root/run-command.c

DEFINITIONS

1. child_process_init
2. child_process_clear
3. cleanup_children
4. cleanup_children_on_signal
5. cleanup_children_on_exit
6. mark_child_for_cleanup
7. clear_child_for_cleanup
8. close_pair
9. dup_devnull
10. locate_in_PATH
11. exists_in_PATH
12. sane_execvp
13. prepare_shell_cmd
14. execv_shell_cmd
15. notify_parent
16. set_cloexec
17. wait_or_whine
18. start_command
19. finish_command
20. finish_command_in_signal
21. run_command
22. run_command_v_opt
23. run_command_v_opt_cd_env
24. run_thread
25. die_async
26. async_die_is_recursing
27. git_atexit_dispatch
28. git_atexit_clear
29. git_atexit
30. start_async
31. finish_async
32. find_hook
33. run_hook_ve
34. run_hook_le
35. capture_command

#include "cache.h"
#include "run-command.h"
#include "exec_cmd.h"
#include "sigchain.h"
#include "argv-array.h"

void child_process_init(struct child_process *child)
{
        memset(child, 0, sizeof(*child));
        argv_array_init(&child->args);
        argv_array_init(&child->env_array);
}

void child_process_clear(struct child_process *child)
{
        argv_array_clear(&child->args);
        argv_array_clear(&child->env_array);
}

struct child_to_clean {
        pid_t pid;
        struct child_to_clean *next;
};
static struct child_to_clean *children_to_clean;
static int installed_child_cleanup_handler;

static void cleanup_children(int sig, int in_signal)
{
        while (children_to_clean) {
                struct child_to_clean *p = children_to_clean;
                children_to_clean = p->next;
                kill(p->pid, sig);
                if (!in_signal)
                        free(p);
        }
}

static void cleanup_children_on_signal(int sig)
{
        cleanup_children(sig, 1);
        sigchain_pop(sig);
        raise(sig);
}

static void cleanup_children_on_exit(void)
{
        cleanup_children(SIGTERM, 0);
}

static void mark_child_for_cleanup(pid_t pid)
{
        struct child_to_clean *p = xmalloc(sizeof(*p));
        p->pid = pid;
        p->next = children_to_clean;
        children_to_clean = p;

        if (!installed_child_cleanup_handler) {
                atexit(cleanup_children_on_exit);
                sigchain_push_common(cleanup_children_on_signal);
                installed_child_cleanup_handler = 1;
        }
}

static void clear_child_for_cleanup(pid_t pid)
{
        struct child_to_clean **pp;

        for (pp = &children_to_clean; *pp; pp = &(*pp)->next) {
                struct child_to_clean *clean_me = *pp;

                if (clean_me->pid == pid) {
                        *pp = clean_me->next;
                        free(clean_me);
                        return;
                }
        }
}

static inline void close_pair(int fd[2])
{
        close(fd[0]);
        close(fd[1]);
}

#ifndef GIT_WINDOWS_NATIVE
static inline void dup_devnull(int to)
{
        int fd = open("/dev/null", O_RDWR);
        if (fd < 0)
                die_errno(_("open /dev/null failed"));
        if (dup2(fd, to) < 0)
                die_errno(_("dup2(%d,%d) failed"), fd, to);
        close(fd);
}
#endif

static char *locate_in_PATH(const char *file)
{
        const char *p = getenv("PATH");
        struct strbuf buf = STRBUF_INIT;

        if (!p || !*p)
                return NULL;

        while (1) {
                const char *end = strchrnul(p, ':');

                strbuf_reset(&buf);

                /* POSIX specifies an empty entry as the current directory. */
                if (end != p) {
                        strbuf_add(&buf, p, end - p);
                        strbuf_addch(&buf, '/');
                }
                strbuf_addstr(&buf, file);

                if (!access(buf.buf, F_OK))
                        return strbuf_detach(&buf, NULL);

                if (!*end)
                        break;
                p = end + 1;
        }

        strbuf_release(&buf);
        return NULL;
}

static int exists_in_PATH(const char *file)
{
        char *r = locate_in_PATH(file);
        free(r);
        return r != NULL;
}

int sane_execvp(const char *file, char * const argv[])
{
        if (!execvp(file, argv))
                return 0; /* cannot happen ;-) */

