/*
 * Copyright (C) 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
 * Licensed under the GPL
 */

#include <stdio.h>
#include <stddef.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <fcntl.h>
#include <string.h>
#include <sys/stat.h>
#include <sys/mman.h>
#include <sys/param.h>
#include "init.h"
#include "kern_constants.h"
#include "os.h"
#include "user.h"

/* Modified by which_tmpdir, which is called during early boot */
static char *default_tmpdir = "/tmp";

/*
 *  Modified when creating the physical memory file and when checking
 * the tmp filesystem for usability, both happening during early boot.
 */
static char *tempdir = NULL;

static void __init find_tempdir(void)
{
        const char *dirs[] = { "TMP", "TEMP", "TMPDIR", NULL };
        int i;
        char *dir = NULL;

        if (tempdir != NULL)
                /* We've already been called */
                return;
        for (i = 0; dirs[i]; i++) {
                dir = getenv(dirs[i]);
                if ((dir != NULL) && (*dir != '\0'))
                        break;
        }
        if ((dir == NULL) || (*dir == '\0'))
                dir = default_tmpdir;

        tempdir = malloc(strlen(dir) + 2);
        if (tempdir == NULL) {
                fprintf(stderr, "Failed to malloc tempdir, "
                        "errno = %d\n", errno);
                return;
        }
        strcpy(tempdir, dir);
        strcat(tempdir, "/");
}

/*
 * This will return 1, with the first character in buf being the
 * character following the next instance of c in the file.  This will
 * read the file as needed.  If there's an error, -errno is returned;
 * if the end of the file is reached, 0 is returned.
 */
static int next(int fd, char *buf, size_t size, char c)
{
        ssize_t n;
        size_t len;
        char *ptr;

        while ((ptr = strchr(buf, c)) == NULL) {
                n = read(fd, buf, size - 1);
                if (n == 0)
                        return 0;
                else if (n < 0)
                        return -errno;

                buf[n] = '\0';
        }

        ptr++;
        len = strlen(ptr);
        memmove(buf, ptr, len + 1);

        /*
         * Refill the buffer so that if there's a partial string that we care
         * about, it will be completed, and we can recognize it.
         */
        n = read(fd, &buf[len], size - len - 1);
        if (n < 0)
                return -errno;

        buf[len + n] = '\0';
        return 1;
}

/* which_tmpdir is called only during early boot */
static int checked_tmpdir = 0;

/*
 * Look for a tmpfs mounted at /dev/shm.  I couldn't find a cleaner
 * way to do this than to parse /proc/mounts.  statfs will return the
 * same filesystem magic number and fs id for both /dev and /dev/shm
 * when they are both tmpfs, so you can't tell if they are different
 * filesystems.  Also, there seems to be no other way of finding the
 * mount point of a filesystem from within it.
 *
 * If a /dev/shm tmpfs entry is found, then we switch to using it.
 * Otherwise, we stay with the default /tmp.
 */
static void which_tmpdir(void)
{
        int fd, found;
        char buf[128] = { '\0' };

        if (checked_tmpdir)
                return;

        checked_tmpdir = 1;

        printf("Checking for tmpfs mount on /dev/shm...");

        fd = open("/proc/mounts", O_RDONLY);
        if (fd < 0) {
                printf("failed to open /proc/mounts, errno = %d\n", errno);
                return;
        }

        while (1) {
                found = next(fd, buf, ARRAY_SIZE(buf), ' ');
                if (found != 1)
                        break;

                if (!strncmp(buf, "/dev/shm", strlen("/dev/shm")))
                        goto found;

                found = next(fd, buf, ARRAY_SIZE(buf), '\n');
                if (found != 1)
                        break;
        }

err:
        if (found == 0)
                printf("nothing mounted on /dev/shm\n");
        else if (found < 0)
                printf("read returned errno %d\n", -found);

out:
        close(fd);

        return;

found:
        found = next(fd, buf, ARRAY_SIZE(buf), ' ');
        if (found != 1)
                goto err;

        if (strncmp(buf, "tmpfs", strlen("tmpfs"))) {
                printf("not tmpfs\n");
                goto out;
        }

        printf("OK\n");
        default_tmpdir = "/dev/shm";
        goto out;
}

static int __init make_tempfile(const char *template, char **out_tempname,
                                int do_unlink)
{
        char *tempname;
        int fd;

        which_tmpdir();
        tempname = malloc(MAXPATHLEN);
        if (tempname == NULL)
                return -1;

        find_tempdir();
        if ((tempdir == NULL) || (strlen(tempdir) >= MAXPATHLEN))
                return -1;

        if (template[0] != '/')
                strcpy(tempname, tempdir);
        else
                tempname[0] = '\0';
        strncat(tempname, template, MAXPATHLEN-1-strlen(tempname));
        fd = mkstemp(tempname);
        if (fd < 0) {
                fprintf(stderr, "open - cannot create %s: %s\n", tempname,
                        strerror(errno));
                goto out;
        }
        if (do_unlink && (unlink(tempname) < 0)) {
                perror("unlink");
                goto out;
        }
        if (out_tempname) {
                *out_tempname = tempname;
        } else
                free(tempname);
        return fd;
out:
        free(tempname);
        return -1;
}

#define TEMPNAME_TEMPLATE "vm_file-XXXXXX"

static int __init create_tmp_file(unsigned long long len)
{
        int fd, err;
        char zero;

        fd = make_tempfile(TEMPNAME_TEMPLATE, NULL, 1);
        if (fd < 0)
                exit(1);

        err = fchmod(fd, 0777);
        if (err < 0) {
                perror("fchmod");
                exit(1);
        }

        /*
         * Seek to len - 1 because writing a character there will
         * increase the file size by one byte, to the desired length.
         */
        if (lseek64(fd, len - 1, SEEK_SET) < 0) {
                perror("lseek64");
                exit(1);
        }

        zero = 0;

        err = write(fd, &zero, 1);
        if (err != 1) {
                perror("write");
                exit(1);
        }

        return fd;
}

int __init create_mem_file(unsigned long long len)
{
        int err, fd;

        fd = create_tmp_file(len);

        err = os_set_exec_close(fd);
        if (err < 0) {
                errno = -err;
                perror("exec_close");
        }
        return fd;
}


void __init check_tmpexec(void)
{
        void *addr;
        int err, fd = create_tmp_file(UM_KERN_PAGE_SIZE);

        addr = mmap(NULL, UM_KERN_PAGE_SIZE,
                    PROT_READ | PROT_WRITE | PROT_EXEC, MAP_PRIVATE, fd, 0);
        printf("Checking PROT_EXEC mmap in %s...",tempdir);
        fflush(stdout);
        if (addr == MAP_FAILED) {
                err = errno;
                perror("failed");
                close(fd);
                if (err == EPERM)
                        printf("%s must be not mounted noexec\n",tempdir);
                exit(1);
        }
        printf("OK\n");
        munmap(addr, UM_KERN_PAGE_SIZE);

        close(fd);
}