106 lines
3.6 KiB
Markdown
106 lines
3.6 KiB
Markdown
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# Flashing firmware tutorial
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Updating the firmware is possible using the **internal method**, where the updates
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happen from a running system, or using the **external method**, where the system
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is in a shut down state and an external programmer is attached to write into the
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flash IC.
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## Contents
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* [Flashing internaly](int_flashrom.md)
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* [Flashing firmware standalone](ext_standalone.md)
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* [Flashing firmware externally supplying direct power](ext_power.md)
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* [Flashing firmware externally without supplying direct power](no_ext_power.md)
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## General advice
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* It's recommended to only flash the BIOS region.
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* Always verify the firmware image.
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* If you flash externally and have transmission errors:
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* Use short wires
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* Reduce clock frequency
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* Check power supply
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* Make sure that there are no other bus masters (EC, ME, SoC, ...)
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## Internal method
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This method using [flashrom] is available on many platforms, as long as they
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aren't locked down.
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There are various protection schemes that make it impossible to modify or
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replace a firmware from a running system. coreboot allows to disable these
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mechanisms, making it possible to overwrite (or update) the firmware from a
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running system.
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Usually you must use the **external method** once to install a retrofitted
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coreboot and then you can use the **internal method** for future updates.
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There are multiple ways to update the firmware:
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* Using flashrom's *internal* programmer to directly write into the firmware
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flash IC, running on the target machine itself
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* A proprietary software to update the firmware, running on the target machine
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itself
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* A UEFI firmware update capsule
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More details on flashrom's
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* [internal programmer](int_flashrom.md)
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## External method
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External flashing is possible on many platforms, but requires disassembling
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the target hardware. You need to buy a flash programmer, that
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exposes the same interface as your flash IC (likely SPI).
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Please also have a look at the mainboard-specific documentation for details.
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After exposing the firmware flash IC, read the schematics and use one of the
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possible methods:
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* [Flashing firmware standalone](ext_standalone.md)
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* [Flashing firmware externally supplying direct power](ext_power.md)
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* [Flashing firmware externally without supplying direct power](no_ext_power.md)
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**WARNING:** Using the wrong method or accidentally using the wrong pinout might
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permanently damage your hardware!
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## Using a layout file
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On platforms where the flash IC is shared with other components you might want
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to write only a part of the flash IC. On Intel for example there are IFD, ME and
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GBE which don't need to be updated to install coreboot.
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To make [flashrom] only write the *bios* region, leaving Intel ME and Intel IFD
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untouched, you can use a layout file, which can be created using ifdtool
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```bash
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ifdtool -f rom.layout coreboot.rom
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```
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and looks similar to:
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```
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00000000:00000fff fd
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00500000:00bfffff bios
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00003000:004fffff me
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00001000:00002fff gbe
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```
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By specifying *-l* and *-i* [flashrom] writes a single region:
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```bash
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flashrom -l rom.layout -i bios -w coreboot.rom -p <programmer>
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```
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## Using an IFD to determine the layout
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flashrom version 1.0 supports reading the layout from the IFD (first 4KiB of
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the ROM). You don't need to manually specify a layout it, but it only works
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under the following conditions:
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* Only available on Intel ICH7+
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* There's only one flash IC when flashing externally
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```bash
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flashrom --ifd -i bios -w coreboot.rom -p <programmer>
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```
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**TODO** explain FMAP regions, normal/fallback mechanism, flash lock mechanisms
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[flashrom]: https://www.flashrom.org/Flashrom
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