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

#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/vfs.h>
#include <linux/magic.h>
#include <init.h>
#include <kern_util.h>
#include <os.h>
#include "internal.h"

/*
 * kasan_map_memory - maps memory from @start with a size of @len.
 * The allocated memory is filled with zeroes upon success.
 * @start: the start address of the memory to be mapped
 * @len: the length of the memory to be mapped
 *
 * This function is used to map shadow memory for KASAN in uml
 */
void kasan_map_memory(void *start, size_t len)
{
        if (mmap(start,
                 len,
                 PROT_READ|PROT_WRITE,
                 MAP_FIXED|MAP_ANONYMOUS|MAP_PRIVATE|MAP_NORESERVE,
                 -1,
                 0) == MAP_FAILED) {
                os_info("Couldn't allocate shadow memory: %s\n.",
                        strerror(errno));
                exit(1);
        }

        if (madvise(start, len, MADV_DONTDUMP)) {
                os_info("Couldn't set MAD_DONTDUMP on shadow memory: %s\n.",
                        strerror(errno));
                exit(1);
        }

        if (madvise(start, len, MADV_DONTFORK)) {
                os_info("Couldn't set MADV_DONTFORK on shadow memory: %s\n.",
                        strerror(errno));
                exit(1);
        }
}

/* Set by make_tempfile() during early boot. */
char *tempdir = NULL;

/* Check if dir is on tmpfs. Return 0 if yes, -1 if no or error. */
static int __init check_tmpfs(const char *dir)
{
        struct statfs st;

        os_info("Checking if %s is on tmpfs...", dir);
        if (statfs(dir, &st) < 0) {
                os_info("%s\n", strerror(errno));
        } else if (st.f_type != TMPFS_MAGIC) {
                os_info("no\n");
        } else {
                os_info("OK\n");
                return 0;
        }
        return -1;
}

/*
 * Choose the tempdir to use. We want something on tmpfs so that our memory is
 * not subject to the host's vm.dirty_ratio. If a tempdir is specified in the
 * environment, we use that even if it's not on tmpfs, but we warn the user.
 * Otherwise, we try common tmpfs locations, and if no tmpfs directory is found
 * then we fall back to /tmp.
 */
static char * __init choose_tempdir(void)
{
        static const char * const vars[] = {
                "TMPDIR",
                "TMP",
                "TEMP",
                NULL
        };
        static const char fallback_dir[] = "/tmp";
        static const char * const tmpfs_dirs[] = {
                "/dev/shm",
                fallback_dir,
                NULL
        };
        int i;
        const char *dir;

        os_info("Checking environment variables for a tempdir...");
        for (i = 0; vars[i]; i++) {
                dir = getenv(vars[i]);
                if ((dir != NULL) && (*dir != '\0')) {
                        os_info("%s\n", dir);
                        if (check_tmpfs(dir) >= 0)
                                goto done;
                        else
                                goto warn;
                }
        }
        os_info("none found\n");

        for (i = 0; tmpfs_dirs[i]; i++) {
                dir = tmpfs_dirs[i];
                if (check_tmpfs(dir) >= 0)
                        goto done;
        }

        dir = fallback_dir;
warn:
        os_warn("Warning: tempdir %s is not on tmpfs\n", dir);
done:
        /* Make a copy since getenv results may not remain valid forever. */
        return strdup(dir);
}

/*
 * Create an unlinked tempfile in a suitable tempdir. template must be the
 * basename part of the template with a leading '/'.
 */
static int __init make_tempfile(const char *template)
{
        char *tempname;
        int fd;

        if (tempdir == NULL) {
                tempdir = choose_tempdir();
                if (tempdir == NULL) {
                        os_warn("Failed to choose tempdir: %s\n",
                                strerror(errno));
                        return -1;
                }
        }

#ifdef O_TMPFILE
        fd = open(tempdir, O_CLOEXEC | O_RDWR | O_EXCL | O_TMPFILE, 0700);
        /*
         * If the running system does not support O_TMPFILE flag then retry
         * without it.
         */
        if (fd != -1 || (errno != EINVAL && errno != EISDIR &&
                        errno != EOPNOTSUPP))
                return fd;
#endif

        tempname = malloc(strlen(tempdir) + strlen(template) + 1);
        if (tempname == NULL)
                return -1;

        strcpy(tempname, tempdir);
        strcat(tempname, template);
        fd = mkstemp(tempname);
        if (fd < 0) {
                os_warn("open - cannot create %s: %s\n", tempname,
                        strerror(errno));
                goto out;
        }
        if (unlink(tempname) < 0) {
                perror("unlink");
                goto close;
        }
        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);
        if (fd < 0)
                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);
        os_info("Checking PROT_EXEC mmap in %s...", tempdir);
        if (addr == MAP_FAILED) {
                err = errno;
                os_warn("%s\n", strerror(err));
                close(fd);
                if (err == EPERM)
                        os_warn("%s must be not mounted noexec\n", tempdir);
                exit(1);
        }
        os_info("OK\n");
        munmap(addr, UM_KERN_PAGE_SIZE);

        close(fd);
}