setgid program to completely drop its
* privileges, which is often a useful assertion to make when you are doing
* a security audit over a program.
*
* The general idea is that a program which uses just setregid() will be
* 100% compatible with BSD. A program which uses just setgid() will be
* 100% compatible with POSIX with saved IDs.
*
* SMP: There are not races, the GIDs are checked only by filesystem
* operations (as far as semantic preservation is concerned).
*/
asmlinkage long sys_setregid(gid_t rgid, gid_t egid)
{
int old_rgid = current->gid;
int old_egid = current->egid;
int new_rgid = old_rgid;
int new_egid = old_egid;
int retval;
retval = security_task_setgid(rgid, egid, (gid_t)-1, LSM_SETID_RE);
if (retval)
return retval;
if (rgid != (gid_t) -1) {
if ((old_rgid == rgid) ||
(current->egid==rgid) ||
capable(CAP_SETGID))
new_rgid = rgid;
else
return -EPERM;
}
if (egid != (gid_t) -1) {
if ((old_rgid == egid) ||
(current->egid == egid) ||
(current->sgid == egid) ||
capable(CAP_SETGID))
new_egid = egid;
else {
return -EPERM;
}
}
if (new_egid != old_egid)
{
current->mm->dumpable = suid_dumpable;
smp_wmb();
}
if (rgid != (gid_t) -1 ||
(egid != (gid_t) -1 && egid != old_rgid))
current->sgid = new_egid;
current->fsgid = new_egid;
current->egid = new_egid;
current->gid = new_rgid;
key_fsgid_changed(current);
return 0;
}
/*
* setgid() is implemented like SysV w/ SAVED_IDS
*
* SMP: Same implicit races as above.
*/
asmlinkage long sys_setgid(gid_t gid)
{
int old_egid = current->egid;
int retval;
retval = security_task_setgid(gid, (gid_t)-1, (gid_t)-1, LSM_SETID_ID);
if (retval)
return retval;
if (capable(CAP_SETGID))
{
if(old_egid != gid)
{
current->mm->dumpable = suid_dumpable;
smp_wmb();
}
current->gid = current->egid = current->sgid = current->fsgid = gid;
}
else if ((gid == current->gid) || (gid == current->sgid))
{
if(old_egid != gid)
{
current->mm->dumpable = suid_dumpable;
smp_wmb();
}
current->egid = current->fsgid = gid;
}
else
return -EPERM;
key_fsgid_changed(current);
return 0;
}
static int set_user(uid_t new_ruid, int dumpclear)
{
struct user_struct *new_user;
new_user = alloc_uid(new_ruid);
if (!new_user)
return -EAGAIN;
if (atomic_read(&new_user->processes) >=
current->signal->rlim[RLIMIT_NPROC].rlim_cur &&
new_user != &root_user) {
free_uid(new_user);
return -EAGAIN;
}
switch_uid(new_user);
if(dumpclear)
{
current->mm->dumpable = suid_dumpable;
smp_wmb();
}
current->uid = new_ruid;
return 0;
}
/*
* Unprivileged users may change the real uid to the effective uid
* or vice versa. (BSD-style)
*
* If you set the real uid at all, or set the effective uid to a value not
* equal to the real uid, then the saved uid is set to the new effective uid.
*
* This makes it possible for a setuid program to completely drop its
* privileges, which is often a useful assertion to make when you are doing
* a security audit over a program.
*
* The general idea is that a program which uses just setreuid() will be
* 100% compatible with BSD. A program which uses just setuid() will be
* 100% compatible with POSIX with saved IDs.
*/
asmlinkage long sys_setreuid(uid_t ruid, uid_t euid)
{
int old_ruid, old_euid, old_suid, new_ruid, new_euid;
int retval;
retval = security_task_setuid(ruid, euid, (uid_t)-1, LSM_SETID_RE);
if (retval)
return retval;
new_ruid = old_ruid = current->uid;
new_euid = old_euid = current->euid;
old_suid = current->suid;
if (ruid != (uid_t) -1) {
new_ruid = ruid;
if ((old_ruid != ruid) &&
(current->euid != ruid) &&
!capable(CAP_SETUID))
return -EPERM;
}
if (euid != (uid_t) -1) {
new_euid = euid;
if ((old_ruid != euid) &&
(current->euid != euid) &&
(current->suid != euid) &&
!capable(CAP_SETUID))
return -EPERM;
}
if (new_ruid != old_ruid && set_user(new_ruid, new_euid != old_euid) < 0)
return -EAGAIN;
if (new_euid != old_euid)
{
current->mm->dumpable = suid_dumpable;
smp_wmb();
}
current->fsuid = current->euid = new_euid;
if (ruid != (uid_t) -1 ||
(euid != (uid_t) -1 && euid != old_ruid))
current->suid = current->euid;
current->fsuid = current->euid;
key_fsuid_changed(current);
return security_task_post_setuid(old_ruid, old_euid, old_suid, LSM_SETID_RE);
}
/*
* setuid() is implemented like SysV with SAVED_IDS
*
* Note that SAVED_ID's is deficient in that a setuid root program
* like sendmail, for example, cannot set its uid to be a normal
* user and then switch back, because if you're root, setuid() sets
* the saved uid too. If you don't like this, blame the bright people
* in the POSIX committee and/or USG. Note that the BSD-style setreuid()
* will allow a root program to temporarily drop privileges and be able to
* regain them by swapping the real and effective uid.
