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-rw-r--r--switch_root.c254
1 files changed, 24 insertions, 230 deletions
diff --git a/switch_root.c b/switch_root.c
index 638a6637..be5720ed 100644
--- a/switch_root.c
+++ b/switch_root.c
@@ -49,203 +49,11 @@ enum {
err_usage,
};
-static int readFD(int fd, char **buf)
-{
- char *p;
- size_t size = 16384;
- int s = 0, filesize = 0;
-
- if (!(*buf = calloc (16384, sizeof (char))))
- return -1;
-
- do {
- p = *buf + filesize;
- s = read(fd, p, 16384 - s);
- if (s < 0)
- break;
- filesize += s;
- /* only exit for empty reads */
- if (s == 0)
- break;
- else if (s == 16384) {
- *buf = realloc(*buf, size + 16384);
- memset(*buf + size, '\0', 16384);
- size += s;
- s = 0;
- } else {
- size += s;
- }
- } while (1);
-
- *buf = realloc(*buf, filesize+1);
- (*buf)[filesize] = '\0';
-
- return *buf ? filesize : -1;
-}
-
-static char *getKernelCmdLine(void)
-{
- static char *cmdline = NULL;
- int fd = -1;
- int errnum;
-
- fd = open("./proc/cmdline", O_RDONLY);
- if (fd < 0) {
- errnum = errno;
- fprintf(stderr, "Error: Could not open ./proc/cmdline: %m\n");
- errno = errnum;
- return NULL;
- }
-
- if (readFD(fd, &cmdline) < 0) {
- errnum = errno;
- fprintf(stderr, "Error: could not read ./proc/cmdline: %m\n");
- close(fd);
- errno = errnum;
- return NULL;
- }
- close(fd);
-
- return cmdline;
-}
-
-/* get the start of a kernel arg "arg". returns everything after it
- * (useful for things like getting the args to init=). so if you only
- * want one arg, you need to terminate it at the n */
-static char *getKernelArg(char *arg)
-{
- char *start;
- char *cmdline;
- int len;
-
- cmdline = start = getKernelCmdLine();
- if (start == NULL)
- return NULL;
-
- while (*start) {
- if (isspace(*start)) {
- start++;
- continue;
- }
-
- len = strlen(arg);
- /* don't return if it's a different argument that merely starts
- * like this one. */
- if (strncmp(start, arg, len) == 0) {
- if (start[len] == '=')
- return start + len + 1;
- if (!start[len] || isspace(start[len]))
- return start + len;
- }
- while (*++start && !isspace(*start))
- ;
- }
-
- return NULL;
-}
-
-#define MAX_INIT_ARGS 32
-static int build_init_args(char **init, char ***initargs_out)
-{
- const char *initprogs[] = { "./sbin/init", "./etc/init",
- "./bin/init", "./bin/sh", NULL };
- const char *ignoreargs[] = { "console=", "BOOT_IMAGE=", NULL };
- char *cmdline = NULL;
- char **initargs;
-
- int i = 0;
-
- *init = getKernelArg("init");
-
- if (*init == NULL) {
- int j;
- cmdline = getKernelCmdLine();
- if (cmdline == NULL)
- return -1;
-
- for (j = 0; initprogs[j] != NULL; j++) {
- if (!access(initprogs[j], X_OK)) {
- *init = strdup(initprogs[j]);
- break;
- }
- }
- }
-
- initargs = (char **)calloc(MAX_INIT_ARGS+1, sizeof (char *));
- if (initargs == NULL)
- return -1;
-
- if (cmdline && *init) {
- initargs[i++] = *init;
- } else {
- cmdline = *init;
- initargs[0] = NULL;
- }
-
- if (cmdline) {
- char quote = '\0';
- char *chptr;
- char *start;
-
- start = chptr = cmdline;
- for (; (i < MAX_INIT_ARGS) && (*start != '\0'); i++) {
- while (*chptr && (*chptr != quote)) {
- if (isspace(*chptr) && quote == '\0')
- break;
- if (*chptr == '"' || *chptr == '\'')
- quote = *chptr;
- chptr++;
- }
-
- if (quote == '"' || quote == '\'')
- chptr++;
- if (*chptr != '\0')
- *(chptr++) = '\0';
-
- /* There are some magic parameters added *after*
- * everything you pass, including a console= from the
- * x86_64 kernel and BOOT_IMAGE= by syslinux. Bash
- * doesn't know what they mean, so it then exits, init
- * gets killed, desaster ensues. *sigh*.
