Initial Release

src/backtrace.cpp

@@ -0,0 +1,102 @@
+#include <csignal>
+#include <cstdio>
+#include <cstdlib>
+#include <cstring>
+#include <sys/prctl.h>
+#include <sys/wait.h>
+#include <unistd.h>
+
+static void msg(const char *msg, const char *arg) {
+  if (write(STDERR_FILENO, msg, strlen(msg)) != 0) {
+  }
+  if (write(STDERR_FILENO, arg, strlen(arg)) != 0) {
+  }
+  if (write(STDERR_FILENO, "\n", 1) != 0) {
+  }
+}
+
+static char binpath[512]; // NOLINT
+static char pid_s[11];    // NOLINT
+
+static void get_pid_binpath() {
+  pid_t pid = getpid();
+  sprintf(pid_s, "%d", pid); // NOLINT
+  size_t ret = readlink("/proc/self/exe", binpath, 511);
+  if (ret < 0)
+    return;
+  binpath[ret] = 0; // NOLINT
+}
+
+static const auto lldb{"/usr/bin/lldb"};
+static const auto default_debugger{"/usr/bin/gdbserver"};
+
+static auto get_debugger() -> const char * {
+  const char *debugger = secure_getenv("JITDEBUG");
+  if (not debugger)
+    return default_debugger;
+  if (strcmp(debugger, "on") == 0)
+    return default_debugger;
+  if (strcmp(debugger, "1") == 0)
+    return default_debugger;
+  if (strcmp(debugger, "true") == 0)
+    return default_debugger;
+  return debugger;
+}
+const char *const debugger = get_debugger();
+
+void start_debugger(const char * dbg, const char **argv) {
+#if defined(PR_SET_PTRACER)
+  prctl(PR_SET_PTRACER, PR_SET_PTRACER_ANY, 0, 0, 0); // NOLINT
+#endif
+  int child_pid = fork();
+  if (!child_pid) {
+    dup2(2, 1); // redirect output to stderr
+    msg("debugging with ", dbg);
+    execv(dbg, const_cast<char *const *>(argv)); // NOLINT
+    _exit(1);
+  } else {
+    int stat(0);
+    waitpid(child_pid, &stat, 0);
+  }
+}
+
+extern "C" void sighdl_debugger(int no, siginfo_t * /*sigi*/, void * /*uco*/) {
+  get_pid_binpath();
+  const char *argv[] = {// NOLINT
+                        debugger, "--attach", "[::1]:7777", pid_s, nullptr};
+  start_debugger(debugger, argv);
+  (void)raise(no);
+}
+
+extern "C" void sighdl_backtrace(int no, siginfo_t * /*sigi*/, void * /*uco*/) {
+  get_pid_binpath();
+  const char *argv[] = {// NOLINT
+                        lldb,     "--batch", "-p",    pid_s,
+                        "--one-line", "bt",      binpath, nullptr};
+  start_debugger(lldb, argv);
+  (void)raise(no);
+}
+
+static void install_crash_handler(void (*hdlr)(int, siginfo_t *, void *)) {
+  struct sigaction action {};
+  sigemptyset(&action.sa_mask);
+  action.sa_flags = SA_SIGINFO | SA_RESETHAND;
+#ifdef SA_FULLDUMP
+  action.sa_flags |= SA_FULLDUMP;
+#endif
+  action.sa_sigaction = hdlr;
+  sigaction(SIGBUS, &action, nullptr);
+  sigaction(SIGSEGV, &action, nullptr);
+  sigaction(SIGABRT, &action, nullptr);
+  sigaction(SIGTRAP, &action, nullptr);
+  sigaction(SIGFPE, &action, nullptr);
+}
+
+extern "C" void install_debugger() { install_crash_handler(sighdl_debugger); }
+extern "C" void install_backtrace() { install_crash_handler(sighdl_backtrace); }
+extern "C" void install_jitdebugger() {
+  if (secure_getenv("JITDEBUG"))
+    install_debugger();
+  else
+    install_backtrace();
+}