/* * linux/kernel/sys.c * * Copyright (C) 1991, 1992 Linus Torvalds */ #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include /* * this indicates whether you can reboot with ctrl-alt-del: the default is yes */ int C_A_D = 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. */ struct notifier_block *reboot_notifier_list = NULL; int register_reboot_notifier(struct notifier_block * nb) { return notifier_chain_register(&reboot_notifier_list, nb); } int unregister_reboot_notifier(struct notifier_block * nb) { return notifier_chain_unregister(&reboot_notifier_list, nb); } 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; unsigned int priority; int error; if (which > 2 || which < 0) return -EINVAL; /* normalize: avoid signed division (rounding problems) */ error = ESRCH; 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; } read_lock(&tasklist_lock); 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; } read_unlock(&tasklist_lock); 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; read_lock(&tasklist_lock); for_each_task (p) { if (!proc_sel(p, which, who)) continue; if (p->priority > max_prio) max_prio = p->priority; } read_unlock(&tasklist_lock); /* 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; } extern asmlinkage int 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 magic1, int magic2, int cmd, void * arg) { char buffer[256]; /* We only trust the superuser with rebooting the system. */ if (!suser()) return -EPERM; /* For safety, we require "magic" arguments. */ if (magic1 != LINUX_REBOOT_MAGIC1 || (magic2 != LINUX_REBOOT_MAGIC2 && magic2 != LINUX_REBOOT_MAGIC2A)) return -EINVAL; lock_kernel(); switch (cmd) { case LINUX_REBOOT_CMD_RESTART: notifier_call_chain(&reboot_notifier_list, SYS_RESTART, NULL); 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); printk(KERN_EMERG "System halted.\n"); machine_halt(); do_exit(0); break; case LINUX_REBOOT_CMD_POWER_OFF: notifier_call_chain(&reboot_notifier_list, SYS_POWER_OFF, NULL); printk(KERN_EMERG "Power down.\n"); machine_power_off(); do_exit(0); break; case LINUX_REBOOT_CMD_RESTART2: if (strncpy_from_user(&buffer[0], (char *)arg, sizeof(buffer) - 1) < 0) { unlock_kernel(); return -EFAULT; } buffer[sizeof(buffer) - 1] = '\0'; notifier_call_chain(&reboot_notifier_list, SYS_RESTART, buffer); printk(KERN_EMERG "Restarting system with command '%s'.\n", buffer); machine_restart(buffer); break; default: unlock_kernel(); return -EINVAL; break; }; unlock_kernel(); 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) { notifier_call_chain(&reboot_notifier_list, SYS_RESTART, NULL); machine_restart(NULL); } 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. * * SMP: There are not races, the gid's are checked only by filesystem * operations (as far as semantic preservation is concerned). */ 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 * * SMP: Same implicit races as above. */ 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 long fs; if (acct_active) { strncpy(ac.ac_comm, current->comm, ACCT_COMM); ac.ac_comm[ACCT_COMM-1] = '\0'; ac.ac_utime = current->times.tms_utime; ac.ac_stime = current->times.tms_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, (char *)&ac, sizeof(struct acct), &acct_file.f_pos); set_fs(fs); } return 0; } asmlinkage int sys_acct(const char *name) { int error = -EPERM; lock_kernel(); if (!suser()) goto out; if (name == (char *)0) { if (acct_active) { if (acct_file.f_op->release) acct_file.f_op->release(acct_file.f_dentry->d_inode, &acct_file); if (acct_file.f_dentry != NULL) dput(acct_file.f_dentry); acct_active = 0; } error = 0; } else { error = -EBUSY; if (!acct_active) { struct dentry *dentry; struct inode *inode; char *tmp; tmp = getname(name); error = PTR_ERR(tmp); if (IS_ERR(tmp)) goto out; dentry = open_namei(tmp, O_RDWR, 0600); putname(tmp); error = PTR_ERR(dentry); if (IS_ERR(dentry)) goto out; inode = dentry->d_inode; error = -EACCES; if (!S_ISREG(inode->i_mode)) { dput(dentry); goto out; } error = -EIO; if (!inode->i_op || !inode->i_op->default_file_ops || !inode->i_op->default_file_ops->write) { dput(dentry); goto out; } acct_file.f_mode = 3; acct_file.f_flags = 0; acct_file.f_count = 1; acct_file.f_dentry = dentry; 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) { error = acct_file.f_op->open(inode, &acct_file); if (error) { dput(dentry); goto out; } } acct_active = 1; error = 0; } } out: