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-rw-r--r--resources/utilities/ich9deblob/gbe/struct.h73
1 files changed, 73 insertions, 0 deletions
diff --git a/resources/utilities/ich9deblob/gbe/struct.h b/resources/utilities/ich9deblob/gbe/struct.h
index 294ff30..cbc2635 100644
--- a/resources/utilities/ich9deblob/gbe/struct.h
+++ b/resources/utilities/ich9deblob/gbe/struct.h
@@ -29,12 +29,19 @@
#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
@@ -52,4 +59,70 @@ struct GBEREGIONRECORD_8K {
// 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