ich9deblob: move gbe/struct.h to gbe/gbe.h

1 files changed, 128 insertions, 0 deletions

diff --git a/resources/utilities/ich9deblob/gbe/gbe.h b/resources/utilities/ich9deblob/gbe/gbe.h
new file mode 100644
index 0000000..cbc2635
--- /dev/null
+++ b/resources/utilities/ich9deblob/gbe/gbe.h
@@ -0,0 +1,128 @@
+/*
+ *  gbe/struct.h
+ *  This file is part of the ich9deblob utility from the libreboot project
+ *
+ *  Copyright (C) 2014 Steve Shenton <sgsit@libreboot.org>
+ *                     Francis Rowe <info@gluglug.org.uk>
+ *
+ *  This program is free software: you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation, either version 3 of the License, or
+ *  (at your option) any later version.
+ *
+ *  This program is distributed in the hope that 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.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+ 
+// Purpose: provide struct representing gbe region.
+// Map actual buffers of this regions, directly to instances of these
+// structs. This makes working with gbe really easy.
+ 
+// bit fields used, corresponding to datasheet. See links to datasheets
+// and documentation in ich9deblob.c
+
+#ifndef GBESTRUCT_H
+#define GBESTRUCT_H
+
+#include <stdio.h>
+#include <string.h>
+
+#define GBEREGIONSIZE 0x2000 // 8 KiB
+// These will have a modified descriptor+gbe based on what's in the factory.rom
+// These will be joined into a single 12KiB buffer (descriptor, then gbe) and saved to a file
+// NOTE: The GBE region of 8K is actually 2x 4K regions in a single region; both 4K blocks can be identical (and by default, are)
+// The 2nd one is a "backup", but we don't know when it's used. perhaps it's used when the checksum on the first one does not match?
+
+// ---------------------------------------------------------------------
+// Gbe struct representing the data
+// ---------------------------------------------------------------------
+
+struct GBEREGIONRECORD_4K {
+	unsigned char macAddress[6]; // 0x03 words, or 0x06 bytes
+	unsigned char otherStuff[120];  // 0x3c words, or 0x7E bytes
+	unsigned short checkSum; // when added to the sum of all words above, this should be 0xBABA
+	unsigned char padding1[3968];
+};
+
+// main and backup region in gbe
+struct GBEREGIONRECORD_8K {
+	struct GBEREGIONRECORD_4K main;
+	struct GBEREGIONRECORD_4K backup;
+	// Backup region:
+	// This is actually "main" on X200, since the real main has a bad checksum
+	// and other errors. You should do what you need on this one (if modifying
+	// lenovobios's gbe region) and then copy to main
+};
+
+// ---------------------------------------------------------------------
+// Gbe functions
+// ---------------------------------------------------------------------
+
+// Read a 16-bit unsigned int from a supplied region buffer
+unsigned short gbeGetRegionWordFrom8kBuffer(int index, char* regionData)
+{
+	return *((unsigned short*)(regionData + (index * 2)));
+}
+
+// checksum calculation for 8k gbe region (algorithm based on datasheet)
+// also works for 4k buffers, so long as isBackup remains false
+unsigned short gbeGetChecksumFrom8kBuffer(char* regionData, unsigned short desiredValue, char isBackup)
+{
+	int i;
+	
+	unsigned short regionWord; // store words here for adding to checksum
+	unsigned short checksum = 0; // this gbe's checksum
+	unsigned short offset = 0; // in bytes, from the start of the gbe region.
+	
+	// if isBackup is true, use 2nd gbe region ("backup" region)
+	if (isBackup) offset = 0x1000>>1; // this function uses *word* not *byte* indexes.
+
+	for (i = 0; i < 0x3F; i++) {
+		regionWord = gbeGetRegionWordFrom8kBuffer(i+offset, regionData);
+		checksum += regionWord;
+	}
+	checksum = desiredValue - checksum;
+	return checksum;
+}
+
+// checksum calculation for 4k gbe struct (algorithm based on datasheet)
+unsigned short gbeGetChecksumFrom4kStruct(struct GBEREGIONRECORD_4K gbeStruct4k, unsigned short desiredValue)
+{
+	char gbeBuffer4k[GBEREGIONSIZE>>1];
+	memcpy(&gbeBuffer4k, &gbeStruct4k, GBEREGIONSIZE>>1);
+	return gbeGetChecksumFrom8kBuffer(gbeBuffer4k, desiredValue, 0);
+}
+
+// modify the gbe region extracted from a factory.rom dump 
+struct GBEREGIONRECORD_8K deblobbedGbeStructFromFactory(struct GBEREGIONRECORD_8K factoryGbeStruct8k) 
+{	
+	// Correct the main gbe region. By default, the X200 (as shipped from Lenovo) comes
+	// with a broken main gbe region, where the backup gbe region is used instead. Modify
+	// the descriptor so that the main region is usable.
+	
+	struct GBEREGIONRECORD_8K deblobbedGbeStruct8k;
+	memcpy(&deblobbedGbeStruct8k, &factoryGbeStruct8k, GBEREGIONSIZE);
+	
+	deblobbedGbeStruct8k.backup.checkSum = gbeGetChecksumFrom4kStruct(deblobbedGbeStruct8k.backup, 0xBABA);
+	memcpy(&deblobbedGbeStruct8k.main, &deblobbedGbeStruct8k.backup, GBEREGIONSIZE>>1);
+	
+	// Debugging:
+	// calculate the 0x3F'th 16-bit uint to make the desired final checksum for GBe
+	// observed checksum matches (from X200 factory.rom dumps) on main: 0x3ABA 0x34BA 0x40BA. spec defined as 0xBABA.
+	// X200 ships with a broken main gbe region by default (invalid checksum, and more)
+	// The "backup" gbe regions on these machines are correct, though, and is what the machines default to
+	// For libreboot's purpose, we can do much better than that by fixing the main one... below is only debugging
+	printf("\nfactory Gbe (main): calculated Gbe checksum: 0x%hx and actual GBe checksum: 0x%hx\n", gbeGetChecksumFrom4kStruct(factoryGbeStruct8k.main, 0xBABA), factoryGbeStruct8k.main.checkSum);
+	printf("factory Gbe (backup) calculated Gbe checksum: 0x%hx and actual GBe checksum: 0x%hx\n", gbeGetChecksumFrom4kStruct(factoryGbeStruct8k.backup, 0xBABA), factoryGbeStruct8k.backup.checkSum);
+	printf("\ndeblobbed Gbe (main): calculated Gbe checksum: 0x%hx and actual GBe checksum: 0x%hx\n", gbeGetChecksumFrom4kStruct(deblobbedGbeStruct8k.main, 0xBABA), deblobbedGbeStruct8k.main.checkSum);
+	printf("deblobbed Gbe (backup) calculated Gbe checksum: 0x%hx and actual GBe checksum: 0x%hx\n", gbeGetChecksumFrom4kStruct(deblobbedGbeStruct8k.backup, 0xBABA), deblobbedGbeStruct8k.backup.checkSum);
+	
+	return deblobbedGbeStruct8k;
+}
+
+#endif