sim: Add support for generating back traces on errors

Add functionality to generate a back trace if gem5 crashes (SIGABRT or
SIGSEGV). The current implementation uses glibc's stack traversal
support if available and stubs out the call to print_backtrace()
otherwise.

SConstruct

@@ -983,6 +983,21 @@ if not GetOption('without_tcmalloc'):
               "installing tcmalloc (libgoogle-perftools-dev package "\
               "on Ubuntu or RedHat)." + termcap.Normal
 
+
+# Detect back trace implementations. The last implementation in the
+# list will be used by default.
+backtrace_impls = [ "none" ]
+
+if conf.CheckLibWithHeader(None, 'execinfo.h', 'C',
+                           'backtrace_symbols_fd((void*)0, 0, 0);'):
+    backtrace_impls.append("glibc")
+
+if backtrace_impls[-1] == "none":
+    default_backtrace_impl = "none"
+    print termcap.Yellow + termcap.Bold + \
+        "No suitable back trace implementation found." + \
+        termcap.Normal
+
 if not have_posix_clock:
     print "Can't find library for POSIX clocks."
 
@@ -1131,6 +1146,8 @@ sticky_vars.AddVariables(
     BoolVariable('USE_KVM', 'Enable hardware virtualized (KVM) CPU models', have_kvm),
     EnumVariable('PROTOCOL', 'Coherence protocol for Ruby', 'None',
                   all_protocols),
+    EnumVariable('BACKTRACE_IMPL', 'Post-mortem dump implementation',
+                 backtrace_impls[-1], backtrace_impls)
     )
 
 # These variables get exported to #defines in config/*.hh (see src/SConscript).

src/base/atomicio.hh

@@ -41,4 +41,28 @@
 ssize_t atomic_read(int fd, void *s, size_t n);
 ssize_t atomic_write(int fd, const void *s, size_t n);
 
+/**
+ * Statically allocate a string and write it to a file descriptor.
+ *
+ * @warning The return value will from atomic_write will be ignored
+ * which means that errors will be ignored. This is normally fine as
+ * this macro is intended to be used in fatal signal handlers where
+ * error handling might not be feasible.
+ */
+#define STATIC_MSG(fd, m)                                       \
+    do {                                                        \
+        static const char msg[] = m;                            \
+        atomic_write(fd, msg, sizeof(msg) - 1);                 \
+    } while(0)
+
+/**
+ * Statically allocate a string and write it to STDERR.
+ *
+ * @warning The return value will from atomic_write will be ignored
+ * which means that errors will be ignored. This is normally fine as
+ * this macro is intended to be used in fatal signal handlers where
+ * error handling might not be feasible.
+ */
+#define STATIC_ERR(m) STATIC_MSG(STDERR_FILENO, m)
+
 #endif // __BASE_ATOMICIO_HH__

src/sim/SConscript

@@ -41,6 +41,7 @@ SimObject('SubSystem.py')
 
 Source('arguments.cc')
 Source('async.cc')
+Source('backtrace_%s.cc' % env['BACKTRACE_IMPL'])
 Source('core.cc')
 Source('tags.cc')
 Source('cxx_config.cc')

src/sim/backtrace.hh

@@ -0,0 +1,50 @@
+/*
+ * Copyright (c) 2015 ARM Limited
+ * All rights reserved
+ *
+ * The license below extends only to copyright in the software and shall
+ * not be construed as granting a license to any other intellectual
+ * property including but not limited to intellectual property relating
+ * to a hardware implementation of the functionality of the software
+ * licensed hereunder.  You may use the software subject to the license
+ * terms below provided that you ensure that this notice is replicated
+ * unmodified and in its entirety in all distributions of the software,
+ * modified or unmodified, in source code or in binary form.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met: redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer;
+ * redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the distribution;
+ * neither the name of the copyright holders nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ * Authors: Andreas Sandberg
+ */
+#ifndef __SIM_BACKTRACE_HH__
+#define __SIM_BACKTRACE_HH__
+
+/**
+ * Print a gem5 post-mortem report
+ *
+ * @note This is usually called from a signal handler. Implementations
+ * must support this use case.
+ */
+void print_backtrace();
+
+#endif // __SIM_BACKTRACE_HH__

src/sim/backtrace_glibc.cc

@@ -0,0 +1,66 @@
+/*
+ * Copyright (c) 2015 ARM Limited
+ * All rights reserved
+ *
+ * The license below extends only to copyright in the software and shall
+ * not be construed as granting a license to any other intellectual
+ * property including but not limited to intellectual property relating
+ * to a hardware implementation of the functionality of the software
+ * licensed hereunder.  You may use the software subject to the license
+ * terms below provided that you ensure that this notice is replicated
+ * unmodified and in its entirety in all distributions of the software,
+ * modified or unmodified, in source code or in binary form.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met: redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer;
+ * redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the distribution;
+ * neither the name of the copyright holders nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ * Authors: Andreas Sandberg
+ */
+
+#include "sim/backtrace.hh"
+
+#include <execinfo.h>
+#include <unistd.h>
+
+#include "base/atomicio.hh"
+
+#define SAFE_MSG(m)                                             \
+    do {                                                        \
+        static const char msg[] = m;                            \
+        atomic_write(STDERR_FILENO, msg, sizeof(msg) - 1);      \
+    } while(0)
+
+void
+print_backtrace()
+{
+    void *buffer[32];
+    int size;
+
+    size = backtrace(buffer, sizeof(buffer) / sizeof(*buffer));
+
+    STATIC_ERR("--- BEGIN LIBC BACKTRACE ---\n");
+    backtrace_symbols_fd(buffer, size, STDERR_FILENO);
+    if (size == sizeof(buffer))
+        STATIC_ERR("Warning: Backtrace may have been truncated.\n");
+    STATIC_ERR("--- END LIBC BACKTRACE ---\n");
+}

