// SPDX-License-Identifier: GPL-2.0
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <ctype.h>
#include <fcntl.h>
#include <string.h>
#include <linux/compiler.h>
#include <linux/string.h>
#include <errno.h>
#include <sys/wait.h>
#include "subcmd-util.h"
#include "run-command.h"
#include "exec-cmd.h"

#define STRERR_BUFSIZE 128

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

static inline void dup_devnull(int to)
{
        int fd = open("/dev/null", O_RDWR);
        dup2(fd, to);
        close(fd);
}

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

        /*
         * 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) {
                        if (cmd->out > 0)
                                close(cmd->out);
                        return -ERR_RUN_COMMAND_PIPE;
                }
                cmd->in = fdin[1];
        }

        need_out = !cmd->no_stdout
                && !cmd->stdout_to_stderr
                && cmd->out < 0;
        if (need_out) {
                if (pipe(fdout) < 0) {
                        if (need_in)
                                close_pair(fdin);
                        else if (cmd->in)
                                close(cmd->in);
                        return -ERR_RUN_COMMAND_PIPE;
                }
                cmd->out = fdout[0];
        }

        need_err = !cmd->no_stderr && cmd->err < 0;
        if (need_err) {
                if (pipe(fderr) < 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);
                        return -ERR_RUN_COMMAND_PIPE;
                }
                cmd->err = fderr[0];
        }

        fflush(NULL);
        cmd->pid = fork();
        if (!cmd->pid) {
                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);
                }

                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("exec %s: cd to %s failed (%s)", cmd->argv[0],
                            cmd->dir, str_error_r(errno, sbuf, sizeof(sbuf)));
                if (cmd->env) {
                        for (; *cmd->env; cmd->env++) {
                                if (strchr(*cmd->env, '='))
                                        putenv((char*)*cmd->env);
                                else
                                        unsetenv(*cmd->env);
                        }
                }
                if (cmd->preexec_cb)
                        cmd->preexec_cb();
                if (cmd->no_exec_cmd)
                        exit(cmd->no_exec_cmd(cmd));
                if (cmd->exec_cmd) {
                        execv_cmd(cmd->argv);
                } else {
                        execvp(cmd->argv[0], (char *const*) cmd->argv);
                }
                exit(127);
        }

        if (cmd->pid < 0) {
                int err = 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);
                if (need_err)
                        close_pair(fderr);
                return err == ENOENT ?
                        -ERR_RUN_COMMAND_EXEC :
                        -ERR_RUN_COMMAND_FORK;
        }

        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]);

        return 0;
}

static int wait_or_whine(struct child_process *cmd, bool block)
{
        bool finished = cmd->finished;
        int result = cmd->finish_result;

        while (!finished) {
                int status, code;
                pid_t waiting = waitpid(cmd->pid, &status, block ? 0 : WNOHANG);

                if (!block && waiting == 0)
                        break;

                if (waiting < 0 && errno == EINTR)
                        continue;

                finished = true;
                if (waiting < 0) {
                        char sbuf[STRERR_BUFSIZE];

                        fprintf(stderr, " Error: waitpid failed (%s)",
                                str_error_r(errno, sbuf, sizeof(sbuf)));
                        result = -ERR_RUN_COMMAND_WAITPID;
                } else if (waiting != cmd->pid) {
                        result = -ERR_RUN_COMMAND_WAITPID_WRONG_PID;
                } else if (WIFSIGNALED(status)) {
                        result = -ERR_RUN_COMMAND_WAITPID_SIGNAL;
                } else if (!WIFEXITED(status)) {
                        result = -ERR_RUN_COMMAND_WAITPID_NOEXIT;
                } else {
                        code = WEXITSTATUS(status);
                        switch (code) {
                        case 127:
                                result = -ERR_RUN_COMMAND_EXEC;
                                break;
                        case 0:
                                result = 0;
                                break;
                        default:
                                result = -code;
                                break;
                        }
                }
        }
        if (finished) {
                cmd->finished = 1;
                cmd->finish_result = result;
        }
        return result;
}

/*
 * Conservative estimate of number of characaters needed to hold an a decoded
 * integer, assume each 3 bits needs a character byte and plus a possible sign
 * character.
 */
#ifndef is_signed_type
#define is_signed_type(type) (((type)(-1)) < (type)1)
#endif
#define MAX_STRLEN_TYPE(type) (sizeof(type) * 8 / 3 + (is_signed_type(type) ? 1 : 0))

int check_if_command_finished(struct child_process *cmd)
{
#ifdef __linux__
        char filename[6 + MAX_STRLEN_TYPE(typeof(cmd->pid)) + 7 + 1];
        char status_line[256];
        FILE *status_file;

        /*
         * Check by reading /proc/<pid>/status as calling waitpid causes
         * stdout/stderr to be closed and data lost.
         */
        sprintf(filename, "/proc/%u/status", cmd->pid);
        status_file = fopen(filename, "r");
        if (status_file == NULL) {
                /* Open failed assume finish_command was called. */
                return true;
        }
        while (fgets(status_line, sizeof(status_line), status_file) != NULL) {
                char *p;

                if (strncmp(status_line, "State:", 6))
                        continue;

                fclose(status_file);
                p = status_line + 6;
                while (isspace(*p))
                        p++;
                return *p == 'Z' ? 1 : 0;
        }
        /* Read failed assume finish_command was called. */
        fclose(status_file);
        return 1;
#else
        wait_or_whine(cmd, /*block=*/false);
        return cmd->finished;
#endif
}

int finish_command(struct child_process *cmd)
{
        return wait_or_whine(cmd, /*block=*/true);
}

int run_command(struct child_process *cmd)
{
        int code = start_command(cmd);
        if (code)
                return code;
        return finish_command(cmd);
}

static void prepare_run_command_v_opt(struct child_process *cmd,
                                      const char **argv,
                                      int opt)
{
        memset(cmd, 0, sizeof(*cmd));
        cmd->argv = argv;
        cmd->no_stdin = opt & RUN_COMMAND_NO_STDIN ? 1 : 0;
        cmd->exec_cmd = opt & RUN_EXEC_CMD ? 1 : 0;
        cmd->stdout_to_stderr = opt & RUN_COMMAND_STDOUT_TO_STDERR ? 1 : 0;
}

int run_command_v_opt(const char **argv, int opt)
{
        struct child_process cmd;
        prepare_run_command_v_opt(&cmd, argv, opt);
        return run_command(&cmd);
}