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minix/servers/pm/signal.c

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/* This file handles signals, which are asynchronous events and are generally
* a messy and unpleasant business. Signals can be generated by the KILL
* system call, or from the keyboard (SIGINT) or from the clock (SIGALRM).
* In all cases control eventually passes to check_sig() to see which processes
* can be signaled. The actual signaling is done by sig_proc().
*
* The entry points into this file are:
* do_sigaction: perform the SIGACTION system call
* do_sigpending: perform the SIGPENDING system call
* do_sigprocmask: perform the SIGPROCMASK system call
* do_sigreturn: perform the SIGRETURN system call
* do_sigsuspend: perform the SIGSUSPEND system call
* do_kill: perform the KILL system call
* do_alarm: perform the ALARM system call by calling set_alarm()
* set_alarm: tell the clock task to start or stop a timer
* do_pause: perform the PAUSE system call
* ksig_pending: the kernel notified about pending signals
* sig_proc: interrupt or terminate a signaled process
* check_sig: check which processes to signal with sig_proc()
* check_pending: check if a pending signal can now be delivered
*/
#include "pm.h"
#include <sys/stat.h>
#include <sys/ptrace.h>
#include <minix/callnr.h>
#include <minix/endpoint.h>
#include <minix/com.h>
#include <minix/vm.h>
#include <signal.h>
#include <sys/resource.h>
#include <sys/sigcontext.h>
#include <string.h>
#include "mproc.h"
#include "param.h"
FORWARD _PROTOTYPE( void unpause, (int pro, int for_trace) );
FORWARD _PROTOTYPE( void handle_ksig, (int proc_nr, sigset_t sig_map) );
FORWARD _PROTOTYPE( void cause_sigalrm, (struct timer *tp) );
/*===========================================================================*
* do_sigaction *
*===========================================================================*/
PUBLIC int do_sigaction()
{
int r;
struct sigaction svec;
struct sigaction *svp;
if (m_in.sig_nr == SIGKILL) return(OK);
if (m_in.sig_nr < 1 || m_in.sig_nr > _NSIG) return (EINVAL);
svp = &mp->mp_sigact[m_in.sig_nr];
if ((struct sigaction *) m_in.sig_osa != (struct sigaction *) NULL) {
r = sys_datacopy(PM_PROC_NR,(vir_bytes) svp,
who_e, (vir_bytes) m_in.sig_osa, (phys_bytes) sizeof(svec));
if (r != OK) return(r);
}
if ((struct sigaction *) m_in.sig_nsa == (struct sigaction *) NULL)
return(OK);
/* Read in the sigaction structure. */
r = sys_datacopy(who_e, (vir_bytes) m_in.sig_nsa,
PM_PROC_NR, (vir_bytes) &svec, (phys_bytes) sizeof(svec));
if (r != OK) return(r);
if (svec.sa_handler == SIG_IGN) {
sigaddset(&mp->mp_ignore, m_in.sig_nr);
sigdelset(&mp->mp_sigpending, m_in.sig_nr);
sigdelset(&mp->mp_catch, m_in.sig_nr);
sigdelset(&mp->mp_sig2mess, m_in.sig_nr);
} else if (svec.sa_handler == SIG_DFL) {
sigdelset(&mp->mp_ignore, m_in.sig_nr);
sigdelset(&mp->mp_catch, m_in.sig_nr);
sigdelset(&mp->mp_sig2mess, m_in.sig_nr);
} else if (svec.sa_handler == SIG_MESS) {
if (! (mp->mp_flags & PRIV_PROC)) return(EPERM);
sigdelset(&mp->mp_ignore, m_in.sig_nr);
sigaddset(&mp->mp_sig2mess, m_in.sig_nr);
sigdelset(&mp->mp_catch, m_in.sig_nr);
} else {
sigdelset(&mp->mp_ignore, m_in.sig_nr);
sigaddset(&mp->mp_catch, m_in.sig_nr);
sigdelset(&mp->mp_sig2mess, m_in.sig_nr);
}
mp->mp_sigact[m_in.sig_nr].sa_handler = svec.sa_handler;
sigdelset(&svec.sa_mask, SIGKILL);
mp->mp_sigact[m_in.sig_nr].sa_mask = svec.sa_mask;
mp->mp_sigact[m_in.sig_nr].sa_flags = svec.sa_flags;
mp->mp_sigreturn = (vir_bytes) m_in.sig_ret;
return(OK);
}
/*===========================================================================*
* do_sigpending *
*===========================================================================*/
PUBLIC int do_sigpending()
{
mp->mp_reply.reply_mask = (long) mp->mp_sigpending;
return OK;
}
/*===========================================================================*
* do_sigprocmask *
*===========================================================================*/
PUBLIC int do_sigprocmask()
{
/* Note that the library interface passes the actual mask in sigmask_set,
* not a pointer to the mask, in order to save a copy. Similarly,
* the old mask is placed in the return message which the library
* interface copies (if requested) to the user specified address.
