diff options
Diffstat (limited to 'arch/um/os-Linux')
-rw-r--r-- | arch/um/os-Linux/mem.c | 372 |
1 files changed, 75 insertions, 297 deletions
diff --git a/arch/um/os-Linux/mem.c b/arch/um/os-Linux/mem.c index 3c4af77..897e9ad 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"); |