sys.c



/*
* linux/kernel/sys.c
*
* Copyright (C) 1991, 1992 Linus Torvalds
*/

#include <linux/config.h>
#include <linux/errno.h>
#include <linux/sched.h>
#include <linux/kernel.h>
#include <linux/times.h>
#include <linux/utsname.h>
#include <linux/param.h>
#include <linux/resource.h>
#include <linux/signal.h>
#include <linux/string.h>
#include <linux/ptrace.h>
#include <linux/stat.h>
#include <linux/mman.h>
#include <linux/mm.h>
#include <linux/fcntl.h>
#include <linux/acct.h>
#include <linux/tty.h>
#if defined(CONFIG_APM) && defined(CONFIG_APM_POWER_OFF)
#include <linux/apm_bios.h>
#endif

#include <asm/segment.h>
#include <asm/io.h>

/*
* this indicates whether you can reboot with ctrl-alt-del: the default is yes
*/
int C_A_D = 1;

extern void adjust_clock(void);

asmlinkage int sys_ni_syscall(void)
{
return -ENOSYS;
}

static int proc_sel(struct task_struct *p, int which, int who)
{
if(p->pid)
{
switch (which) {
case PRIO_PROCESS:
if (!who && p == current)
return 1;
return(p->pid == who);
case PRIO_PGRP:
if (!who)
who = current->pgrp;
return(p->pgrp == who);
case PRIO_USER:
if (!who)
who = current->uid;
return(p->uid == who);
}
}
return 0;
}


asmlinkage int sys_setpriority(int which, int who, int niceval)
{
struct task_struct *p;
int error = ESRCH;
unsigned int priority;

if (which > 2 || which < 0)
return -EINVAL;

/* normalize: avoid signed division (rounding problems) */
priority = niceval;
if (niceval < 0)
priority = -niceval;
if (priority > 20)
priority = 20;
priority = (priority * DEF_PRIORITY + 10) / 20 + DEF_PRIORITY;

if (niceval >= 0) {
priority = 2*DEF_PRIORITY - priority;
if (!priority)
priority = 1;
}

for_each_task(p) {
if (!proc_sel(p, which, who))
continue;
if (p->uid != current->euid &&
p->uid != current->uid && !suser()) {
error = EPERM;
continue;
}
if (error == ESRCH)
error = 0;
if (priority > p->priority && !suser())
error = EACCES;
else
p->priority = priority;
}
return -error;
}


/*
* Ugh. To avoid negative return values, "getpriority()" will
* not return the normal nice-value, but a value that has been
* offset by 20 (ie it returns 0..40 instead of -20..20)
*/
asmlinkage int sys_getpriority(int which, int who)
{
struct task_struct *p;
long max_prio = -ESRCH;

if (which > 2 || which < 0)
return -EINVAL;

for_each_task (p) {
if (!proc_sel(p, which, who))
continue;
if (p->priority > max_prio)
max_prio = p->priority;
}

/* scale the priority from timeslice to 0..40 */
if (max_prio > 0)
max_prio = (max_prio * 20 + DEF_PRIORITY/2) / DEF_PRIORITY;
return max_prio;
}

#ifndef __alpha__

/*
* Why do these exist? Binary compatibility with some other standard?
* If so, maybe they should be moved into the appropriate arch
* directory.
*/

asmlinkage int sys_profil(void)
{
return -ENOSYS;
}

asmlinkage int sys_ftime(void)
{
return -ENOSYS;
}

asmlinkage int sys_break(void)
{
return -ENOSYS;
}

asmlinkage int sys_stty(void)
{
return -ENOSYS;
}

asmlinkage int sys_gtty(void)
{
return -ENOSYS;
}

asmlinkage int sys_prof(void)
{
return -ENOSYS;
}

#endif

extern void hard_reset_now(void);
extern asmlinkage sys_kill(int, int);

/*
* 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 int sys_reboot(int magic, int magic_too, int flag)
{
if (!suser())
return -EPERM;
if (magic != 0xfee1dead || magic_too != 672274793)
return -EINVAL;
if (flag == 0x01234567)
hard_reset_now();
else if (flag == 0x89ABCDEF)
C_A_D = 1;
else if (!flag)
C_A_D = 0;
else if (flag == 0xCDEF0123) {
printk(KERN_EMERG "System halted\n");
sys_kill(-1, SIGKILL);
#if defined(CONFIG_APM) && defined(CONFIG_APM_POWER_OFF)
apm_set_power_state(APM_STATE_OFF);
#endif
do_exit(0);
} else
return -EINVAL;
return (0);
}