        /*
         * When a command can't be found because one of the directories
         * listed in $PATH is unsearchable, execvp reports EACCES, but
         * careful usability testing (read: analysis of occasional bug
         * reports) reveals that "No such file or directory" is more
         * intuitive.
         *
         * We avoid commands with "/", because execvp will not do $PATH
         * lookups in that case.
         *
         * The reassignment of EACCES to errno looks like a no-op below,
         * but we need to protect against exists_in_PATH overwriting errno.
         */
        if (errno == EACCES && !strchr(file, '/'))
                errno = exists_in_PATH(file) ? EACCES : ENOENT;
        else if (errno == ENOTDIR && !strchr(file, '/'))
                errno = ENOENT;
        return -1;
}

static const char **prepare_shell_cmd(const char **argv)
{
        int argc, nargc = 0;
        const char **nargv;

        for (argc = 0; argv[argc]; argc++)
                ; /* just counting */
        /* +1 for NULL, +3 for "sh -c" plus extra $0 */
        nargv = xmalloc(sizeof(*nargv) * (argc + 1 + 3));

        if (argc < 1)
                die("BUG: shell command is empty");

        if (strcspn(argv[0], "|&;<>()$`\\\"' \t\n*?[#~=%") != strlen(argv[0])) {
#ifndef GIT_WINDOWS_NATIVE
                nargv[nargc++] = SHELL_PATH;
#else
                nargv[nargc++] = "sh";
#endif
                nargv[nargc++] = "-c";

                if (argc < 2)
                        nargv[nargc++] = argv[0];
                else {
                        struct strbuf arg0 = STRBUF_INIT;
                        strbuf_addf(&arg0, "%s \"$@\"", argv[0]);
                        nargv[nargc++] = strbuf_detach(&arg0, NULL);
                }
        }

        for (argc = 0; argv[argc]; argc++)
                nargv[nargc++] = argv[argc];
        nargv[nargc] = NULL;

        return nargv;
}

#ifndef GIT_WINDOWS_NATIVE
static int execv_shell_cmd(const char **argv)
{
        const char **nargv = prepare_shell_cmd(argv);
        trace_argv_printf(nargv, "trace: exec:");
        sane_execvp(nargv[0], (char **)nargv);
        free(nargv);
        return -1;
}
#endif

#ifndef GIT_WINDOWS_NATIVE
static int child_notifier = -1;

static void notify_parent(void)
{
        /*
         * execvp failed.  If possible, we'd like to let start_command
         * know, so failures like ENOENT can be handled right away; but
         * otherwise, finish_command will still report the error.
         */
        xwrite(child_notifier, "", 1);
}
#endif

static inline void set_cloexec(int fd)
{
        int flags = fcntl(fd, F_GETFD);
        if (flags >= 0)
                fcntl(fd, F_SETFD, flags | FD_CLOEXEC);
}

static int wait_or_whine(pid_t pid, const char *argv0, int in_signal)
{
        int status, code = -1;
        pid_t waiting;
        int failed_errno = 0;

        while ((waiting = waitpid(pid, &status, 0)) < 0 && errno == EINTR)
                ;       /* nothing */
        if (in_signal)
                return 0;

        if (waiting < 0) {
                failed_errno = errno;
                error("waitpid for %s failed: %s", argv0, strerror(errno));
        } else if (waiting != pid) {
                error("waitpid is confused (%s)", argv0);
        } else if (WIFSIGNALED(status)) {
                code = WTERMSIG(status);
                if (code != SIGINT && code != SIGQUIT)
                        error("%s died of signal %d", argv0, code);
                /*
                 * This return value is chosen so that code & 0xff
                 * mimics the exit code that a POSIX shell would report for
                 * a program that died from this signal.
                 */
                code += 128;
        } else if (WIFEXITED(status)) {
                code = WEXITSTATUS(status);
                /*
                 * Convert special exit code when execvp failed.
                 */
                if (code == 127) {
                        code = -1;
                        failed_errno = ENOENT;
                }
        } else {
                error("waitpid is confused (%s)", argv0);
        }

        clear_child_for_cleanup(pid);

        errno = failed_errno;
        return code;
}

int start_command(struct child_process *cmd)
{
        int need_in, need_out, need_err;
        int fdin[2], fdout[2], fderr[2];
        int failed_errno;
        char *str;

        if (!cmd->argv)
                cmd->argv = cmd->args.argv;
        if (!cmd->env)
                cmd->env = cmd->env_array.argv;