- */
- int j;
- for (j = 0; ignoreargs[j] != NULL; j++) {
- if (cmdline == *init && !strncmp(start, ignoreargs[j], strlen(ignoreargs[j]))) {
- if (!*chptr)
- initargs[i] = NULL;
- else
- i--;
- start = chptr;
- break;
- }
- }
- if (start == chptr)
- continue;
-
- if (start[0] == '\0')
- i--;
- else
- initargs[i] = strdup(start);
- start = chptr;
- }
- }
-
- if (initargs[i-1] != NULL)
- initargs[i] = NULL;
-
- *initargs_out = initargs;
-
-
- return 0;
-}
-
-static void switchroot(const char *newroot)
+static int switchroot(const char *newroot)
{
/* Don't try to unmount the old "/", there's no way to do it. */
const char *umounts[] = { "/dev", "/proc", "/sys", NULL };
- char *init, **initargs;
int errnum;
- int rc;
int i;
for (i = 0; umounts[i] != NULL; i++) {
@@ -260,36 +68,32 @@ static void switchroot(const char *newroot)
}
}
- chdir(newroot);
-
- rc = build_init_args(&init, &initargs);
- if (rc < 0)
- return;
+ if (chdir(newroot) < 0) {
+ errnum=errno;
+ fprintf(stderr, "switchroot: chdir failed: %m\n");
+ errno=errnum;
+ return -1;
+ }
if (mount(newroot, "/", NULL, MS_MOVE, NULL) < 0) {
errnum = errno;
fprintf(stderr, "switchroot: mount failed: %m\n");
errno = errnum;
- return;
+ return -1;
}
if (chroot(".")) {
errnum = errno;
fprintf(stderr, "switchroot: chroot failed: %m\n");
errno = errnum;
- return;
+ return -2;
}
-
- if (access(initargs[0], X_OK))
- fprintf(stderr, "WARNING: can't access %s\n", initargs[0]);
-
- execv(initargs[0], initargs);
- return;
+ return 1;
}
static void usage(FILE *output)
{
- fprintf(output, "usage: switchroot {-n|--newroot} <newrootdir>\n");
+ fprintf(output, "usage: switchroot <newrootdir> <init> <args to init>\n");
if (output == stderr)
exit(err_usage);
exit(ok);
@@ -297,32 +101,22 @@ static void usage(FILE *output)
int main(int argc, char *argv[])
{
- int i;
- char *newroot = NULL;
-
- for (i = 1; i < argc; i++) {
- if (!strcmp(argv[i], "--help")
- || !strcmp(argv[i], "-h")
- || !strcmp(argv[i], "--usage")) {
- usage(stdout);
- } else if (!strcmp(argv[i], "-n")
- || !strcmp(argv[i], "--newroot")) {
- newroot = argv[++i];
- } else if (!strncmp(argv[i], "--newroot=", 10)) {
- newroot = argv[i] + 10;
- } else {
- usage(stderr);
- }
- }
-
- if (newroot == NULL || newroot[0] == '\0') {
+ char *newroot = argv[1];
+ char *init = argv[2];
+ char **initargs = &argv[2];
+
+ if (newroot == NULL || newroot[0] == '\0' ||
+ init == NULL || init[0] == '\0' ) {
usage(stderr);
}
- switchroot(newroot);
-
- fprintf(stderr, "switchroot has failed. Sorry.\n");
- return 1;
+ if (switchroot(newroot) < 0) {
+ fprintf(stderr, "switchroot has failed. Sorry.\n");
+ return 1;
+ }
+ if (access(initargs[0], X_OK))
+ fprintf(stderr, "WARNING: can't access %s\n", initargs[0]);
+ execv(initargs[0], initargs);
}
/*
generated by cgit v1.2.3 (git 2.25.1) at 2024-11-28 05:51:05 +0000