uml: Simplify tempdir logic. (0d71832e) · Commits · 戴 / test

arch/um/os-Linux/mem.c

+75 −297

Original line number	Diff line number	Diff line
		@@ -12,336 +12,116 @@
		#include <string.h>
		#include <sys/stat.h>
		#include <sys/mman.h>
		#include <sys/param.h>
		#include <sys/vfs.h>
		#include <linux/magic.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.
		*/
		/* Set by make_tempfile() during early boot. */
		static char *tempdir = NULL;

		static void __init find_tempdir(void)
		/* Check if dir is on tmpfs. Return 0 if yes, -1 if no or error. */
		static int __init check_tmpfs(const char *dir)
		{
		const char *dirs[] = { "TMP", "TEMP", "TMPDIR", NULL };
		int i;
		char *dir = NULL;
		struct statfs st;

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

		/*
		* Computes the length of s when encoded with three-digit octal escape sequences
		* for the characters in chars.
		* 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 size_t octal_encoded_length(const char s, const char chars)
		static char * __init choose_tempdir(void)
		{
		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,
		static const char * const vars[] = {
		"TMPDIR",
		"TMP",
		"TEMP",
		NULL
		};

		/* 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,
		static const char fallback_dir[] = "/tmp";
		static const char * const tmpfs_dirs[] = {
		"/dev/shm",
		fallback_dir,
		NULL
		};

		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;
		int i;
		const char *dir;

		printf("Checking environment variables for a tempdir...");
		for (i = 0; vars[i]; i++) {
		dir = getenv(vars[i]);
		if ((dir != NULL) && (*dir != '\0')) {
		printf("%s\n", dir);
		if (check_tmpfs(dir) >= 0)
		goto done;
		else
		*outcome = OUTCOME_NON_TMPFS_MOUNT;
		break;

		case MATCH_PARENT:
		/* This mount obscures any previous ones. */
		*outcome = OUTCOME_NOTHING_MOUNTED;
		break;
		goto warn;
		}
		}
		printf("none found\n");

		return next(fd, buf, bufsize, '\n');
		for (i = 0; tmpfs_dirs[i]; i++) {
		dir = tmpfs_dirs[i];
		if (check_tmpfs(dir) >= 0)
		goto done;
		}

		/* which_tmpdir is called only during early boot */
		static int checked_tmpdir = 0;
		dir = fallback_dir;
		warn:
		printf("Warning: tempdir %s is not on tmpfs\n", dir);
		done:
		/* Make a copy since getenv results may not remain valid forever. */
		return strdup(dir);
		}

		/*
		* 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.
		* Create an unlinked tempfile in a suitable tempdir. template must be the
		* basename part of the template with a leading '/'.
		*/
		static void which_tmpdir(void)
		static int __init make_tempfile(const char *template)
		{
		char *tempname;
		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;
		}
		if (tempdir == NULL) {
		tempdir = choose_tempdir();
		if (tempdir == NULL) {
		fprintf(stderr, "Failed to choose tempdir: %s\n",
		strerror(errno));
		return -1;
		}

		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);
		tempname = malloc(strlen(tempdir) + strlen(template) + 1);
		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));
		strcat(tempname, template);
		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)) {
		if (unlink(tempname) < 0) {
		perror("unlink");
		goto close;
		}
		if (out_tempname) {
		*out_tempname = tempname;
		} else
		free(tempname);
		return fd;
		close:
		@@ -351,14 +131,14 @@ out:
		return -1;
		}

		#define TEMPNAME_TEMPLATE "vm_file-XXXXXX"
		#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);
		fd = make_tempfile(TEMPNAME_TEMPLATE);
		if (fd < 0)
		exit(1);

		@@ -402,7 +182,6 @@ int __init create_mem_file(unsigned long long len)
		return fd;
		}


		void __init check_tmpexec(void)
		{
		void *addr;
		@@ -411,10 +190,9 @@ void __init check_tmpexec(void)
		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");
		printf("%s\n", strerror(err));
		close(fd);
		if (err == EPERM)
		printf("%s must be not mounted noexec\n", tempdir);

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