        /*
         * In case of errors we must keep the promise to close FDs
         * that have been passed in via ->in and ->out.
         */

        need_in = !cmd->no_stdin && cmd->in < 0;
        if (need_in) {
                if (pipe(fdin) < 0) {
                        failed_errno = errno;
                        if (cmd->out > 0)
                                close(cmd->out);
                        str = "standard input";
                        goto fail_pipe;
                }
                cmd->in = fdin[1];
        }

        need_out = !cmd->no_stdout
                && !cmd->stdout_to_stderr
                && cmd->out < 0;
        if (need_out) {
                if (pipe(fdout) < 0) {
                        failed_errno = errno;
                        if (need_in)
                                close_pair(fdin);
                        else if (cmd->in)
                                close(cmd->in);
                        str = "standard output";
                        goto fail_pipe;
                }
                cmd->out = fdout[0];
        }

        need_err = !cmd->no_stderr && cmd->err < 0;
        if (need_err) {
                if (pipe(fderr) < 0) {
                        failed_errno = errno;
                        if (need_in)
                                close_pair(fdin);
                        else if (cmd->in)
                                close(cmd->in);
                        if (need_out)
                                close_pair(fdout);
                        else if (cmd->out)
                                close(cmd->out);
                        str = "standard error";
fail_pipe:
                        error("cannot create %s pipe for %s: %s",
                                str, cmd->argv[0], strerror(failed_errno));
                        child_process_clear(cmd);
                        errno = failed_errno;
                        return -1;
                }
                cmd->err = fderr[0];
        }

        trace_argv_printf(cmd->argv, "trace: run_command:");
        fflush(NULL);

#ifndef GIT_WINDOWS_NATIVE
{
        int notify_pipe[2];
        if (pipe(notify_pipe))
                notify_pipe[0] = notify_pipe[1] = -1;

        cmd->pid = fork();
        failed_errno = errno;
        if (!cmd->pid) {
                /*
                 * Redirect the channel to write syscall error messages to
                 * before redirecting the process's stderr so that all die()
                 * in subsequent call paths use the parent's stderr.
                 */
                if (cmd->no_stderr || need_err) {
                        int child_err = dup(2);
                        set_cloexec(child_err);
                        set_error_handle(fdopen(child_err, "w"));
                }

                close(notify_pipe[0]);
                set_cloexec(notify_pipe[1]);
                child_notifier = notify_pipe[1];
                atexit(notify_parent);

                if (cmd->no_stdin)
                        dup_devnull(0);
                else if (need_in) {
                        dup2(fdin[0], 0);
                        close_pair(fdin);
                } else if (cmd->in) {
                        dup2(cmd->in, 0);
                        close(cmd->in);
                }

                if (cmd->no_stderr)
                        dup_devnull(2);
                else if (need_err) {
                        dup2(fderr[1], 2);
                        close_pair(fderr);
                } else if (cmd->err > 1) {
                        dup2(cmd->err, 2);
                        close(cmd->err);
                }

                if (cmd->no_stdout)
                        dup_devnull(1);
                else if (cmd->stdout_to_stderr)
                        dup2(2, 1);
                else if (need_out) {
                        dup2(fdout[1], 1);
                        close_pair(fdout);
                } else if (cmd->out > 1) {
                        dup2(cmd->out, 1);
                        close(cmd->out);
                }

