linux: add CRASHPAD_SIMULATE_CRASH()

Bug: crashpad:30
Change-Id: I135864a0e31119de3a814ee5ab5729336f6284a3
Reviewed-on: https://chromium-review.googlesource.com/927116
Commit-Queue: Joshua Peraza <jperaza@chromium.org>
Reviewed-by: Mark Mentovai <mark@chromium.org>

client/BUILD.gn

@@ -44,7 +44,10 @@ static_library("client") {
   }
 
   if (crashpad_is_linux || crashpad_is_android) {
-    sources += [ "crashpad_client_linux.cc" ]
+    sources += [
+      "crashpad_client_linux.cc",
+      "simulate_crash_linux.h",
+    ]
   }
 
   if (crashpad_is_linux || crashpad_is_android || crashpad_is_fuchsia) {

client/client.gyp

@@ -50,6 +50,7 @@
         'simple_string_dictionary.h',
         'simple_address_range_bag.h',
         'simulate_crash.h',
+        'simulate_crash_linux.h',
         'simulate_crash_mac.cc',
         'simulate_crash_mac.h',
         'simulate_crash_win.h',
@@ -73,6 +74,7 @@
         ['OS=="android"', {
           'sources/': [
             ['include', '^crashpad_client_linux\\.cc$'],
+            ['include', '^simulate_crash_linux\\.h$'],
           ],
         }],
       ],

client/crashpad_client.h

@@ -24,6 +24,7 @@
 #include "base/files/file_path.h"
 #include "base/macros.h"
 #include "build/build_config.h"
+#include "util/misc/capture_context.h"
 
 #if defined(OS_MACOSX)
 #include "base/mac/scoped_mach_port.h"
@@ -168,6 +169,17 @@ class CrashpadClient {
       const std::map<std::string, std::string>& annotations,
       const std::vector<std::string>& arguments,
       int socket);
+
+  //! \brief Requests that the handler capture a dump even though there hasn't
+  //!     been a crash.
+  //!
+  //! TODO(jperaza): Floating point information in the context is zeroed out
+  //! until CaptureContext() supports collecting that information.
+  //!
+  //! \param[in] context A NativeCPUContext, generally captured by
+  //!     CaptureContext() or similar.
+  static void DumpWithoutCrash(NativeCPUContext* context);
+
 #endif  // OS_LINUX || OS_ANDROID || DOXYGEN
 
 #if defined(OS_MACOSX) || DOXYGEN

client/crashpad_client_linux.cc

@@ -27,6 +27,7 @@
 #include "util/file/file_io.h"
 #include "util/linux/exception_handler_client.h"
 #include "util/linux/exception_information.h"
+#include "util/linux/scoped_pr_set_ptracer.h"
 #include "util/misc/from_pointer_cast.h"
 #include "util/posix/double_fork_and_exec.h"
 #include "util/posix/signals.h"
@@ -82,7 +83,7 @@ void BuildHandlerArgvStrings(
   }
 }
 
-void ConvertArgvStrings(const std::vector<std::string> argv_strings,
+void ConvertArgvStrings(const std::vector<std::string>& argv_strings,
                         std::vector<const char*>* argv) {
   argv->clear();
   argv->reserve(argv_strings.size() + 1);
@@ -92,8 +93,22 @@ void ConvertArgvStrings(const std::vector<std::string> argv_strings,
   argv->push_back(nullptr);
 }
 
+class SignalHandler {
+ public:
+  virtual void HandleCrashFatal(int signo,
+                                siginfo_t* siginfo,
+                                void* context) = 0;
+  virtual void HandleCrashNonFatal(int signo,
+                                   siginfo_t* siginfo,
+                                   void* context) = 0;
+
+ protected:
+  SignalHandler() = default;
+  ~SignalHandler() = default;
+};
+
 // Launches a single use handler to snapshot this process.
-class LaunchAtCrashHandler {
+class LaunchAtCrashHandler : public SignalHandler {
  public:
   static LaunchAtCrashHandler* Get() {
     static LaunchAtCrashHandler* instance = new LaunchAtCrashHandler();
@@ -110,6 +125,37 @@ class LaunchAtCrashHandler {
     return Signals::InstallCrashHandlers(HandleCrash, 0, nullptr);
   }
 
+  void HandleCrashNonFatal(int signo,
+                           siginfo_t* siginfo,
+                           void* context) override {
+    exception_information_.siginfo_address =
+        FromPointerCast<decltype(exception_information_.siginfo_address)>(
+            siginfo);
+    exception_information_.context_address =
+        FromPointerCast<decltype(exception_information_.context_address)>(
+            context);
+    exception_information_.thread_id = syscall(SYS_gettid);
+
+    ScopedPrSetPtracer set_ptracer(getpid(), /* may_log= */ false);
+
+    pid_t pid = fork();
+    if (pid < 0) {
+      return;
+    }
+    if (pid == 0) {
+      execv(argv_[0], const_cast<char* const*>(argv_.data()));
+      _exit(EXIT_FAILURE);
+    }
+
+    int status;
+    waitpid(pid, &status, 0);
+  }
+
+  void HandleCrashFatal(int signo, siginfo_t* siginfo, void* context) override {
+    HandleCrashNonFatal(signo, siginfo, context);
+    Signals::RestoreHandlerAndReraiseSignalOnReturn(siginfo, nullptr);
+  }
+
  private:
   LaunchAtCrashHandler() = default;
 
