Introduce Virtio-loopback epsilon release:

Epsilon release introduces a new compatibility layer which make virtio-loopback
design to work with QEMU and rust-vmm vhost-user backend without require any
changes.

Signed-off-by: Timos Ampelikiotis <t.ampelikiotis@virtualopensystems.com>
Change-Id: I52e57563e08a7d0bdc002f8e928ee61ba0c53dd9

1 files changed, 1205 insertions, 0 deletions

diff --git a/linux-user/signal.c b/linux-user/signal.c
new file mode 100644
index 000000000..6d5e5b698
--- /dev/null
+++ b/linux-user/signal.c
@@ -0,0 +1,1205 @@
+/*
+ *  Emulation of Linux signals
+ *
+ *  Copyright (c) 2003 Fabrice Bellard
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation; either version 2 of the License, or
+ *  (at your option) any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program; if not, see <http://www.gnu.org/licenses/>.
+ */
+#include "qemu/osdep.h"
+#include "qemu/bitops.h"
+#include "exec/gdbstub.h"
+#include "hw/core/tcg-cpu-ops.h"
+
+#include <sys/ucontext.h>
+#include <sys/resource.h>
+
+#include "qemu.h"
+#include "user-internals.h"
+#include "strace.h"
+#include "loader.h"
+#include "trace.h"
+#include "signal-common.h"
+#include "host-signal.h"
+#include "safe-syscall.h"
+
+static struct target_sigaction sigact_table[TARGET_NSIG];
+
+static void host_signal_handler(int host_signum, siginfo_t *info,
+                                void *puc);
+
+/* Fallback addresses into sigtramp page. */
+abi_ulong default_sigreturn;
+abi_ulong default_rt_sigreturn;
+
+/*
+ * System includes define _NSIG as SIGRTMAX + 1,
+ * but qemu (like the kernel) defines TARGET_NSIG as TARGET_SIGRTMAX
+ * and the first signal is SIGHUP defined as 1
+ * Signal number 0 is reserved for use as kill(pid, 0), to test whether
+ * a process exists without sending it a signal.
+ */
+#ifdef __SIGRTMAX
+QEMU_BUILD_BUG_ON(__SIGRTMAX + 1 != _NSIG);
+#endif
+static uint8_t host_to_target_signal_table[_NSIG] = {
+    [SIGHUP] = TARGET_SIGHUP,
+    [SIGINT] = TARGET_SIGINT,
+    [SIGQUIT] = TARGET_SIGQUIT,
+    [SIGILL] = TARGET_SIGILL,
+    [SIGTRAP] = TARGET_SIGTRAP,
+    [SIGABRT] = TARGET_SIGABRT,
+/*    [SIGIOT] = TARGET_SIGIOT,*/
+    [SIGBUS] = TARGET_SIGBUS,
+    [SIGFPE] = TARGET_SIGFPE,
+    [SIGKILL] = TARGET_SIGKILL,
+    [SIGUSR1] = TARGET_SIGUSR1,
+    [SIGSEGV] = TARGET_SIGSEGV,
+    [SIGUSR2] = TARGET_SIGUSR2,
+    [SIGPIPE] = TARGET_SIGPIPE,
+    [SIGALRM] = TARGET_SIGALRM,
+    [SIGTERM] = TARGET_SIGTERM,
+#ifdef SIGSTKFLT
+    [SIGSTKFLT] = TARGET_SIGSTKFLT,
+#endif
+    [SIGCHLD] = TARGET_SIGCHLD,
+    [SIGCONT] = TARGET_SIGCONT,
+    [SIGSTOP] = TARGET_SIGSTOP,
+    [SIGTSTP] = TARGET_SIGTSTP,
+    [SIGTTIN] = TARGET_SIGTTIN,
+    [SIGTTOU] = TARGET_SIGTTOU,
+    [SIGURG] = TARGET_SIGURG,
+    [SIGXCPU] = TARGET_SIGXCPU,
+    [SIGXFSZ] = TARGET_SIGXFSZ,
+    [SIGVTALRM] = TARGET_SIGVTALRM,
+    [SIGPROF] = TARGET_SIGPROF,
+    [SIGWINCH] = TARGET_SIGWINCH,
+    [SIGIO] = TARGET_SIGIO,
+    [SIGPWR] = TARGET_SIGPWR,
+    [SIGSYS] = TARGET_SIGSYS,
+    /* next signals stay the same */
+};
+
+static uint8_t target_to_host_signal_table[TARGET_NSIG + 1];
+
+/* valid sig is between 1 and _NSIG - 1 */
+int host_to_target_signal(int sig)
+{
+    if (sig < 1 || sig >= _NSIG) {
+        return sig;
+    }
+    return host_to_target_signal_table[sig];
+}
+
+/* valid sig is between 1 and TARGET_NSIG */
+int target_to_host_signal(int sig)
+{
+    if (sig < 1 || sig > TARGET_NSIG) {
+        return sig;
+    }
+    return target_to_host_signal_table[sig];
+}
+
+static inline void target_sigaddset(target_sigset_t *set, int signum)
+{
+    signum--;
+    abi_ulong mask = (abi_ulong)1 << (signum % TARGET_NSIG_BPW);
+    set->sig[signum / TARGET_NSIG_BPW] |= mask;
+}
+
+static inline int target_sigismember(const target_sigset_t *set, int signum)
+{
+    signum--;
+    abi_ulong mask = (abi_ulong)1 << (signum % TARGET_NSIG_BPW);
+    return ((set->sig[signum / TARGET_NSIG_BPW] & mask) != 0);
+}
+
+void host_to_target_sigset_internal(target_sigset_t *d,
+                                    const sigset_t *s)
+{
+    int host_sig, target_sig;
