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minix/servers/pm/signal.c
Jorrit Herder f1153541c7 Fixed bug in PM that caused update program not to be scheduled, so that 
sync was not periodically run. Chain of timers was accidentially broken.

Kernel sends SIGKSTOP signal on shutdown. FS calls sync to clean up.
2005-07-20 15:27:42 +00:00

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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 <minix/callnr.h>
#include <minix/com.h>
#include <signal.h>
#include <sys/sigcontext.h>
#include <string.h>
#include "mproc.h"
#include "param.h"
#define CORE_MODE 0777 /* mode to use on core image files */
#define DUMPED 0200 /* bit set in status when core dumped */
FORWARD _PROTOTYPE( void dump_core, (struct mproc *rmp) );
FORWARD _PROTOTYPE( void unpause, (int pro) );
FORWARD _PROTOTYPE( void handle_sig, (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, (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, (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.
*/
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);
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);
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, (struct sigmsg *) m_in.sig_context, m_in.sig_flags);
check_pending(mp);
return(r);
}
/*===========================================================================*
* do_kill *
*===========================================================================*/
PUBLIC int do_kill()
{
/* Perform the kill(pid, signo) system call. */
DEBUG(m_in.pid == 11, printf("PM: detected do_kill PRINTER\n"));
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;
sigset_t sig_map;
while (TRUE) {
sys_getksig(&proc_nr, &sig_map); /* get an arbitrary pending signal */
if (NONE == proc_nr) { /* stop if no more pending signals */
break;
} else {
handle_sig(proc_nr, sig_map); /* handle the received signal */
sys_endksig(proc_nr); /* tell kernel it's done */
}
}
return(SUSPEND); /* prevents sending reply */
}
/*===========================================================================*
* handle_sig *
*===========================================================================*/
PRIVATE void handle_sig(proc_nr, sig_map)
int proc_nr;
sigset_t sig_map;
{
register struct mproc *rmp;
int i;
pid_t proc_id, id;
rmp = &mproc[proc_nr];
if ((rmp->mp_flags & (IN_USE | ZOMBIE)) != IN_USE) 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 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;
switch (i) {
case SIGINT:
case SIGQUIT:
id = 0; break; /* broadcast to process group */
case SIGKILL:
id = -1; break; /* broadcast to all except INIT */
case SIGALRM:
/* Disregard SIGALRM when the target process has not
* requested an alarm.
*/
if ((rmp->mp_flags & ALARM_ON) == 0) continue;
rmp->mp_flags &= ~ALARM_ON;
/* fall through */
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, m_in.seconds));
}
/*===========================================================================*
* set_alarm *
*===========================================================================*/
PUBLIC int set_alarm(proc_nr, sec)
int proc_nr; /* 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;
/* First determine remaining time of previous alarm, if set. */
if (mproc[proc_nr].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].mp_timer);
remaining = (int) ((exptime - uptime + (HZ-1))/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) (HZ * (unsigned long) (unsigned) sec);
if ( (unsigned long) ticks / HZ != (unsigned) sec)
ticks = LONG_MAX; /* eternity (really TMR_NEVER) */
if (ticks != 0) {
pm_set_timer(&mproc[proc_nr].mp_timer, ticks, cause_sigalrm, proc_nr);
mproc[proc_nr].mp_flags |= ALARM_ON;
} else if (mproc[proc_nr].mp_flags & ALARM_ON) {
pm_cancel_timer(&mproc[proc_nr].mp_timer);
mproc[proc_nr].mp_flags &= ~ALARM_ON;
}
return(remaining);
}
/*===========================================================================*
* cause_sigalrm *
*===========================================================================*/
PRIVATE void cause_sigalrm(tp)
struct timer *tp;
{
int proc_nr;
register struct mproc *rmp;
proc_nr = tmr_arg(tp)->ta_int; /* get process from timer */
rmp = &mproc[proc_nr];
if ((rmp->mp_flags & (IN_USE | ZOMBIE)) != 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 new_sp;
int s;
int slot;
int sigflags;
struct sigmsg sm;
slot = (int) (rmp - mproc);
if ((rmp->mp_flags & (IN_USE | ZOMBIE)) != IN_USE) {
printf("PM: signal %d sent to %s process %d\n",
(rmp->mp_flags & ZOMBIE) ? "zombie" : "dead", signo, slot);
panic(__FILE__,"", NO_NUM);
}
if ((rmp->mp_flags & TRACED) && signo != SIGKILL) {
/* A traced process has special handling. */
unpause(slot);
stop_proc(rmp, signo); /* a signal causes it to stop */
return;
}
/* Some signals are ignored by default. */
if (sigismember(&rmp->mp_ignore, signo)) {
DEBUG(m_in.pid == 11, printf("PM: sig_proc ignored sig\n"));
return;
}
if (sigismember(&rmp->mp_sigmask, signo)) {
/* Signal should be blocked. */
sigaddset(&rmp->mp_sigpending, signo);
return;
}
if (rmp->mp_flags & ONSWAP) {
/* Process is swapped out, leave signal pending. */
sigaddset(&rmp->mp_sigpending, signo);
swap_inqueue(rmp);
return;
}
sigflags = rmp->mp_sigact[signo].sa_flags;
if (sigismember(&rmp->mp_catch, signo)) {
DEBUG(m_in.pid == 11, printf("PM: sig_proc catch sig!\n"));
if (rmp->mp_flags & SIGSUSPENDED)
sm.sm_mask = rmp->mp_sigmask2;
else
sm.sm_mask = rmp->mp_sigmask;
sm.sm_signo = signo;
sm.sm_sighandler = (vir_bytes) rmp->mp_sigact[signo].sa_handler;
sm.sm_sigreturn = rmp->mp_sigreturn;
if ((s=get_stack_ptr(slot, &new_sp)) != OK)
panic(__FILE__,"couldn't get new stack pointer",s);
sm.sm_stkptr = new_sp;
/* Make room for the sigcontext and sigframe struct. */
new_sp -= sizeof(struct sigcontext)
+ 3 * sizeof(char *) + 2 * sizeof(int);
if (adjust(rmp, rmp->mp_seg[D].mem_len, new_sp) != OK)
goto doterminate;
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;
}
DEBUG(m_in.pid == 11, printf("PM: sig_proc about to call sys_sigsend for %d \n",slot));
if (OK == (s=sys_sigsend(slot, &sm))) {
sigdelset(&rmp->mp_sigpending, signo);
/* If process is hanging on PAUSE, WAIT, SIGSUSPEND, tty,
* pipe, etc., release it.