*
* The library interface must set SIG_INQUIRE if the 'act' argument
* is NULL.
*
* KILL and STOP can't be masked.
*/
int i;
mp->mp_reply.reply_mask = (long) mp->mp_sigmask;
switch (m_in.sig_how) {
case SIG_BLOCK:
sigdelset((sigset_t *)&m_in.sig_set, SIGKILL);
sigdelset((sigset_t *)&m_in.sig_set, SIGSTOP);
for (i = 1; i <= _NSIG; i++) {
if (sigismember((sigset_t *)&m_in.sig_set, i))
sigaddset(&mp->mp_sigmask, i);
}
break;
case SIG_UNBLOCK:
for (i = 1; i <= _NSIG; i++) {
if (sigismember((sigset_t *)&m_in.sig_set, i))
sigdelset(&mp->mp_sigmask, i);
}
check_pending(mp);
break;
case SIG_SETMASK:
sigdelset((sigset_t *) &m_in.sig_set, SIGKILL);
sigdelset((sigset_t *) &m_in.sig_set, SIGSTOP);
mp->mp_sigmask = (sigset_t) m_in.sig_set;
check_pending(mp);
break;
case SIG_INQUIRE:
break;
default:
return(EINVAL);
break;
}
return OK;
}
/*===========================================================================*
* do_sigsuspend *
*===========================================================================*/
PUBLIC int do_sigsuspend()
{
mp->mp_sigmask2 = mp->mp_sigmask; /* save the old mask */
mp->mp_sigmask = (sigset_t) m_in.sig_set;
sigdelset(&mp->mp_sigmask, SIGKILL);
mp->mp_flags |= SIGSUSPENDED;
check_pending(mp);
return(SUSPEND);
}
/*===========================================================================*
* do_sigreturn *
*===========================================================================*/
PUBLIC int do_sigreturn()
{
/* A user signal handler is done. Restore context and check for
* pending unblocked signals.
*/
int r;
mp->mp_sigmask = (sigset_t) m_in.sig_set;
sigdelset(&mp->mp_sigmask, SIGKILL);
r = sys_sigreturn(who_e, (struct sigmsg *) m_in.sig_context);
check_pending(mp);
return(r);
}
/*===========================================================================*
* do_kill *
*===========================================================================*/
PUBLIC int do_kill()
{
/* Perform the kill(pid, signo) system call. */
return check_sig(m_in.pid, m_in.sig_nr);
}
/*===========================================================================*
* ksig_pending *
*===========================================================================*/
PUBLIC int ksig_pending()
{
/* Certain signals, such as segmentation violations originate in the kernel.
* When the kernel detects such signals, it notifies the PM to take further
* action. The PM requests the kernel to send messages with the process
* slot and bit map for all signaled processes. The File System, for example,
* uses this mechanism to signal writing on broken pipes (SIGPIPE).
*
* The kernel has notified the PM about pending signals. Request pending
* signals until all signals are handled. If there are no more signals,
* NONE is returned in the process number field.
