1 files changed, 369 insertions, 0 deletions
diff --git a/arch/um/os-Linux/signal.c b/arch/um/os-Linux/signal.c
new file mode 100644
index 000000000..0a2ea8403
--- /dev/null
+++ b/arch/um/os-Linux/signal.c
@@ -0,0 +1,369 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2015 Anton Ivanov (aivanov@{brocade.com,kot-begemot.co.uk})
+ * Copyright (C) 2015 Thomas Meyer (thomas@m3y3r.de)
+ * Copyright (C) 2004 PathScale, Inc
+ * Copyright (C) 2004 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
+ */
+
+#include <stdlib.h>
+#include <stdarg.h>
+#include <errno.h>
+#include <signal.h>
+#include <string.h>
+#include <strings.h>
+#include <as-layout.h>
+#include <kern_util.h>
+#include <os.h>
+#include <sysdep/mcontext.h>
+#include <um_malloc.h>
+#include <sys/ucontext.h>
+
+void (*sig_info[NSIG])(int, struct siginfo *, struct uml_pt_regs *) = {
+	[SIGTRAP]	= relay_signal,
+	[SIGFPE]	= relay_signal,
+	[SIGILL]	= relay_signal,
+	[SIGWINCH]	= winch,
+	[SIGBUS]	= bus_handler,
+	[SIGSEGV]	= segv_handler,
+	[SIGIO]		= sigio_handler,
+};
+
+static void sig_handler_common(int sig, struct siginfo *si, mcontext_t *mc)
+{
+	struct uml_pt_regs r;
+	int save_errno = errno;
+
+	r.is_user = 0;
+	if (sig == SIGSEGV) {
+		/* For segfaults, we want the data from the sigcontext. */
+		get_regs_from_mc(&r, mc);
+		GET_FAULTINFO_FROM_MC(r.faultinfo, mc);
+	}
+
+	/* enable signals if sig isn't IRQ signal */
+	if ((sig != SIGIO) && (sig != SIGWINCH))
+		unblock_signals_trace();
+
+	(*sig_info[sig])(sig, si, &r);
+
+	errno = save_errno;
+}
+
+/*
+ * 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 SIGALRM_BIT 1
+#define SIGALRM_MASK (1 << SIGALRM_BIT)
+
+static int signals_enabled;
+static unsigned int signals_pending;
+static unsigned int signals_active = 0;
+
+void sig_handler(int sig, struct siginfo *si, mcontext_t *mc)
+{
+	int enabled;
+
+	enabled = signals_enabled;
+	if (!enabled && (sig == SIGIO)) {
+		signals_pending |= SIGIO_MASK;
+		return;
+	}
+
+	block_signals_trace();
+
+	sig_handler_common(sig, si, mc);
+
+	set_signals_trace(enabled);
+}
+
+static void timer_real_alarm_handler(mcontext_t *mc)
+{
+	struct uml_pt_regs regs;
+
+	if (mc != NULL)
+		get_regs_from_mc(&regs, mc);
+	else
+		memset(&regs, 0, sizeof(regs));
+	timer_handler(SIGALRM, NULL, &regs);
+}
+
+void timer_alarm_handler(int sig, struct siginfo *unused_si, mcontext_t *mc)
+{
+	int enabled;
+
+	enabled = signals_enabled;
+	if (!signals_enabled) {
+		signals_pending |= SIGALRM_MASK;
+		return;
+	}
+
+	block_signals_trace();
+
+	signals_active |= SIGALRM_MASK;
+
+	timer_real_alarm_handler(mc);
+
+	signals_active &= ~SIGALRM_MASK;
+
+	set_signals_trace(enabled);
+}
+
+void deliver_alarm(void) {
+    timer_alarm_handler(SIGALRM, NULL, NULL);
+}
+
+void timer_set_signal_handler(void)
+{
+	set_handler(SIGALRM);
+}
+
+void set_sigstack(void *sig_stack, int size)
+{
+	stack_t stack = {
+		.ss_flags = 0,
+		.ss_sp = sig_stack,
+		.ss_size = size - sizeof(void *)
+	};
+
+	if (sigaltstack(&stack, NULL) != 0)
+		panic("enabling signal stack failed, errno = %d\n", errno);
+}
+
+static void sigusr1_handler(int sig, struct siginfo *unused_si, mcontext_t *mc)
+{
+	uml_pm_wake();
+}
+
+void register_pm_wake_signal(void)
+{
+	set_handler(SIGUSR1);
+}
+
+static void (*handlers[_NSIG])(int sig, struct siginfo *si, mcontext_t *mc) = {
+	[SIGSEGV] = sig_handler,
+	[SIGBUS] = sig_handler,
+	[SIGILL] = sig_handler,