*/
unpause(slot);
return;
}
panic(__FILE__, "warning, sys_sigsend failed", s);
}
else if (sigismember(&rmp->mp_sig2mess, signo)) {
if (OK != (s=sys_kill(slot,signo)))
panic(__FILE__, "warning, sys_kill failed", s);
return;
}
doterminate:
DEBUG(m_in.pid == 11, printf("PM: sig_proc doterminate\n"));
/* Signal should not or cannot be caught. Take default action. */
if (sigismember(&ign_sset, signo)) return;
rmp->mp_sigstatus = (char) signo;
if (sigismember(&core_sset, signo)) {
if (rmp->mp_flags & ONSWAP) {
/* Process is swapped out, leave signal pending. */
sigaddset(&rmp->mp_sigpending, signo);
swap_inqueue(rmp);
return;
}
/* Switch to the user's FS environment and dump core. */
tell_fs(CHDIR, slot, FALSE, 0);
dump_core(rmp);
}
DEBUG(m_in.pid == 11, printf("PM: about to exit proc\n"));
mm_exit(rmp, 0); /* 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;
if ((rmp->mp_flags & ZOMBIE) && signo != 0) 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;
/* 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) {
DEBUG(m_in.pid == 11, printf("PM: check_sig, EPERM\n"));
error_code = EPERM;
continue;
}
count++;
if (signo == 0) 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.
*/
DEBUG(m_in.pid == 11, printf("PM: calling sig_proc with signo %d\n", signo));
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 | ZOMBIE)) != 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)
int pro; /* which process number */
{
/* 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;
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. */
tell_fs(UNPAUSE, pro, 0, 0);
}
/*===========================================================================*
* dump_core *
*===========================================================================*/
PRIVATE void dump_core(rmp)
register struct mproc *rmp; /* whose core is to be dumped */
{
/* Make a core dump on the file "core", if possible. */
int s, fd, fake_fd, nr_written, seg, slot;
char *buf;
vir_bytes current_sp;
phys_bytes left; /* careful; 64K might overflow vir_bytes */
unsigned nr_to_write; /* unsigned for arg to write() but < INT_MAX */
long trace_data, trace_off;
slot = (int) (rmp - mproc);
/* Can core file be written? We are operating in the user's FS environment,
* so no special permission checks are needed.
*/
if (rmp->mp_realuid != rmp->mp_effuid) return;
if ( (fd = open(core_name, O_WRONLY | O_CREAT | O_TRUNC | O_NONBLOCK,
CORE_MODE)) < 0) return;
rmp->mp_sigstatus |= DUMPED;
/* Make sure the stack segment is up to date.
* We don't want adjust() to fail unless current_sp is preposterous,
* but it might fail due to safety checking. Also, we don't really want
* the adjust() for sending a signal to fail due to safety checking.
* Maybe make SAFETY_BYTES a parameter.
*/
if ((s=get_stack_ptr(slot, &current_sp)) != OK)
panic(__FILE__,"couldn't get new stack pointer",s);
adjust(rmp, rmp->mp_seg[D].mem_len, current_sp);
/* Write the memory map of all segments to begin the core file. */
if (write(fd, (char *) rmp->mp_seg, (unsigned) sizeof rmp->mp_seg)
!= (unsigned) sizeof rmp->mp_seg) {
close(fd);
return;
}
/* Write out the whole kernel process table entry to get the regs. */
trace_off = 0;
while (sys_trace(3, slot, trace_off, &trace_data) == OK) {
if (write(fd, (char *) &trace_data, (unsigned) sizeof (long))
!= (unsigned) sizeof (long)) {
close(fd);
return;
}
trace_off += sizeof (long);
}
/* Loop through segments and write the segments themselves out. */
for (seg = 0; seg < NR_LOCAL_SEGS; seg++) {
rw_seg(1, fd, slot, seg,
(phys_bytes) rmp->mp_seg[seg].mem_len << CLICK_SHIFT);
}
close(fd);
}
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