/*
* 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)
{
if (C_A_D)
hard_reset_now();
else
kill_proc(1, 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 w/ Saved ID's.
*/
asmlinkage int sys_setregid(gid_t rgid, gid_t egid)
{
int old_rgid = current->gid;
int old_egid = current->egid;

if (rgid != (gid_t) -1) {
if ((old_rgid == rgid) ||
(current->egid==rgid) ||
suser())
current->gid = rgid;
else
return(-EPERM);
}
if (egid != (gid_t) -1) {
if ((old_rgid == egid) ||
(current->egid == egid) ||
(current->sgid == egid) ||
suser())
current->fsgid = current->egid = egid;
else {
current->gid = old_rgid;
return(-EPERM);
}
}
if (rgid != (gid_t) -1 ||
(egid != (gid_t) -1 && egid != old_rgid))
current->sgid = current->egid;
current->fsgid = current->egid;
if (current->egid != old_egid)
current->dumpable = 0;
return 0;
}

/*
* setgid() is implemented like SysV w/ SAVED_IDS
*/
asmlinkage int sys_setgid(gid_t gid)
{
int old_egid = current->egid;

if (suser())
current->gid = current->egid = current->sgid = current->fsgid = gid;
else if ((gid == current->gid) || (gid == current->sgid))
current->egid = current->fsgid = gid;
else
return -EPERM;
if (current->egid != old_egid)
current->dumpable = 0;
return 0;
}


static char acct_active = 0;
static struct file acct_file;

int acct_process(long exitcode)
{
struct acct ac;
unsigned short fs;

if (acct_active) {
strncpy(ac.ac_comm, current->comm, ACCT_COMM);
ac.ac_comm[ACCT_COMM-1] = '\0';
ac.ac_utime = current->utime;
ac.ac_stime = current->stime;
ac.ac_btime = CT_TO_SECS(current->start_time) + (xtime.tv_sec - (jiffies / HZ));
ac.ac_etime = CURRENT_TIME - ac.ac_btime;
ac.ac_uid = current->uid;
ac.ac_gid = current->gid;
ac.ac_tty = (current)->tty == NULL ? -1 :
kdev_t_to_nr(current->tty->device);
ac.ac_flag = 0;
if (current->flags & PF_FORKNOEXEC)
ac.ac_flag |= AFORK;
if (current->flags & PF_SUPERPRIV)
ac.ac_flag |= ASU;
if (current->flags & PF_DUMPCORE)
ac.ac_flag |= ACORE;
if (current->flags & PF_SIGNALED)
ac.ac_flag |= AXSIG;
ac.ac_minflt = current->min_flt;
ac.ac_majflt = current->maj_flt;
ac.ac_exitcode = exitcode;

/* Kernel segment override */
fs = get_fs();
set_fs(KERNEL_DS);

acct_file.f_op->write(acct_file.f_inode, &acct_file,
(char *)&ac, sizeof(struct acct));

set_fs(fs);
}
return 0;
}

asmlinkage int sys_acct(const char *name)
{
struct inode *inode = (struct inode *)0;
char *tmp;
int error;

if (!suser())
return -EPERM;

if (name == (char *)0) {
if (acct_active) {
if (acct_file.f_op->release)
acct_file.f_op->release(acct_file.f_inode, &acct_file);

if (acct_file.f_inode != (struct inode *) 0)
iput(acct_file.f_inode);

acct_active = 0;
}
return 0;
} else {
if (!acct_active) {

if ((error = getname(name, &tmp)) != 0)
return (error);

error = open_namei(tmp, O_RDWR, 0600, &inode, 0);
putname(tmp);

if (error)
return (error);

if (!S_ISREG(inode->i_mode)) {
iput(inode);
return -EACCES;
}

if (!inode->i_op || !inode->i_op->default_file_ops ||
!inode->i_op->default_file_ops->write) {
iput(inode);
return -EIO;
}

acct_file.f_mode = 3;
acct_file.f_flags = 0;
acct_file.f_count = 1;
acct_file.f_inode = inode;
acct_file.f_pos = inode->i_size;
acct_file.f_reada = 0;
acct_file.f_op = inode->i_op->default_file_ops;

if (acct_file.f_op->open)
if (acct_file.f_op->open(acct_file.f_inode, &acct_file)) {
iput(inode);
return -EIO;
}

acct_active = 1;
return 0;
} else
return -EBUSY;
}
}

#ifndef __alpha__

/*
* Why do these exist? Binary compatibility with some other standard?
* If so, maybe they should be moved into the appropriate arch
* directory.
*/