@@ -117,27 +163,7 @@ class LaunchAtCrashHandler {
 
   static void HandleCrash(int signo, siginfo_t* siginfo, void* context) {
     auto state = Get();
-    auto exception_information = &state->exception_information_;
+    state->HandleCrashFatal(signo, siginfo, context);
-
-    exception_information->siginfo_address =
-        FromPointerCast<decltype(exception_information->siginfo_address)>(
-            siginfo);
-    exception_information->context_address =
-        FromPointerCast<decltype(exception_information->context_address)>(
-            context);
-    exception_information->thread_id = syscall(SYS_gettid);
-
-    pid_t pid = fork();
-    if (pid < 0) {
-      return;
-    }
-    if (pid == 0) {
-      execv(state->argv_[0], const_cast<char* const*>(state->argv_.data()));
-      return;
-    }
-
-    int status;
-    waitpid(pid, &status, 0);
   }
 
   std::vector<std::string> argv_strings_;
@@ -147,6 +173,11 @@ class LaunchAtCrashHandler {
   DISALLOW_COPY_AND_ASSIGN(LaunchAtCrashHandler);
 };
 
+// A pointer to the currently installed crash signal handler. This allows
+// the static method CrashpadClient::DumpWithoutCrashing to simulate a crash
+// using the currently configured crash handling strategy.
+static SignalHandler* g_crash_handler;
+
 }  // namespace
 
 CrashpadClient::CrashpadClient() {}
@@ -181,7 +212,12 @@ bool CrashpadClient::StartHandlerAtCrash(
       handler, database, metrics_dir, url, annotations, arguments, &argv);
 
   auto signal_handler = LaunchAtCrashHandler::Get();
-  return signal_handler->Initialize(&argv);
+  if (signal_handler->Initialize(&argv)) {
+    DCHECK(!g_crash_handler);
+    g_crash_handler = signal_handler;
+    return true;
+  }
+  return false;
 }
 
 bool CrashpadClient::StartHandlerForClient(
@@ -201,4 +237,34 @@ bool CrashpadClient::StartHandlerForClient(
   return DoubleForkAndExec(argv, socket, true, nullptr);
 }
 
+// static
+void CrashpadClient::DumpWithoutCrash(NativeCPUContext* context) {
+  if (!g_crash_handler) {
+    LOG(WARNING) << "No crash handler installed";
+    return;
+  }
+
+#if defined(ARCH_CPU_X86)
+  memset(&context->__fpregs_mem, 0, sizeof(context->__fpregs_mem));
+  context->__fpregs_mem.status = 0xffff0000;
+#elif defined(ARCH_CPU_X86_64)
+  memset(&context->__fpregs_mem, 0, sizeof(context->__fpregs_mem));
+#elif defined(ARCH_CPU_ARMEL)
+  memset(context->uc_regspace, 0, sizeof(context->uc_regspace));
+#elif defined(ARCH_CPU_ARM64)
+  memset(context->uc_mcontext.__reserved,
+         0,
+         sizeof(context->uc_mcontext.__reserved));
+#else
+#error Port.
+#endif
+
+  siginfo_t siginfo;
+  siginfo.si_signo = Signals::kSimulatedSigno;
+  siginfo.si_errno = 0;
+  siginfo.si_code = 0;
+  g_crash_handler->HandleCrashNonFatal(
+      siginfo.si_signo, &siginfo, reinterpret_cast<void*>(context));
+}
+
 }  // namespace crashpad

client/simulate_crash.h

@@ -21,6 +21,8 @@
 #include "client/simulate_crash_mac.h"
 #elif defined(OS_WIN)
 #include "client/simulate_crash_win.h"
+#elif defined(OS_LINUX) || defined(OS_ANDROID)
+#include "client/simulate_crash_linux.h"
 #endif
 
 #endif  // CRASHPAD_CLIENT_SIMULATE_CRASH_H_

client/simulate_crash_linux.h

@@ -0,0 +1,31 @@
+// Copyright 2018 The Crashpad Authors. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef CRASHPAD_CLIENT_SIMULATE_CRASH_LINUX_H_
+#define CRASHPAD_CLIENT_SIMULATE_CRASH_LINUX_H_
+
+#include "client/crashpad_client.h"
+#include "util/misc/capture_context.h"
+
+//! \file
+
+//! \brief Captures the CPU context and simulates an exception without crashing.
+#define CRASHPAD_SIMULATE_CRASH()                                            \
+  do {                                                                       \
+    crashpad::NativeCPUContext simulate_crash_cpu_context;                   \
+    crashpad::CaptureContext(&simulate_crash_cpu_context);                   \
+    crashpad::CrashpadClient::DumpWithoutCrash(&simulate_crash_cpu_context); \
+  } while (false)
+
+#endif  // CRASHPAD_CLIENT_SIMULATE_CRASH_LINUX_H_

util/misc/capture_context.h

@@ -37,6 +37,10 @@ using NativeCPUContext = CONTEXT;
 using NativeCPUContext = ucontext_t;
 #endif  // OS_MACOSX
 
+// No NativeCPUContext defined for Fuchsia yet.
+// https://crashpad.chromium.org/bug/196.
+#if !defined(OS_FUCHSIA)
+
 //! \brief Saves the CPU context.
 //!
 //! The CPU context will be captured as accurately and completely as possible,
@@ -76,6 +80,8 @@ using NativeCPUContext = ucontext_t;
 //!     \endcode
 void CaptureContext(NativeCPUContext* cpu_context);
 
+#endif  // !OS_FUCHSIA
+
 }  // namespace crashpad
 
 #endif  // CRASHPAD_UTIL_MISC_CAPTURE_CONTEXT_H_

util/posix/signals.h

@@ -24,6 +24,9 @@ namespace crashpad {
 //! \brief Utilities for handling POSIX signals.
 class Signals {
  public:
+  //! \brief A signal number used by Crashpad to simulate signals.
+  static constexpr int kSimulatedSigno = -1;
+
   //! \brief The type used for `struct sigaction::sa_sigaction`.
   using Handler = void (*)(int, siginfo_t*, void*);