// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright (C) 2002 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
 */

#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <errno.h>
#include <sched.h>
#include <pthread.h>
#include <linux/limits.h>
#include <sys/socket.h>
#include <sys/wait.h>
#include <kern_util.h>
#include <os.h>
#include <um_malloc.h>

struct helper_data {
        void (*pre_exec)(void*);
        void *pre_data;
        char **argv;
        int fd;
        char *buf;
};

static int helper_child(void *arg)
{
        struct helper_data *data = arg;
        char **argv = data->argv;
        int err, ret;

        if (data->pre_exec != NULL)
                (*data->pre_exec)(data->pre_data);
        err = execvp_noalloc(data->buf, argv[0], argv);

        /* If the exec succeeds, we don't get here */
        CATCH_EINTR(ret = write(data->fd, &err, sizeof(err)));

        return 0;
}

/* Returns either the pid of the child process we run or -E* on failure. */
int run_helper(void (*pre_exec)(void *), void *pre_data, char **argv)
{
        struct helper_data data;
        unsigned long stack, sp;
        int pid, fds[2], ret, n;

        stack = alloc_stack(0, __uml_cant_sleep());
        if (stack == 0)
                return -ENOMEM;

        ret = socketpair(AF_UNIX, SOCK_STREAM, 0, fds);
        if (ret < 0) {
                ret = -errno;
                printk(UM_KERN_ERR "run_helper : pipe failed, errno = %d\n",
                       errno);
                goto out_free;
        }

        ret = os_set_exec_close(fds[1]);
        if (ret < 0) {
                printk(UM_KERN_ERR "run_helper : setting FD_CLOEXEC failed, "
                       "ret = %d\n", -ret);
                goto out_close;
        }

        sp = stack + UM_KERN_PAGE_SIZE;
        data.pre_exec = pre_exec;
        data.pre_data = pre_data;
        data.argv = argv;
        data.fd = fds[1];
        data.buf = __uml_cant_sleep() ? uml_kmalloc(PATH_MAX, UM_GFP_ATOMIC) :
                                        uml_kmalloc(PATH_MAX, UM_GFP_KERNEL);
        pid = clone(helper_child, (void *) sp, CLONE_VM, &data);
        if (pid < 0) {
                ret = -errno;
                printk(UM_KERN_ERR "run_helper : clone failed, errno = %d\n",
                       errno);
                goto out_free2;
        }

        close(fds[1]);
        fds[1] = -1;

        /*
         * Read the errno value from the child, if the exec failed, or get 0 if
         * the exec succeeded because the pipe fd was set as close-on-exec.
         */
        n = read(fds[0], &ret, sizeof(ret));
        if (n == 0) {
                ret = pid;
        } else {
                if (n < 0) {
                        n = -errno;
                        printk(UM_KERN_ERR "run_helper : read on pipe failed, "
                               "ret = %d\n", -n);
                        ret = n;
                }
                CATCH_EINTR(waitpid(pid, NULL, __WALL));
        }

        if (ret < 0)
                printk(UM_KERN_ERR "run_helper : failed to exec %s on host: %s\n",
                       argv[0], strerror(-ret));

out_free2:
        kfree(data.buf);
out_close:
        if (fds[1] != -1)
                close(fds[1]);
        close(fds[0]);
out_free:
        free_stack(stack, 0);
        return ret;
}

int run_helper_thread(int (*proc)(void *), void *arg, unsigned int flags,
                      unsigned long *stack_out)
{
        unsigned long stack, sp;
        int pid, status, err;

        /* To share memory space, use os_run_helper_thread() instead. */
        if (flags & CLONE_VM)
                return -EINVAL;

        stack = alloc_stack(0, __uml_cant_sleep());
        if (stack == 0)
                return -ENOMEM;

        sp = stack + UM_KERN_PAGE_SIZE;
        pid = clone(proc, (void *) sp, flags, arg);
        if (pid < 0) {
                err = -errno;
                printk(UM_KERN_ERR "run_helper_thread : clone failed, "
                       "errno = %d\n", errno);
                return err;
        }
        if (stack_out == NULL) {
                CATCH_EINTR(pid = waitpid(pid, &status, __WALL));
                if (pid < 0) {
                        err = -errno;
                        printk(UM_KERN_ERR "run_helper_thread - wait failed, "
                               "errno = %d\n", errno);
                        pid = err;
                }
                if (!WIFEXITED(status) || (WEXITSTATUS(status) != 0))
                        printk(UM_KERN_ERR "run_helper_thread - thread "
                               "returned status 0x%x\n", status);
                free_stack(stack, 0);
        } else
                *stack_out = stack;
        return pid;
}

int helper_wait(int pid)
{
        int ret, status;
        int wflags = __WALL;

        CATCH_EINTR(ret = waitpid(pid, &status, wflags));
        if (ret < 0) {
                printk(UM_KERN_ERR "helper_wait : waitpid process %d failed, "
                       "errno = %d\n", pid, errno);
                return -errno;
        } else if (!WIFEXITED(status) || WEXITSTATUS(status) != 0) {
                printk(UM_KERN_ERR "helper_wait : process %d exited with "
                       "status 0x%x\n", pid, status);
                return -ECHILD;
        } else
                return 0;
}

struct os_helper_thread {
        pthread_t handle;
};

int os_run_helper_thread(struct os_helper_thread **td_out,
                         void *(*routine)(void *), void *arg)
{
        struct os_helper_thread *td;
        sigset_t sigset, oset;
        int err, flags;

        flags = __uml_cant_sleep() ? UM_GFP_ATOMIC : UM_GFP_KERNEL;
        td = uml_kmalloc(sizeof(*td), flags);
        if (!td)
                return -ENOMEM;

        sigfillset(&sigset);
        if (sigprocmask(SIG_SETMASK, &sigset, &oset) < 0) {
                err = -errno;
                kfree(td);
                return err;
        }

        err = pthread_create(&td->handle, NULL, routine, arg);

        if (sigprocmask(SIG_SETMASK, &oset, NULL) < 0)
                panic("Failed to restore the signal mask: %d", errno);

        if (err != 0)
                kfree(td);
        else
                *td_out = td;

        return -err;
}

void os_kill_helper_thread(struct os_helper_thread *td)
{
        pthread_cancel(td->handle);
        pthread_join(td->handle, NULL);
        kfree(td);
}

void os_fix_helper_thread_signals(void)
{
        sigset_t sigset;

        sigemptyset(&sigset);

        sigaddset(&sigset, SIGWINCH);
        sigaddset(&sigset, SIGPIPE);
        sigaddset(&sigset, SIGPROF);
        sigaddset(&sigset, SIGINT);
        sigaddset(&sigset, SIGTERM);
        sigaddset(&sigset, SIGCHLD);
        sigaddset(&sigset, SIGALRM);
        sigaddset(&sigset, SIGIO);
        sigaddset(&sigset, SIGUSR1);

        pthread_sigmask(SIG_SETMASK, &sigset, NULL);
}