/*
 * Copyright (C) 2002 Jeff Dike (jdike@karaya.com)
 * Licensed under the GPL
 */

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <sched.h>
#include <limits.h>
#include <sys/signal.h>
#include <sys/wait.h>
#include <sys/socket.h>
#include "user.h"
#include "kern_util.h"
#include "os.h"
#include "um_malloc.h"
#include "kern_constants.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 errval;

        if (data->pre_exec != NULL)
                (*data->pre_exec)(data->pre_data);
        errval = execvp_noalloc(data->buf, argv[0], argv);
        printk("helper_child - execvp of '%s' failed - errno = %d\n", argv[0],
               -errval);
        write(data->fd, &errval, sizeof(errval));
        kill(os_getpid(), SIGKILL);
        return 0;
}

/* Returns either the pid of the child process we run or -E* on failure.
 * XXX The alloc_stack here breaks if this is called in the tracing thread, so
 * we need to receive a preallocated stack (a local buffer is ok). */
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, __cant_sleep());
        if (stack == 0)
                return -ENOMEM;

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

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

        sp = stack + UM_KERN_PAGE_SIZE - sizeof(void *);
        data.pre_exec = pre_exec;
        data.pre_data = pre_data;
        data.argv = argv;
        data.fd = fds[1];
        data.buf = __cant_sleep() ? kmalloc(PATH_MAX, UM_GFP_ATOMIC) :
                                        kmalloc(PATH_MAX, UM_GFP_KERNEL);
        pid = clone(helper_child, (void *) sp, CLONE_VM, &data);
        if (pid < 0) {
                ret = -errno;
                printk("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("run_helper : read on pipe failed, ret = %d\n",
                               -n);
                        ret = n;
                        kill(pid, SIGKILL);
                }
                CATCH_EINTR(waitpid(pid, NULL, __WCLONE));
        }

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;

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

        sp = stack + UM_KERN_PAGE_SIZE - sizeof(void *);
        pid = clone(proc, (void *) sp, flags, arg);
        if (pid < 0) {
                err = -errno;
                printk("run_helper_thread : clone failed, errno = %d\n",
                       errno);
                return err;
        }
        if (stack_out == NULL) {
                CATCH_EINTR(pid = waitpid(pid, &status, __WCLONE));
                if (pid < 0) {
                        err = -errno;
                        printk("run_helper_thread - wait failed, errno = %d\n",
                               errno);
                        pid = err;
                }
                if (!WIFEXITED(status) || (WEXITSTATUS(status) != 0))
                        printk("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 nohang, char *pname)
{
        int ret, status;
        int wflags = __WCLONE;

        if (nohang)
                wflags |= WNOHANG;

        if (!pname)
                pname = "helper_wait";

        CATCH_EINTR(ret = waitpid(pid, &status, wflags));
        if (ret < 0) {
                printk(UM_KERN_ERR "%s : waitpid process %d failed, "
                       "errno = %d\n", pname, pid, errno);
                return -errno;
        } else if (nohang && ret == 0) {
                printk(UM_KERN_ERR "%s : process %d has not exited\n",
                       pname, pid);
                return -ECHILD;
        } else if (!WIFEXITED(status) || WEXITSTATUS(status) != 0) {
                printk(UM_KERN_ERR "%s : process %d didn't exit with "
                       "status 0\n", pname, pid);
                return -ECHILD;
        } else
                return 0;
}