unlock_kernel(); return error; } /* * 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, old_euid, new_ruid; new_ruid = old_ruid = current->uid; old_euid = current->euid; if (ruid != (uid_t) -1) { if ((old_ruid == ruid) || (current->euid==ruid) || suser()) new_ruid = 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 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; if(new_ruid != old_ruid) { /* What if a process setreuid()'s and this brings the * new uid over his NPROC rlimit? We can check this now * cheaply with the new uid cache, so if it matters * we should be checking for it. -DaveM */ charge_uid(current, -1); current->uid = new_ruid; if(new_ruid) charge_uid(current, 1); } 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; int old_ruid, new_ruid; old_ruid = new_ruid = current->uid; if (suser()) new_ruid = 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; if(new_ruid != old_ruid) { /* See comment above about NPROC rlimit issues... */ charge_uid(current, -1); current->uid = new_ruid; if(new_ruid) charge_uid(current, 1); } return 0; } /* * This function implementes a generic ability to update ruid, euid, * and suid. This allows you to implement the 4.4 compatible seteuid(). */ asmlinkage int sys_setresuid(uid_t ruid, uid_t euid, uid_t suid) { if (current->uid != 0 && current->euid != 0 && current->suid != 0) { 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) { /* See above commentary about NPROC rlimit issues here. */ charge_uid(current, -1); current->uid = ruid; if(ruid) charge_uid(current, 1); } if (euid != (uid_t) -1) { if (euid != current->euid) current->dumpable = 0; current->euid = euid; current->fsuid = euid; } if (suid != (uid_t) -1) current->suid = suid; return 0; } asmlinkage int sys_getresuid(uid_t *ruid, uid_t *euid, uid_t *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 int sys_setresgid(gid_t rgid, gid_t egid, gid_t sgid) { if (current->uid != 0 && current->euid != 0 && current->suid != 0) { 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 (rgid != (gid_t) -1) current->gid = rgid; if (egid != (gid_t) -1) { if (egid != current->egid) current->dumpable = 0; current->egid = egid; current->fsgid = egid; } if (sgid != (gid_t) -1) current->sgid = sgid; return 0; } asmlinkage int sys_getresgid(gid_t *rgid, gid_t *egid, gid_t *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 int sys_setfsuid(uid_t uid) { int old_fsuid; 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; 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) { /* * 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) if (copy_to_user(tbuf, ¤t->times, sizeof(struct tms))) return -EFAULT; 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; int err = -EINVAL; if (!pid) pid = current->pid; if (!pgid) pgid = pid; if (pgid < 0) return -EINVAL; if((p = find_task_by_pid(pid)) == NULL) return -ESRCH; /* From this point forward we keep holding onto the tasklist lock * so that our parent does not change from under us. -DaveM */ read_lock(&tasklist_lock); err = -ESRCH; if (p->p_pptr == current || p->p_opptr == current) { err = -EPERM; if (p->session != current->session) goto out; err = -EACCES; if (p->did_exec) goto out; } else if (p != current) goto out; err = -EPERM; if (p->leader) goto out; if (pgid != pid) { struct task_struct * tmp; for_each_task (tmp) { if (tmp->pgrp == pgid && tmp->session == current->session) goto ok_pgid; } goto out; } ok_pgid: p->pgrp = pgid; err = 0; out: /* All paths lead to here, thus we are safe. -DaveM */ read_unlock(&tasklist_lock); return err; } asmlinkage int sys_getpgid(pid_t pid) { if (!pid) { return current->pgrp; } else { struct task_struct *p = find_task_by_pid(pid); if(p) return p->pgrp; else return -ESRCH; } } asmlinkage int sys_getpgrp(void) { /* SMP - assuming writes are word atomic this is fine */ return current->pgrp; } asmlinkage int sys_getsid(pid_t pid) { if (!pid) { return current->session; } else { struct task_struct *p = find_task_by_pid(pid); if(p) return p->session; else return -ESRCH; } } asmlinkage int sys_setsid(void) { struct task_struct * p; int err = -EPERM; read_lock(&tasklist_lock); for_each_task(p) { if (p->pgrp == current->pid) goto out; } current->leader = 1; current->session = current->pgrp = current->pid; current->tty = NULL; current->tty_old_pgrp = 0; err = current->pgrp; out: read_unlock(&tasklist_lock); return err; } /* * Supplementary group ID's */ asmlinkage