diff options
Diffstat (limited to 'resources/utilities/ich9deblob/gbe')
| -rw-r--r-- | resources/utilities/ich9deblob/gbe/struct.h | 73 |
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 |