blob: e9800b0b5689b6abc750606ab886826709964e56 [file] [log] [blame]
/*
* Copyright (C) 2004 PathScale, Inc
* Copyright (C) 2004 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
* Licensed under the GPL
*/
#include <stdlib.h>
#include <stdarg.h>
#include <errno.h>
#include <signal.h>
#include <strings.h>
#include "os.h"
#include "sysdep/barrier.h"
#include "sysdep/sigcontext.h"
#include "user.h"
/*
* These are the asynchronous signals. 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)
/*
* 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();
sig_handler_common_skas(sig, sc);
set_signals(enabled);
}
static void real_alarm_handler(struct sigcontext *sc)
{
struct uml_pt_regs regs;
if (sc != NULL)
copy_sc(&regs, sc);
regs.is_user = 0;
unblock_signals();
timer_handler(SIGVTALRM, &regs);
}
void alarm_handler(int sig, struct sigcontext *sc)
{
int enabled;
enabled = signals_enabled;
if (!signals_enabled) {
pending |= SIGVTALRM_MASK;
return;
}
block_signals();
real_alarm_handler(sc);
set_signals(enabled);
}
void timer_init(void)
{
set_handler(SIGVTALRM, (__sighandler_t) alarm_handler,
SA_ONSTACK | SA_RESTART, SIGUSR1, SIGIO, SIGWINCH, -1);
}
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);
void handle_signal(int sig, struct sigcontext *sc)
{
unsigned long pending = 1UL << sig;
do {
int nested, bail;
/*
* pending comes back with one bit set for each
* interrupt that arrived while setting up the stack,
* plus a bit for this interrupt, plus the zero bit is
* set if this is a nested interrupt.
* If bail is true, then we interrupted another
* handler setting up the stack. In this case, we
* have to return, and the upper handler will deal
* with this interrupt.
*/
bail = to_irq_stack(&pending);
if (bail)
return;
nested = pending & 1;
pending &= ~1;
while ((sig = ffs(pending)) != 0){
sig--;
pending &= ~(1 << sig);
(*handlers[sig])(sig, sc);
}
/*
* Again, pending comes back with a mask of signals
* that arrived while tearing down the stack. If this
* is non-zero, we just go back, set up the stack
* again, and handle the new interrupts.
*/
if (!nested)
pending = from_irq_stack(nested);
} while (pending);
}
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)
sig_handler_common_skas(SIGIO, NULL);
if (save_pending & SIGVTALRM_MASK)
real_alarm_handler(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;
}