+    target_sigemptyset(d);
+    for (host_sig = 1; host_sig < _NSIG; host_sig++) {
+        target_sig = host_to_target_signal(host_sig);
+        if (target_sig < 1 || target_sig > TARGET_NSIG) {
+            continue;
+        }
+        if (sigismember(s, host_sig)) {
+            target_sigaddset(d, target_sig);
+        }
+    }
+}
+
+void host_to_target_sigset(target_sigset_t *d, const sigset_t *s)
+{
+    target_sigset_t d1;
+    int i;
+
+    host_to_target_sigset_internal(&d1, s);
+    for(i = 0;i < TARGET_NSIG_WORDS; i++)
+        d->sig[i] = tswapal(d1.sig[i]);
+}
+
+void target_to_host_sigset_internal(sigset_t *d,
+                                    const target_sigset_t *s)
+{
+    int host_sig, target_sig;
+    sigemptyset(d);
+    for (target_sig = 1; target_sig <= TARGET_NSIG; target_sig++) {
+        host_sig = target_to_host_signal(target_sig);
+        if (host_sig < 1 || host_sig >= _NSIG) {
+            continue;
+        }
+        if (target_sigismember(s, target_sig)) {
+            sigaddset(d, host_sig);
+        }
+    }
+}
+
+void target_to_host_sigset(sigset_t *d, const target_sigset_t *s)
+{
+    target_sigset_t s1;
+    int i;
+
+    for(i = 0;i < TARGET_NSIG_WORDS; i++)
+        s1.sig[i] = tswapal(s->sig[i]);
+    target_to_host_sigset_internal(d, &s1);
+}
+
+void host_to_target_old_sigset(abi_ulong *old_sigset,
+                               const sigset_t *sigset)
+{
+    target_sigset_t d;
+    host_to_target_sigset(&d, sigset);
+    *old_sigset = d.sig[0];
+}
+
+void target_to_host_old_sigset(sigset_t *sigset,
+                               const abi_ulong *old_sigset)
+{
+    target_sigset_t d;
+    int i;
+
+    d.sig[0] = *old_sigset;
+    for(i = 1;i < TARGET_NSIG_WORDS; i++)
+        d.sig[i] = 0;
+    target_to_host_sigset(sigset, &d);
+}
+
+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);
+}
+
+/* Wrapper for sigprocmask function
+ * Emulates a sigprocmask in a safe way for the guest. Note that set and oldset
+ * are host signal set, not guest ones. Returns -TARGET_ERESTARTSYS if
+ * a signal was already pending and the syscall must be restarted, or
+ * 0 on success.
+ * If set is NULL, this is guaranteed not to fail.
+ */
+int do_sigprocmask(int how, const sigset_t *set, sigset_t *oldset)
+{
+    TaskState *ts = (TaskState *)thread_cpu->opaque;
+
+    if (oldset) {
+        *oldset = ts->signal_mask;
+    }
+
+    if (set) {
+        int i;
+
+        if (block_signals()) {
+            return -TARGET_ERESTARTSYS;
+        }
+
+        switch (how) {
+        case SIG_BLOCK:
+            sigorset(&ts->signal_mask, &ts->signal_mask, set);
+            break;
+        case SIG_UNBLOCK:
+            for (i = 1; i <= NSIG; ++i) {
+                if (sigismember(set, i)) {
+                    sigdelset(&ts->signal_mask, i);
+                }
+            }
+            break;
+        case SIG_SETMASK:
+            ts->signal_mask = *set;
+            break;
+        default:
+            g_assert_not_reached();
+        }
+
+        /* Silently ignore attempts to change blocking status of KILL or STOP */
+        sigdelset(&ts->signal_mask, SIGKILL);
+        sigdelset(&ts->signal_mask, SIGSTOP);
+    }
+    return 0;
+}
+
+#if !defined(TARGET_NIOS2)
+/* Just set the guest's signal mask to the specified value; the
+ * caller is assumed to have called block_signals() already.
+ */
+void set_sigmask(const sigset_t *set)
+{
+    TaskState *ts = (TaskState *)thread_cpu->opaque;
+
+    ts->signal_mask = *set;
+}
+#endif
+
+/* sigaltstack management */
+
+int on_sig_stack(unsigned long sp)
+{
+    TaskState *ts = (TaskState *)thread_cpu->opaque;
+
+    return (sp - ts->sigaltstack_used.ss_sp
+            < ts->sigaltstack_used.ss_size);
+}
+
+int sas_ss_flags(unsigned long sp)
+{
+    TaskState *ts = (TaskState *)thread_cpu->opaque;
+
+    return (ts->sigaltstack_used.ss_size == 0 ? SS_DISABLE
+            : on_sig_stack(sp) ? SS_ONSTACK : 0);
+}
+
+abi_ulong target_sigsp(abi_ulong sp, struct target_sigaction *ka)
+{
+    /*
+     * This is the X/Open sanctioned signal stack switching.