int sys_getgroups(int gidsetsize, gid_t *grouplist) { int i; /* * SMP: Nobody else can change our grouplist. Thus we are * safe. */ if (gidsetsize < 0) return -EINVAL; i = current->ngroups; if (gidsetsize) { if (i > gidsetsize) return -EINVAL; if (copy_to_user(grouplist, current->groups, sizeof(gid_t)*i)) return -EFAULT; } return i; } /* * SMP: Our groups are not shared. We can copy to/from them safely * without another task interfering. */ asmlinkage int sys_setgroups(int gidsetsize, gid_t *grouplist) { if (!suser()) return -EPERM; if ((unsigned) gidsetsize > NGROUPS) return -EINVAL; if(copy_from_user(current->groups, grouplist, gidsetsize * sizeof(gid_t))) return -EFAULT; current->ngroups = gidsetsize; return 0; } int in_group_p(gid_t grp) { if (grp != current->fsgid) { int i = current->ngroups; if (i) { gid_t *groups = current->groups; do { if (*groups == grp) goto out; groups++; i--; } while (i); } return 0; } out: return 1; } asmlinkage int sys_newuname(struct new_utsname * name) { if (!name) return -EFAULT; if (copy_to_user(name,&system_utsname,sizeof *name)) return -EFAULT; return 0; } asmlinkage int sys_sethostname(char *name, int len) { if (!suser()) return -EPERM; if (len < 0 || len > __NEW_UTS_LEN) return -EINVAL; if(copy_from_user(system_utsname.nodename, name, len)) return -EFAULT; system_utsname.nodename[len] = 0; #ifdef CONFIG_TRANS_NAMES translations_dirty = 1; #endif return 0; } asmlinkage int sys_gethostname(char *name, int len) { int i; if (len < 0) return -EINVAL; i = 1 + strlen(system_utsname.nodename); if (i > len) i = len; return copy_to_user(name, system_utsname.nodename, i) ? -EFAULT : 0; } /* * Only setdomainname; getdomainname can be implemented by calling * uname() */ asmlinkage int sys_setdomainname(char *name, int len) { if (!suser()) return -EPERM; if (len < 0 || len > __NEW_UTS_LEN) return -EINVAL; if(copy_from_user(system_utsname.domainname, name, len)) return -EFAULT; system_utsname.domainname[len] = 0; #ifdef CONFIG_TRANS_NAMES translations_dirty = 1; #endif return 0; } asmlinkage int sys_getrlimit(unsigned int resource, struct rlimit *rlim) { if (resource >= RLIM_NLIMITS) return -EINVAL; else return copy_to_user(rlim, current->rlim + resource, sizeof(*rlim)) ? -EFAULT : 0; } asmlinkage int sys_setrlimit(unsigned int resource, struct rlimit *rlim) { struct rlimit new_rlim, *old_rlim; if (resource >= RLIM_NLIMITS) return -EINVAL; if(copy_from_user(&new_rlim, rlim, sizeof(*rlim))) return -EFAULT; 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). * * This is SMP safe. Either we are called from sys_getrusage on ourselves * below (we know we aren't going to exit/disappear and only we change our * rusage counters), or we are called from wait4() on a process which is * either stopped or zombied. In the zombied case the task won't get * reaped till shortly after the call to getrusage(), in both cases the * task being examined is in a frozen state so the counters won't change. */ int getrusage(struct task_struct *p, int who, struct rusage *ru) { struct rusage r; memset((char *) &r, 0, sizeof(r)); switch (who) { case RUSAGE_SELF: r.ru_utime.tv_sec = CT_TO_SECS(p->times.tms_utime); r.ru_utime.tv_usec = CT_TO_USECS(p->times.tms_utime); r.ru_stime.tv_sec = CT_TO_SECS(p->times.tms_stime); r.ru_stime.tv_usec = CT_TO_USECS(p->times.tms_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->times.tms_cutime); r.ru_utime.tv_usec = CT_TO_USECS(p->times.tms_cutime); r.ru_stime.tv_sec = CT_TO_SECS(p->times.tms_cstime); r.ru_stime.tv_usec = CT_TO_USECS(p->times.tms_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->times.tms_utime + p->times.tms_cutime); r.ru_utime.tv_usec = CT_TO_USECS(p->times.tms_utime + p->times.tms_cutime); r.ru_stime.tv_sec = CT_TO_SECS(p->times.tms_stime + p->times.tms_cstime); r.ru_stime.tv_usec = CT_TO_USECS(p->times.tms_stime + p->times.tms_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; } return copy_to_user(ru, &r, sizeof(r)) ? -EFAULT : 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) { mask = xchg(¤t->fs->umask, mask & S_IRWXUGO); return mask; } asmlinkage int sys_prctl(int option, unsigned long arg2, unsigned long arg3, unsigned long arg4, unsigned long arg5) { int error = 0; int sig; switch (option) { case PR_SET_PDEATHSIG: sig = arg2; if (sig > _NSIG) { error = -EINVAL; break; } current->pdeath_signal = sig; break; default: error = -EINVAL; break; } return error; }