*/
int proc_nr_e;
sigset_t sig_map;
while (TRUE) {
int r;
/* get an arbitrary pending signal */
if((r=sys_getksig(&proc_nr_e, &sig_map)) != OK)
panic(__FILE__,"sys_getksig failed", r);
if (NONE == proc_nr_e) { /* stop if no more pending signals */
break;
} else {
int proc_nr_p;
if(pm_isokendpt(proc_nr_e, &proc_nr_p) != OK)
panic(__FILE__,"sys_getksig strange process", proc_nr_e);
handle_ksig(proc_nr_e, sig_map); /* handle the received signal */
/* If the process still exists to the kernel after the signal
* has been handled ...
*/
if ((mproc[proc_nr_p].mp_flags & (IN_USE | EXITING)) == IN_USE)
{
if((r=sys_endksig(proc_nr_e)) != OK) /* ... tell kernel it's done */
panic(__FILE__,"sys_endksig failed", r);
}
}
}
return(SUSPEND); /* prevents sending reply */
}
/*===========================================================================*
* handle_ksig *
*===========================================================================*/
PRIVATE void handle_ksig(proc_nr_e, sig_map)
int proc_nr_e;
sigset_t sig_map;
{
register struct mproc *rmp;
int i, proc_nr;
pid_t proc_id, id;
if(pm_isokendpt(proc_nr_e, &proc_nr) != OK || proc_nr < 0) {
printf("PM: handle_ksig: %d?? not ok\n", proc_nr_e);
return;
}
rmp = &mproc[proc_nr];
if ((rmp->mp_flags & (IN_USE | EXITING)) != IN_USE) {
printf("PM: handle_ksig: %d?? exiting / not in use\n", proc_nr_e);
return;
}
proc_id = rmp->mp_pid;
mp = &mproc[0]; /* pretend signals are from PM */
mp->mp_procgrp = rmp->mp_procgrp; /* get process group right */
/* Check each bit in turn to see if a signal is to be sent. Unlike
* kill(), the kernel may collect several unrelated signals for a
* process and pass them to PM in one blow. Thus loop on the bit
* map. For SIGINT, SIGWINCH and SIGQUIT, use proc_id 0 to indicate
* a broadcast to the recipient's process group. For SIGKILL, use
* proc_id -1 to indicate a systemwide broadcast.
*/
for (i = 1; i <= _NSIG; i++) {
if (!sigismember(&sig_map, i)) continue;
#if 0
printf("PM: sig %d for %d from kernel\n",
i, proc_nr_e);
#endif
switch (i) {
case SIGINT:
case SIGQUIT:
case SIGWINCH:
id = 0; break; /* broadcast to process group */
default:
id = proc_id;
break;
}
check_sig(id, i);
}
}
/*===========================================================================*
* do_alarm *
*===========================================================================*/
PUBLIC int do_alarm()
{
/* Perform the alarm(seconds) system call. */
return(set_alarm(who_e, m_in.seconds));
}
/*===========================================================================*
* set_alarm *
*===========================================================================*/
PUBLIC int set_alarm(proc_nr_e, sec)
int proc_nr_e; /* process that wants the alarm */
int sec; /* how many seconds delay before the signal */
{
/* This routine is used by do_alarm() to set the alarm timer. It is also used
* to turn the timer off when a process exits with the timer still on.
*/
clock_t ticks; /* number of ticks for alarm */
clock_t exptime; /* needed for remaining time on previous alarm */
clock_t uptime; /* current system time */
int remaining; /* previous time left in seconds */
int s;
int proc_nr_n;
if(pm_isokendpt(proc_nr_e, &proc_nr_n) != OK)
return EINVAL;
/* First determine remaining time of previous alarm, if set. */
if (mproc[proc_nr_n].mp_flags & ALARM_ON) {
if ( (s=getuptime(&uptime)) != OK)
panic(__FILE__,"set_alarm couldn't get uptime", s);
exptime = *tmr_exp_time(&mproc[proc_nr_n].mp_timer);
remaining = (int) ((exptime - uptime + (system_hz-1))/system_hz);
if (remaining < 0) remaining = 0;
} else {
remaining = 0;
}
/* Tell the clock task to provide a signal message when the time comes.
