[Backtracing][Linux] Add Linux crash handler to the runtime.

include/swift/Runtime/Backtrace.h

@@ -17,10 +17,17 @@
 #ifndef SWIFT_RUNTIME_BACKTRACE_H
 #define SWIFT_RUNTIME_BACKTRACE_H
 
+#ifdef __linux__
+#include <sys/types.h>
+#include <sys/wait.h>
+
+#include <signal.h>
+#endif // defined(__linux__)
+
 #include "swift/Runtime/Config.h"
+#include "swift/Runtime/CrashInfo.h"
 
 #include "swift/shims/Visibility.h"
-#include "swift/shims/CrashInfo.h"
 
 #include <inttypes.h>
 
@@ -50,7 +57,11 @@ typedef int ErrorCode;
 
 SWIFT_RUNTIME_STDLIB_INTERNAL ErrorCode _swift_installCrashHandler();
 
+#ifdef __linux__
+SWIFT_RUNTIME_STDLIB_INTERNAL bool _swift_spawnBacktracer(const ArgChar * const *argv, int memserver_fd);
+#else
 SWIFT_RUNTIME_STDLIB_INTERNAL bool _swift_spawnBacktracer(const ArgChar * const *argv);
+#endif
 
 enum class UnwindAlgorithm {
  Auto = 0,
@@ -125,6 +136,39 @@ SWIFT_RUNTIME_STDLIB_INTERNAL BacktraceSettings _swift_backtraceSettings;
 
 SWIFT_RUNTIME_STDLIB_SPI SWIFT_CC(swift) bool _swift_isThunkFunction(const char *mangledName);
 
+/// Try to demangle a symbol.
+///
+/// Unlike other entry points that do this, we try both Swift and C++ here.
+///
+/// @param mangledName is the symbol name to be demangled.
+/// @param mangledNameLength is the length of this name.
+/// @param outputBuffer is a pointer to a buffer in which to place the result.
+/// @param outputBufferSize points to a variable that contains the size of the
+/// output buffer.
+/// @param status returns the status codes defined in the C++ ABI.
+///
+/// If outputBuffer is nullptr, the function will allocate memory for the
+/// result using malloc(). In this case, outputBufferSize may be nullptr;
+/// if it is *not* nullptr, it will be set to the size of buffer that was
+/// allocated. This is not necessarily the length of the string (it may be
+/// somewhat higher).
+///
+/// Otherwise, the result will be written into the output buffer, and the
+/// size of the result will be written into outputBufferSize. If the buffer
+/// is too small, the result will be truncated, but outputBufferSize will
+/// still be set to the number of bytes that would have been required to
+/// copy out the full result (including a trailing NUL).
+///
+/// The unusual behaviour here is a consequence of the way the C++ ABI's
+/// demangling function works.
+///
+/// @returns a pointer to the output if demangling was successful.
+SWIFT_RUNTIME_STDLIB_SPI
+char *_swift_backtrace_demangle(const char *mangledName,
+ size_t mangledNameLength,
+ char *outputBuffer,
+ size_t *outputBufferSize,
+ int *status);
 #ifdef __cplusplus
 } // namespace backtrace
 } // namespace runtime

