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install/nvmutil: Safer cat/de-cat instructions 

Signed-off-by: Leah Rowe <leah@libreboot.org>
master
Leah Rowe 2025-01-04 15:34:11 +00:00
parent 2361a1de72
commit c587cee2ac
1 changed files with 15 additions and 3 deletions
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18
site/docs/install/nvmutil.md
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@ -140,7 +140,16 @@ a single-flash setup. In that case, it's recommended to dump
both chips, as `spi1.rom` and `spi2.rom`; you can then cat
them together:
cat spi1.rom spi2.rom > rom.bin
cat spi1.rom spi2.rom > rom.bin # WARNING: see note below
**WARNING: After concatenating the files, please ensure that you did so in
the correct order. In `hexdump -C rom.bin` you can check for the Intel Flash
Descriptor near the start of the file, for the bytes `5a a5 f0 0f`. You may
alternatively attempt extraction with `ifdtool -x rom.bin`, adding
the `--platform OPTION` option if needed, based on output from `--help` if
you need to (it lists platform strings for certain newer Intel platforms). If
ifdtool extraction fails, then that is another indication that you did not
cat the files correctly.**
If your GbE region is locked (per IFD settings), you can dump
and flash it using external flashing equipment. The Libreboot
@ -251,8 +260,11 @@ the `-p internal` parameter to something else. In this
situation, you should re-split the file accordingly, if
you have a dual-IC flash set, like so:
dd if=rom.bin.new of=spi2.rom bs=1M skip=8
dd if=rom.bin.new of=spi1.rom bs=1M count=8
dd if=rom.bin.new of=spi2.rom bs=1M skip=8 # WARNING: see note below
dd if=rom.bin.new of=spi1.rom bs=1M count=8 # WARNING: see note below
**WARNING: The commands above assume SPI1 is 8MB and SPI2 is 4MB, making 12MB
total. Please adapt accordingly, for your own configuration.**
These files would then be flashed externally, separately,
using an external programmer.