init: add initramfs_internal.h

The new header only exports a single unpack function and a CPIO_HDRLEN
constant for future test use.

Signed-off-by: David Disseldorp <ddiss@suse.de>
Link: https://lore.kernel.org/r/20250304061020.9815-2-ddiss@suse.de
Signed-off-by: Christian Brauner <brauner@kernel.org>

diff --git a/init/initramfs.c b/init/initramfs.c
index b2f7583bb1f5c2c637880d9cde10446bd60934fc..002e83ae12ac7586cc1bd9328f24505d5d6823da 100644 (file)
--- a/init/initramfs.c
+++ b/init/initramfs.c
@@ -20,6 +20,7 @@
 #include <linux/security.h>
 
 #include "do_mounts.h"
+#include "initramfs_internal.h"
 
 static __initdata bool csum_present;
 static __initdata u32 io_csum;
@@ -256,7 +257,7 @@ static __initdata char *header_buf, *symlink_buf, *name_buf;
 
 static int __init do_start(void)
 {
-       read_into(header_buf, 110, GotHeader);
+       read_into(header_buf, CPIO_HDRLEN, GotHeader);
        return 0;
 }
 
@@ -497,14 +498,23 @@ static unsigned long my_inptr __initdata; /* index of next byte to be processed
 
 #include <linux/decompress/generic.h>
 
-static char * __init unpack_to_rootfs(char *buf, unsigned long len)
+/**
+ * unpack_to_rootfs - decompress and extract an initramfs archive
+ * @buf: input initramfs archive to extract
+ * @len: length of initramfs data to process
+ *
+ * Returns: NULL for success or an error message string
+ *
+ * This symbol shouldn't be used externally. It's available for unit tests.
+ */
+char * __init unpack_to_rootfs(char *buf, unsigned long len)
 {
        long written;
        decompress_fn decompress;
        const char *compress_name;
        static __initdata char msg_buf[64];
 
-       header_buf = kmalloc(110, GFP_KERNEL);
+       header_buf = kmalloc(CPIO_HDRLEN, GFP_KERNEL);
        symlink_buf = kmalloc(PATH_MAX + N_ALIGN(PATH_MAX) + 1, GFP_KERNEL);
        name_buf = kmalloc(N_ALIGN(PATH_MAX), GFP_KERNEL);
 

diff --git a/init/initramfs_internal.h b/init/initramfs_internal.h
new file mode 100644 (file)
index 0000000..233dad1
--- /dev/null
+++ b/init/initramfs_internal.h
@@ -0,0 +1,8 @@
+// SPDX-License-Identifier: GPL-2.0
+#ifndef __INITRAMFS_INTERNAL_H__
+#define __INITRAMFS_INTERNAL_H__
+
+char *unpack_to_rootfs(char *buf, unsigned long len);
+#define CPIO_HDRLEN 110
+
+#endif