*/
asmlinkage long sys_setuid(uid_t uid)
{
int old_euid = current->euid;
int old_ruid, old_suid, new_ruid, new_suid;
int retval;
retval = security_task_setuid(uid, (uid_t)-1, (uid_t)-1, LSM_SETID_ID);
if (retval)
return retval;
old_ruid = new_ruid = current->uid;
old_suid = current->suid;
new_suid = old_suid;
if (capable(CAP_SETUID)) {
if (uid != old_ruid && set_user(uid, old_euid != uid) < 0)
return -EAGAIN;
new_suid = uid;
} else if ((uid != current->uid) && (uid != new_suid))
return -EPERM;
if (old_euid != uid)
{
current->mm->dumpable = suid_dumpable;
smp_wmb();
}
current->fsuid = current->euid = uid;
current->suid = new_suid;
key_fsuid_changed(current);
return security_task_post_setuid(old_ruid, old_euid, old_suid, LSM_SETID_ID);
}
/*
* This function implements a generic ability to update ruid, euid,
* and suid. This allows you to implement the 4.4 compatible seteuid().
*/
asmlinkage long sys_setresuid(uid_t ruid, uid_t euid, uid_t suid)
{
int old_ruid = current->uid;
int old_euid = current->euid;
int old_suid = current->suid;
int retval;
retval = security_task_setuid(ruid, euid, suid, LSM_SETID_RES);
if (retval)
return retval;
if (!capable(CAP_SETUID)) {
if ((ruid != (uid_t) -1) && (ruid != current->uid) &&
(ruid != current->euid) && (ruid != current->suid))
return -EPERM;
if ((euid != (uid_t) -1) && (euid != current->uid) &&
(euid != current->euid) && (euid != current->suid))
return -EPERM;
if ((suid != (uid_t) -1) && (suid != current->uid) &&
(suid != current->euid) && (suid != current->suid))
return -EPERM;
}
if (ruid != (uid_t) -1) {
if (ruid != current->uid && set_user(ruid, euid != current->euid) < 0)
return -EAGAIN;
}
if (euid != (uid_t) -1) {
if (euid != current->euid)
{
current->mm->dumpable = suid_dumpable;
smp_wmb();
}
current->euid = euid;
}
current->fsuid = current->euid;
if (suid != (uid_t) -1)
current->suid = suid;
key_fsuid_changed(current);
return security_task_post_setuid(old_ruid, old_euid, old_suid, LSM_SETID_RES);
}
asmlinkage long sys_getresuid(uid_t __user *ruid, uid_t __user *euid, uid_t __user *suid)
{
int retval;
if (!(retval = put_user(current->uid, ruid)) &&
!(retval = put_user(current->euid, euid)))
retval = put_user(current->suid, suid);
return retval;
}
/*
* Same as above, but for rgid, egid, sgid.
*/
asmlinkage long sys_setresgid(gid_t rgid, gid_t egid, gid_t sgid)
{
int retval;
retval = security_task_setgid(rgid, egid, sgid, LSM_SETID_RES);
if (retval)
return retval;
if (!capable(CAP_SETGID)) {
if ((rgid != (gid_t) -1) && (rgid != current->gid) &&
(rgid != current->egid) && (rgid != current->sgid))
return -EPERM;
if ((egid != (gid_t) -1) && (egid != current->gid) &&
(egid != current->egid) && (egid != current->sgid))
return -EPERM;
if ((sgid != (gid_t) -1) && (sgid != current->gid) &&
(sgid != current->egid) && (sgid != current->sgid))
return -EPERM;
}
if (egid != (gid_t) -1) {
if (egid != current->egid)
{
current->mm->dumpable = suid_dumpable;
smp_wmb();
}
current->egid = egid;
}
current->fsgid = current->egid;
if (rgid != (gid_t) -1)
current->gid = rgid;
if (sgid != (gid_t) -1)
current->sgid = sgid;
key_fsgid_changed(current);
return 0;
}
asmlinkage long sys_getresgid(gid_t __user *rgid, gid_t __user *egid, gid_t __user *sgid)
{
int retval;
if (!(retval = put_user(current->gid, rgid)) &&
!(retval = put_user(current->egid, egid)))
retval = put_user(current->sgid, sgid);
return retval;
}
/*
* "setfsuid()" sets the fsuid - the uid used for filesystem checks. This
* is used for "access()" and for the NFS daemon (letting nfsd stay at
* whatever uid it wants to). It normally shadows "euid", except when
* explicitly set by setfsuid() or for access..