asmlinkage int sys_phys(void)
{
return -ENOSYS;
}

asmlinkage int sys_lock(void)
{
return -ENOSYS;
}

asmlinkage int sys_mpx(void)
{
return -ENOSYS;
}

asmlinkage int sys_ulimit(void)
{
return -ENOSYS;
}

asmlinkage int sys_old_syscall(void)
{
return -ENOSYS;
}

#endif

/*
* 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 w/ Saved ID's.
*/
asmlinkage int sys_setreuid(uid_t ruid, uid_t euid)
{
int old_ruid = current->uid;
int old_euid = current->euid;

if (ruid != (uid_t) -1) {
if ((old_ruid == ruid) ||
(current->euid==ruid) ||
suser())
current->uid = ruid;
else
return(-EPERM);
}
if (euid != (uid_t) -1) {
if ((old_ruid == euid) ||
(current->euid == euid) ||
(current->suid == euid) ||
suser())
current->fsuid = current->euid = euid;
else {
current->uid = old_ruid;
return(-EPERM);
}
}
if (ruid != (uid_t) -1 ||
(euid != (uid_t) -1 && euid != old_ruid))
current->suid = current->euid;
current->fsuid = current->euid;
if (current->euid != old_euid)
current->dumpable = 0;
return 0;
}

/*
* setuid() is implemented like SysV w/ 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 int sys_setuid(uid_t uid)
{
int old_euid = current->euid;

if (suser())
current->uid = current->euid = current->suid = current->fsuid = uid;
else if ((uid == current->uid) || (uid == current->suid))
current->fsuid = current->euid = uid;
else
return -EPERM;
if (current->euid != old_euid)
current->dumpable = 0;
return(0);
}

/*
* "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 int sys_setfsuid(uid_t uid)
{
int old_fsuid = current->fsuid;

if (uid == current->uid || uid == current->euid ||
uid == current->suid || uid == current->fsuid || suser())
current->fsuid = uid;
if (current->fsuid != old_fsuid)
current->dumpable = 0;
return old_fsuid;
}

/*
* Samma på svenska..
*/
asmlinkage int sys_setfsgid(gid_t gid)
{
int old_fsgid = current->fsgid;

if (gid == current->gid || gid == current->egid ||
gid == current->sgid || gid == current->fsgid || suser())
current->fsgid = gid;
if (current->fsgid != old_fsgid)
current->dumpable = 0;
return old_fsgid;
}


asmlinkage long sys_times(struct tms * tbuf)
{
if (tbuf) {
int error = verify_area(VERIFY_WRITE,tbuf,sizeof *tbuf);
if (error)
return error;
put_user(current->utime,&tbuf->tms_utime);
put_user(current->stime,&tbuf->tms_stime);
put_user(current->cutime,&tbuf->tms_cutime);
put_user(current->cstime,&tbuf->tms_cstime);
}
return jiffies;
}

/*
* 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
*
* Auch. Had to add the 'did_exec' flag to conform completely to POSIX.
* LBT 04.03.94
*/
asmlinkage int sys_setpgid(pid_t pid, pid_t pgid)
{
struct task_struct * p;

if (!pid)
pid = current->pid;
if (!pgid)
pgid = pid;
if (pgid < 0)
return -EINVAL;
for_each_task(p) {
if (p->pid == pid)
goto found_task;
}
return -ESRCH;

found_task:
if (p->p_pptr == current || p->p_opptr == current) {
if (p->session != current->session)
return -EPERM;
if (p->did_exec)
return -EACCES;
} else if (p != current)
return -ESRCH;
if (p->leader)
return -EPERM;
if (pgid != pid) {
struct task_struct * tmp;
for_each_task (tmp) {
if (tmp->pgrp == pgid &&
tmp->session == current->session)
goto ok_pgid;
}
return -EPERM;
}

ok_pgid:
p->pgrp = pgid;
return 0;
}

asmlinkage int sys_getpgid(pid_t pid)
{
struct task_struct * p;

if (!pid)
return current->pgrp;
for_each_task(p) {
if (p->pid == pid)
return p->pgrp;
}
return -ESRCH;
}

asmlinkage int sys_getpgrp(void)
{
return current->pgrp;
}

asmlinkage int sys_getsid(pid_t pid)
{
struct task_struct * p;

if (!pid)
return current->session;
for_each_task(p) {
if (p->pid == pid)
return p->session;
}
return -ESRCH;
}

asmlinkage int sys_setsid(void)
{
struct task_struct * p;

for_each_task(p) {
if (p->pgrp == current->pid)
return -EPERM;
}

current->leader = 1;
current->session = current->pgrp = current->pid;
current->tty = NULL;
current->tty_old_pgrp = 0;
return current->pgrp;
}