*
* Large delays cause a lot of problems. First, the alarm system call
* takes an unsigned seconds count and the library has cast it to an int.
* That probably works, but on return the library will convert "negative"
* unsigneds to errors. Presumably no one checks for these errors, so
* force this call through. Second, If unsigned and long have the same
* size, converting from seconds to ticks can easily overflow. Finally,
* the kernel has similar overflow bugs adding ticks.
*
* Fixing this requires a lot of ugly casts to fit the wrong interface
* types and to avoid overflow traps. ALRM_EXP_TIME has the right type
* (clock_t) although it is declared as long. How can variables like
* this be declared properly without combinatorial explosion of message
* types?
*/
ticks = (clock_t) (system_hz * (unsigned long) (unsigned) sec);
if ( (unsigned long) ticks / system_hz != (unsigned) sec)
ticks = LONG_MAX; /* eternity (really TMR_NEVER) */
if (ticks != 0) {
pm_set_timer(&mproc[proc_nr_n].mp_timer, ticks,
cause_sigalrm, proc_nr_e);
mproc[proc_nr_n].mp_flags |= ALARM_ON;
} else if (mproc[proc_nr_n].mp_flags & ALARM_ON) {
pm_cancel_timer(&mproc[proc_nr_n].mp_timer);
mproc[proc_nr_n].mp_flags &= ~ALARM_ON;
}
return(remaining);
}
/*===========================================================================*
* cause_sigalrm *
*===========================================================================*/
PRIVATE void cause_sigalrm(tp)
struct timer *tp;
{
int proc_nr_n;
register struct mproc *rmp;
/* get process from timer */
if(pm_isokendpt(tmr_arg(tp)->ta_int, &proc_nr_n) != OK) {
printf("PM: ignoring timer for invalid endpoint %d\n",
tmr_arg(tp)->ta_int);
return;
}
rmp = &mproc[proc_nr_n];
if ((rmp->mp_flags & (IN_USE | EXITING)) != IN_USE) return;
if ((rmp->mp_flags & ALARM_ON) == 0) return;
rmp->mp_flags &= ~ALARM_ON;
check_sig(rmp->mp_pid, SIGALRM);
}
/*===========================================================================*
* do_pause *
*===========================================================================*/
PUBLIC int do_pause()
{
/* Perform the pause() system call. */
mp->mp_flags |= PAUSED;
return(SUSPEND);
}
/*===========================================================================*
* sig_proc *
*===========================================================================*/
PUBLIC void sig_proc(rmp, signo)
register struct mproc *rmp; /* pointer to the process to be signaled */
int signo; /* signal to send to process (1 to _NSIG) */
{
/* Send a signal to a process. Check to see if the signal is to be caught,
* ignored, tranformed into a message (for system processes) or blocked.
* - If the signal is to be transformed into a message, request the KERNEL to
* send the target process a system notification with the pending signal as an
* argument.
* - If the signal is to be caught, request the KERNEL to push a sigcontext
* structure and a sigframe structure onto the catcher's stack. Also, KERNEL
* will reset the program counter and stack pointer, so that when the process
* next runs, it will be executing the signal handler. When the signal handler
* returns, sigreturn(2) will be called. Then KERNEL will restore the signal
* context from the sigcontext structure.
* If there is insufficient stack space, kill the process.