+     */
+    TaskState *ts = (TaskState *)thread_cpu->opaque;
+
+    if ((ka->sa_flags & TARGET_SA_ONSTACK) && !sas_ss_flags(sp)) {
+        return ts->sigaltstack_used.ss_sp + ts->sigaltstack_used.ss_size;
+    }
+    return sp;
+}
+
+void target_save_altstack(target_stack_t *uss, CPUArchState *env)
+{
+    TaskState *ts = (TaskState *)thread_cpu->opaque;
+
+    __put_user(ts->sigaltstack_used.ss_sp, &uss->ss_sp);
+    __put_user(sas_ss_flags(get_sp_from_cpustate(env)), &uss->ss_flags);
+    __put_user(ts->sigaltstack_used.ss_size, &uss->ss_size);
+}
+
+abi_long target_restore_altstack(target_stack_t *uss, CPUArchState *env)
+{
+    TaskState *ts = (TaskState *)thread_cpu->opaque;
+    size_t minstacksize = TARGET_MINSIGSTKSZ;
+    target_stack_t ss;
+
+#if defined(TARGET_PPC64)
+    /* ELF V2 for PPC64 has a 4K minimum stack size for signal handlers */
+    struct image_info *image = ts->info;
+    if (get_ppc64_abi(image) > 1) {
+        minstacksize = 4096;
+    }
+#endif
+
+    __get_user(ss.ss_sp, &uss->ss_sp);
+    __get_user(ss.ss_size, &uss->ss_size);
+    __get_user(ss.ss_flags, &uss->ss_flags);
+
+    if (on_sig_stack(get_sp_from_cpustate(env))) {
+        return -TARGET_EPERM;
+    }
+
+    switch (ss.ss_flags) {
+    default:
+        return -TARGET_EINVAL;
+
+    case TARGET_SS_DISABLE:
+        ss.ss_size = 0;
+        ss.ss_sp = 0;
+        break;
+
+    case TARGET_SS_ONSTACK:
+    case 0:
+        if (ss.ss_size < minstacksize) {
+            return -TARGET_ENOMEM;
+        }
+        break;
+    }
+
+    ts->sigaltstack_used.ss_sp = ss.ss_sp;
+    ts->sigaltstack_used.ss_size = ss.ss_size;
+    return 0;
+}
+
+/* siginfo conversion */
+
+static inline void host_to_target_siginfo_noswap(target_siginfo_t *tinfo,
+                                                 const siginfo_t *info)
+{
+    int sig = host_to_target_signal(info->si_signo);
+    int si_code = info->si_code;
+    int si_type;
+    tinfo->si_signo = sig;
+    tinfo->si_errno = 0;
+    tinfo->si_code = info->si_code;
+
+    /* This memset serves two purposes:
+     * (1) ensure we don't leak random junk to the guest later
+     * (2) placate false positives from gcc about fields
+     *     being used uninitialized if it chooses to inline both this
+     *     function and tswap_siginfo() into host_to_target_siginfo().
+     */
+    memset(tinfo->_sifields._pad, 0, sizeof(tinfo->_sifields._pad));
+
+    /* This is awkward, because we have to use a combination of
+     * the si_code and si_signo to figure out which of the union's
+     * members are valid. (Within the host kernel it is always possible
+     * to tell, but the kernel carefully avoids giving userspace the
+     * high 16 bits of si_code, so we don't have the information to
+     * do this the easy way...) We therefore make our best guess,
+     * bearing in mind that a guest can spoof most of the si_codes
+     * via rt_sigqueueinfo() if it likes.
+     *
+     * Once we have made our guess, we record it in the top 16 bits of
+     * the si_code, so that tswap_siginfo() later can use it.
+     * tswap_siginfo() will strip these top bits out before writing
+     * si_code to the guest (sign-extending the lower bits).
+     */
+
+    switch (si_code) {
+    case SI_USER:
+    case SI_TKILL:
+    case SI_KERNEL:
+        /* Sent via kill(), tkill() or tgkill(), or direct from the kernel.
+         * These are the only unspoofable si_code values.
+         */
+        tinfo->_sifields._kill._pid = info->si_pid;
+        tinfo->_sifields._kill._uid = info->si_uid;
+        si_type = QEMU_SI_KILL;
+        break;
+    default:
+        /* Everything else is spoofable. Make best guess based on signal */
+        switch (sig) {
+        case TARGET_SIGCHLD:
+            tinfo->_sifields._sigchld._pid = info->si_pid;
+            tinfo->_sifields._sigchld._uid = info->si_uid;
+            tinfo->_sifields._sigchld._status = info->si_status;
+            tinfo->_sifields._sigchld._utime = info->si_utime;
+            tinfo->_sifields._sigchld._stime = info->si_stime;
+            si_type = QEMU_SI_CHLD;
+            break;
+        case TARGET_SIGIO:
+            tinfo->_sifields._sigpoll._band = info->si_band;
+            tinfo->_sifields._sigpoll._fd = info->si_fd;
+            si_type = QEMU_SI_POLL;
+            break;
+        default:
+            /* Assume a sigqueue()/mq_notify()/rt_sigqueueinfo() source. */
+            tinfo->_sifields._rt._pid = info->si_pid;
+            tinfo->_sifields._rt._uid = info->si_uid;
+            /* XXX: potential problem if 64 bit */
+            tinfo->_sifields._rt._sigval.sival_ptr
+                = (abi_ulong)(unsigned long)info->si_value.sival_ptr;
+            si_type = QEMU_SI_RT;
+            break;
+        }
+        break;
+    }
+
+    tinfo->si_code = deposit32(si_code, 16, 16, si_type);
+}
+
+void tswap_siginfo(target_siginfo_t *tinfo,
+                   const target_siginfo_t *info)
+{
+    int si_type = extract32(info->si_code, 16, 16);
+    int si_code = sextract32(info->si_code, 0, 16);
+
+    __put_user(info->si_signo, &tinfo->si_signo);
+    __put_user(info->si_errno, &tinfo->si_errno);
+    __put_user(si_code, &tinfo->si_code);
+
+    /* We can use our internal marker of which fields in the structure
+     * are valid, rather than duplicating the guesswork of
+     * host_to_target_siginfo_noswap() here.
