Imported Upstream version 2013.11.12upstream/2013.11.12

1 files changed, 336 insertions, 0 deletions

diff --git a/initvm.c b/initvm.c
new file mode 100644
index 0000000..bed0cc4
--- /dev/null
+++ b/initvm.c
@@ -0,0 +1,336 @@
+/*
+ * NAME
+ *	initvm - init for qemu, setup binfmt_misc launch build
+ *	
+ * SYNOPSIS
+ *	initvm
+ *
+ * DESCRIPTION
+ *	This is the kernel init script for virtual machines which will
+ *	be running executables for an embedded (non-native)
+ *	architecture. It registers binfmt_misc handlers for qemu and
+ *	executes the build script, and tests many assumptions.
+ *
+ * FILES
+ *	/.build/qemu-reg
+ *		text file with lines to stuff into the binfmt_misc
+ *		filesystem registration file
+ *	/.build/build
+ *		build script to execute once binfmts are set up
+ *
+ * AUTHOR
+ *	James Perkins <james.perkins@linuxfoundation.org>
+ */
+
+#include <sys/mount.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <stdlib.h>
+#include <string.h>
+#include <errno.h>
+#include <stdio.h>
+
+/* to enable debugging, compile with -DDEBUG */
+#ifdef DEBUG
+#define DBG(x) 		do { x; } while(0)
+#else
+#define DBG(x)
+#endif
+
+/* function return codes */
+enum okfail { FAIL=0, OK=1 };
+
+/* qemu registration fields, see kernel/Documentation/binfmt_misc.txt */
+enum fields { ignore=0, name, type, offset, magic, mask, interpreter, flags };
+const char * const fieldnames[] = {
+	"ignore", "name", "type", "offset",
+	"magic", "mask", "interpreter", "flags"
+};
+const int n_fields = 8;
+
+/* files in useful places */
+#define SYSFS_BINFMT_MISC	"/proc/sys/fs/binfmt_misc"
+#define SYSFS_BINFMT_MISC_REG	"/proc/sys/fs/binfmt_misc/register"
+#define SYSFS_BINFMT_MISC_STAT	"/proc/sys/fs/binfmt_misc/status"
+
+/* /usr/lib/build/x paths are copied to /.build inside a virtual machine */
+#define BINFMT_REGF_0		"/.build/qemu-reg"
+#define BINFMT_REGF_1		"/usr/lib/build/qemu-reg"
+#define BUILD			"/.build/build"
+
+/* useful constant arrays */
+static char *rx_files[] = { "/proc", "/proc/sys", "/proc/sys/fs",
+	 SYSFS_BINFMT_MISC, NULL };
+static char *w_files[] = { SYSFS_BINFMT_MISC_REG, NULL };
+
+static char* const args[] = { BUILD, NULL };
+
+/* test access modes for files, return OK or FAIL */
+enum okfail test_access_files(char *files[], int mode, const char *errstr)
+{
+	int i;
+
+	for (i = 0; files[i] != NULL; i++) {
+		if (access(files[i], mode) != 0) {
+			fprintf(stderr, "%s: %s: fails test\n",
+				files[i], errstr);
+			return FAIL;
+		}
+	}
+
+	return OK;
+}
+
+/* find a string in the given file, return OK or FAIL */
+enum okfail strfile(const char *filename, const char *string)
+{
+	char buf[BUFSIZ];
+	FILE *fp;
+	enum okfail found = FAIL;
+
+	fp = fopen(filename, "r");
+	if (fp == NULL)
+	{
+		perror(filename);
+		return FAIL;
+	}
+	while (fgets(buf, sizeof(buf), fp) != NULL)
+	{
+		if (strcmp(buf, string) == 0) {
+			found = OK;
+			break;
+		}
+
+	}
+	(void)fclose(fp);
+
+	return found;
+}
+
+/* write the file with given string, return OK or FAIL */
+enum okfail write_file_string(const char *filename, const char *string)
+{
+	int fd;
+
+	if ((fd = open(filename, O_WRONLY)) == -1)
+	{
+		perror(filename);
+		return FAIL;
+	}
+
+	if (write(fd, string, strlen(string)) == -1)
+	{
+		perror("write");
+		fprintf(stderr, "%s: write failed\n", filename);
+		close(fd);
+		return FAIL;
+	}
+
+	close(fd);
+	return OK;
+}
+
+#ifdef DEBUG
+/* dump contents of the file to stderr, return OK or FAIL */
+enum okfail dump_file(char *path)
+{
+	FILE *fp;
+	char buf[BUFSIZ];
+
+	fp = fopen(path, "r");
+	if (fp == NULL) {
+		perror(path);
+		return FAIL;
+	}
+
+	while (fgets(buf, sizeof(buf), fp) != NULL)
+	{
+		fputs(buf, stderr);
+	}
+
+	fclose(fp);
+	return OK;
+}
+#endif /* DEBUG */
+
+/* parse datafile and register (to regfile) all binary formats found */
+enum okfail binfmt_register(char *datafile, char *regfile)
+{
+	char buf[BUFSIZ];
+	FILE *fp;
+	int line;
+
+	fp = fopen(datafile, "r");
+	if (fp == NULL)
+	{
+		perror(datafile);
+		return FAIL;
+	}
+
+	for (line = 1; fgets(buf, sizeof(buf), fp) != NULL; line++)
+	{
+		char tokens[BUFSIZ];
+		char *s = tokens;
+		char *f[n_fields];	/* field content pointers */
+		int n;			/* current field */
+		char path[BUFSIZ];
+
+		if (buf[0] != ':')	/* non-data input line */
+		{
+			goto skip;
+		}
+
+		/* copy buf and tokenize :-seperated fields into f[] */
+		strcpy(tokens, buf);
+		for (n = 0; s != NULL && n < n_fields; n++)
+		{
+			f[n] = strsep(&s, ":");
+		}
+
+#ifdef DEBUG
+		int i;
+		fprintf(stderr, "DEBUG: line %d, fields %d:\n",  line, n);
+		for (i = name; i < n; i++)
+		{
+			fprintf(stderr, " %s %s\n", fieldnames[i], f[i]);
+		}
+#endif /* DEBUG */
+
+		if (n == n_fields && s != NULL)
+		{
+			fprintf(stderr, "%s: line %d: extra fields, ignoring."