include/swift/Runtime/CrashInfo.h

@@ -0,0 +1,98 @@
+//===--- CrashInfo.h - Swift Backtracing Crash Information ------*- C++ -*-===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2023 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See https://swift.org/LICENSE.txt for license information
+// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
+//
+//===----------------------------------------------------------------------===//
+//
+// Defines the CrashInfo type that holds information about why the program
+// crashed.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef SWIFT_CRASHINFO_H
+#define SWIFT_CRASHINFO_H
+
+#include <inttypes.h>
+
+#ifdef __cplusplus
+namespace swift {
+namespace runtime {
+namespace backtrace {
+extern "C" {
+#endif
+
+// Note: The "pointers" below are pointers in a different process's address
+// space, which might not even share our bitness. That is why they are
+// `uint64_t`s, rather than pointers or `uintptr_t`s.
+
+// The address of this structure in memory is passed to swift-backtrace.
+struct CrashInfo {
+ // The thread ID for the crashing thread.
+ uint64_t crashing_thread;
+
+ // The signal number corresponding to this crash.
+ uint64_t signal;
+
+ // The fault address.
+ uint64_t fault_address;
+
+#ifdef __APPLE__
+ // Points to the mcontext_t structure for the crashing thread; other
+ // threads' contexts can be recovered using Mach APIs later.
+ uint64_t mctx;
+#elif defined(__linux__)
+ // The head of the thread list; points at a "struct thread" (see below).
+ uint64_t thread_list;
+#endif
+};
+
+#ifdef __linux__
+
+// A memory server request packet.
+struct memserver_req {
+ // Address to read.
+ uint64_t addr;
+
+ // Number of bytes to read.
+ uint64_t len;
+};
+
+// A memory server response packet.
+struct memserver_resp {
+ // Address that was read from.
+ uint64_t addr;
+
+ // Number of bytes, *or* negative to indicate an error.
+ int64_t len;
+
+ // Followed by len bytes of data if len > 0
+};
+
+// Holds details of a running thread.
+struct thread {
+ // Points at the next thread.
+ uint64_t next;
+
+ // The thread ID for this thread.
+ int64_t tid;
+
+ // Points to the Linux ucontext_t structure.
+ uint64_t uctx;
+};
+
+#endif
+
+#ifdef __cplusplus
+} // extern "C"
+} // namespace backtrace
+} // namespace runtime
+} // namespace swift
+#endif
+
+#endif // SWIFT_CRASHINFO_H

include/swift/Runtime/Debug.h

@@ -124,6 +124,9 @@ swift_dynamicCastFailure(const void *sourceType, const char *sourceName,
 SWIFT_RUNTIME_EXPORT
 void swift_reportError(uint32_t flags, const char *message);
 
+SWIFT_RUNTIME_EXPORT
+void swift_reportWarning(uint32_t flags, const char *message);
+
 // Halt due to an overflow in swift_retain().
 SWIFT_RUNTIME_ATTRIBUTE_NORETURN SWIFT_RUNTIME_ATTRIBUTE_NOINLINE
 void swift_abortRetainOverflow();

stdlib/public/runtime/Backtrace.cpp

@@ -52,6 +52,12 @@
 #include <cstring>
 #include <cerrno>
 
+#ifdef _WIN32
+// We'll probably want dbghelp.h here
+#else
+#include <cxxabi.h>
+#endif
+
 #define DEBUG_BACKTRACING_SETTINGS 0
 
 #ifndef lengthof
@@ -773,6 +779,54 @@ _swift_backtraceSetupEnvironment()
  *penv = 0;
 }
 
+#ifdef __linux__
+struct spawn_info {
+ const char *path;
+ char * const *argv;
+ char * const *envp;
+ int memserver;
+};
+
+uint8_t spawn_stack[4096];
+
+int
+do_spawn(void *ptr) {
+ struct spawn_info *pinfo = (struct spawn_info *)ptr;
+
+ /* Ensure that the memory server is always on fd 4 */
+ if (pinfo->memserver != 4) {
+ dup2(pinfo->memserver, 4);
+ close(pinfo->memserver);
+ }
+
+ /* Clear the signal mask */
+ sigset_t mask;
+ sigfillset(&mask);
+ sigprocmask(SIG_UNBLOCK, &mask, NULL);
+
+ return execvpe(pinfo->path, pinfo->argv, pinfo->envp);
+}
+
+int
+safe_spawn(pid_t *ppid, const char *path, int memserver,
+ char * const argv[], char * const envp[])
+{
+ struct spawn_info info = { path, argv, envp, memserver };
+
+ /* The CLONE_VFORK is *required* because info is on the stack; we don't
+ want to return until *after* the subprocess has called execvpe(). */
+ int ret = clone(do_spawn, spawn_stack + sizeof(spawn_stack),
+ CLONE_VFORK|CLONE_VM, &info);
+ if (ret < 0)
+ return ret;
+
+ close(memserver);
+
+ *ppid = ret;
+ return 0;
+}
+#endif // defined(__linux__)
+
 #endif // SWIFT_BACKTRACE_ON_CRASH_SUPPORTED
 
 } // namespace
@@ -796,13 +850,93 @@ _swift_isThunkFunction(const char *mangledName) {
  return ctx.isThunkSymbol(mangledName);
 }
 
