erts: Improve crash dumps

This commit improves crash dumps in several ways:
  *  Suspends schedulers to get a current snapshot
  *  Dumps information about scheduler
  *  Dumps stack trace of current running process
     (including Garbing processes)

2 files changed, 56 insertions, 1 deletions

diff --git a/erts/emulator/sys/unix/erl_unix_sys.h b/erts/emulator/sys/unix/erl_unix_sys.h
index bc55fab8fb..1932e97742 100644
--- a/erts/emulator/sys/unix/erl_unix_sys.h
+++ b/erts/emulator/sys/unix/erl_unix_sys.h
@@ -45,7 +45,7 @@
 #include <fcntl.h>
 #include "erl_errno.h"
 #include <signal.h>
-
+#include <setjmp.h>
 
 #if HAVE_SYS_SOCKETIO_H
 #   include <sys/socketio.h>
@@ -349,4 +349,28 @@ extern int exit_async(void);
 
 #define ERTS_EXIT_AFTER_DUMP _exit
 
+#if !defined(__APPLE__) && !defined(__MACH__)
+/* Some OS X versions do not allow (ab)using signal handlers like this */
+#define ERTS_HAVE_TRY_CATCH 1
+
+/* We try to simulate a try catch in C with the help of signal handlers.
+ * Only use this as a very last resort, as it is not very portable and
+ * quite unstable. It is also not thread safe, so make sure that only
+ * one thread can call this at a time!
+ */
+extern void erts_sys_sigsegv_handler(int);
+extern jmp_buf erts_sys_sigsegv_jmp;
+#define ERTS_SYS_TRY_CATCH(EXPR,CATCH)                                  \
+    do {                                                                \
+        SIGFUNC prev_handler = sys_signal(SIGSEGV,                      \
+                                          erts_sys_sigsegv_handler);    \
+        if (!setjmp(erts_sys_sigsegv_jmp)) {                            \
+            EXPR;                                                       \
+        } else {                                                        \
+            CATCH;                                                      \
+        }                                                               \
+        sys_signal(SIGSEGV,prev_handler);                               \
+    } while(0)
+#endif
+
 #endif /* #ifndef _ERL_UNIX_SYS_H */
diff --git a/erts/emulator/sys/unix/sys.c b/erts/emulator/sys/unix/sys.c
index 74d67cbd57..57f9fbef53 100644
--- a/erts/emulator/sys/unix/sys.c
+++ b/erts/emulator/sys/unix/sys.c
@@ -223,6 +223,8 @@ static int sig_suspend_fds[2] = {-1, -1};
 static int async_fd[2];
 #endif
 
+jmp_buf erts_sys_sigsegv_jmp;
+
 #if CHLDWTHR || defined(ERTS_SMP)
 erts_mtx_t chld_stat_mtx;
 #endif
@@ -683,6 +685,35 @@ void sys_sigrelease(int sig)
     sigprocmask(SIG_UNBLOCK, &mask, (sigset_t *)NULL);
 }
 
+void erts_sys_sigsegv_handler(int signo) {
+    if (signo == SIGSEGV) {
+        longjmp(erts_sys_sigsegv_jmp, 1);
+    }
+}
+
+/*
+ * Function returns 1 if we can read from all values in between
+ * start and stop.
+ */
+int
+erts_sys_is_area_readable(char *start, char *stop) {
+    int fds[2];
+    if (!pipe(fds)) {
+        /* We let write try to figure out if the pointers are readable */
+        int res = write(fds[1], start, (char*)stop - (char*)start);
+        if (res == -1) {
+            close(fds[0]);
+            close(fds[1]);
+            return 0;
+        }
+        close(fds[0]);
+        close(fds[1]);
+        return 1;
+    }
+    return 0;
+
+}
+
 static ERTS_INLINE int
 prepare_crash_dump(int secs)
 {