+				" Content: %s", datafile, line, buf);
+			goto skip;
+		}
+
+		if (n < n_fields)
+		{
+			fprintf(stderr, "%s: line %d: missing fields, ignoring."
+				" Content: %s", datafile, line, buf);
+			goto skip;
+		}
+
+
+		if (access(f[interpreter], X_OK) != 0) {
+			fprintf(stderr, 
+				"%s: line %d: interpreter '%s' not found,"
+				" ignoring\n", datafile, line, f[interpreter]);
+			goto skip;
+		}
+
+		if (!write_file_string(regfile, buf)) {
+			fprintf(stderr, "%s: line %d: write failed."
+				" Content: %s\n", datafile, line, buf);
+			(void)fclose(fp);
+			return FAIL;
+		}
+
+		/* verify registration completed correctly */
+		snprintf(path, sizeof(path), SYSFS_BINFMT_MISC "/%s", f[name]);
+
+		if (access(path, R_OK) != 0) {
+			fprintf(stderr, 
+				"%s: line %d: binfmt path not created, content '%s'\n",
+				path, line, buf);
+			(void)fclose(fp);
+			return FAIL;
+		}
+
+		DBG(fprintf(stderr, "dumping: %s\n", path));
+		DBG(dump_file(path));
+
+skip:
+		;
+	}
+
+
+	(void)fclose(fp);
+
+	return OK;
+}
+
+/* set up/verify binfmt FS support, program more binfmts, and launch build */
+int main(int argc, char* argv[], char* env[])
+{
+	int retval;
+	char buf[BUFSIZ];
+
+	/* mount proc filesystem if it isn't already */
+	if (mount("proc", "/proc", "proc", MS_MGC_VAL, NULL) == -1) {
+		if (errno != EBUSY) {
+			perror("mount: /proc");
+			exit(1);
+		}
+	}
+
+	/* try to load binfmt module if present, no big deal if it fails */
+	if ((retval = system("/sbin/modprobe binfmt_misc")) != 0) {
+		DBG(fprintf(stderr, "modprobe binfmt_misc exit code %d\n",
+			retval));
+	}
+
+	/* mount binfmt filesystem */
+	if (mount("binfmt_misc", SYSFS_BINFMT_MISC, "binfmt_misc", MS_MGC_VAL,
+		NULL) == -1) {
+		if (errno != EBUSY) {
+			perror("mount: binfmt_misc, " SYSFS_BINFMT_MISC);
+		}
+	}
+
+	/* verify all paths resulting from this are OK */
+	if (!test_access_files(rx_files, R_OK|X_OK, "read/search")) {
+		exit(1);
+	}
+	if (!test_access_files(w_files, W_OK, "write")) {
+		exit(1);
+	}
+
+	if (!strfile("/proc/filesystems", "nodev\tbinfmt_misc\n")) {
+		fprintf(stderr,
+			"/proc/filesystems: binfmt_misc support missing\n");
+		exit(1);
+	}
+
+	if (!strfile(SYSFS_BINFMT_MISC_STAT, "enabled\n")) {
+		fprintf(stderr,
+			"%s: binfmt_misc filesystem support not enabled\n",
+			SYSFS_BINFMT_MISC_STAT);
+		exit(1);
+	}
+
+	if (getenv("BUILD_DIR"))
+	    sprintf(buf, "%s/qemu-reg", getenv("BUILD_DIR"));
+
+        if (!buf || !binfmt_register(buf, SYSFS_BINFMT_MISC_REG)) {
+		/* setup all done, do the registration */
+		if (!binfmt_register(BINFMT_REGF_0, SYSFS_BINFMT_MISC_REG)) {
+			fprintf(stderr, "%s: failed. Trying alternate binfmt file\n",
+				BINFMT_REGF_0);
+			if (!binfmt_register(BINFMT_REGF_1, SYSFS_BINFMT_MISC_REG)) {
+				fprintf(stderr, "%s: binfmt registration failed\n",
+					BINFMT_REGF_1);
+				exit(1);
+			}
+		}
+	}
+
+	/* if we are the init process, start build */
+	if (getpid() == 1)
+	{
+		if (access(BUILD, F_OK) != 0) {
+			fprintf(stderr, "%s: build executable missing\n",
+				BUILD);
+			exit(1);
+		}
+		if (access(BUILD, X_OK) != 0) {
+			fprintf(stderr, "%s: not executable\n", BUILD);
+			exit(1);
+		}
+		execve(BUILD, args, env);
+		perror("execve");
+		exit(1);
+	}
+
+	/* success! */
+	exit(0);
+}