                if (cmd->dir && chdir(cmd->dir))
                        die_errno("exec '%s': cd to '%s' failed", cmd->argv[0],
                            cmd->dir);
                if (cmd->env) {
                        for (; *cmd->env; cmd->env++) {
                                if (strchr(*cmd->env, '='))
                                        putenv((char *)*cmd->env);
                                else
                                        unsetenv(*cmd->env);
                        }
                }
                if (cmd->git_cmd)
                        execv_git_cmd(cmd->argv);
                else if (cmd->use_shell)
                        execv_shell_cmd(cmd->argv);
                else
                        sane_execvp(cmd->argv[0], (char *const*) cmd->argv);
                if (errno == ENOENT) {
                        if (!cmd->silent_exec_failure)
                                error("cannot run %s: %s", cmd->argv[0],
                                        strerror(ENOENT));
                        exit(127);
                } else {
                        die_errno("cannot exec '%s'", cmd->argv[0]);
                }
        }
        if (cmd->pid < 0)
                error("cannot fork() for %s: %s", cmd->argv[0],
                        strerror(errno));
        else if (cmd->clean_on_exit)
                mark_child_for_cleanup(cmd->pid);

        /*
         * Wait for child's execvp. If the execvp succeeds (or if fork()
         * failed), EOF is seen immediately by the parent. Otherwise, the
         * child process sends a single byte.
         * Note that use of this infrastructure is completely advisory,
         * therefore, we keep error checks minimal.
         */
        close(notify_pipe[1]);
        if (read(notify_pipe[0], &notify_pipe[1], 1) == 1) {
                /*
                 * At this point we know that fork() succeeded, but execvp()
                 * failed. Errors have been reported to our stderr.
                 */
                wait_or_whine(cmd->pid, cmd->argv[0], 0);
                failed_errno = errno;
                cmd->pid = -1;
        }
        close(notify_pipe[0]);
}
#else
{
        int fhin = 0, fhout = 1, fherr = 2;
        const char **sargv = cmd->argv;

        if (cmd->no_stdin)
                fhin = open("/dev/null", O_RDWR);
        else if (need_in)
                fhin = dup(fdin[0]);
        else if (cmd->in)
                fhin = dup(cmd->in);

        if (cmd->no_stderr)
                fherr = open("/dev/null", O_RDWR);
        else if (need_err)
                fherr = dup(fderr[1]);
        else if (cmd->err > 2)
                fherr = dup(cmd->err);

        if (cmd->no_stdout)
                fhout = open("/dev/null", O_RDWR);
        else if (cmd->stdout_to_stderr)
                fhout = dup(fherr);
        else if (need_out)
                fhout = dup(fdout[1]);
        else if (cmd->out > 1)
                fhout = dup(cmd->out);

        if (cmd->git_cmd)
                cmd->argv = prepare_git_cmd(cmd->argv);
        else if (cmd->use_shell)
                cmd->argv = prepare_shell_cmd(cmd->argv);

        cmd->pid = mingw_spawnvpe(cmd->argv[0], cmd->argv, (char**) cmd->env,
                        cmd->dir, fhin, fhout, fherr);
        failed_errno = errno;
        if (cmd->pid < 0 && (!cmd->silent_exec_failure || errno != ENOENT))
                error("cannot spawn %s: %s", cmd->argv[0], strerror(errno));
        if (cmd->clean_on_exit && cmd->pid >= 0)
                mark_child_for_cleanup(cmd->pid);

        if (cmd->git_cmd)
                free(cmd->argv);

        cmd->argv = sargv;
        if (fhin != 0)
                close(fhin);
        if (fhout != 1)
                close(fhout);
        if (fherr != 2)
                close(fherr);
}
#endif

        if (cmd->pid < 0) {
                if (need_in)
                        close_pair(fdin);
                else if (cmd->in)
                        close(cmd->in);
                if (need_out)
                        close_pair(fdout);
                else if (cmd->out)
                        close(cmd->out);
                if (need_err)
                        close_pair(fderr);
                else if (cmd->err)
                        close(cmd->err);
                child_process_clear(cmd);
                errno = failed_errno;
                return -1;
        }

        if (need_in)
                close(fdin[0]);
        else if (cmd->in)
                close(cmd->in);

        if (need_out)
                close(fdout[1]);
        else if (cmd->out)
                close(cmd->out);

        if (need_err)
                close(fderr[1]);
        else if (cmd->err)
                close(cmd->err);