*/
asmlinkage long sys_setfsuid(uid_t uid)
{
int old_fsuid;
old_fsuid = current->fsuid;
if (security_task_setuid(uid, (uid_t)-1, (uid_t)-1, LSM_SETID_FS))
return old_fsuid;
if (uid == current->uid || uid == current->euid ||
uid == current->suid || uid == current->fsuid ||
capable(CAP_SETUID))
{
if (uid != old_fsuid)
{
current->mm->dumpable = suid_dumpable;
smp_wmb();
}
current->fsuid = uid;
}
key_fsuid_changed(current);
security_task_post_setuid(old_fsuid, (uid_t)-1, (uid_t)-1, LSM_SETID_FS);
return old_fsuid;
}
/*
* Samma på svenska..
*/
asmlinkage long sys_setfsgid(gid_t gid)
{
int old_fsgid;
old_fsgid = current->fsgid;
if (security_task_setgid(gid, (gid_t)-1, (gid_t)-1, LSM_SETID_FS))
return old_fsgid;
if (gid == current->gid || gid == current->egid ||
gid == current->sgid || gid == current->fsgid ||
capable(CAP_SETGID))
{
if (gid != old_fsgid)
{
current->mm->dumpable = suid_dumpable;
smp_wmb();
}
current->fsgid = gid;
key_fsgid_changed(current);
}
return old_fsgid;
}
asmlinkage long sys_times(struct tms __user * tbuf)
{
/*
* In the SMP world we might just be unlucky and have one of
* the times increment as we use it. Since the value is an
* atomically safe type this is just fine. Conceptually its
* as if the syscall took an instant longer to occur.
*/
if (tbuf) {
struct tms tmp;
cputime_t utime, stime, cutime, cstime;
#ifdef CONFIG_SMP
if (thread_group_empty(current)) {
/*
* Single thread case without the use of any locks.
*
* We may race with release_task if two threads are
* executing. However, release task first adds up the
* counters (__exit_signal) before removing the task
* from the process tasklist (__unhash_process).
* __exit_signal also acquires and releases the
* siglock which results in the proper memory ordering
* so that the list modifications are always visible
* after the counters have been updated.
*
* If the counters have been updated by the second thread
* but the thread has not yet been removed from the list
* then the other branch will be executing which will
* block on tasklist_lock until the exit handling of the
* other task is finished.
*
* This also implies that the sighand->siglock cannot
* be held by another processor. So we can also
* skip acquiring that lock.
*/
utime = cputime_add(current->signal->utime, current->utime);
stime = cputime_add(current->signal->utime, current->stime);
cutime = current->signal->cutime;
cstime = current->signal->cstime;
} else
#endif
{
/* Process with multiple threads */
struct task_struct *tsk = current;
struct task_struct *t;
read_lock(&tasklist_lock);
utime = tsk->signal->utime;
stime = tsk->signal->stime;
t = tsk;
do {
utime = cputime_add(utime, t->utime);
stime = cputime_add(stime, t->stime);
t = next_thread(t);
} while (t != tsk);
/*
* While we have tasklist_lock read-locked, no dying thread
* can be updating current->signal->[us]time. Instead,
* we got their counts included in the live thread loop.
* However, another thread can come in right now and
* do a wait call that updates current->signal->c[us]time.
* To make sure we always see that pair updated atomically,
* we take the siglock around fetching them.
*/
spin_lock_irq(&tsk->sighand->siglock);
cutime = tsk->signal->cutime;
cstime = tsk->signal->cstime;
spin_unlock_irq(&tsk->sighand->siglock);
read_unlock(&tasklist_lock);
}
tmp.tms_utime = cputime_to_clock_t(utime);
tmp.tms_stime = cputime_to_clock_t(stime);
tmp.tms_cutime = cputime_to_clock_t(cutime);
tmp.tms_cstime = cputime_to_clock_t(cstime);
if (copy_to_user(tbuf, &tmp, sizeof(struct tms)))
return -EFAULT;
}
return (long) jiffies_64_to_clock_t(get_jiffies_64());
}
/*
* This needs some heavy checking ...
* I just haven't the stomach for it. I also don't fully
* understand sessions/pgrp etc. Let somebody who does explain it.
*
* OK, I think I have the protection semantics right.... this is really
* only important on a multi-user system anyway, to make sure one user
* can't send a signal to a process owned by another. -TYT, 12/12/91