+     */
+    switch (si_type) {
+    case QEMU_SI_KILL:
+        __put_user(info->_sifields._kill._pid, &tinfo->_sifields._kill._pid);
+        __put_user(info->_sifields._kill._uid, &tinfo->_sifields._kill._uid);
+        break;
+    case QEMU_SI_TIMER:
+        __put_user(info->_sifields._timer._timer1,
+                   &tinfo->_sifields._timer._timer1);
+        __put_user(info->_sifields._timer._timer2,
+                   &tinfo->_sifields._timer._timer2);
+        break;
+    case QEMU_SI_POLL:
+        __put_user(info->_sifields._sigpoll._band,
+                   &tinfo->_sifields._sigpoll._band);
+        __put_user(info->_sifields._sigpoll._fd,
+                   &tinfo->_sifields._sigpoll._fd);
+        break;
+    case QEMU_SI_FAULT:
+        __put_user(info->_sifields._sigfault._addr,
+                   &tinfo->_sifields._sigfault._addr);
+        break;
+    case QEMU_SI_CHLD:
+        __put_user(info->_sifields._sigchld._pid,
+                   &tinfo->_sifields._sigchld._pid);
+        __put_user(info->_sifields._sigchld._uid,
+                   &tinfo->_sifields._sigchld._uid);
+        __put_user(info->_sifields._sigchld._status,
+                   &tinfo->_sifields._sigchld._status);
+        __put_user(info->_sifields._sigchld._utime,
+                   &tinfo->_sifields._sigchld._utime);
+        __put_user(info->_sifields._sigchld._stime,
+                   &tinfo->_sifields._sigchld._stime);
+        break;
+    case QEMU_SI_RT:
+        __put_user(info->_sifields._rt._pid, &tinfo->_sifields._rt._pid);
+        __put_user(info->_sifields._rt._uid, &tinfo->_sifields._rt._uid);
+        __put_user(info->_sifields._rt._sigval.sival_ptr,
+                   &tinfo->_sifields._rt._sigval.sival_ptr);
+        break;
+    default:
+        g_assert_not_reached();
+    }
+}
+
+void host_to_target_siginfo(target_siginfo_t *tinfo, const siginfo_t *info)
+{
+    target_siginfo_t tgt_tmp;
+    host_to_target_siginfo_noswap(&tgt_tmp, info);
+    tswap_siginfo(tinfo, &tgt_tmp);
+}
+
+/* XXX: we support only POSIX RT signals are used. */
+/* XXX: find a solution for 64 bit (additional malloced data is needed) */
+void target_to_host_siginfo(siginfo_t *info, const target_siginfo_t *tinfo)
+{
+    /* This conversion is used only for the rt_sigqueueinfo syscall,
+     * and so we know that the _rt fields are the valid ones.
+     */
+    abi_ulong sival_ptr;
+
+    __get_user(info->si_signo, &tinfo->si_signo);
+    __get_user(info->si_errno, &tinfo->si_errno);
+    __get_user(info->si_code, &tinfo->si_code);
+    __get_user(info->si_pid, &tinfo->_sifields._rt._pid);
+    __get_user(info->si_uid, &tinfo->_sifields._rt._uid);
+    __get_user(sival_ptr, &tinfo->_sifields._rt._sigval.sival_ptr);
+    info->si_value.sival_ptr = (void *)(long)sival_ptr;
+}
+
+static int fatal_signal (int sig)
+{
+    switch (sig) {
+    case TARGET_SIGCHLD:
+    case TARGET_SIGURG:
+    case TARGET_SIGWINCH:
+        /* Ignored by default.  */
+        return 0;
+    case TARGET_SIGCONT:
+    case TARGET_SIGSTOP:
+    case TARGET_SIGTSTP:
+    case TARGET_SIGTTIN:
+    case TARGET_SIGTTOU:
+        /* Job control signals.  */
+        return 0;
+    default:
+        return 1;
+    }
+}
+
+/* returns 1 if given signal should dump core if not handled */
+static int core_dump_signal(int sig)
+{
+    switch (sig) {
+    case TARGET_SIGABRT:
+    case TARGET_SIGFPE:
+    case TARGET_SIGILL:
+    case TARGET_SIGQUIT:
+    case TARGET_SIGSEGV:
+    case TARGET_SIGTRAP:
+    case TARGET_SIGBUS:
+        return (1);
+    default:
+        return (0);
+    }
+}
+
+static void signal_table_init(void)
+{
+    int host_sig, target_sig, count;
+
+    /*
+     * Signals are supported starting from TARGET_SIGRTMIN and going up
+     * until we run out of host realtime signals.
+     * glibc at least uses only the lower 2 rt signals and probably
+     * nobody's using the upper ones.
+     * it's why SIGRTMIN (34) is generally greater than __SIGRTMIN (32)
+     * To fix this properly we need to do manual signal delivery multiplexed
+     * over a single host signal.
+     * Attempts for configure "missing" signals via sigaction will be
+     * silently ignored.
