![Tristan Schmelcher](/assets/img/avatar_default.png)
Inferring the mount hierarchy correctly from /proc/mounts is hard when MS_MOVE may have been used, and the previous code did it wrongly. This change simplifies the logic to only require that /dev/shm be _on_ tmpfs (which can be checked trivially with statfs) rather than that it be a _mountpoint_ of tmpfs, since there isn't a compelling reason to be that strict. We also now check for tmpfs on whatever directory we ultimately use so that the user is better informed. This change also moves the more standard TMPDIR environment variable check ahead of the others. Applies to 3.12. Signed-off-by: Tristan Schmelcher <tschmelcher@google.com> Signed-off-by: Richard Weinberger <richard@nod.at>
206 lines
4 KiB
C
206 lines
4 KiB
C
/*
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* Copyright (C) 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
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* Licensed under the GPL
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*/
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#include <stdio.h>
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#include <stddef.h>
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#include <stdlib.h>
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#include <unistd.h>
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#include <errno.h>
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#include <fcntl.h>
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#include <string.h>
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#include <sys/stat.h>
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#include <sys/mman.h>
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#include <sys/vfs.h>
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#include <linux/magic.h>
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#include <init.h>
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#include <os.h>
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/* Set by make_tempfile() during early boot. */
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static char *tempdir = NULL;
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/* Check if dir is on tmpfs. Return 0 if yes, -1 if no or error. */
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static int __init check_tmpfs(const char *dir)
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{
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struct statfs st;
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printf("Checking if %s is on tmpfs...", dir);
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if (statfs(dir, &st) < 0) {
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printf("%s\n", strerror(errno));
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} else if (st.f_type != TMPFS_MAGIC) {
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printf("no\n");
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} else {
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printf("OK\n");
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return 0;
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}
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return -1;
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}
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/*
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* Choose the tempdir to use. We want something on tmpfs so that our memory is
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* not subject to the host's vm.dirty_ratio. If a tempdir is specified in the
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* environment, we use that even if it's not on tmpfs, but we warn the user.
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* Otherwise, we try common tmpfs locations, and if no tmpfs directory is found
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* then we fall back to /tmp.
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*/
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static char * __init choose_tempdir(void)
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{
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static const char * const vars[] = {
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"TMPDIR",
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"TMP",
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"TEMP",
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NULL
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};
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static const char fallback_dir[] = "/tmp";
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static const char * const tmpfs_dirs[] = {
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"/dev/shm",
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fallback_dir,
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NULL
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};
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int i;
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const char *dir;
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printf("Checking environment variables for a tempdir...");
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for (i = 0; vars[i]; i++) {
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dir = getenv(vars[i]);
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if ((dir != NULL) && (*dir != '\0')) {
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printf("%s\n", dir);
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if (check_tmpfs(dir) >= 0)
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goto done;
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else
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goto warn;
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}
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}
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printf("none found\n");
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for (i = 0; tmpfs_dirs[i]; i++) {
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dir = tmpfs_dirs[i];
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if (check_tmpfs(dir) >= 0)
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goto done;
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}
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dir = fallback_dir;
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warn:
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printf("Warning: tempdir %s is not on tmpfs\n", dir);
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done:
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/* Make a copy since getenv results may not remain valid forever. */
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return strdup(dir);
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}
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/*
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* Create an unlinked tempfile in a suitable tempdir. template must be the
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* basename part of the template with a leading '/'.
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*/
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static int __init make_tempfile(const char *template)
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{
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char *tempname;
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int fd;
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if (tempdir == NULL) {
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tempdir = choose_tempdir();
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if (tempdir == NULL) {
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fprintf(stderr, "Failed to choose tempdir: %s\n",
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strerror(errno));
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return -1;
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}
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}
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tempname = malloc(strlen(tempdir) + strlen(template) + 1);
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if (tempname == NULL)
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return -1;
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strcpy(tempname, tempdir);
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strcat(tempname, template);
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fd = mkstemp(tempname);
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if (fd < 0) {
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fprintf(stderr, "open - cannot create %s: %s\n", tempname,
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strerror(errno));
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goto out;
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}
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if (unlink(tempname) < 0) {
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perror("unlink");
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goto close;
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}
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free(tempname);
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return fd;
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close:
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close(fd);
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out:
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free(tempname);
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return -1;
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}
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#define TEMPNAME_TEMPLATE "/vm_file-XXXXXX"
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static int __init create_tmp_file(unsigned long long len)
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{
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int fd, err;
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char zero;
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fd = make_tempfile(TEMPNAME_TEMPLATE);
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if (fd < 0)
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exit(1);
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err = fchmod(fd, 0777);
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if (err < 0) {
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perror("fchmod");
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exit(1);
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}
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/*
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* Seek to len - 1 because writing a character there will
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* increase the file size by one byte, to the desired length.
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*/
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if (lseek64(fd, len - 1, SEEK_SET) < 0) {
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perror("lseek64");
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exit(1);
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}
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zero = 0;
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err = write(fd, &zero, 1);
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if (err != 1) {
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perror("write");
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exit(1);
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}
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return fd;
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}
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int __init create_mem_file(unsigned long long len)
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{
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int err, fd;
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fd = create_tmp_file(len);
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err = os_set_exec_close(fd);
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if (err < 0) {
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errno = -err;
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perror("exec_close");
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}
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return fd;
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}
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void __init check_tmpexec(void)
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{
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void *addr;
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int err, fd = create_tmp_file(UM_KERN_PAGE_SIZE);
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addr = mmap(NULL, UM_KERN_PAGE_SIZE,
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PROT_READ | PROT_WRITE | PROT_EXEC, MAP_PRIVATE, fd, 0);
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printf("Checking PROT_EXEC mmap in %s...", tempdir);
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if (addr == MAP_FAILED) {
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err = errno;
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printf("%s\n", strerror(err));
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close(fd);
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if (err == EPERM)
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printf("%s must be not mounted noexec\n", tempdir);
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exit(1);
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}
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printf("OK\n");
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munmap(addr, UM_KERN_PAGE_SIZE);
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close(fd);
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}
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