Minimal initramfs support (based on Al Viro's work).

2 files changed, 155 insertions, 0 deletions

diff --git a/usr/Makefile b/usr/Makefile
new file mode 100644
index 00000000000000..d3c2c0bb8773b6
--- /dev/null
+++ b/usr/Makefile
@@ -0,0 +1,18 @@
+
+include arch/$(ARCH)/Makefile
+
+obj-y := initramfs_data.o
+
+host-progs := gen_init_cpio
+
+clean-files := initramfs_data.cpio.gz
+
+$(obj)/initramfs_data.o: $(obj)/initramfs_data.cpio.gz
+	$(OBJCOPY) $(ARCHBLOBLFLAGS) \
+		--rename-section .data=.init.initramfs \
+		$(obj)/initramfs_data.cpio.gz $(obj)/initramfs_data.o
+	$(STRIP) -s $(obj)/initramfs_data.o
+
+$(obj)/initramfs_data.cpio.gz: $(obj)/gen_init_cpio
+	( cd $(obj) ; ./gen_init_cpio | gzip -9c > initramfs_data.cpio.gz )
+
diff --git a/usr/gen_init_cpio.c b/usr/gen_init_cpio.c
new file mode 100644
index 00000000000000..a6024faf9d02d7
--- /dev/null
+++ b/usr/gen_init_cpio.c
@@ -0,0 +1,137 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <string.h>
+#include <unistd.h>
+#include <time.h>
+
+static unsigned int offset;
+static unsigned int ino = 721;
+
+static void push_rest(const char *name)
+{
+	unsigned int name_len = strlen(name) + 1;
+	unsigned int tmp_ofs;
+
+	fputs(name, stdout);
+	putchar(0);
+	offset += name_len;
+
+	tmp_ofs = name_len + 110;
+	while (tmp_ofs & 3) {
+		putchar(0);
+		offset++;
+		tmp_ofs++;
+	}
+}
+
+static void push_hdr(const char *s)
+{
+	fputs(s, stdout);
+	offset += 110;
+}
+
+static void cpio_trailer(void)
+{
+	char s[256];
+	const char *name = "TRAILER!!!";
+
+	sprintf(s, "%s%08X%08X%08lX%08lX%08X%08lX"
+	       "%08X%08X%08X%08X%08X%08X%08X",
+		"070701",		/* magic */
+		0,			/* ino */
+		0,			/* mode */
+		(long) 0,		/* uid */
+		(long) 0,		/* gid */
+		1,			/* nlink */
+		(long) 0,		/* mtime */
+		0,			/* filesize */
+		0,			/* major */
+		0,			/* minor */
+		0,			/* rmajor */
+		0,			/* rminor */
+		strlen(name) + 1,	/* namesize */
+		0);			/* chksum */
+	push_hdr(s);
+	push_rest(name);
+
+	while (offset % 512) {
+		putchar(0);
+		offset++;
+	}
+}
+
+static void cpio_mkdir(const char *name, unsigned int mode,
+		       uid_t uid, gid_t gid)
+{
+	char s[256];
+	time_t mtime = time(NULL);
+
+	sprintf(s,"%s%08X%08X%08lX%08lX%08X%08lX"
+	       "%08X%08X%08X%08X%08X%08X%08X",
+		"070701",		/* magic */
+		ino++,			/* ino */
+		S_IFDIR | mode,		/* mode */
+		(long) uid,		/* uid */
+		(long) gid,		/* gid */
+		2,			/* nlink */
+		(long) mtime,		/* mtime */
+		0,			/* filesize */
+		3,			/* major */
+		1,			/* minor */
+		0,			/* rmajor */
+		0,			/* rminor */
+		strlen(name) + 1,	/* namesize */
+		0);			/* chksum */
+	push_hdr(s);
+	push_rest(name);
+}
+
+static void cpio_mknod(const char *name, unsigned int mode,
+		       uid_t uid, gid_t gid, int dev_type,
+		       unsigned int maj, unsigned int min)
+{
+	char s[256];
+	time_t mtime = time(NULL);
+
+	if (dev_type == 'b')
+		mode |= S_IFBLK;
+	else
+		mode |= S_IFCHR;
+
+	sprintf(s,"%s%08X%08X%08lX%08lX%08X%08lX"
+	       "%08X%08X%08X%08X%08X%08X%08X",
+		"070701",		/* magic */
+		ino++,			/* ino */
+		mode,			/* mode */
+		(long) uid,		/* uid */
+		(long) gid,		/* gid */
+		1,			/* nlink */
+		(long) mtime,		/* mtime */
+		0,			/* filesize */
+		3,			/* major */
+		1,			/* minor */
+		maj,			/* rmajor */
+		min,			/* rminor */
+		strlen(name) + 1,	/* namesize */
+		0);			/* chksum */
+	push_hdr(s);
+	push_rest(name);
+}
+
+int main (int argc, char *argv[])
+{
+	cpio_mkdir("/dev", 0700, 0, 0);
+	cpio_mknod("/dev/console", 0600, 0, 0, 'c', 5, 1);
+	cpio_mkdir("/root", 0700, 0, 0);
+	cpio_trailer();
+
+	exit(0);
+
+	/* silence compiler warnings */
+	return 0;
+	(void) argc;
+	(void) argv;
+}
+