*/
vir_bytes cur_sp;
int s;
int slot;
int sigflags;
int exit_type;
slot = (int) (rmp - mproc);
if ((rmp->mp_flags & (IN_USE | EXITING)) != IN_USE) {
printf("PM: signal %d sent to exiting process %d\n", signo, slot);
panic(__FILE__,"", NO_NUM);
}
if (rmp->mp_fs_call != PM_IDLE || rmp->mp_fs_call2 != PM_IDLE)
{
sigaddset(&rmp->mp_sigpending, signo);
rmp->mp_flags |= PM_SIG_PENDING;
/* keep the process from running */
sys_nice(rmp->mp_endpoint, PRIO_STOP);
return;
}
if ((rmp->mp_flags & TRACED) && signo != SIGKILL) {
/* A traced process has special handling. */
unpause(slot, TRUE /*for_trace*/);
stop_proc(rmp, signo); /* a signal causes it to stop */
return;
}
/* Some signals are ignored by default. */
if (sigismember(&rmp->mp_ignore, signo)) {
return;
}
if (sigismember(&rmp->mp_sigmask, signo)) {
/* Signal should be blocked. */
sigaddset(&rmp->mp_sigpending, signo);
return;
}
sigflags = rmp->mp_sigact[signo].sa_flags;
if (sigismember(&rmp->mp_catch, signo)) {
if (rmp->mp_flags & SIGSUSPENDED)
rmp->mp_sigmsg.sm_mask = rmp->mp_sigmask2;
else
rmp->mp_sigmsg.sm_mask = rmp->mp_sigmask;
rmp->mp_sigmsg.sm_signo = signo;
rmp->mp_sigmsg.sm_sighandler =
(vir_bytes) rmp->mp_sigact[signo].sa_handler;
rmp->mp_sigmsg.sm_sigreturn = rmp->mp_sigreturn;
rmp->mp_sigmask |= rmp->mp_sigact[signo].sa_mask;
if (sigflags & SA_NODEFER)
sigdelset(&rmp->mp_sigmask, signo);
else
sigaddset(&rmp->mp_sigmask, signo);
if (sigflags & SA_RESETHAND) {
sigdelset(&rmp->mp_catch, signo);
rmp->mp_sigact[signo].sa_handler = SIG_DFL;
}
sigdelset(&rmp->mp_sigpending, signo);
/* Stop process from running before we fiddle with its stack. */
sys_nice(rmp->mp_endpoint, PRIO_STOP);
if(vm_push_sig(rmp->mp_endpoint, &cur_sp) != OK)
goto doterminate;
rmp->mp_sigmsg.sm_stkptr = cur_sp;
/* Check to see if process is hanging on a PAUSE, WAIT or SIGSUSPEND
* call.
*/
if (rmp->mp_flags & (PAUSED | WAITING | SIGSUSPENDED)) {
rmp->mp_flags &= ~(PAUSED | WAITING | SIGSUSPENDED);
setreply(slot, EINTR);
/* Ask the kernel to deliver the signal */
s= sys_sigsend(rmp->mp_endpoint, &rmp->mp_sigmsg);
if (s != OK)
panic(__FILE__, "sys_sigsend failed", s);
/* Done */
return;
}
/* Ask FS to unpause the process. Deliver the signal when FS is
* ready.
*/
unpause(slot, FALSE /*!for_trace*/);
return;
}
else if (sigismember(&rmp->mp_sig2mess, signo)) {
/* Mark event pending in process slot and send notification. */
sigaddset(&rmp->mp_sigpending, signo);
notify(rmp->mp_endpoint);
return;
}
doterminate:
/* Signal should not or cannot be caught. Take default action. */
if (sigismember(&ign_sset, signo)) {
return;
}
rmp->mp_sigstatus = (char) signo;
exit_type = PM_EXIT;
if (sigismember(&core_sset, signo) && slot != FS_PROC_NR) {
printf("PM: coredump signal %d for %d / %s\n", signo, rmp->mp_pid,
rmp->mp_name);
exit_type = PM_DUMPCORE;
}
exit_proc(rmp, 0, exit_type); /* terminate process */
}
/*===========================================================================*
* check_sig *
*===========================================================================*/
PUBLIC int check_sig(proc_id, signo)
pid_t proc_id; /* pid of proc to sig, or 0 or -1, or -pgrp */
int signo; /* signal to send to process (0 to _NSIG) */
{
/* Check to see if it is possible to send a signal. The signal may have to be
* sent to a group of processes. This routine is invoked by the KILL system
* call, and also when the kernel catches a DEL or other signal.
*/
register struct mproc *rmp;
int count; /* count # of signals sent */
int error_code;
if (signo < 0 || signo > _NSIG) return(EINVAL);
/* Return EINVAL for attempts to send SIGKILL to INIT alone. */
if (proc_id == INIT_PID && signo == SIGKILL) return(EINVAL);
/* Search the proc table for processes to signal.
