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43 lines
2.9 KiB
Markdown
43 lines
2.9 KiB
Markdown
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# T440p Blobs
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- [Overview](#overview)
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- [Using Your Own Blobs](#using-your-own-blobs)
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## Overview
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Coreboot on the T440p requires the following binary blobs:
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- `mrc.bin` - Consists of Intel’s Memory Reference Code (MRC) and [is used to initialize the DRAM](https://doc.coreboot.org/northbridge/intel/haswell/mrc.bin.html).
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- `me.bin` - Consists of Intel’s Management Engine (ME), which we modify using [me_cleaner](https://github.com/corna/me_cleaner) to remove all but the modules which are necessary for the CPU to function.
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- `gbe.bin` - Consists of hardware/software configuration data for the Gigabit Ethernet (GbE) controller. Intel publishes the data structure [here](https://web.archive.org/web/20230122164346/https://www.intel.com/content/dam/www/public/us/en/documents/design-guides/i-o-controller-hub-8-9-nvm-map-guide.pdf), and an [ImHex](https://github.com/WerWolv/ImHex) hex editor pattern is available [here](https://github.com/rbreslow/ImHex-Patterns/blob/rb/intel-ich8/patterns/intel/ich8_lan_nvm.hexpat).
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- `ifd.bin` - Consists of the Intel Flash Descriptor (IFD). Intel publishes the data structure [here](https://web.archive.org/web/20221208011432/https://www.intel.com/content/dam/www/public/us/en/documents/datasheets/io-controller-hub-8-datasheet.pdf), and an ImHex hex editor pattern is available [here](https://github.com/rbreslow/ImHex-Patterns/blob/rb/intel-ich8/patterns/intel/ich8_flash_descriptor.hexpat).
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Heads supplies an IFD and GbE blob, which we extracted from a donor board. We changed the MAC address of the GbE blob to `00:de:ad:c0:ff:ee` using [nvmutil](https://libreboot.org/docs/install/nvmutil.html), to support anonymity and build reproducibility.
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When building any T440p board variant with `make`, the build system will download a copy of the MRC and Intel ME. We extract `mrc.bin` from a Chromebook firmware image and `me.bin` from a Lenovo firmware update.
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## Using Your Own Blobs
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You can compile Heads using the Intel ME, GbE, and and IFD blobs from your original ROM.
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However, it's worth noting that our analysis showed [no tangible difference](https://github.com/osresearch/heads/pull/1282#issuecomment-1386292403) between the Intel ME from a donor board and Lenovo's website. Also, we found [no meaningful difference](https://github.com/osresearch/heads/pull/1282#issuecomment-1400634600) between the IFD and and GbE blobs extracted from two T440ps, asides from the LAN MAC address.
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First, make sure you've built Heads at least once in order to download the Coreboot sources:
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```console
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$ make BOARD=t440p-hotp-maximized
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```
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Then, supply the path to the Coreboot sources via the `COREBOOT_DIR` environment variable, and run the blob-extraction script:
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```console
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$ export COREBOOT_DIR="./build/x86/coreboot-4.17/"
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$ ./blobs/t440p/extract /path/to/original_rom.bin ./blobs/t440p
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```
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Now, you can rebuild Heads:
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```console
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$ make BOARD=t440p-hotp-maximized
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```
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