Implement the meat of the sigaction(2) system call with do_sigaction and
helper routiner block_signals (which is also used to implemement signal
masking so it's global).
Signed-off-by: Stacey Son <s...@freebsd.org>
Signed-off-by: Kyle Evans <kev...@freebsd.org>
Signed-off-by: Warner Losh <i...@bsdimp.com>
---
bsd-user/qemu.h | 21 +++++++++++++
bsd-user/signal.c | 76 +++++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 97 insertions(+)
diff --git a/bsd-user/qemu.h b/bsd-user/qemu.h
index b8c64ca0e5b..c643d6ba246 100644
--- a/bsd-user/qemu.h
+++ b/bsd-user/qemu.h
@@ -226,8 +226,29 @@ int host_to_target_signal(int sig);
void host_to_target_sigset(target_sigset_t *d, const sigset_t *s);
void target_to_host_sigset(sigset_t *d, const target_sigset_t *s);
long do_sigreturn(CPUArchState *regs, abi_ulong addr);
+int do_sigaction(int sig, const struct target_sigaction *act,
+ struct target_sigaction *oact);
void QEMU_NORETURN force_sig(int target_sig);
int qemu_sigorset(sigset_t *dest, const sigset_t *left, const sigset_t *right);
+/**
+ * block_signals: block all signals while handling this guest syscall
+ *
+ * Block all signals, and arrange that the signal mask is returned to
+ * its correct value for the guest before we resume execution of guest code.
+ * If this function returns non-zero, then the caller should immediately
+ * return -TARGET_ERESTARTSYS to the main loop, which will take the pending
+ * signal and restart execution of the syscall.
+ * If block_signals() returns zero, then the caller can continue with
+ * emulation of the system call knowing that no signals can be taken
+ * (and therefore that no race conditions will result).
+ * This should only be called once, because if it is called a second time
+ * it will always return non-zero. (Think of it like a mutex that can't
+ * be recursively locked.)
+ * Signals will be unblocked again by process_pending_signals().
+ *
+ * Return value: non-zero if there was a pending signal, zero if not.
+ */
+int block_signals(void); /* Returns non zero if signal pending */
/* mmap.c */
int target_mprotect(abi_ulong start, abi_ulong len, int prot);
diff --git a/bsd-user/signal.c b/bsd-user/signal.c
index d11f5eddd7e..f055d1db407 100644
--- a/bsd-user/signal.c
+++ b/bsd-user/signal.c
@@ -231,6 +231,22 @@ static void tswap_siginfo(target_siginfo_t *tinfo, const
target_siginfo_t *info)
}
}
+int block_signals(void)
+{
+ TaskState *ts = (TaskState *)thread_cpu->opaque;
+ sigset_t set;
+
+ /*
+ * It's OK to block everything including SIGSEGV, because we won't run any
+ * further guest code before unblocking signals in
+ * process_pending_signals().
+ */
+ sigfillset(&set);
+ sigprocmask(SIG_SETMASK, &set, 0);
+
+ return qatomic_xchg(&ts->signal_pending, 1);
+}
+
/* Returns 1 if given signal should dump core if not handled. */
static int core_dump_signal(int sig)
{
@@ -534,6 +550,66 @@ static int fatal_signal(int sig)
}
}
+/* do_sigaction() return host values and errnos */
+int do_sigaction(int sig, const struct target_sigaction *act,
+ struct target_sigaction *oact)
+{
+ struct target_sigaction *k;
+ struct sigaction act1;
+ int host_sig;
+ int ret = 0;
+
+ if (sig < 1 || sig > TARGET_NSIG || TARGET_SIGKILL == sig ||
+ TARGET_SIGSTOP == sig) {
+ return -EINVAL;
+ }
+
+ if (block_signals()) {
+ return -TARGET_ERESTART;
+ }
+
+ k = &sigact_table[sig - 1];
+ if (oact) {
+ oact->_sa_handler = tswapal(k->_sa_handler);
+ oact->sa_flags = tswap32(k->sa_flags);
+ oact->sa_mask = k->sa_mask;
+ }
+ if (act) {
+ /* XXX: this is most likely not threadsafe. */
+ k->_sa_handler = tswapal(act->_sa_handler);
+ k->sa_flags = tswap32(act->sa_flags);
+ k->sa_mask = act->sa_mask;
+
+ /* Update the host signal state. */
+ host_sig = target_to_host_signal(sig);
+ if (host_sig != SIGSEGV && host_sig != SIGBUS) {
+ memset(&act1, 0, sizeof(struct sigaction));
+ sigfillset(&act1.sa_mask);
+ act1.sa_flags = SA_SIGINFO;
+ if (k->sa_flags & TARGET_SA_RESTART) {
+ act1.sa_flags |= SA_RESTART;
+ }
+ /*
+ * Note: It is important to update the host kernel signal mask to
+ * avoid getting unexpected interrupted system calls.
+ */
+ if (k->_sa_handler == TARGET_SIG_IGN) {
+ act1.sa_sigaction = (void *)SIG_IGN;
+ } else if (k->_sa_handler == TARGET_SIG_DFL) {
+ if (fatal_signal(sig)) {
+ act1.sa_sigaction = host_signal_handler;
+ } else {
+ act1.sa_sigaction = (void *)SIG_DFL;
+ }
+ } else {
+ act1.sa_sigaction = host_signal_handler;
+ }
+ ret = sigaction(host_sig, &act1, NULL);
+ }
+ }
+ return ret;
+}
+
static inline abi_ulong get_sigframe(struct target_sigaction *ka,
CPUArchState *regs, size_t frame_size)
{
--
2.33.1
