/*
 * 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 <os.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, "/");
}

/*
 * Remove bytes from the front of the buffer and refill it so that if there's a
 * partial string that we care about, it will be completed, and we can recognize
 * it.
 */
static int pop(int fd, char *buf, size_t size, size_t npop)
{
        ssize_t n;
        size_t len = strlen(&buf[npop]);

        memmove(buf, &buf[npop], len + 1);
        n = read(fd, &buf[len], size - len - 1);
        if (n < 0)
                return -errno;

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

/*
 * 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;
        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';
        }

        return pop(fd, buf, size, ptr - buf + 1);
}

/*
 * Decode an octal-escaped and space-terminated path of the form used by
 * /proc/mounts. May be used to decode a path in-place. "out" must be at least
 * as large as the input. The output is always null-terminated. "len" gets the
 * length of the output, excluding the trailing null. Returns 0 if a full path
 * was successfully decoded, otherwise an error.
 */
static int decode_path(const char *in, char *out, size_t *len)
{
        char *first = out;
        int c;
        int i;
        int ret = -EINVAL;
        while (1) {
                switch (*in) {
                case '\0':
                        goto out;

                case ' ':
                        ret = 0;
                        goto out;

                case '\\':
                        in++;
                        c = 0;
                        for (i = 0; i < 3; i++) {
                                if (*in < '0' || *in > '7')
                                        goto out;
                                c = (c << 3) | (*in++ - '0');
                        }
                        *(unsigned char *)out++ = (unsigned char) c;
                        break;

                default:
                        *out++ = *in++;
                        break;
                }
        }

out:
        *out = '\0';
        *len = out - first;
        return ret;
}

/*
 * Computes the length of s when encoded with three-digit octal escape sequences
 * for the characters in chars.
 */
static size_t octal_encoded_length(const char *s, const char *chars)
{
        size_t len = strlen(s);
        while ((s = strpbrk(s, chars)) != NULL) {
                len += 3;
                s++;
        }

        return len;
}

enum {
        OUTCOME_NOTHING_MOUNTED,
        OUTCOME_TMPFS_MOUNT,
        OUTCOME_NON_TMPFS_MOUNT,
};

/* Read a line of /proc/mounts data looking for a tmpfs mount at "path". */
static int read_mount(int fd, char *buf, size_t bufsize, const char *path,
                      int *outcome)
{
        int found;
        int match;
        char *space;
        size_t len;

        enum {
                MATCH_NONE,
                MATCH_EXACT,
                MATCH_PARENT,
        };

        found = next(fd, buf, bufsize, ' ');
        if (found != 1)
                return found;

        /*
         * If there's no following space in the buffer, then this path is
         * truncated, so it can't be the one we're looking for.
         */
        space = strchr(buf, ' ');
        if (space) {
                match = MATCH_NONE;
                if (!decode_path(buf, buf, &len)) {
                        if (!strcmp(buf, path))
                                match = MATCH_EXACT;
                        else if (!strncmp(buf, path, len)
                                 && (path[len] == '/' || !strcmp(buf, "/")))
                                match = MATCH_PARENT;
                }

                found = pop(fd, buf, bufsize, space - buf + 1);
                if (found != 1)
                        return found;

                switch (match) {
                case MATCH_EXACT:
                        if (!strncmp(buf, "tmpfs", strlen("tmpfs")))
                                *outcome = OUTCOME_TMPFS_MOUNT;
                        else
                                *outcome = OUTCOME_NON_TMPFS_MOUNT;
                        break;

                case MATCH_PARENT:
                        /* This mount obscures any previous ones. */
                        *outcome = OUTCOME_NOTHING_MOUNTED;
                        break;
                }
        }

        return next(fd, buf, bufsize, '\n');
}

/* 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;
        int found;
        int outcome;
        char *path;
        char *buf;
        size_t bufsize;

        if (checked_tmpdir)
                return;

        checked_tmpdir = 1;

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

        path = realpath("/dev/shm", NULL);
        if (!path) {
                printf("failed to check real path, errno = %d\n", errno);
                return;
        }
        printf("%s...", path);

        /*
         * The buffer needs to be able to fit the full octal-escaped path, a
         * space, and a trailing null in order to successfully decode it.
         */
        bufsize = octal_encoded_length(path, " \t\n\\") + 2;

        if (bufsize < 128)
                bufsize = 128;

        buf = malloc(bufsize);
        if (!buf) {
                printf("malloc failed, errno = %d\n", errno);
                goto out;
        }
        buf[0] = '\0';

        fd = open("/proc/mounts", O_RDONLY);
        if (fd < 0) {
                printf("failed to open /proc/mounts, errno = %d\n", errno);
                goto out1;
        }

        outcome = OUTCOME_NOTHING_MOUNTED;
        while (1) {
                found = read_mount(fd, buf, bufsize, path, &outcome);
                if (found != 1)
                        break;
        }

        if (found < 0) {
                printf("read returned errno %d\n", -found);
        } else {
                switch (outcome) {
                case OUTCOME_TMPFS_MOUNT:
                        printf("OK\n");
                        default_tmpdir = "/dev/shm";
                        break;

                case OUTCOME_NON_TMPFS_MOUNT:
                        printf("not tmpfs\n");
                        break;

                default:
                        printf("nothing mounted on /dev/shm\n");
                        break;
                }
        }

        close(fd);
out1:
        free(buf);
out:
        free(path);
}

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))
                goto out;

        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 close;
        }
        if (out_tempname) {
                *out_tempname = tempname;
        } else
                free(tempname);
        return fd;
close:
        close(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);
}