/*
* Supplementary group ID's
*/
asmlinkage int sys_getgroups(int gidsetsize, gid_t *grouplist)
{
int i;
int * groups;

if (gidsetsize < 0)
return -EINVAL;
groups = current->groups;
for (i = 0 ; i < NGROUPS ; i++) {
if (groups[i] == NOGROUP)
break;
}
if (gidsetsize) {
int error;
error = verify_area(VERIFY_WRITE, grouplist, sizeof(gid_t) * gidsetsize);
if (error)
return error;
if (i > gidsetsize)
return -EINVAL;

for (i = 0 ; i < NGROUPS ; i++) {
if (groups[i] == NOGROUP)
break;
put_user(groups[i], grouplist);
grouplist++;
}
}
return i;
}

asmlinkage int sys_setgroups(int gidsetsize, gid_t *grouplist)
{
int i;

if (!suser())
return -EPERM;
if (gidsetsize > NGROUPS)
return -EINVAL;
i = verify_area(VERIFY_READ, grouplist, sizeof(gid_t) * gidsetsize);
if (i)
return i;
for (i = 0; i < gidsetsize; i++, grouplist++) {
current->groups[i] = get_user(grouplist);
}
if (i < NGROUPS)
current->groups[i] = NOGROUP;
return 0;
}

int in_group_p(gid_t grp)
{
int i;

if (grp == current->fsgid)
return 1;

for (i = 0; i < NGROUPS; i++) {
if (current->groups[i] == NOGROUP)
break;
if (current->groups[i] == grp)
return 1;
}
return 0;
}

asmlinkage int sys_newuname(struct new_utsname * name)
{
int error;

if (!name)
return -EFAULT;
error = verify_area(VERIFY_WRITE, name, sizeof *name);
if (!error)
memcpy_tofs(name,&system_utsname,sizeof *name);
return error;
}

#ifndef __alpha__

/*
* Move these to arch dependent dir since they are for
* backward compatibility only?
*/
asmlinkage int sys_uname(struct old_utsname * name)
{
int error;
if (!name)
return -EFAULT;
error = verify_area(VERIFY_WRITE, name,sizeof *name);
if (error)
return error;
memcpy_tofs(&name->sysname,&system_utsname.sysname,
sizeof (system_utsname.sysname));
memcpy_tofs(&name->nodename,&system_utsname.nodename,
sizeof (system_utsname.nodename));
memcpy_tofs(&name->release,&system_utsname.release,
sizeof (system_utsname.release));
memcpy_tofs(&name->version,&system_utsname.version,
sizeof (system_utsname.version));
memcpy_tofs(&name->machine,&system_utsname.machine,
sizeof (system_utsname.machine));
return 0;
}

asmlinkage int sys_olduname(struct oldold_utsname * name)
{
int error;
if (!name)
return -EFAULT;
error = verify_area(VERIFY_WRITE, name,sizeof *name);
if (error)
return error;
memcpy_tofs(&name->sysname,&system_utsname.sysname,__OLD_UTS_LEN);
put_user(0,name->sysname+__OLD_UTS_LEN);
memcpy_tofs(&name->nodename,&system_utsname.nodename,__OLD_UTS_LEN);
put_user(0,name->nodename+__OLD_UTS_LEN);
memcpy_tofs(&name->release,&system_utsname.release,__OLD_UTS_LEN);
put_user(0,name->release+__OLD_UTS_LEN);
memcpy_tofs(&name->version,&system_utsname.version,__OLD_UTS_LEN);
put_user(0,name->version+__OLD_UTS_LEN);
memcpy_tofs(&name->machine,&system_utsname.machine,__OLD_UTS_LEN);
put_user(0,name->machine+__OLD_UTS_LEN);
return 0;
}

#endif

asmlinkage int sys_sethostname(char *name, int len)
{
int error;

if (!suser())
return -EPERM;
if (len < 0 || len > __NEW_UTS_LEN)
return -EINVAL;
error = verify_area(VERIFY_READ, name, len);
if (error)
return error;
memcpy_fromfs(system_utsname.nodename, name, len);
system_utsname.nodename[len] = 0;
return 0;
}

asmlinkage int sys_gethostname(char *name, int len)
{
int i;

if (len < 0)
return -EINVAL;
i = verify_area(VERIFY_WRITE, name, len);
if (i)
return i;
i = 1+strlen(system_utsname.nodename);
if (i > len)
i = len;
memcpy_tofs(name, system_utsname.nodename, i);
return 0;
}