* (See forkexit.c about pid magic.)
*/
count = 0;
error_code = ESRCH;
for (rmp = &mproc[0]; rmp < &mproc[NR_PROCS]; rmp++) {
if (!(rmp->mp_flags & IN_USE)) continue;
/* Check for selection. */
if (proc_id > 0 && proc_id != rmp->mp_pid) continue;
if (proc_id == 0 && mp->mp_procgrp != rmp->mp_procgrp) continue;
if (proc_id == -1 && rmp->mp_pid <= INIT_PID) continue;
if (proc_id < -1 && rmp->mp_procgrp != -proc_id) continue;
/* Do not kill servers and drivers when broadcasting SIGKILL. */
if (proc_id == -1 && signo == SIGKILL &&
(rmp->mp_flags & PRIV_PROC)) continue;
/* Check for permission. */
if (mp->mp_effuid != SUPER_USER
&& mp->mp_realuid != rmp->mp_realuid
&& mp->mp_effuid != rmp->mp_realuid
&& mp->mp_realuid != rmp->mp_effuid
&& mp->mp_effuid != rmp->mp_effuid) {
error_code = EPERM;
continue;
}
count++;
if (signo == 0 || (rmp->mp_flags & EXITING)) continue;
/* 'sig_proc' will handle the disposition of the signal. The
* signal may be caught, blocked, ignored, or cause process
* termination, possibly with core dump.
*/
sig_proc(rmp, signo);
if (proc_id > 0) break; /* only one process being signaled */
}
/* If the calling process has killed itself, don't reply. */
if ((mp->mp_flags & (IN_USE | EXITING)) != IN_USE) return(SUSPEND);
return(count > 0 ? OK : error_code);
}
/*===========================================================================*
* check_pending *
*===========================================================================*/
PUBLIC void check_pending(rmp)
register struct mproc *rmp;
{
/* Check to see if any pending signals have been unblocked. The
* first such signal found is delivered.
*
* If multiple pending unmasked signals are found, they will be
* delivered sequentially.
*
* There are several places in this file where the signal mask is
* changed. At each such place, check_pending() should be called to
* check for newly unblocked signals.
*/
int i;
for (i = 1; i <= _NSIG; i++) {
if (sigismember(&rmp->mp_sigpending, i) &&
!sigismember(&rmp->mp_sigmask, i)) {
sigdelset(&rmp->mp_sigpending, i);
sig_proc(rmp, i);
break;
}
}
}
/*===========================================================================*
* unpause *
*===========================================================================*/
PRIVATE void unpause(pro, for_trace)
int pro; /* which process number */
int for_trace; /* for tracing */
{
/* A signal is to be sent to a process. If that process is hanging on a
* system call, the system call must be terminated with EINTR. Possible
* calls are PAUSE, WAIT, READ and WRITE, the latter two for pipes and ttys.
* First check if the process is hanging on an PM call. If not, tell FS,
* so it can check for READs and WRITEs from pipes, ttys and the like.
*/
register struct mproc *rmp;
int r;
rmp = &mproc[pro];
/* Check to see if process is hanging on a PAUSE, WAIT or SIGSUSPEND call. */
if (rmp->mp_flags & (PAUSED | WAITING | SIGSUSPENDED)) {
rmp->mp_flags &= ~(PAUSED | WAITING | SIGSUSPENDED);
setreply(pro, EINTR);
return;
}
/* Process is not hanging on an PM call. Ask FS to take a look. */
if (for_trace)
{
if (rmp->mp_fs_call != PM_IDLE)
panic( __FILE__, "unpause: not idle", rmp->mp_fs_call);
rmp->mp_fs_call= PM_UNPAUSE_TR;
}
else
{
if (rmp->mp_fs_call2 != PM_IDLE)
panic( __FILE__, "unpause: not idle", rmp->mp_fs_call2);
rmp->mp_fs_call2= PM_UNPAUSE;
}
r= notify(FS_PROC_NR);
if (r != OK) panic("pm", "unpause: unable to notify FS", r);
}
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