        return 0;
}

int finish_command(struct child_process *cmd)
{
        int ret = wait_or_whine(cmd->pid, cmd->argv[0], 0);
        child_process_clear(cmd);
        return ret;
}

int finish_command_in_signal(struct child_process *cmd)
{
        return wait_or_whine(cmd->pid, cmd->argv[0], 1);
}


int run_command(struct child_process *cmd)
{
        int code;

        if (cmd->out < 0 || cmd->err < 0)
                die("BUG: run_command with a pipe can cause deadlock");

        code = start_command(cmd);
        if (code)
                return code;
        return finish_command(cmd);
}

int run_command_v_opt(const char **argv, int opt)
{
        return run_command_v_opt_cd_env(argv, opt, NULL, NULL);
}

int run_command_v_opt_cd_env(const char **argv, int opt, const char *dir, const char *const *env)
{
        struct child_process cmd = CHILD_PROCESS_INIT;
        cmd.argv = argv;
        cmd.no_stdin = opt & RUN_COMMAND_NO_STDIN ? 1 : 0;
        cmd.git_cmd = opt & RUN_GIT_CMD ? 1 : 0;
        cmd.stdout_to_stderr = opt & RUN_COMMAND_STDOUT_TO_STDERR ? 1 : 0;
        cmd.silent_exec_failure = opt & RUN_SILENT_EXEC_FAILURE ? 1 : 0;
        cmd.use_shell = opt & RUN_USING_SHELL ? 1 : 0;
        cmd.clean_on_exit = opt & RUN_CLEAN_ON_EXIT ? 1 : 0;
        cmd.dir = dir;
        cmd.env = env;
        return run_command(&cmd);
}

#ifndef NO_PTHREADS
static pthread_t main_thread;
static int main_thread_set;
static pthread_key_t async_key;
static pthread_key_t async_die_counter;

static void *run_thread(void *data)
{
        struct async *async = data;
        intptr_t ret;

        pthread_setspecific(async_key, async);
        ret = async->proc(async->proc_in, async->proc_out, async->data);
        return (void *)ret;
}

static NORETURN void die_async(const char *err, va_list params)
{
        vreportf("fatal: ", err, params);

        if (!pthread_equal(main_thread, pthread_self())) {
                struct async *async = pthread_getspecific(async_key);
                if (async->proc_in >= 0)
                        close(async->proc_in);
                if (async->proc_out >= 0)
                        close(async->proc_out);
                pthread_exit((void *)128);
        }

        exit(128);
}

static int async_die_is_recursing(void)
{
        void *ret = pthread_getspecific(async_die_counter);
        pthread_setspecific(async_die_counter, (void *)1);
        return ret != NULL;
}

#else

static struct {
        void (**handlers)(void);
        size_t nr;
        size_t alloc;
} git_atexit_hdlrs;

static int git_atexit_installed;

static void git_atexit_dispatch(void)
{
        size_t i;

        for (i=git_atexit_hdlrs.nr ; i ; i--)
                git_atexit_hdlrs.handlers[i-1]();
}

static void git_atexit_clear(void)
{
        free(git_atexit_hdlrs.handlers);
        memset(&git_atexit_hdlrs, 0, sizeof(git_atexit_hdlrs));
        git_atexit_installed = 0;
}

#undef atexit
int git_atexit(void (*handler)(void))
{
        ALLOC_GROW(git_atexit_hdlrs.handlers, git_atexit_hdlrs.nr + 1, git_atexit_hdlrs.alloc);
        git_atexit_hdlrs.handlers[git_atexit_hdlrs.nr++] = handler;
        if (!git_atexit_installed) {
                if (atexit(&git_atexit_dispatch))
                        return -1;
                git_atexit_installed = 1;
        }
        return 0;
}
#define atexit git_atexit