+     */
+    for (host_sig = SIGRTMIN; host_sig <= SIGRTMAX; host_sig++) {
+        target_sig = host_sig - SIGRTMIN + TARGET_SIGRTMIN;
+        if (target_sig <= TARGET_NSIG) {
+            host_to_target_signal_table[host_sig] = target_sig;
+        }
+    }
+
+    /* generate signal conversion tables */
+    for (target_sig = 1; target_sig <= TARGET_NSIG; target_sig++) {
+        target_to_host_signal_table[target_sig] = _NSIG; /* poison */
+    }
+    for (host_sig = 1; host_sig < _NSIG; host_sig++) {
+        if (host_to_target_signal_table[host_sig] == 0) {
+            host_to_target_signal_table[host_sig] = host_sig;
+        }
+        target_sig = host_to_target_signal_table[host_sig];
+        if (target_sig <= TARGET_NSIG) {
+            target_to_host_signal_table[target_sig] = host_sig;
+        }
+    }
+
+    if (trace_event_get_state_backends(TRACE_SIGNAL_TABLE_INIT)) {
+        for (target_sig = 1, count = 0; target_sig <= TARGET_NSIG; target_sig++) {
+            if (target_to_host_signal_table[target_sig] == _NSIG) {
+                count++;
+            }
+        }
+        trace_signal_table_init(count);
+    }
+}
+
+void signal_init(void)
+{
+    TaskState *ts = (TaskState *)thread_cpu->opaque;
+    struct sigaction act;
+    struct sigaction oact;
+    int i;
+    int host_sig;
+
+    /* initialize signal conversion tables */
+    signal_table_init();
+
+    /* Set the signal mask from the host mask. */
+    sigprocmask(0, 0, &ts->signal_mask);
+
+    sigfillset(&act.sa_mask);
+    act.sa_flags = SA_SIGINFO;
+    act.sa_sigaction = host_signal_handler;
+    for(i = 1; i <= TARGET_NSIG; i++) {
+#ifdef CONFIG_GPROF
+        if (i == TARGET_SIGPROF) {
+            continue;
+        }
+#endif
+        host_sig = target_to_host_signal(i);
+        sigaction(host_sig, NULL, &oact);
+        if (oact.sa_sigaction == (void *)SIG_IGN) {
+            sigact_table[i - 1]._sa_handler = TARGET_SIG_IGN;
+        } else if (oact.sa_sigaction == (void *)SIG_DFL) {
+            sigact_table[i - 1]._sa_handler = TARGET_SIG_DFL;
+        }
+        /* If there's already a handler installed then something has
+           gone horribly wrong, so don't even try to handle that case.  */
+        /* Install some handlers for our own use.  We need at least
+           SIGSEGV and SIGBUS, to detect exceptions.  We can not just
+           trap all signals because it affects syscall interrupt
+           behavior.  But do trap all default-fatal signals.  */
+        if (fatal_signal (i))
+            sigaction(host_sig, &act, NULL);
+    }
+}
+
+/* Force a synchronously taken signal. The kernel force_sig() function
+ * also forces the signal to "not blocked, not ignored", but for QEMU
+ * that work is done in process_pending_signals().
+ */
+void force_sig(int sig)
+{
+    CPUState *cpu = thread_cpu;
+    CPUArchState *env = cpu->env_ptr;
+    target_siginfo_t info = {};
+
+    info.si_signo = sig;
+    info.si_errno = 0;
+    info.si_code = TARGET_SI_KERNEL;
+    info._sifields._kill._pid = 0;
+    info._sifields._kill._uid = 0;
+    queue_signal(env, info.si_signo, QEMU_SI_KILL, &info);
+}
+
+/*
+ * Force a synchronously taken QEMU_SI_FAULT signal. For QEMU the
+ * 'force' part is handled in process_pending_signals().
+ */
+void force_sig_fault(int sig, int code, abi_ulong addr)
+{
+    CPUState *cpu = thread_cpu;
+    CPUArchState *env = cpu->env_ptr;
+    target_siginfo_t info = {};
+
+    info.si_signo = sig;
+    info.si_errno = 0;
+    info.si_code = code;
+    info._sifields._sigfault._addr = addr;
+    queue_signal(env, sig, QEMU_SI_FAULT, &info);
+}
+
+/* Force a SIGSEGV if we couldn't write to memory trying to set
+ * up the signal frame. oldsig is the signal we were trying to handle
+ * at the point of failure.
+ */
+#if !defined(TARGET_RISCV)
+void force_sigsegv(int oldsig)
+{
+    if (oldsig == SIGSEGV) {
+        /* Make sure we don't try to deliver the signal again; this will
+         * end up with handle_pending_signal() calling dump_core_and_abort().
+         */
+        sigact_table[oldsig - 1]._sa_handler = TARGET_SIG_DFL;
+    }
+    force_sig(TARGET_SIGSEGV);
+}
+#endif
+
+void cpu_loop_exit_sigsegv(CPUState *cpu, target_ulong addr,
+                           MMUAccessType access_type, bool maperr, uintptr_t ra)
+{
+    const struct TCGCPUOps *tcg_ops = CPU_GET_CLASS(cpu)->tcg_ops;
+
+    if (tcg_ops->record_sigsegv) {
+        tcg_ops->record_sigsegv(cpu, addr, access_type, maperr, ra);
+    }
+
+    force_sig_fault(TARGET_SIGSEGV,
+                    maperr ? TARGET_SEGV_MAPERR : TARGET_SEGV_ACCERR,
+                    addr);
+    cpu->exception_index = EXCP_INTERRUPT;
+    cpu_loop_exit_restore(cpu, ra);
+}
+
+void cpu_loop_exit_sigbus(CPUState *cpu, target_ulong addr,
+                          MMUAccessType access_type, uintptr_t ra)
+{
+    const struct TCGCPUOps *tcg_ops = CPU_GET_CLASS(cpu)->tcg_ops;
+
+    if (tcg_ops->record_sigbus) {
+        tcg_ops->record_sigbus(cpu, addr, access_type, ra);
+    }
+
+    force_sig_fault(TARGET_SIGBUS, TARGET_BUS_ADRALN, addr);
+    cpu->exception_index = EXCP_INTERRUPT;
+    cpu_loop_exit_restore(cpu, ra);
+}
+
+/* abort execution with signal */
+static void QEMU_NORETURN dump_core_and_abort(int target_sig)
+{
+    CPUState *cpu = thread_cpu;
+    CPUArchState *env = cpu->env_ptr;
+    TaskState *ts = (TaskState *)cpu->opaque;
+    int host_sig, core_dumped = 0;
+    struct sigaction act;
+
+    host_sig = target_to_host_signal(target_sig);
