uml: tidy IRQ code

[safe/jmp/linux-2.6] / arch / um / os-Linux / signal.c

/*
 * Copyright (C) 2004 PathScale, Inc
 * Licensed under the GPL
 */

#include <signal.h>
#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <errno.h>
#include <stdarg.h>
#include <string.h>
#include <sys/mman.h>
#include "user.h"
#include "signal_kern.h"
#include "sysdep/sigcontext.h"
#include "sysdep/barrier.h"
#include "sigcontext.h"
#include "mode.h"
#include "os.h"

/* These are the asynchronous signals.  SIGVTALRM and SIGARLM are handled
 * together under SIGVTALRM_BIT.  SIGPROF is excluded because we want to
 * be able to profile all of UML, not just the non-critical sections.  If
 * profiling is not thread-safe, then that is not my problem.  We can disable
 * profiling when SMP is enabled in that case.
 */
#define SIGIO_BIT 0
#define SIGIO_MASK (1 << SIGIO_BIT)

#define SIGVTALRM_BIT 1
#define SIGVTALRM_MASK (1 << SIGVTALRM_BIT)

#define SIGALRM_BIT 2
#define SIGALRM_MASK (1 << SIGALRM_BIT)

/* These are used by both the signal handlers and
 * block/unblock_signals.  I don't want modifications cached in a
 * register - they must go straight to memory.
 */
static volatile int signals_enabled = 1;
static volatile int pending = 0;

void sig_handler(int sig, struct sigcontext *sc)
{
        int enabled;

        enabled = signals_enabled;
        if(!enabled && (sig == SIGIO)){
                pending |= SIGIO_MASK;
                return;
        }

        block_signals();

        CHOOSE_MODE_PROC(sig_handler_common_tt, sig_handler_common_skas,
                         sig, sc);

        set_signals(enabled);
}

static void real_alarm_handler(int sig, struct sigcontext *sc)
{
        union uml_pt_regs regs;

        if(sig == SIGALRM)
                switch_timers(0);

        if(sc != NULL)
                copy_sc(&regs, sc);
        regs.skas.is_user = 0;
        unblock_signals();
        timer_handler(sig, &regs);

        if(sig == SIGALRM)
                switch_timers(1);
}

void alarm_handler(int sig, struct sigcontext *sc)
{
        int enabled;

        enabled = signals_enabled;
        if(!signals_enabled){
                if(sig == SIGVTALRM)
                        pending |= SIGVTALRM_MASK;
                else pending |= SIGALRM_MASK;

                return;
        }

        block_signals();

        real_alarm_handler(sig, sc);
        set_signals(enabled);
}

void set_sigstack(void *sig_stack, int size)
{
        stack_t stack = ((stack_t) { .ss_flags  = 0,
                                     .ss_sp     = (__ptr_t) sig_stack,
                                     .ss_size   = size - sizeof(void *) });

        if(sigaltstack(&stack, NULL) != 0)
                panic("enabling signal stack failed, errno = %d\n", errno);
}

void remove_sigstack(void)
{
        stack_t stack = ((stack_t) { .ss_flags  = SS_DISABLE,
                                     .ss_sp     = NULL,
                                     .ss_size   = 0 });

        if(sigaltstack(&stack, NULL) != 0)
                panic("disabling signal stack failed, errno = %d\n", errno);
}

void (*handlers[_NSIG])(int sig, struct sigcontext *sc);

extern void hard_handler(int sig);

void set_handler(int sig, void (*handler)(int), int flags, ...)
{
        struct sigaction action;
        va_list ap;
        sigset_t sig_mask;
        int mask;

        handlers[sig] = (void (*)(int, struct sigcontext *)) handler;
        action.sa_handler = hard_handler;

        sigemptyset(&action.sa_mask);

        va_start(ap, flags);
        while((mask = va_arg(ap, int)) != -1)
                sigaddset(&action.sa_mask, mask);
        va_end(ap);

        action.sa_flags = flags;
        action.sa_restorer = NULL;
        if(sigaction(sig, &action, NULL) < 0)
                panic("sigaction failed - errno = %d\n", errno);

        sigemptyset(&sig_mask);
        sigaddset(&sig_mask, sig);
        if(sigprocmask(SIG_UNBLOCK, &sig_mask, NULL) < 0)
                panic("sigprocmask failed - errno = %d\n", errno);
}

int change_sig(int signal, int on)
{
        sigset_t sigset, old;

        sigemptyset(&sigset);
        sigaddset(&sigset, signal);
        sigprocmask(on ? SIG_UNBLOCK : SIG_BLOCK, &sigset, &old);
        return(!sigismember(&old, signal));
}

void block_signals(void)
{
        signals_enabled = 0;
        /* This must return with signals disabled, so this barrier
         * ensures that writes are flushed out before the return.
         * This might matter if gcc figures out how to inline this and
         * decides to shuffle this code into the caller.
         */
        mb();
}

void unblock_signals(void)
{
        int save_pending;

        if(signals_enabled == 1)
                return;

        /* We loop because the IRQ handler returns with interrupts off.  So,
         * interrupts may have arrived and we need to re-enable them and
         * recheck pending.
         */
        while(1){
                /* Save and reset save_pending after enabling signals.  This
                 * way, pending won't be changed while we're reading it.
                 */
                signals_enabled = 1;

                /* Setting signals_enabled and reading pending must
                 * happen in this order.
                 */
                mb();

                save_pending = pending;
                if(save_pending == 0){
                        /* This must return with signals enabled, so
                         * this barrier ensures that writes are
                         * flushed out before the return.  This might
                         * matter if gcc figures out how to inline
                         * this (unlikely, given its size) and decides
                         * to shuffle this code into the caller.
                         */
                        mb();
                        return;
                }

                pending = 0;

                /* We have pending interrupts, so disable signals, as the
                 * handlers expect them off when they are called.  They will
                 * be enabled again above.
                 */

                signals_enabled = 0;

                /* Deal with SIGIO first because the alarm handler might
                 * schedule, leaving the pending SIGIO stranded until we come
                 * back here.
                 */
                if(save_pending & SIGIO_MASK)
                        CHOOSE_MODE_PROC(sig_handler_common_tt,
                                         sig_handler_common_skas, SIGIO, NULL);

                if(save_pending & SIGALRM_MASK)
                        real_alarm_handler(SIGALRM, NULL);

                if(save_pending & SIGVTALRM_MASK)
                        real_alarm_handler(SIGVTALRM, NULL);
        }
}

int get_signals(void)
{
        return signals_enabled;
}

int set_signals(int enable)
{
        int ret;
        if(signals_enabled == enable)
                return enable;

        ret = signals_enabled;
        if(enable)
                unblock_signals();
        else block_signals();

        return ret;
}