+	[SIGFPE] = sig_handler,
+	[SIGTRAP] = sig_handler,
+
+	[SIGIO] = sig_handler,
+	[SIGWINCH] = sig_handler,
+	[SIGALRM] = timer_alarm_handler,
+
+	[SIGUSR1] = sigusr1_handler,
+};
+
+static void hard_handler(int sig, siginfo_t *si, void *p)
+{
+	ucontext_t *uc = p;
+	mcontext_t *mc = &uc->uc_mcontext;
+	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, (struct siginfo *)si, mc);
+		}
+
+		/*
+		 * 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);
+}
+
+void set_handler(int sig)
+{
+	struct sigaction action;
+	int flags = SA_SIGINFO | SA_ONSTACK;
+	sigset_t sig_mask;
+
+	action.sa_sigaction = hard_handler;
+
+	/* block irq ones */
+	sigemptyset(&action.sa_mask);
+	sigaddset(&action.sa_mask, SIGIO);
+	sigaddset(&action.sa_mask, SIGWINCH);
+	sigaddset(&action.sa_mask, SIGALRM);
+
+	if (sig == SIGSEGV)
+		flags |= SA_NODEFER;
+
+	if (sigismember(&action.sa_mask, sig))
+		flags |= SA_RESTART; /* if it's an irq signal */
+
+	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;
+
+	sigemptyset(&sigset);
+	sigaddset(&sigset, signal);
+	if (sigprocmask(on ? SIG_UNBLOCK : SIG_BLOCK, &sigset, NULL) < 0)
+		return -errno;
+
+	return 0;
+}
+
+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.
+	 */
+	barrier();
+}
+
+void unblock_signals(void)
+{
+	int save_pending;
+
+	if (signals_enabled == 1)
+		return;
+
+	signals_enabled = 1;
+
+	/*
+	 * We loop because the IRQ handler returns with interrupts off.  So,
+	 * interrupts may have arrived and we need to re-enable them and
+	 * recheck signals_pending.
+	 */
+	while (1) {
+		/*
+		 * Save and reset save_pending after enabling signals.  This
+		 * way, signals_pending won't be changed while we're reading it.
+		 *
+		 * Setting signals_enabled and reading signals_pending must
+		 * happen in this order, so have the barrier here.
+		 */
+		barrier();
+
+		save_pending = signals_pending;
+		if (save_pending == 0)
+			return;
+
+		signals_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. We need to trace this, as we're
+		 * expected to be enabling interrupts already, but any more
+		 * tracing that happens inside the handlers we call for the
+		 * pending signals will mess up the tracing state.
+		 */
+		signals_enabled = 0;
+		um_trace_signals_off();
+
+		/*
+		 * Deal with SIGIO first because the alarm handler might
+		 * schedule, leaving the pending SIGIO stranded until we come
+		 * back here.
+		 *
+		 * SIGIO's handler doesn't use siginfo or mcontext,
+		 * so they can be NULL.
+		 */
+		if (save_pending & SIGIO_MASK)
+			sig_handler_common(SIGIO, NULL, NULL);
+
+		/* Do not reenter the handler */
+
+		if ((save_pending & SIGALRM_MASK) && (!(signals_active & SIGALRM_MASK)))
+			timer_real_alarm_handler(NULL);
+
+		/* Rerun the loop only if there is still pending SIGIO and not in TIMER handler */
+
+		if (!(signals_pending & SIGIO_MASK) && (signals_active & SIGALRM_MASK))
+			return;
+
+		/* Re-enable signals and trace that we're doing so. */
+		um_trace_signals_on();
+		signals_enabled = 1;
+	}
+}
+
+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;
+}
+
+int set_signals_trace(int enable)
+{
+	int ret;
+	if (signals_enabled == enable)
+		return enable;
+
+	ret = signals_enabled;
+	if (enable)
+		unblock_signals_trace();
+	else
+		block_signals_trace();
+
+	return ret;
+}
+
+int os_is_signal_stack(void)
+{
+	stack_t ss;
+	sigaltstack(NULL, &ss);
+
+	return ss.ss_flags & SS_ONSTACK;
+}