src/sim/backtrace_none.cc

@@ -0,0 +1,45 @@
+/*
+ * Copyright (c) 2015 ARM Limited
+ * All rights reserved
+ *
+ * The license below extends only to copyright in the software and shall
+ * not be construed as granting a license to any other intellectual
+ * property including but not limited to intellectual property relating
+ * to a hardware implementation of the functionality of the software
+ * licensed hereunder.  You may use the software subject to the license
+ * terms below provided that you ensure that this notice is replicated
+ * unmodified and in its entirety in all distributions of the software,
+ * modified or unmodified, in source code or in binary form.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met: redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer;
+ * redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the distribution;
+ * neither the name of the copyright holders nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ * Authors: Andreas Sandberg
+ */
+
+#include "sim/backtrace.hh"
+
+void
+print_backtrace()
+{
+}

src/sim/init_signals.cc

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2012 ARM Limited
+ * Copyright (c) 2012, 2015 ARM Limited
  * All rights reserved
  *
  * The license below extends only to copyright in the software and shall
@@ -41,18 +41,67 @@
  * Authors: Nathan Binkert
  */
 
+#include "sim/init_signals.hh"
+
+#include <sys/types.h>
+#include <unistd.h>
+
 #include <csignal>
 #include <iostream>
 #include <string>
 
+#include "base/atomicio.hh"
 #include "base/cprintf.hh"
 #include "sim/async.hh"
+#include "sim/backtrace.hh"
 #include "sim/core.hh"
 #include "sim/eventq.hh"
-#include "sim/init_signals.hh"
 
 using namespace std;
 
+// Use an separate stack for fatal signal handlers
+static uint8_t fatalSigStack[2 * SIGSTKSZ];
+
+static bool
+setupAltStack()
+{
+    stack_t stack;
+    stack.ss_sp = fatalSigStack;
+    stack.ss_size = sizeof(fatalSigStack);
+    stack.ss_flags = 0;
+
+    return sigaltstack(&stack, NULL) == 0;
+}
+
+static void
+installSignalHandler(int signal, void (*handler)(int sigtype),
+                     int flags = SA_RESTART)
+{
+    struct sigaction sa;
+
+    memset(&sa, 0, sizeof(sa));
+    sigemptyset(&sa.sa_mask);
+    sa.sa_handler = handler;
+    sa.sa_flags = flags;
+
+    if (sigaction(signal, &sa, NULL) == -1)
+        panic("Failed to setup handler for signal %i\n", signal);
+}
+
+static void
+raiseFatalSignal(int signo)
+{
+    // The signal handler should have been reset and unmasked (it was
+    // registered with SA_RESETHAND | SA_NODEFER), just raise the
+    // signal again to invoke the default handler.
+    pthread_kill(pthread_self(), signo);
+
+    // Something is really wrong if the process is alive at this
+    // point, manually try to exit it.
+    STATIC_ERR("Failed to execute default signal handler!\n");
+    _exit(127);
+}
+
 /// Stats signal handler.
 void
 dumpStatsHandler(int sigtype)
@@ -87,7 +136,25 @@ exitNowHandler(int sigtype)
 void
 abortHandler(int sigtype)
 {
-    ccprintf(cerr, "Program aborted at tick %llu\n", curTick());
+    const EventQueue *const eq(curEventQueue());
+    if (eq) {
+        ccprintf(cerr, "Program aborted at tick %llu\n", eq->getCurTick());
+    } else {
+        STATIC_ERR("Program aborted\n\n");
+    }
+
+    print_backtrace();
+    raiseFatalSignal(sigtype);
+}
+
+/// Segmentation fault signal handler.
+static void
+segvHandler(int sigtype)
+{
+    STATIC_ERR("gem5 has encountered a segmentation fault!\n\n");
+
+    print_backtrace();
+    raiseFatalSignal(SIGSEGV);
 }
 
 // Handle SIGIO
@@ -100,20 +167,6 @@ ioHandler(int sigtype)
     getEventQueue(0)->wakeup();
 }
 
-static void
-installSignalHandler(int signal, void (*handler)(int sigtype))
-{
-    struct sigaction sa;
-
-    memset(&sa, 0, sizeof(sa));
-    sigemptyset(&sa.sa_mask);
-    sa.sa_handler = handler;
-    sa.sa_flags = SA_RESTART;
-
-    if (sigaction(signal, &sa, NULL) == -1)
-        panic("Failed to setup handler for signal %i\n", signal);
-}
-
 /*
  * M5 can do several special things when various signals are sent.
  * None are mandatory.
@@ -137,8 +190,19 @@ initSignals()
     // Exit cleanly on Interrupt (Ctrl-C)
     installSignalHandler(SIGINT, exitNowHandler);
 
-    // Print out cycle number on abort
+    // Print the current cycle number and a backtrace on abort. Make
-    installSignalHandler(SIGABRT, abortHandler);
+    // sure the signal is unmasked and the handler reset when a signal
+    // is delivered to be able to invoke the default handler.
+    installSignalHandler(SIGABRT, abortHandler, SA_RESETHAND | SA_NODEFER);
+
+    // Setup a SIGSEGV handler with a private stack
+    if (setupAltStack()) {
+        installSignalHandler(SIGSEGV, segvHandler,
+                             SA_RESETHAND | SA_NODEFER | SA_ONSTACK);
+    } else {
+        warn("Failed to setup stack for SIGSEGV handler, "
+             "using default signal handler.\n");
+    }
 
     // Install a SIGIO handler to handle asynchronous file IO. See the
     // PollQueue class.