[PATCH 13/21] system: enable crash dumps on SIGSEGV, SIGILL, SIGFPE and SIGABRT

["Daniel P. Berrangé" <berrange@redhat.com>]

Expand the current SIGBUS crash dumps onto further signals that
represent program crashes from bad code or guest OS behaviour.
This change covers Windows platforms too, by using the dummy
siginfo struct definition from osdeup.h.

Note that the signal handler gets unregistered before trying the
crash dump, so in the unlikely event that crash dump itself crashes,
QEMU will exit, rather than getting into a loop.

In a debugger we'll still see the full stack history of the original
flaw, just with one extra frame present for the signal handler.

Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
---
 system/signal.c | 33 ++++++++++++++++++++++++++++-----
 1 file changed, 28 insertions(+), 5 deletions(-)

diff --git a/system/signal.c b/system/signal.c
index 615704900bc..4568ded4cdd 100644
--- a/system/signal.c
+++ b/system/signal.c
@@ -56,11 +56,11 @@ static void sig_handler(int n, siginfo_t *siginfo, void *ctx)
 
     memset(&action, 0, sizeof(action));
     action.sa_handler = SIG_DFL;
-    assert(sigaction(SIGBUS, &action, NULL) == 0);
+    assert(sigaction(siginfo->si_signo, &action, NULL) == 0);
     qtldr_crash_dump_signal(siginfo);
-    raise(SIGBUS);
+    raise(siginfo->si_signo);
     sigemptyset(&set);
-    sigaddset(&set, SIGBUS);
+    sigaddset(&set, siginfo->si_signo);
     pthread_sigmask(SIG_UNBLOCK, &set, NULL);
 }
 
@@ -108,10 +108,13 @@ void qemu_init_crash_signals(void)
      */
     memset(&action, 0, sizeof(action));
     action.sa_flags = SA_SIGINFO | SA_ONSTACK;
+    action.sa_sigaction = sig_handler;
+    sigaction(SIGSEGV, &action, NULL);
+    sigaction(SIGABRT, &action, NULL);
+    sigaction(SIGILL, &action, NULL);
+    sigaction(SIGFPE, &action, NULL);
 #ifdef CONFIG_LINUX
     action.sa_sigaction = sigbus_handler;
-#else
-    action.sa_sigaction = sig_handler;
 #endif
     sigaction(SIGBUS, &action, NULL);
 
@@ -120,7 +123,27 @@ void qemu_init_crash_signals(void)
 #endif
 }
 #else /* !CONFIG_SIGACTION */
+
+static void sig_handler(int signo)
+{
+    siginfo_t si = {
+        .si_signo = signo,
+        .si_code = 0,
+        .si_addr = 0x0,
+    };
+    assert(signal(signo, SIG_DFL) == 0);
+    qtldr_crash_dump_signal(&si);
+    raise(signo);
+}
+
 void qemu_init_crash_signals(void)
 {
+#ifndef WIN32
+    signal(SIGBUS, sig_handler);
+#endif
+    signal(SIGSEGV, sig_handler);
+    signal(SIGABRT, sig_handler);
+    signal(SIGILL, sig_handler);
+    signal(SIGFPE, sig_handler);
 }
 #endif /* !CONFIG_SIGACTION */
-- 
2.56.0