// Copyright 2012 Google Inc. // All rights reserved. // // 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 Google Inc. 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. #include "stacktrace.h" #include <sys/param.h> #include <sys/wait.h> #include <assert.h> #include <fcntl.h> #include <stdarg.h> #include <stdio.h> #include <stdlib.h> #include <string.h> #include <unistd.h> #include "defs.h" #include "fs.h" #include "env.h" #include "error.h" #include "run.h" #include "text.h" /// Built-in path to GDB. /// /// This should be an absolute path for deterministic behavior. We also accept /// a basename to cope with any issues that might arise from an invalid /// configure check or a manual override of the GDB constant, in which case the /// exec call below will (try to) locate the binary in the path. /// /// Note that the program pointed to by this variable is not required to exist. /// If it does not, we fail gracefully. /// /// Test cases can override the value of this built-in constant to unit-test the /// behavior of the functions below. const char* kyua_stacktrace_gdb = GDB; #undef GDB // We really want to use the variable, not the macro. /// Time to give to the external GDB process to produce a stack trace. /// /// Test cases can override the value of this built-in constant to unit-test the /// behavior of the functions below. unsigned long kyua_stacktrace_gdb_timeout = 300; /// Maximum length of the core file name, if known. /// /// Some operating systems impose a maximum length on the basename of the core /// file. If MAXCOMLEN is defined, then we need to truncate the program name to /// this length before searching for the core file. If we cannot figure out /// what this limit is, we set it to zero, which we consider later as /// "unlimited". #if !defined(MAXCOMLEN) # define MAXCOMLEN 0 #endif static void run_gdb(const char* program, const char* core_name, FILE* output) KYUA_DEFS_NORETURN; /// Constructs the parameters to run GDB with. /// /// \param original_run_params Parameters used to run the binary that generated /// the core dump. /// /// \return The run parameters with which to run GDB. static kyua_run_params_t gdb_run_params(const kyua_run_params_t* original_run_params) { kyua_run_params_t run_params = *original_run_params; run_params.timeout_seconds = kyua_stacktrace_gdb_timeout; return run_params; } /// Body of a subprocess to execute GDB. /// /// This should be called from the child created by a kyua_run_fork() call, /// which means that we do not have to take care of isolating the process. /// /// \pre The caller must have flushed stdout before spawning this process, to /// prevent double-flushing and/or corruption of data. /// /// \param program Path to the program being debugged. Can be relative to /// the given work directory. /// \param core_name Path to the dumped core. Use find_core() to deduce /// a valid candidate. Can be relative to the given work directory. /// \param output Stream to which to send the output of GDB. static void run_gdb(const char* program, const char* core_name, FILE* output) { // TODO(jmmv): Should be done by kyua_run_fork(), but doing so would change // the semantics of the ATF interface. Need to evaluate this carefully. const kyua_error_t error = kyua_env_unset("TERM"); if (kyua_error_is_set(error)) { kyua_error_warn(error, "Failed to unset TERM; GDB may misbehave"); free(error); } (void)close(STDIN_FILENO); const int input_fd = open("/dev/null", O_RDONLY); assert(input_fd == STDIN_FILENO); const int output_fd = fileno(output); assert(output_fd != -1); // We expect a file-backed stream. if (output_fd != STDOUT_FILENO) { fflush(stdout); (void)dup2(output_fd, STDOUT_FILENO); } if (output_fd != STDERR_FILENO) { fflush(stderr); (void)dup2(output_fd, STDERR_FILENO); } if (output_fd != STDOUT_FILENO && output_fd != STDERR_FILENO) fclose(output); const char* const gdb_args[] = { "gdb", "-batch", "-q", "-ex", "bt", program, core_name, NULL }; kyua_run_exec(kyua_stacktrace_gdb, gdb_args); } /// Truncates a string. /// /// \param source The string to truncate. /// \param [out] buffer Output buffer into which to store the truncated text. /// \param buffer_length Size of the buffer. /// /// \return A pointer to the buffer. static const char* slice(const char* source, char* buffer, const size_t buffer_length) { const size_t source_length = strlen(source); if (source_length < buffer_length) { strcpy(buffer, source); } else { memcpy(buffer, source, buffer_length - 1); buffer[buffer_length - 1] = '\0'; } return buffer; } static char* try_core(const char* format, ...) KYUA_DEFS_FORMAT_PRINTF(1, 2); /// Generates a path and checks if it exists. /// /// \param format Formatting string for the path to generate. /// \param ... Arguments to the formatting string. /// /// \return A dynamically-allocated string containing the generated path if /// there were no errors and the file pointed to by such path exists; NULL /// otherwise. The returned string must be relesed with free() by the caller. static char* try_core(const char* format, ...) { char* path; va_list ap; va_start(ap, format); kyua_error_t error = kyua_text_vprintf(&path, format, ap); va_end(ap); if (kyua_error_is_set(error)) { // Something went really