Simplify switch_root.c a bit

Shift some required functionality from switch_root.c to init.

String manipulation and filtering, and testing for the existence of init
is easier in the init script than in C.

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);
 }
 
 /*