diff options
Diffstat (limited to 'resources')
| -rw-r--r-- | resources/utilities/ich9deblob/ich9deblob.c | 49 |
1 files changed, 34 insertions, 15 deletions
diff --git a/resources/utilities/ich9deblob/ich9deblob.c b/resources/utilities/ich9deblob/ich9deblob.c index 612c75d4..aa55a1f0 100644 --- a/resources/utilities/ich9deblob/ich9deblob.c +++ b/resources/utilities/ich9deblob/ich9deblob.c @@ -3,6 +3,7 @@ * * gcc -o ich9deblob ich9deblob.c ich9desc.c -I. * + * Copyright (C) 2014 Francis Rowe <info@gluglug.org.uk> * Copyright (C) 2014 Steve Shenton <sgsit@libreboot.org> * * This program is free software: you can redistribute it and/or modify @@ -19,58 +20,68 @@ * along with this program. If not, see <http://www.gnu.org/licenses/>. */ - #include <stdio.h> #include <string.h> -#include "ich9desc.c" +#include "ich9desc.c" // structs describing what's in the descriptor and gbe regions -#define DESCRIPTORREGIONSIZE 0x1000 -#define GBEREGIONSIZE 0x2000 +#define DESCRIPTORREGIONSIZE 0x1000 // 4096 bytes / 4KiB +#define GBEREGIONSIZE 0x2000 // 8192 bytes / 8KiB -unsigned short GetChecksum(char* buffer, unsigned short desiredValue); -unsigned short GetRegionWord(int i, char* buffer); +unsigned short GetChecksum(char* buffer, unsigned short desiredValue); // for GBe region (checksum calculation) +unsigned short GetRegionWord(int i, char* buffer); // used for getting each word needed to calculate said checksum int main(int argc, char *argv[]) { // check compiler bit-packs in a compatible way struct DESCRIPTORREGIONRECORD descriptorRegion; unsigned int descriptorRegionStructSize = sizeof(descriptorRegion); - + // basically, it is expected that this code will be used on x86 if (DESCRIPTORREGIONSIZE != descriptorRegionStructSize){ printf("\nerror: compiler incompatibility: descriptor struct length is %i bytes (should be %i)\n", descriptorRegionStructSize, DESCRIPTORREGIONSIZE); return 1; } + // supplied by user, dumped from their machine before flashing libreboot char* factoryRomFilename = "factory.rom"; + // name of the file that this utility will create (deblobbed descriptor+gbe) char* deblobbedDescriptorFilename = "deblobbed_descriptor.bin"; + // Open factory.rom, needed for extracting descriptor and gbe + // ----------------------------------------------- FILE* fp = NULL; - fp = fopen(factoryRomFilename, "rb"); - + fp = fopen(factoryRomFilename, "rb"); // open factory.rom if (NULL == fp) { printf("\nerror: could not open factory.rom\n"); return 1; } - printf("\nfactory.rom opened successfully\n"); + // ----------------------------------------------- + // Create empty descriptor buffer (populated below) char descriptorBuffer[DESCRIPTORREGIONSIZE]; + // Extract the descriptor region from the factory.rom dump + // (goes in descriptorBuffer variable) unsigned int readLen; readLen = fread(descriptorBuffer, sizeof(char), DESCRIPTORREGIONSIZE, fp); - if (DESCRIPTORREGIONSIZE != readLen) + if (DESCRIPTORREGIONSIZE != readLen) // { printf("\nerror: could not read descriptor from factory.rom (%i) bytes read\n", readLen); return 1; } - printf("\ndescriptor region read successfully\n"); // copy descriptor buffer into descriptor struct memory + // descriptorRegion is an instance of a struct that actually + // defines the locations of all these variables in the descriptor, + // as defined in the datasheets. This allows us to map the extracted + // descriptor over the struct so that it can then be modified + // for libreboot's purpose memcpy(&descriptorRegion, &descriptorBuffer, DESCRIPTORREGIONSIZE); // get original GBe region location + // (it will be moved to the beginning of the flash, after the descriptor region) unsigned int flRegionBitShift = 12; unsigned int gbeRegionLocation = descriptorRegion.regionSection.flReg3.BASE << flRegionBitShift; @@ -85,7 +96,8 @@ int main(int argc, char *argv[]) return 1; } - // get rom size + // Get size of ROM image + // This is needed for relocating the BIOS region (per descriptor) fseek(fp, 0L, SEEK_END); int romSize = ftell(fp); @@ -130,7 +142,7 @@ int main(int argc, char *argv[]) // disable ME, apart from chipset bugfixes (ME region still required) //descriptorRegion.mchStraps.mchStrap0.meAlternateDisable = 1; - + // debugging printf("\nRelocated Descriptor start block: %08x ; Descriptor end block: %08x\n", descriptorRegion.regionSection.flReg0.BASE << flRegionBitShift, descriptorRegion.regionSection.flReg0.LIMIT << flRegionBitShift); printf("Relocated BIOS start block: %08x ; BIOS end block: %08x\n", descriptorRegion.regionSection.flReg1.BASE << flRegionBitShift, descriptorRegion.regionSection.flReg1.LIMIT << flRegionBitShift); printf("Relocated ME start block: %08x ; ME end block: %08x\n", descriptorRegion.regionSection.flReg2.BASE << flRegionBitShift, descriptorRegion.regionSection.flReg2.LIMIT << flRegionBitShift); @@ -159,7 +171,13 @@ int main(int argc, char *argv[]) printf("\ndeblobbed descriptor successfully created: deblobbed_descriptor.bin \n"); - unsigned short gbeCalculatedChecksum = GetChecksum(gbeBuffer, 0xBABA); // observed values 0xBABA 0x3ABA 0x34BA. spec defined as 0xBABA. + // calculate the 0x3F'th 16-bit uint to make the desired final checksum for GBe + // observed values (from actual factory.rom dumps) 0xBABA 0x3ABA 0x34BA. spec defined as 0xBABA. + // theoretically, this could be any l33t speak variation of BABA, eg 3434 or BA34, and so on, but this is untested. so far. + // 40BA was also observed in another factory dump for another X200 - this is not l33t speak. + // maybe only the 8 least significant bits are checked? or something deeper than that + unsigned short gbeCalculatedChecksum = GetChecksum(gbeBuffer, 0xBABA); + // get the actual 0x3F'th 16-bit uint that was already in the supplied (pre-compiled) region data unsigned short gbeChecksum = GetRegionWord(0x3F, gbeBuffer); printf("\ncalculated Gbe checksum: 0x%hx actual GBe checksum: 0x%hx\n", gbeCalculatedChecksum, gbeChecksum); @@ -181,6 +199,7 @@ unsigned short GetChecksum(char* regionData, unsigned short desiredValue) return checksum; } +// Read a 16-bit unsigned int from a supplied region buffer unsigned short GetRegionWord(int index, char* regionData) { return *((unsigned short*)(regionData + (index * 2))); |