report that QEMU process was killed by a signal

Currently when rogue script kills QEMU process (using TERM/INT/HUP
signal) it looks indistinguishable from system shutdown. Lets report
that QEMU was killed and leave some clues about the killer identity.
Signed-off-by: NGleb Natapov <gleb@redhat.com>
Signed-off-by: NBlue Swirl <blauwirbel@gmail.com>

os-posix.c

@@ -62,9 +62,9 @@ void os_setup_early_signal_handling(void)
     sigaction(SIGPIPE, &act, NULL);
 }
 
-static void termsig_handler(int signal)
+static void termsig_handler(int signal, siginfo_t *info, void *c)
 {
-    qemu_system_shutdown_request();
+    qemu_system_killed(info->si_signo, info->si_pid);
 }
 
 static void sigchld_handler(int signal)
@@ -77,7 +77,8 @@ void os_setup_signal_handling(void)
     struct sigaction act;
 
     memset(&act, 0, sizeof(act));
-    act.sa_handler = termsig_handler;
+    act.sa_sigaction = termsig_handler;
+    act.sa_flags = SA_SIGINFO;
     sigaction(SIGINT,  &act, NULL);
     sigaction(SIGHUP,  &act, NULL);
     sigaction(SIGTERM, &act, NULL);

sysemu.h

@@ -66,6 +66,8 @@ void qemu_system_vmstop_request(int reason);
 int qemu_shutdown_requested(void);
 int qemu_reset_requested(void);
 int qemu_powerdown_requested(void);
+void qemu_system_killed(int signal, pid_t pid);
+void qemu_kill_report(void);
 extern qemu_irq qemu_system_powerdown;
 void qemu_system_reset(void);
 

vl.c

@@ -1215,7 +1215,8 @@ typedef struct QEMUResetEntry {
 static QTAILQ_HEAD(reset_handlers, QEMUResetEntry) reset_handlers =
     QTAILQ_HEAD_INITIALIZER(reset_handlers);
 static int reset_requested;
-static int shutdown_requested;
+static int shutdown_requested, shutdown_signal = -1;
+static pid_t shutdown_pid;
 static int powerdown_requested;
 static int debug_requested;
 static int vmstop_requested;
@@ -1227,6 +1228,15 @@ int qemu_shutdown_requested(void)
     return r;
 }
 
+void qemu_kill_report(void)
+{
+    if (shutdown_signal != -1) {
+        fprintf(stderr, "Got signal %d from pid %d\n",
+                         shutdown_signal, shutdown_pid);
+        shutdown_signal = -1;
+    }
+}
+
 int qemu_reset_requested(void)
 {
     int r = reset_requested;
@@ -1300,6 +1310,13 @@ void qemu_system_reset_request(void)
     qemu_notify_event();
 }
 
+void qemu_system_killed(int signal, pid_t pid)
+{
+    shutdown_signal = signal;
+    shutdown_pid = pid;
+    qemu_system_shutdown_request();
+}
+
 void qemu_system_shutdown_request(void)
 {
     shutdown_requested = 1;
@@ -1443,6 +1460,7 @@ static void main_loop(void)
             vm_stop(VMSTOP_DEBUG);
         }
         if (qemu_shutdown_requested()) {
+            qemu_kill_report();
             monitor_protocol_event(QEVENT_SHUTDOWN, NULL);
             if (no_shutdown) {
                 vm_stop(VMSTOP_SHUTDOWN);