linux/arch/um/os-Linux/mem.c

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/*
* 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);
}