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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.
master
Victor Lowther 16 years ago
parent
47507b21a8
commit
faf882394b
2 changed files with 30 additions and 231 deletions
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  1. 7
      modules.d/99base/init
  2. 254
      switch_root.c

7
modules.d/99base/init
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@ -96,7 +96,12 @@ source_all pre-pivot @@ -96,7 +96,12 @@ source_all pre-pivot
getarg break && emergency_shell
kill $(pidof udevd)
echo "Switching to real root filesystem $root"
exec switch_root -n "$NEWROOT" || {
initargs=""
for x in $CMDLINE; do
[ "${x%%=*}" = "console" -o "${x%%=*}" = "BOOT_IMAGE" ] && continue
initargs="$initargs $x"
done
exec switch_root "$NEWROOT" "$INIT" $initargs || {
# davej doesn't like initrd bugs
echo "Something went very badly wrong in the initrd. Please "
echo "file a bug against mkinitrd."

254
switch_root.c
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@ -49,203 +49,11 @@ enum { @@ -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) @@ -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) @@ -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);
}

/*

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