/*
* Only setdomainname; getdomainname can be implemented by calling
* uname()
*/
asmlinkage int sys_setdomainname(char *name, int len)
{
int error;

if (!suser())
return -EPERM;
if (len < 0 || len > __NEW_UTS_LEN)
return -EINVAL;
error = verify_area(VERIFY_READ, name, len);
if (error)
return error;
memcpy_fromfs(system_utsname.domainname, name, len);
system_utsname.domainname[len] = 0;
return 0;
}

asmlinkage int sys_getrlimit(unsigned int resource, struct rlimit *rlim)
{
int error;

if (resource >= RLIM_NLIMITS)
return -EINVAL;
error = verify_area(VERIFY_WRITE,rlim,sizeof *rlim);
if (error)
return error;
memcpy_tofs(rlim, current->rlim + resource, sizeof(*rlim));
return 0;
}

asmlinkage int sys_setrlimit(unsigned int resource, struct rlimit *rlim)
{
struct rlimit new_rlim, *old_rlim;
int err;

if (resource >= RLIM_NLIMITS)
return -EINVAL;
err = verify_area(VERIFY_READ, rlim, sizeof(*rlim));
if (err)
return err;
memcpy_fromfs(&new_rlim, rlim, sizeof(*rlim));
old_rlim = current->rlim + resource;
if (((new_rlim.rlim_cur > old_rlim->rlim_max) ||
(new_rlim.rlim_max > old_rlim->rlim_max)) &&
!suser())
return -EPERM;
if (resource == RLIMIT_NOFILE) {
if (new_rlim.rlim_cur > NR_OPEN || new_rlim.rlim_max > NR_OPEN)
return -EPERM;
}
*old_rlim = new_rlim;
return 0;
}

/*
* It would make sense to put struct rusage in the task_struct,
* except that would make the task_struct be *really big*. After
* task_struct gets moved into malloc'ed memory, it would
* make sense to do this. It will make moving the rest of the information
* a lot simpler! (Which we're not doing right now because we're not
* measuring them yet).
*/
int getrusage(struct task_struct *p, int who, struct rusage *ru)
{
int error;
struct rusage r;

error = verify_area(VERIFY_WRITE, ru, sizeof *ru);
if (error)
return error;
memset((char *) &r, 0, sizeof(r));
switch (who) {
case RUSAGE_SELF:
r.ru_utime.tv_sec = CT_TO_SECS(p->utime);
r.ru_utime.tv_usec = CT_TO_USECS(p->utime);
r.ru_stime.tv_sec = CT_TO_SECS(p->stime);
r.ru_stime.tv_usec = CT_TO_USECS(p->stime);
r.ru_minflt = p->min_flt;
r.ru_majflt = p->maj_flt;
r.ru_nswap = p->nswap;
break;
case RUSAGE_CHILDREN:
r.ru_utime.tv_sec = CT_TO_SECS(p->cutime);
r.ru_utime.tv_usec = CT_TO_USECS(p->cutime);
r.ru_stime.tv_sec = CT_TO_SECS(p->cstime);
r.ru_stime.tv_usec = CT_TO_USECS(p->cstime);
r.ru_minflt = p->cmin_flt;
r.ru_majflt = p->cmaj_flt;
r.ru_nswap = p->cnswap;
break;
default:
r.ru_utime.tv_sec = CT_TO_SECS(p->utime + p->cutime);
r.ru_utime.tv_usec = CT_TO_USECS(p->utime + p->cutime);
r.ru_stime.tv_sec = CT_TO_SECS(p->stime + p->cstime);
r.ru_stime.tv_usec = CT_TO_USECS(p->stime + p->cstime);
r.ru_minflt = p->min_flt + p->cmin_flt;
r.ru_majflt = p->maj_flt + p->cmaj_flt;
r.ru_nswap = p->nswap + p->cnswap;
break;
}
memcpy_tofs(ru, &r, sizeof(r));
return 0;
}

asmlinkage int sys_getrusage(int who, struct rusage *ru)
{
if (who != RUSAGE_SELF && who != RUSAGE_CHILDREN)
return -EINVAL;
return getrusage(current, who, ru);
}

asmlinkage int sys_umask(int mask)
{
int old = current->fs->umask;

current->fs->umask = mask & S_IRWXUGO;
return (old);
}