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lib: Add early cpio decoder

Add a simple cpio decoder without library dependencies for the purpose
of extracting components from the initramfs blob for early kernel
uses.  Intended consumers so far are microcode and ACPI override.

Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
Link: http://lkml.kernel.org/r/1349043837-22659-2-git-send-email-trenn@suse.de
Cc: Len Brown <lenb@kernel.org>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Signed-off-by: Thomas Renninger <trenn@suse.de>
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
  • Loading branch information...
commit e6459606b04e6385ccd3c2060fc10f78a92c7700 1 parent 979570e
H. Peter Anvin authored
Showing with 163 additions and 1 deletion.
  1. +17 −0 include/linux/earlycpio.h
  2. +1 −1  lib/Makefile
  3. +145 −0 lib/earlycpio.c
View
17 include/linux/earlycpio.h
@@ -0,0 +1,17 @@
+#ifndef _LINUX_EARLYCPIO_H
+#define _LINUX_EARLYCPIO_H
+
+#include <linux/types.h>
+
+#define MAX_CPIO_FILE_NAME 18
+
+struct cpio_data {
+ void *data;
+ size_t size;
+ char name[MAX_CPIO_FILE_NAME];
+};
+
+struct cpio_data find_cpio_data(const char *path, void *data, size_t len,
+ long *offset);
+
+#endif /* _LINUX_EARLYCPIO_H */
View
2  lib/Makefile
@@ -12,7 +12,7 @@ lib-y := ctype.o string.o vsprintf.o cmdline.o \
idr.o int_sqrt.o extable.o prio_tree.o \
sha1.o md5.o irq_regs.o reciprocal_div.o argv_split.o \
proportions.o flex_proportions.o prio_heap.o ratelimit.o show_mem.o \
- is_single_threaded.o plist.o decompress.o
+ is_single_threaded.o plist.o decompress.o earlycpio.o
lib-$(CONFIG_MMU) += ioremap.o
lib-$(CONFIG_SMP) += cpumask.o
View
145 lib/earlycpio.c
@@ -0,0 +1,145 @@
+/* ----------------------------------------------------------------------- *
+ *
+ * Copyright 2012 Intel Corporation; author H. Peter Anvin
+ *
+ * This file is part of the Linux kernel, and is made available
+ * under the terms of the GNU General Public License version 2, as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * General Public License for more details.
+ *
+ * ----------------------------------------------------------------------- */
+
+/*
+ * earlycpio.c
+ *
+ * Find a specific cpio member; must precede any compressed content.
+ * This is used to locate data items in the initramfs used by the
+ * kernel itself during early boot (before the main initramfs is
+ * decompressed.) It is the responsibility of the initramfs creator
+ * to ensure that these items are uncompressed at the head of the
+ * blob. Depending on the boot loader or package tool that may be a
+ * separate file or part of the same file.
+ */
+
+#include <linux/earlycpio.h>
+#include <linux/kernel.h>
+#include <linux/string.h>
+
+enum cpio_fields {
+ C_MAGIC,
+ C_INO,
+ C_MODE,
+ C_UID,
+ C_GID,
+ C_NLINK,
+ C_MTIME,
+ C_FILESIZE,
+ C_MAJ,
+ C_MIN,
+ C_RMAJ,
+ C_RMIN,
+ C_NAMESIZE,
+ C_CHKSUM,
+ C_NFIELDS
+};
+
+/**
+ * cpio_data find_cpio_data - Search for files in an uncompressed cpio
+ * @path: The directory to search for, including a slash at the end
+ * @data: Pointer to the the cpio archive or a header inside
+ * @len: Remaining length of the cpio based on data pointer
+ * @offset: When a matching file is found, this is the offset to the
+ * beginning of the cpio. It can be used to iterate through
+ * the cpio to find all files inside of a directory path
+ *
+ * @return: struct cpio_data containing the address, length and
+ * filename (with the directory path cut off) of the found file.
+ * If you search for a filename and not for files in a directory,
+ * pass the absolute path of the filename in the cpio and make sure
+ * the match returned an empty filename string.
+ */
+
+struct cpio_data __cpuinit find_cpio_data(const char *path, void *data,
+ size_t len, long *offset)
+{
+ const size_t cpio_header_len = 8*C_NFIELDS - 2;
+ struct cpio_data cd = { NULL, 0, "" };
+ const char *p, *dptr, *nptr;
+ unsigned int ch[C_NFIELDS], *chp, v;
+ unsigned char c, x;
+ size_t mypathsize = strlen(path);
+ int i, j;
+
+ p = data;
+
+ while (len > cpio_header_len) {
+ if (!*p) {
+ /* All cpio headers need to be 4-byte aligned */
+ p += 4;
+ len -= 4;
+ continue;
+ }
+
+ j = 6; /* The magic field is only 6 characters */
+ chp = ch;
+ for (i = C_NFIELDS; i; i--) {
+ v = 0;
+ while (j--) {
+ v <<= 4;
+ c = *p++;
+
+ x = c - '0';
+ if (x < 10) {
+ v += x;
+ continue;
+ }
+
+ x = (c | 0x20) - 'a';
+ if (x < 6) {
+ v += x + 10;
+ continue;
+ }
+
+ goto quit; /* Invalid hexadecimal */
+ }
+ *chp++ = v;
+ j = 8; /* All other fields are 8 characters */
+ }
+
+ if ((ch[C_MAGIC] - 0x070701) > 1)
+ goto quit; /* Invalid magic */
+
+ len -= cpio_header_len;
+
+ dptr = PTR_ALIGN(p + ch[C_NAMESIZE], 4);
+ nptr = PTR_ALIGN(dptr + ch[C_FILESIZE], 4);
+
+ if (nptr > p + len || dptr < p || nptr < dptr)
+ goto quit; /* Buffer overrun */
+
+ if ((ch[C_MODE] & 0170000) == 0100000 &&
+ ch[C_NAMESIZE] >= mypathsize &&
+ !memcmp(p, path, mypathsize)) {
+ *offset = (long)nptr - (long)data;
+ if (ch[C_NAMESIZE] - mypathsize >= MAX_CPIO_FILE_NAME) {
+ pr_warn(
+ "File %s exceeding MAX_CPIO_FILE_NAME [%d]\n",
+ p, MAX_CPIO_FILE_NAME);
+ }
+ strlcpy(cd.name, p + mypathsize, MAX_CPIO_FILE_NAME);
+
+ cd.data = (void *)dptr;
+ cd.size = ch[C_FILESIZE];
+ return cd; /* Found it! */
+ }
+ len -= (nptr - p);
+ p = nptr;
+ }
+
+quit:
+ return cd;
+}
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