initramfs: add option to preserve mtime from initramfs cpio images

When unpacking the cpio into the initramfs, mtimes are not preserved by default. This patch adds an INITRAMFS_PRESERVE_MTIME option that allows mtimes stored in the cpio image to be used when constructing the initramfs. For embedded applications that run exclusively out of the initramfs, this is invaluable: When building embedded application initramfs images, its nice to know when the files were actually created during the build process - that makes it easier to see what files were modified when so we can compare the files that are being used on the image with the files used during the build process. This might help (for example) to determine if the target system has all the updated files you expect to see w/o having to check MD5s etc. In our environment, the whole system runs off the initramfs partition, and seeing the modified times of the shared libraries (for example) helps us find bugs that may have been introduced by the build system incorrectly propogating outdated shared libraries into the image. Similarly, many of the initializion/configuration files in /etc might be dynamically built by the build system, and knowing when they were modified helps us sanity check whether the target system has the "latest" files etc. Finally, we might use last modified times to determine whether a hot fix should be applied or not to the running ramfs. Signed-off-by: Nye Liu <nyet@nyet.org> Cc: Al Viro <viro@zeniv.linux.org.uk> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

initramfs: add option to preserve mtime from initramfs cpio images
When unpacking the cpio into the initramfs, mtimes are not preserved by default. This patch adds an INITRAMFS_PRESERVE_MTIME option that allows mtimes stored in the cpio image to be used when constructing the initramfs. For embedded applications that run exclusively out of the initramfs, this is invaluable: When building embedded application initramfs images, its nice to know when the files were actually created during the build process - that makes it easier to see what files were modified when so we can compare the files that are being used on the image with the files used during the build process. This might help (for example) to determine if the target system has all the updated files you expect to see w/o having to check MD5s etc. In our environment, the whole system runs off the initramfs partition, and seeing the modified times of the shared libraries (for example) helps us find bugs that may have been introduced by the build system incorrectly propogating outdated shared libraries into the image. Similarly, many of the initializion/configuration files in /etc might be dynamically built by the build system, and knowing when they were modified helps us sanity check whether the target system has the "latest" files etc. Finally, we might use last modified times to determine whether a hot fix should be applied or not to the running ramfs. Signed-off-by: Nye Liu <nyet@nyet.org> Cc: Al Viro <viro@zeniv.linux.org.uk> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Nye Liu · Linus Torvalds
1 parent 9ba16087d9
Showing 1 changed file with 53 additions and 0 deletions Side-by-side Diff
init/initramfs.c
@@ -6,6 +6,7 @@
 #include <linux/delay.h>
 #include <linux/string.h>
 #include <linux/syscalls.h>
+#include <linux/utime.h>
  
 static __initdata char *message;
 static void __init error(char *x)
@@ -72,6 +73,49 @@
 	}
 }
  
+static long __init do_utime(char __user *filename, time_t mtime)
+{
+	struct timespec t[2];
+
+	t[0].tv_sec = mtime;
+	t[0].tv_nsec = 0;
+	t[1].tv_sec = mtime;
+	t[1].tv_nsec = 0;
+
+	return do_utimes(AT_FDCWD, filename, t, AT_SYMLINK_NOFOLLOW);
+}
+
+static __initdata LIST_HEAD(dir_list);
+struct dir_entry {
+	struct list_head list;
+	char *name;
+	time_t mtime;
+};
+
+static void __init dir_add(const char *name, time_t mtime)
+{
+	struct dir_entry *de = kmalloc(sizeof(struct dir_entry), GFP_KERNEL);
+	if (!de)
+		panic("can't allocate dir_entry buffer");
+	INIT_LIST_HEAD(&de->list);
+	de->name = kstrdup(name, GFP_KERNEL);
+	de->mtime = mtime;
+	list_add(&de->list, &dir_list);
+}
+
+static void __init dir_utime(void)
+{
+	struct dir_entry *de, *tmp;
+	list_for_each_entry_safe(de, tmp, &dir_list, list) {
+		list_del(&de->list);
+		do_utime(de->name, de->mtime);
+		kfree(de->name);
+		kfree(de);
+	}
+}
+
+static __initdata time_t mtime;
+
 /* cpio header parsing */
  
 static __initdata unsigned long ino, major, minor, nlink;
@@ -97,6 +141,7 @@
 	uid = parsed[2];
 	gid = parsed[3];
 	nlink = parsed[4];
+	mtime = parsed[5];
 	body_len = parsed[6];
 	major = parsed[7];
 	minor = parsed[8];
@@ -130,6 +175,7 @@
 	count -= n;
 }
  
+static __initdata char *vcollected;
 static __initdata char *collected;
 static __initdata int remains;
 static __initdata char *collect;
@@ -271,6 +317,7 @@
 			if (wfd >= 0) {
 				sys_fchown(wfd, uid, gid);
 				sys_fchmod(wfd, mode);
+				vcollected = kstrdup(collected, GFP_KERNEL);
 				state = CopyFile;
 			}
 		}
  
