v4.19.13 snapshot.
diff --git a/arch/um/os-Linux/signal.c b/arch/um/os-Linux/signal.c
new file mode 100644
index 0000000..bf0acb8
--- /dev/null
+++ b/arch/um/os-Linux/signal.c
@@ -0,0 +1,347 @@
+/*
+ * 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)
+ * Licensed under the GPL
+ */
+
+#include <stdlib.h>
+#include <stdarg.h>
+#include <errno.h>
+#include <signal.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,
+ [SIGALRM] = timer_handler
+};
+
+static void sig_handler_common(int sig, struct siginfo *si, mcontext_t *mc)
+{
+ struct uml_pt_regs *r;
+ int save_errno = errno;
+
+ r = uml_kmalloc(sizeof(struct uml_pt_regs), UM_GFP_ATOMIC);
+ if (!r)
+ panic("out of memory");
+
+ 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) && (sig != SIGALRM))
+ unblock_signals();
+
+ (*sig_info[sig])(sig, si, r);
+
+ errno = save_errno;
+
+ free(r);
+}
+
+/*
+ * 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();
+
+ sig_handler_common(sig, si, mc);
+
+ set_signals(enabled);
+}
+
+static void timer_real_alarm_handler(mcontext_t *mc)
+{
+ struct uml_pt_regs *regs;
+
+ regs = uml_kmalloc(sizeof(struct uml_pt_regs), UM_GFP_ATOMIC);
+ if (!regs)
+ panic("out of memory");
+
+ if (mc != NULL)
+ get_regs_from_mc(regs, mc);
+ timer_handler(SIGALRM, NULL, regs);
+
+ free(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();
+
+ signals_active |= SIGALRM_MASK;
+
+ timer_real_alarm_handler(mc);
+
+ signals_active &= ~SIGALRM_MASK;
+
+ set_signals(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 (*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
+};
+
+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;
+
+ /*
+ * 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.
+ */
+ signals_enabled = 1;
+
+ /*
+ * Setting signals_enabled and reading signals_pending must
+ * happen in this order.
+ */
+ 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.
+ */
+
+ signals_enabled = 0;
+
+ /*
+ * 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;
+
+ }
+}
+
+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 os_is_signal_stack(void)
+{
+ stack_t ss;
+ sigaltstack(NULL, &ss);
+
+ return ss.ss_flags & SS_ONSTACK;
+}