1 files changed, 75 insertions, 297 deletions

diff --git a/arch/um/os-Linux/mem.c b/arch/um/os-Linux/mem.c
index 3c4af77e51a2..897e9ad0c108 100644
--- a/arch/um/os-Linux/mem.c
+++ b/arch/um/os-Linux/mem.c
@@ -12,337 +12,117 @@
 #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;
-
-        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;
+        struct statfs st;
 
-        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';
+        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;
         }
-
-        return pop(fd, buf, size, ptr - buf + 1);
+        return -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.
+ * 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 int decode_path(const char *in, char *out, size_t *len)
+static char * __init choose_tempdir(void)
 {
-        char *first = out;
-        int c;
+        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;
-        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;
+        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
+                                goto warn;
                 }
         }
+        printf("none found\n");
 
-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;
-                }
+        for (i = 0; tmpfs_dirs[i]; i++) {
+                dir = tmpfs_dirs[i];
+                if (check_tmpfs(dir) >= 0)
+                        goto done;
         }
 
-        return next(fd, buf, bufsize, '\n');
+        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);
 }
 
-/* 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.
+ * 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));
+        strcpy(tempname, tempdir);
+        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);
+        free(tempname);
         return fd;
 close:
         close(fd);
@@ -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;
@@ -410,14 +189,13 @@ 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);
+        printf("Checking PROT_EXEC mmap in %s...", tempdir);
         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);
+                        printf("%s must be not mounted noexec\n", tempdir);
                 exit(1);
         }
         printf("OK\n");