+// Try to demangle a symbol.
+SWIFT_RUNTIME_STDLIB_SPI char *
+_swift_backtrace_demangle(const char *mangledName,
+ size_t mangledNameLength,
+ char *outputBuffer,
+ size_t *outputBufferSize,
+ int *status) {
+ llvm::StringRef name = llvm::StringRef(mangledName, mangledNameLength);
+
+ // You must provide buffer size if you're providing your own output buffer
+ if (outputBuffer && !outputBufferSize) {
+ return nullptr;
+ }
+
+ if (Demangle::isSwiftSymbol(name)) {
+ // This is a Swift mangling
+ auto options = DemangleOptions::SimplifiedUIDemangleOptions();
+ auto result = Demangle::demangleSymbolAsString(name, options);
+ size_t bufferSize;
+
+ if (outputBufferSize) {
+ bufferSize = *outputBufferSize;
+ *outputBufferSize = result.length() + 1;
+ }
+
+ if (outputBuffer == nullptr) {
+ outputBuffer = (char *)::malloc(result.length() + 1);
+ bufferSize = result.length() + 1;
+ }
+
+ size_t toCopy = std::min(bufferSize - 1, result.length());
+ ::memcpy(outputBuffer, result.data(), toCopy);
+ outputBuffer[toCopy] = '\0';
+
+ *status = 0;
+ return outputBuffer;
+#ifndef _WIN32
+ } else if (name.startswith("_Z")) {
+ // Try C++
+ size_t resultLen;
+ char *result = abi::__cxa_demangle(mangledName, nullptr, &resultLen, status);
+
+ if (result) {
+ size_t bufferSize;
+
+ if (outputBufferSize) {
+ bufferSize = *outputBufferSize;
+ *outputBufferSize = resultLen;
+ }
+
+ if (outputBuffer == nullptr) {
+ return result;
+ }
+
+ size_t toCopy = std::min(bufferSize - 1, resultLen - 1);
+ ::memcpy(outputBuffer, result, toCopy);
+ outputBuffer[toCopy] = '\0';
+
+ free(result);
+
+ *status = 0;
+ return outputBuffer;
+ }
+#else
+ // On Windows, the mangling is different.
+ // ###TODO: Call __unDName()
+#endif
+ } else {
+ *status = -2;
+ }
+
+ return nullptr;
+}
+
 // N.B. THIS FUNCTION MUST BE SAFE TO USE FROM A CRASH HANDLER. On Linux
 // and macOS, that means it must be async-signal-safe. On Windows, there
 // isn't an equivalent notion but a similar restriction applies.
 SWIFT_RUNTIME_STDLIB_INTERNAL bool
+#ifdef __linux__
+_swift_spawnBacktracer(const ArgChar * const *argv, int memserver_fd)
+#else
 _swift_spawnBacktracer(const ArgChar * const *argv)
+#endif
 {
-#if TARGET_OS_OSX || TARGET_OS_MACCATALYST
+#if !SWIFT_BACKTRACE_ON_CRASH_SUPPORTED
+ return false;
+#elif TARGET_OS_OSX || TARGET_OS_MACCATALYST || defined(__linux__)
  pid_t child;
  const char *env[BACKTRACE_MAX_ENV_VARS + 1];
 
@@ -817,10 +951,16 @@ _swift_spawnBacktracer(const ArgChar * const *argv)
 
  // SUSv3 says argv and envp are "completely constant" and that the reason
  // posix_spawn() et al use char * const * is for compatibility.
+#ifdef __linux__
+ int ret = safe_spawn(&child, swiftBacktracePath, memserver_fd,
+ const_cast<char * const *>(argv),
+ const_cast<char * const *>(env));
+#else
  int ret = posix_spawn(&child, swiftBacktracePath,
  &backtraceFileActions, &backtraceSpawnAttrs,
  const_cast<char * const *>(argv),
  const_cast<char * const *>(env));
+#endif
  if (ret < 0)
  return false;
 
@@ -835,10 +975,7 @@ _swift_spawnBacktracer(const ArgChar * const *argv)
 
  return false;
 
- // ###TODO: Linux
  // ###TODO: Windows
-#else
- return false;
 #endif
 }
 

stdlib/public/runtime/CMakeLists.txt

@@ -81,7 +81,8 @@ set(swift_runtime_sources
 
 set(swift_runtime_backtracing_sources
  Backtrace.cpp
- CrashHandlerMacOS.cpp)
+ CrashHandlerMacOS.cpp
+ CrashHandlerLinux.cpp)
 
 # Acknowledge that the following sources are known.
 set(LLVM_OPTIONAL_SOURCES