+    trace_user_force_sig(env, target_sig, host_sig);
+    gdb_signalled(env, target_sig);
+
+    /* dump core if supported by target binary format */
+    if (core_dump_signal(target_sig) && (ts->bprm->core_dump != NULL)) {
+        stop_all_tasks();
+        core_dumped =
+            ((*ts->bprm->core_dump)(target_sig, env) == 0);
+    }
+    if (core_dumped) {
+        /* we already dumped the core of target process, we don't want
+         * a coredump of qemu itself */
+        struct rlimit nodump;
+        getrlimit(RLIMIT_CORE, &nodump);
+        nodump.rlim_cur=0;
+        setrlimit(RLIMIT_CORE, &nodump);
+        (void) fprintf(stderr, "qemu: uncaught target signal %d (%s) - %s\n",
+            target_sig, strsignal(host_sig), "core dumped" );
+    }
+
+    /* The proper exit code for dying from an uncaught signal is
+     * -<signal>.  The kernel doesn't allow exit() or _exit() to pass
+     * a negative value.  To get the proper exit code we need to
+     * actually die from an uncaught signal.  Here the default signal
+     * handler is installed, we send ourself a signal and we wait for
+     * it to arrive. */
+    sigfillset(&act.sa_mask);
+    act.sa_handler = SIG_DFL;
+    act.sa_flags = 0;
+    sigaction(host_sig, &act, NULL);
+
+    /* For some reason raise(host_sig) doesn't send the signal when
+     * statically linked on x86-64. */
+    kill(getpid(), host_sig);
+
+    /* Make sure the signal isn't masked (just reuse the mask inside
+    of act) */
+    sigdelset(&act.sa_mask, host_sig);
+    sigsuspend(&act.sa_mask);
+
+    /* unreachable */
+    abort();
+}
+
+/* queue a signal so that it will be send to the virtual CPU as soon
+   as possible */
+int queue_signal(CPUArchState *env, int sig, int si_type,
+                 target_siginfo_t *info)
+{
+    CPUState *cpu = env_cpu(env);
+    TaskState *ts = cpu->opaque;
+
+    trace_user_queue_signal(env, sig);
+
+    info->si_code = deposit32(info->si_code, 16, 16, si_type);
+
+    ts->sync_signal.info = *info;
+    ts->sync_signal.pending = sig;
+    /* signal that a new signal is pending */
+    qatomic_set(&ts->signal_pending, 1);
+    return 1; /* indicates that the signal was queued */
+}
+
+
+/* Adjust the signal context to rewind out of safe-syscall if we're in it */
+static inline void rewind_if_in_safe_syscall(void *puc)
+{
+#ifdef HAVE_SAFE_SYSCALL
+    ucontext_t *uc = (ucontext_t *)puc;
+    uintptr_t pcreg = host_signal_pc(uc);
+
+    if (pcreg > (uintptr_t)safe_syscall_start
+        && pcreg < (uintptr_t)safe_syscall_end) {
+        host_signal_set_pc(uc, (uintptr_t)safe_syscall_start);
+    }
+#endif
+}
+
+static void host_signal_handler(int host_sig, siginfo_t *info, void *puc)
+{
+    CPUArchState *env = thread_cpu->env_ptr;
+    CPUState *cpu = env_cpu(env);
+    TaskState *ts = cpu->opaque;
+    target_siginfo_t tinfo;
+    ucontext_t *uc = puc;
+    struct emulated_sigtable *k;
+    int guest_sig;
+    uintptr_t pc = 0;
+    bool sync_sig = false;
+
+    /*
+     * Non-spoofed SIGSEGV and SIGBUS are synchronous, and need special
+     * handling wrt signal blocking and unwinding.
+     */
+    if ((host_sig == SIGSEGV || host_sig == SIGBUS) && info->si_code > 0) {
+        MMUAccessType access_type;
+        uintptr_t host_addr;
+        abi_ptr guest_addr;
+        bool is_write;
+
+        host_addr = (uintptr_t)info->si_addr;
+
+        /*
+         * Convert forcefully to guest address space: addresses outside
+         * reserved_va are still valid to report via SEGV_MAPERR.
+         */
+        guest_addr = h2g_nocheck(host_addr);
+
+        pc = host_signal_pc(uc);
+        is_write = host_signal_write(info, uc);
+        access_type = adjust_signal_pc(&pc, is_write);
+
+        if (host_sig == SIGSEGV) {
+            bool maperr = true;
+
+            if (info->si_code == SEGV_ACCERR && h2g_valid(host_addr)) {
+                /* If this was a write to a TB protected page, restart. */
+                if (is_write &&
+                    handle_sigsegv_accerr_write(cpu, &uc->uc_sigmask,
+                                                pc, guest_addr)) {
+                    return;
+                }
+
+                /*
+                 * With reserved_va, the whole address space is PROT_NONE,
+                 * which means that we may get ACCERR when we want MAPERR.
+                 */
+                if (page_get_flags(guest_addr) & PAGE_VALID) {
+                    maperr = false;
+                } else {
+                    info->si_code = SEGV_MAPERR;
+                }
+            }
+
+            sigprocmask(SIG_SETMASK, &uc->uc_sigmask, NULL);
+            cpu_loop_exit_sigsegv(cpu, guest_addr, access_type, maperr, pc);
+        } else {
+            sigprocmask(SIG_SETMASK, &uc->uc_sigmask, NULL);
+            if (info->si_code == BUS_ADRALN) {
+                cpu_loop_exit_sigbus(cpu, guest_addr, access_type, pc);
+            }
+        }
+
+        sync_sig = true;
+    }
+
+    /* get target signal number */
+    guest_sig = host_to_target_signal(host_sig);
+    if (guest_sig < 1 || guest_sig > TARGET_NSIG) {
+        return;
+    }
+    trace_user_host_signal(env, host_sig, guest_sig);
+
+    host_to_target_siginfo_noswap(&tinfo, info);
+    k = &ts->sigtab[guest_sig - 1];
+    k->info = tinfo;
+    k->pending = guest_sig;
+    ts->signal_pending = 1;
+
+    /*
+     * For synchronous signals, unwind the cpu state to the faulting
+     * insn and then exit back to the main loop so that the signal
+     * is delivered immediately.