wrong (and should not have happened). Ignore // this core file candidate. kyua_error_free(error); return NULL; } if (access(path, F_OK) == -1) { free(path); return NULL; } else { return path; } } /// Simple version of basename() that operates on constant strings. /// /// This is not 100% compatible with basename() because it may return an /// unexpected string if the path ends with a slash. For our purposes, this /// does not matter, so we can use this simplified trick. /// /// \param path Path from which to compute the basename. /// /// \return A pointer within the input path pointing at the last component. static const char* const_basename(const char* path) { const char* last_slash = strrchr(path, '/'); return last_slash == NULL ? path : last_slash + 1; } /// Looks for a core file for the given program. /// /// \param name The basename of the binary that generated the core. /// \param directory The directory from which the program was run. We expect to /// find the core file in this directory. /// \param dead_pid PID of the process that generated the core. This is needed /// in some platforms. /// /// \return The path to the core file if found; otherwise none. char* kyua_stacktrace_find_core(const char* name, const char* directory, const pid_t dead_pid) { char* candidate = NULL; // TODO(jmmv): Other than checking all these defaults, in NetBSD we should // also inspect the value of the kern.defcorename sysctl(2) MIB and use that // as the first candidate. // // In Linux, the way to determine the name is by looking at // /proc/sys/kernel/core_{pattern,uses_pid} as described by core(5). // Unfortunately, there does not seem to be a standard API to parse these // files, which makes checking for core files quite difficult if the // defaults have been modified. // Default NetBSD naming scheme. if (candidate == NULL && MAXCOMLEN > 0) { char truncated[MAXCOMLEN + 1]; candidate = try_core("%s/%s.core", directory, slice(name, truncated, sizeof(truncated))); } // Common naming scheme without the MAXCOMLEN truncation. if (candidate == NULL) candidate = try_core("%s/%s.core", directory, name); // Common naming scheme found in Linux systems. if (candidate == NULL) candidate = try_core("%s/core.%d", directory, (int)dead_pid); // Default Mac OS X naming scheme. if (candidate == NULL) candidate = try_core("/cores/core.%d", (int)dead_pid); // Common naming scheme found in Linux systems. Attempted last due to the // genericity of the core file name. if (candidate == NULL) candidate = try_core("%s/core", directory); if (candidate != NULL) { char* abs_candidate; kyua_error_t error = kyua_fs_make_absolute(candidate, &abs_candidate); if (kyua_error_is_set(error)) { kyua_error_free(error); return candidate; // Return possibly-relative path as a best guess. } else { free(candidate); return abs_candidate; } } else { return candidate; } } /// Gathers a stacktrace of a crashed program. /// /// \param program The name of the binary that crashed and dumped a core file. /// Can be either absolute or relative. /// \param dead_pid The PID of the process that dumped core. /// \param original_run_params Parameters with which the original binary was /// executed. These are reused to run GDB, but adjusted with GDB-specific /// settings. Of special interest, the work directory is used to search for /// the core file. /// \param output Stream into which to dump the stack trace and any additional /// information. /// /// \post If anything goes wrong, the diagnostic messages are written to the /// output. This function returns no errors. void kyua_stacktrace_dump(const char* program, const pid_t dead_pid, const kyua_run_params_t* original_run_params, FILE* output) { fprintf(output, "Process with PID %d dumped core; attempting to gather " "stack trace\n", dead_pid); const kyua_run_params_t run_params = gdb_run_params(original_run_params); kyua_error_t error = kyua_error_ok(); char* core_file = kyua_stacktrace_find_core(const_basename(program), run_params.work_directory, dead_pid); if (core_file == NULL) { fprintf(output, "Cannot find any core file\n"); goto out; } // We must flush the output stream right before invoking fork, so that the // subprocess does not have any unflushed data. Failure to do so results in // the messages above being written twice to the output. fflush(output); pid_t pid; error = kyua_run_fork(&run_params, &pid); if (!kyua_error_is_set(error) && pid == 0) { run_gdb(program, core_file, output); } assert(pid != -1 && pid != 0); if (kyua_error_is_set(error)) goto out_core_file; int status; bool timed_out; error = kyua_run_wait(pid, &status, &timed_out); if (kyua_error_is_set(error)) goto out_core_file; if (timed_out) { fprintf(output, "GDB failed; timed out\n"); } else { if (WIFEXITED(status)) { if (WEXITSTATUS(status) == EXIT_SUCCESS) fprintf(output, "GDB exited successfully\n"); else fprintf(output, "GDB failed with code %d; see output above for " "details\n", WEXITSTATUS(status)); } else { assert(WIFSIGNALED(status)); fprintf(output, "GDB received signal %d; see output above for " "details\n", WTERMSIG(status)); } } out_core_file: free(core_file); out: if (kyua_error_is_set(error)) { kyua_error_fprintf(output, error, "Failed to gather stacktrace"); free(error); } }