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minix/servers/mm/signal.c
Ben Gras 9865aeaa79 Initial revision
2005-04-21 14:53:53 +00:00

646 lines
21 KiB
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_ksig: accept a signal originating in the kernel (e.g., SIGINT)
* 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 "mm.h"
#include <minix/utils.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_ksig, (int proc_nr, sigset_t sig_map) );
/*===========================================================================*
* 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(MM_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,
MM_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);
} else {
sigdelset(&mp->mp_ignore, m_in.sig_nr);
if (svec.sa_handler == SIG_DFL)
sigdelset(&mp->mp_catch, m_in.sig_nr);
else
sigaddset(&mp->mp_catch, 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. */
return check_sig(m_in.pid, m_in.sig_nr);
}
/*===========================================================================*
* do_ksig_pending *
*===========================================================================*/
PUBLIC int ksig_pending()
{
/* The kernel has notified the MM 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_getsig(&proc_nr, &sig_map); /* get an arbitrary pending signal */
if (NONE == proc_nr) { /* stop if no more pending signals */
break;
} else {
handle_ksig(proc_nr, sig_map); /* handle the receive signal */
}
}
return(SUSPEND); /* prevents sending reply */
}
/*===========================================================================*
* do_ksig *
*===========================================================================*/
PUBLIC int do_ksig()
{
/* Certain signals, such as segmentation violations and DEL, originate in the
* kernel. When the kernel detects such signals, it sets bits in a bit map.
* As soon as MM is awaiting new work, the kernel sends MM a message containing
* the process slot and bit map. That message comes here. The File System
* also uses this mechanism to signal writing on broken pipes (SIGPIPE).
*/
int proc_nr;
sigset_t sig_map;
/* Only kernel may make this call. */
if (who != HARDWARE) return(EPERM);
proc_nr = m_in.SIG_PROC;
sig_map = (sigset_t) m_in.SIG_MAP;
handle_ksig(proc_nr, sig_map);
return(SUSPEND);
}
/*===========================================================================*
* handle_ksig *
*===========================================================================*/
PRIVATE void handle_ksig(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 kernel signals are from MM */
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 MM 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. This only applies for a KERNEL
* generated signal.
*/
if ((rmp->mp_flags & ALARM_ON) == 0) continue;
rmp->mp_flags &= ~ALARM_ON;
/* fall through */
default:
id = proc_id;
break;
}
check_sig(id, i);
sys_endsig(proc_nr); /* tell kernel it's done */
}
}
/*===========================================================================*
* 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 */
int remaining; /* previous time left in seconds */
int s;
if (sec != 0) mproc[proc_nr].mp_flags |= ALARM_ON;
else mproc[proc_nr].mp_flags &= ~ALARM_ON;
/* 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 ((s=sys_signalrm(proc_nr, &ticks)) != OK)
panic("MM couldn't set signal alarm", s);
remaining = (int) ((ticks + (HZ-1))/HZ);
if (remaining < 0) remaining = INT_MAX; /* true value is too large */
return(remaining);
}
/*===========================================================================*
* 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, or blocked. If the signal is to be caught, coordinate with
* 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("MM: signal %d sent to %s process %d\n",
(rmp->mp_flags & ZOMBIE) ? "zombie" : "dead", signo, slot);
panic("", 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)) 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 & ONSWAP) {
/* Process is swapped out, leave signal pending. */
sigaddset(&rmp->mp_sigpending, signo);
swap_inqueue(rmp);
return;
}
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=p_getsp(slot, &new_sp)) != OK)
panic("MM 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;
}
sys_sendsig(slot, &sm);
sigdelset(&rmp->mp_sigpending, signo);
/* If process is hanging on PAUSE, WAIT, SIGSUSPEND, tty, pipe, etc.,
* release it.
*/
unpause(slot);
return;
}
doterminate:
/* 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);
}
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[INIT_PROC_NR]; 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) {
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.
*/
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 MM 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 MM 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=p_getsp(slot, &current_sp)) != OK)
panic("MM 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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