+     */
+    if (sync_sig) {
+        cpu->exception_index = EXCP_INTERRUPT;
+        cpu_loop_exit_restore(cpu, pc);
+    }
+
+    rewind_if_in_safe_syscall(puc);
+
+    /*
+     * Block host signals until target signal handler entered. We
+     * can't block SIGSEGV or SIGBUS while we're executing guest
+     * code in case the guest code provokes one in the window between
+     * now and it getting out to the main loop. Signals will be
+     * unblocked again in process_pending_signals().
+     *
+     * WARNING: we cannot use sigfillset() here because the uc_sigmask
+     * field is a kernel sigset_t, which is much smaller than the
+     * libc sigset_t which sigfillset() operates on. Using sigfillset()
+     * would write 0xff bytes off the end of the structure and trash
+     * data on the struct.
+     * We can't use sizeof(uc->uc_sigmask) either, because the libc
+     * headers define the struct field with the wrong (too large) type.
+     */
+    memset(&uc->uc_sigmask, 0xff, SIGSET_T_SIZE);
+    sigdelset(&uc->uc_sigmask, SIGSEGV);
+    sigdelset(&uc->uc_sigmask, SIGBUS);
+
+    /* interrupt the virtual CPU as soon as possible */
+    cpu_exit(thread_cpu);
+}
+
+/* do_sigaltstack() returns target values and errnos. */
+/* compare linux/kernel/signal.c:do_sigaltstack() */
+abi_long do_sigaltstack(abi_ulong uss_addr, abi_ulong uoss_addr,
+                        CPUArchState *env)
+{
+    target_stack_t oss, *uoss = NULL;
+    abi_long ret = -TARGET_EFAULT;
+
+    if (uoss_addr) {
+        /* Verify writability now, but do not alter user memory yet. */
+        if (!lock_user_struct(VERIFY_WRITE, uoss, uoss_addr, 0)) {
+            goto out;
+        }
+        target_save_altstack(&oss, env);
+    }
+
+    if (uss_addr) {
+        target_stack_t *uss;
+
+        if (!lock_user_struct(VERIFY_READ, uss, uss_addr, 1)) {
+            goto out;
+        }
+        ret = target_restore_altstack(uss, env);
+        if (ret) {
+            goto out;
+        }
+    }
+
+    if (uoss_addr) {
+        memcpy(uoss, &oss, sizeof(oss));
+        unlock_user_struct(uoss, uoss_addr, 1);
+        uoss = NULL;
+    }
+    ret = 0;
+
+ out:
+    if (uoss) {
+        unlock_user_struct(uoss, uoss_addr, 0);
+    }
+    return ret;
+}
+
+/* do_sigaction() return target values and host errnos */
+int do_sigaction(int sig, const struct target_sigaction *act,
+                 struct target_sigaction *oact, abi_ulong ka_restorer)
+{
+    struct target_sigaction *k;
+    struct sigaction act1;
+    int host_sig;
+    int ret = 0;
+
+    trace_signal_do_sigaction_guest(sig, TARGET_NSIG);
+
+    if (sig < 1 || sig > TARGET_NSIG) {
+        return -TARGET_EINVAL;
+    }
+
+    if (act && (sig == TARGET_SIGKILL || sig == TARGET_SIGSTOP)) {
+        return -TARGET_EINVAL;
+    }
+
+    if (block_signals()) {
+        return -TARGET_ERESTARTSYS;
+    }
+
+    k = &sigact_table[sig - 1];
+    if (oact) {
+        __put_user(k->_sa_handler, &oact->_sa_handler);
+        __put_user(k->sa_flags, &oact->sa_flags);
+#ifdef TARGET_ARCH_HAS_SA_RESTORER
+        __put_user(k->sa_restorer, &oact->sa_restorer);
+#endif
+        /* Not swapped.  */
+        oact->sa_mask = k->sa_mask;
+    }
+    if (act) {
+        /* FIXME: This is not threadsafe.  */
+        __get_user(k->_sa_handler, &act->_sa_handler);
+        __get_user(k->sa_flags, &act->sa_flags);
+#ifdef TARGET_ARCH_HAS_SA_RESTORER
+        __get_user(k->sa_restorer, &act->sa_restorer);
+#endif
+#ifdef TARGET_ARCH_HAS_KA_RESTORER
+        k->ka_restorer = ka_restorer;
+#endif
+        /* To be swapped in target_to_host_sigset.  */
+        k->sa_mask = act->sa_mask;
+
+        /* we update the host linux signal state */
+        host_sig = target_to_host_signal(sig);
+        trace_signal_do_sigaction_host(host_sig, TARGET_NSIG);
+        if (host_sig > SIGRTMAX) {
+            /* we don't have enough host signals to map all target signals */
+            qemu_log_mask(LOG_UNIMP, "Unsupported target signal #%d, ignored\n",
+                          sig);
+            /*
+             * we don't return an error here because some programs try to
+             * register an handler for all possible rt signals even if they
+             * don't need it.
+             * An error here can abort them whereas there can be no problem
+             * to not have the signal available later.
+             * This is the case for golang,
+             *   See https://github.com/golang/go/issues/33746
+             * So we silently ignore the error.
