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>

2 files changed, 146 insertions, 1 deletions

diff --git a/lib/Makefile b/lib/Makefile
index 42d283edc4d3..0924041b6959 100644
--- a/lib/Makefile
+++ b/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
diff --git a/lib/earlycpio.c b/lib/earlycpio.c
new file mode 100644
index 000000000000..8078ef49cb79
--- /dev/null
+++ b/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;
+}