From ffd0153e6dffcc29cf79d0191860047dba0438bb Mon Sep 17 00:00:00 2001
From: Lukas Larsson <lukas@erlang-solutions.com>
Date: Thu, 4 Dec 2014 11:09:06 +0100
Subject: 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)
---
 erts/emulator/sys/unix/erl_unix_sys.h | 26 +++++++++++++++++++++++++-
 erts/emulator/sys/unix/sys.c          | 31 +++++++++++++++++++++++++++++++
 erts/emulator/sys/win32/erl_win_sys.h | 12 ++++++++++++
 erts/emulator/sys/win32/sys.c         | 21 +++++++++++++++++++++
 4 files changed, 89 insertions(+), 1 deletion(-)

(limited to 'erts/emulator/sys')

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)
 {
diff --git a/erts/emulator/sys/win32/erl_win_sys.h b/erts/emulator/sys/win32/erl_win_sys.h
index 838f0c61eb..fde32c8684 100644
--- a/erts/emulator/sys/win32/erl_win_sys.h
+++ b/erts/emulator/sys/win32/erl_win_sys.h
@@ -236,4 +236,16 @@ typedef long ssize_t;
 int init_async(int);
 int exit_async(void);
 #endif
+
+#define ERTS_HAVE_TRY_CATCH 1
+
+#define ERTS_SYS_TRY_CATCH(EXPR,CATCH)                                  \
+    __try {                                                             \
+    EXPR;                                                               \
+    }                                                                   \
+    __except(GetExceptionCode() == EXCEPTION_ACCESS_VIOLATION ? EXCEPTION_EXECUTE_HANDLER : EXCEPTION_CONTINUE_SEARCH) \
+    {                                                                   \
+        CATCH;                                                          \
+    }
+
 #endif
diff --git a/erts/emulator/sys/win32/sys.c b/erts/emulator/sys/win32/sys.c
index 164ef95629..5d51659b4e 100644
--- a/erts/emulator/sys/win32/sys.c
+++ b/erts/emulator/sys/win32/sys.c
@@ -247,6 +247,27 @@ void erl_sys_args(int* argc, char** argv)
 #endif
 }
 
+/*
+ * 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) {
+    volatile char tmp;
+    __try
+    {
+        while(start < stop) {
+            tmp = *start;
+            start++;
+        }
+    }
+    __except(EXCEPTION_EXECUTE_HANDLER)
+    {
+        return 0;
+    }
+    return 1;
+}
+
 int erts_sys_prepare_crash_dump(int secs)
 {
     Port *heart_port;
-- 
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