lib: Add early cpio decoder
H. Peter Anvin [Sun, 30 Sep 2012 22:23:52 +0000 (00:23 +0200)]
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>

include/linux/earlycpio.h [new file with mode: 0644]
lib/Makefile
lib/earlycpio.c [new file with mode: 0644]

diff --git a/include/linux/earlycpio.h b/include/linux/earlycpio.h
new file mode 100644 (file)
index 0000000..111f46d
--- /dev/null
@@ -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 */
index 42d283e..0924041 100644 (file)
@@ -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
diff --git a/lib/earlycpio.c b/lib/earlycpio.c
new file mode 100644 (file)
index 0000000..8078ef4
--- /dev/null
@@ -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;
+}