#endif

int start_async(struct async *async)
{
        int need_in, need_out;
        int fdin[2], fdout[2];
        int proc_in, proc_out;

        need_in = async->in < 0;
        if (need_in) {
                if (pipe(fdin) < 0) {
                        if (async->out > 0)
                                close(async->out);
                        return error("cannot create pipe: %s", strerror(errno));
                }
                async->in = fdin[1];
        }

        need_out = async->out < 0;
        if (need_out) {
                if (pipe(fdout) < 0) {
                        if (need_in)
                                close_pair(fdin);
                        else if (async->in)
                                close(async->in);
                        return error("cannot create pipe: %s", strerror(errno));
                }
                async->out = fdout[0];
        }

        if (need_in)
                proc_in = fdin[0];
        else if (async->in)
                proc_in = async->in;
        else
                proc_in = -1;

        if (need_out)
                proc_out = fdout[1];
        else if (async->out)
                proc_out = async->out;
        else
                proc_out = -1;

#ifdef NO_PTHREADS
        /* Flush stdio before fork() to avoid cloning buffers */
        fflush(NULL);

        async->pid = fork();
        if (async->pid < 0) {
                error("fork (async) failed: %s", strerror(errno));
                goto error;
        }
        if (!async->pid) {
                if (need_in)
                        close(fdin[1]);
                if (need_out)
                        close(fdout[0]);
                git_atexit_clear();
                exit(!!async->proc(proc_in, proc_out, async->data));
        }

        mark_child_for_cleanup(async->pid);

        if (need_in)
                close(fdin[0]);
        else if (async->in)
                close(async->in);

        if (need_out)
                close(fdout[1]);
        else if (async->out)
                close(async->out);
#else
        if (!main_thread_set) {
                /*
                 * We assume that the first time that start_async is called
                 * it is from the main thread.
                 */
                main_thread_set = 1;
                main_thread = pthread_self();
                pthread_key_create(&async_key, NULL);
                pthread_key_create(&async_die_counter, NULL);
                set_die_routine(die_async);
                set_die_is_recursing_routine(async_die_is_recursing);
        }

        if (proc_in >= 0)
                set_cloexec(proc_in);
        if (proc_out >= 0)
                set_cloexec(proc_out);
        async->proc_in = proc_in;
        async->proc_out = proc_out;
        {
                int err = pthread_create(&async->tid, NULL, run_thread, async);
                if (err) {
                        error("cannot create thread: %s", strerror(err));
                        goto error;
                }
        }
#endif
        return 0;

error:
        if (need_in)
                close_pair(fdin);
        else if (async->in)
                close(async->in);

        if (need_out)
                close_pair(fdout);
        else if (async->out)
                close(async->out);
        return -1;
}

int finish_async(struct async *async)
{
#ifdef NO_PTHREADS
        return wait_or_whine(async->pid, "child process", 0);
#else
        void *ret = (void *)(intptr_t)(-1);

        if (pthread_join(async->tid, &ret))
                error("pthread_join failed");
        return (int)(intptr_t)ret;
#endif
}

const char *find_hook(const char *name)
{
        static struct strbuf path = STRBUF_INIT;

        strbuf_reset(&path);
        strbuf_git_path(&path, "hooks/%s", name);
        if (access(path.buf, X_OK) < 0)
                return NULL;
        return path.buf;
}

int run_hook_ve(const char *const *env, const char *name, va_list args)
{
        struct child_process hook = CHILD_PROCESS_INIT;
        const char *p;

        p = find_hook(name);
        if (!p)
                return 0;

        argv_array_push(&hook.args, p);
        while ((p = va_arg(args, const char *)))
                argv_array_push(&hook.args, p);
        hook.env = env;
        hook.no_stdin = 1;
        hook.stdout_to_stderr = 1;

        return run_command(&hook);
}

int run_hook_le(const char *const *env, const char *name, ...)
{
        va_list args;
        int ret;

        va_start(args, name);
        ret = run_hook_ve(env, name, args);
        va_end(args);

        return ret;
}

int capture_command(struct child_process *cmd, struct strbuf *buf, size_t hint)
{
        cmd->out = -1;
        if (start_command(cmd) < 0)
                return -1;

        if (strbuf_read(buf, cmd->out, hint) < 0) {
                close(cmd->out);
                finish_command(cmd); /* throw away exit code */
                return -1;
        }

        close(cmd->out);
        return finish_command(cmd);
}