diff options
Diffstat (limited to 'resources/utilities/ich9deblob/gbe/gbe.c')
| -rw-r--r-- | resources/utilities/ich9deblob/gbe/gbe.c | 107 |
1 files changed, 107 insertions, 0 deletions
diff --git a/resources/utilities/ich9deblob/gbe/gbe.c b/resources/utilities/ich9deblob/gbe/gbe.c new file mode 100644 index 0000000..b1c55dd --- /dev/null +++ b/resources/utilities/ich9deblob/gbe/gbe.c @@ -0,0 +1,107 @@ +/* + * gbe/gbe.c + * 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/>. + */ + +/* + * Provide gbe related functions. + */ + +#include <stdio.h> +#include <string.h> + +/* structs describing the data from gbe region */ +#include "gbe.h" + +/* + * --------------------------------------------------------------------- + * 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) + * this function uses *word* not *byte* indexes, hence the bit shift. + */ + if (isBackup) offset = GBEREGIONSIZE_4K>>1; + + 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_4K]; + memcpy(&gbeBuffer4k, &gbeStruct4k, GBEREGIONSIZE_4K); + 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 + * it so that the main region is usable. + */ + + struct GBEREGIONRECORD_8K deblobbedGbeStruct8k; + memcpy(&deblobbedGbeStruct8k, &factoryGbeStruct8k, GBEREGIONSIZE_8K); + + deblobbedGbeStruct8k.backup.checkSum = gbeGetChecksumFrom4kStruct(deblobbedGbeStruct8k.backup, 0xBABA); + memcpy(&deblobbedGbeStruct8k.main, &deblobbedGbeStruct8k.backup, GBEREGIONSIZE_4K); + + /* + * 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; +} |