+             */
+            return 0;
+        }
+        if (host_sig != SIGSEGV && host_sig != SIGBUS) {
+            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
+               ignore state to avoid getting unexpected interrupted
+               syscalls */
+            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 void handle_pending_signal(CPUArchState *cpu_env, int sig,
+                                  struct emulated_sigtable *k)
+{
+    CPUState *cpu = env_cpu(cpu_env);
+    abi_ulong handler;
+    sigset_t set;
+    target_sigset_t target_old_set;
+    struct target_sigaction *sa;
+    TaskState *ts = cpu->opaque;
+
+    trace_user_handle_signal(cpu_env, sig);
+    /* dequeue signal */
+    k->pending = 0;
+
+    sig = gdb_handlesig(cpu, sig);
+    if (!sig) {
+        sa = NULL;
+        handler = TARGET_SIG_IGN;
+    } else {
+        sa = &sigact_table[sig - 1];
+        handler = sa->_sa_handler;
+    }
+
+    if (unlikely(qemu_loglevel_mask(LOG_STRACE))) {
+        print_taken_signal(sig, &k->info);
+    }
+
+    if (handler == TARGET_SIG_DFL) {
+        /* default handler : ignore some signal. The other are job control or fatal */
+        if (sig == TARGET_SIGTSTP || sig == TARGET_SIGTTIN || sig == TARGET_SIGTTOU) {
+            kill(getpid(),SIGSTOP);
+        } else if (sig != TARGET_SIGCHLD &&
+                   sig != TARGET_SIGURG &&
+                   sig != TARGET_SIGWINCH &&
+                   sig != TARGET_SIGCONT) {
+            dump_core_and_abort(sig);
+        }
+    } else if (handler == TARGET_SIG_IGN) {
+        /* ignore sig */
+    } else if (handler == TARGET_SIG_ERR) {
+        dump_core_and_abort(sig);
+    } else {
+        /* compute the blocked signals during the handler execution */
+        sigset_t *blocked_set;
+
+        target_to_host_sigset(&set, &sa->sa_mask);
+        /* SA_NODEFER indicates that the current signal should not be
+           blocked during the handler */
+        if (!(sa->sa_flags & TARGET_SA_NODEFER))
+            sigaddset(&set, target_to_host_signal(sig));
+
+        /* save the previous blocked signal state to restore it at the
+           end of the signal execution (see do_sigreturn) */
+        host_to_target_sigset_internal(&target_old_set, &ts->signal_mask);
+
+        /* block signals in the handler */
+        blocked_set = ts->in_sigsuspend ?
+            &ts->sigsuspend_mask : &ts->signal_mask;
+        sigorset(&ts->signal_mask, blocked_set, &set);
+        ts->in_sigsuspend = 0;
+
+        /* if the CPU is in VM86 mode, we restore the 32 bit values */
+#if defined(TARGET_I386) && !defined(TARGET_X86_64)
+        {
+            CPUX86State *env = cpu_env;
+            if (env->eflags & VM_MASK)
+                save_v86_state(env);
+        }
+#endif
+        /* prepare the stack frame of the virtual CPU */
+#if defined(TARGET_ARCH_HAS_SETUP_FRAME)
+        if (sa->sa_flags & TARGET_SA_SIGINFO) {
+            setup_rt_frame(sig, sa, &k->info, &target_old_set, cpu_env);
+        } else {
+            setup_frame(sig, sa, &target_old_set, cpu_env);
+        }
+#else
+        /* These targets do not have traditional signals.  */
+        setup_rt_frame(sig, sa, &k->info, &target_old_set, cpu_env);
+#endif
+        if (sa->sa_flags & TARGET_SA_RESETHAND) {
+            sa->_sa_handler = TARGET_SIG_DFL;
+        }
+    }
+}
+
+void process_pending_signals(CPUArchState *cpu_env)
+{
+    CPUState *cpu = env_cpu(cpu_env);
+    int sig;
+    TaskState *ts = cpu->opaque;
+    sigset_t set;
+    sigset_t *blocked_set;
+
+    while (qatomic_read(&ts->signal_pending)) {
+        /* FIXME: This is not threadsafe.  */
+        sigfillset(&set);
+        sigprocmask(SIG_SETMASK, &set, 0);
+
+    restart_scan:
+        sig = ts->sync_signal.pending;
+        if (sig) {
+            /* Synchronous signals are forced,
+             * see force_sig_info() and callers in Linux
+             * Note that not all of our queue_signal() calls in QEMU correspond
+             * to force_sig_info() calls in Linux (some are send_sig_info()).
+             * However it seems like a kernel bug to me to allow the process
+             * to block a synchronous signal since it could then just end up
+             * looping round and round indefinitely.
+             */
+            if (sigismember(&ts->signal_mask, target_to_host_signal_table[sig])
+                || sigact_table[sig - 1]._sa_handler == TARGET_SIG_IGN) {
+                sigdelset(&ts->signal_mask, target_to_host_signal_table[sig]);
+                sigact_table[sig - 1]._sa_handler = TARGET_SIG_DFL;
+            }
+
+            handle_pending_signal(cpu_env, sig, &ts->sync_signal);
+        }
+
+        for (sig = 1; sig <= TARGET_NSIG; sig++) {
+            blocked_set = ts->in_sigsuspend ?
+                &ts->sigsuspend_mask : &ts->signal_mask;
+
+            if (ts->sigtab[sig - 1].pending &&
+                (!sigismember(blocked_set,
+                              target_to_host_signal_table[sig]))) {
+                handle_pending_signal(cpu_env, sig, &ts->sigtab[sig - 1]);
+                /* Restart scan from the beginning, as handle_pending_signal
+                 * might have resulted in a new synchronous signal (eg SIGSEGV).
+                 */
+                goto restart_scan;
+            }
+        }
+
+        /* if no signal is pending, unblock signals and recheck (the act
+         * of unblocking might cause us to take another host signal which
+         * will set signal_pending again).
+         */
+        qatomic_set(&ts->signal_pending, 0);
+        ts->in_sigsuspend = 0;
+        set = ts->signal_mask;
+        sigdelset(&set, SIGSEGV);
+        sigdelset(&set, SIGBUS);
+        sigprocmask(SIG_SETMASK, &set, 0);
+    }
+    ts->in_sigsuspend = 0;
+}