@@ -278,12 +325,14 @@
 		sys_mkdir(collected, mode);
 		sys_chown(collected, uid, gid);
 		sys_chmod(collected, mode);
+		dir_add(collected, mtime);
 	} else if (S_ISBLK(mode) || S_ISCHR(mode) ||
 		   S_ISFIFO(mode) || S_ISSOCK(mode)) {
 		if (maybe_link() == 0) {
 			sys_mknod(collected, mode, rdev);
 			sys_chown(collected, uid, gid);
 			sys_chmod(collected, mode);
+			do_utime(collected, mtime);
 		}
 	}
 	return 0;
@@ -294,6 +343,8 @@
 	if (count >= body_len) {
 		sys_write(wfd, victim, body_len);
 		sys_close(wfd);
+		do_utime(vcollected, mtime);
+		kfree(vcollected);
 		eat(body_len);
 		state = SkipIt;
 		return 0;
@@ -311,6 +362,7 @@
 	clean_path(collected, 0);
 	sys_symlink(collected + N_ALIGN(name_len), collected);
 	sys_lchown(collected, uid, gid);
+	do_utime(collected, mtime);
 	state = SkipIt;
 	next_state = Reset;
 	return 0;
@@ -466,6 +518,7 @@
 		buf += inptr;
 		len -= inptr;
 	}
+	dir_utime();
 	kfree(window);
 	kfree(name_buf);
 	kfree(symlink_buf);
...	...	@@ -6,6 +6,7 @@
6	6	#include <linux/delay.h>
7	7	#include <linux/string.h>
8	8	#include <linux/syscalls.h>
	9	+#include <linux/utime.h>
9	10
10	11	static __initdata char *message;
11	12	static void __init error(char *x)
...	...	@@ -72,6 +73,49 @@
72	73	}
73	74	}
74	75
	76	+static long __init do_utime(char __user *filename, time_t mtime)
	77	+{
	78	+ struct timespec t[2];
	79	+
	80	+ t[0].tv_sec = mtime;
	81	+ t[0].tv_nsec = 0;
	82	+ t[1].tv_sec = mtime;
	83	+ t[1].tv_nsec = 0;
	84	+
	85	+ return do_utimes(AT_FDCWD, filename, t, AT_SYMLINK_NOFOLLOW);
	86	+}
	87	+
	88	+static __initdata LIST_HEAD(dir_list);
	89	+struct dir_entry {
	90	+ struct list_head list;
	91	+ char *name;
	92	+ time_t mtime;
	93	+};
	94	+
	95	+static void __init dir_add(const char *name, time_t mtime)
	96	+{
	97	+ struct dir_entry *de = kmalloc(sizeof(struct dir_entry), GFP_KERNEL);
	98	+ if (!de)
	99	+ panic("can't allocate dir_entry buffer");
	100	+ INIT_LIST_HEAD(&de->list);
	101	+ de->name = kstrdup(name, GFP_KERNEL);
	102	+ de->mtime = mtime;
	103	+ list_add(&de->list, &dir_list);
	104	+}
	105	+
	106	+static void __init dir_utime(void)
	107	+{
	108	+ struct dir_entry de, tmp;
	109	+ list_for_each_entry_safe(de, tmp, &dir_list, list) {
	110	+ list_del(&de->list);
	111	+ do_utime(de->name, de->mtime);
	112	+ kfree(de->name);
	113	+ kfree(de);
	114	+ }
	115	+}
	116	+
	117	+static __initdata time_t mtime;
	118	+
75	119	/* cpio header parsing */
76	120
77	121	static __initdata unsigned long ino, major, minor, nlink;
...	...	@@ -97,6 +141,7 @@
97	141	uid = parsed[2];
98	142	gid = parsed[3];
99	143	nlink = parsed[4];
	144	+ mtime = parsed[5];
100	145	body_len = parsed[6];
101	146	major = parsed[7];
102	147	minor = parsed[8];
...	...	@@ -130,6 +175,7 @@
130	175	count -= n;
131	176	}
132	177
	178	+static __initdata char *vcollected;
133	179	static __initdata char *collected;
134	180	static __initdata int remains;
135	181	static __initdata char *collect;
...	...	@@ -271,6 +317,7 @@
271	317	if (wfd >= 0) {
272	318	sys_fchown(wfd, uid, gid);
273	319	sys_fchmod(wfd, mode);
	320	+ vcollected = kstrdup(collected, GFP_KERNEL);
274	321	state = CopyFile;
275	322	}
276	323	}
277	324
...	...	@@ -278,12 +325,14 @@
278	325	sys_mkdir(collected, mode);
279	326	sys_chown(collected, uid, gid);
280	327	sys_chmod(collected, mode);
	328	+ dir_add(collected, mtime);
281	329	} else if (S_ISBLK(mode) \|\| S_ISCHR(mode) \|\|
282	330	S_ISFIFO(mode) \|\| S_ISSOCK(mode)) {
283	331	if (maybe_link() == 0) {
284	332	sys_mknod(collected, mode, rdev);
285	333	sys_chown(collected, uid, gid);
286	334	sys_chmod(collected, mode);
	335	+ do_utime(collected, mtime);
287	336	}
288	337	}
289	338	return 0;
...	...	@@ -294,6 +343,8 @@
294	343	if (count >= body_len) {
295	344	sys_write(wfd, victim, body_len);
296	345	sys_close(wfd);
	346	+ do_utime(vcollected, mtime);
	347	+ kfree(vcollected);
297	348	eat(body_len);
298	349	state = SkipIt;
299	350	return 0;
...	...	@@ -311,6 +362,7 @@
311	362	clean_path(collected, 0);
312	363	sys_symlink(collected + N_ALIGN(name_len), collected);
313	364	sys_lchown(collected, uid, gid);
	365	+ do_utime(collected, mtime);
314	366	state = SkipIt;
315	367	next_state = Reset;
316	368	return 0;
...	...	@@ -466,6 +518,7 @@
466	518	buf += inptr;
467	519	len -= inptr;
468	520	}
	521	+ dir_utime();
469	522	kfree(window);
470	523	kfree(name_buf);
471	524	kfree(symlink_buf);