c7a3152273
Current doc transpiles to something completely unreadable. Change-Id: I197deb52974c88e067bc1615986a42c889214888 Signed-off-by: Evgeny Zinoviev <me@ch1p.io> Reviewed-on: https://review.coreboot.org/c/coreboot/+/38933 Tested-by: build bot (Jenkins) <no-reply@coreboot.org> Reviewed-by: Patrick Rudolph <siro@das-labor.org> Reviewed-by: Patrick Georgi <pgeorgi@google.com>
78 lines
3.5 KiB
Markdown
78 lines
3.5 KiB
Markdown
# IFD Layout
|
|
|
|
A coreboot image for an Intel SoC contains two separate definitions of the
|
|
layout of the flash. The Intel Flash Descriptor (IFD) which defines offsets and
|
|
sizes of various regions of flash and the [coreboot FMAP](../lib/flashmap.md).
|
|
|
|
The FMAP should define all of the of the regions defined by the IFD to ensure
|
|
that those regions are accounted for by coreboot and will not be accidentally
|
|
modified.
|
|
|
|
## IFD mapping
|
|
|
|
The names of the IFD regions in the FMAP should follow the convention of
|
|
starting with the prefix `SI_` which stands for `silicon initialization` as a
|
|
way to categorize anything required by the SoC but not provided by coreboot.
|
|
|
|
```eval_rst
|
|
+------------+------------------+-----------+-------------------------------------------+
|
|
| IFD Region | IFD Region name | FMAP Name | Notes |
|
|
| index | | | |
|
|
+============+==================+===========+===========================================+
|
|
| 0 | Flash Descriptor | SI_DESC | Always the top 4KB of flash |
|
|
+------------+------------------+-----------+-------------------------------------------+
|
|
| 1 | BIOS | SI_BIOS | This is the region that contains coreboot |
|
|
+------------+------------------+-----------+-------------------------------------------+
|
|
| 2 | Intel ME | SI_ME | |
|
|
+------------+------------------+-----------+-------------------------------------------+
|
|
| 3 | Gigabit Ethernet | SI_GBE | |
|
|
+------------+------------------+-----------+-------------------------------------------+
|
|
| 4 | Platform Data | SI_PDR | |
|
|
+------------+------------------+-----------+-------------------------------------------+
|
|
| 8 | EC Firmware | SI_EC | Most Chrome OS devices do not use this |
|
|
| | | | region; EC firmware is stored in BIOS |
|
|
| | | | region of flash |
|
|
+------------+------------------+-----------+-------------------------------------------+
|
|
```
|
|
|
|
## Validation
|
|
|
|
The ifdtool can be used to manipulate a firmware image with a IFD. This tool
|
|
will not take into account the FMAP while modifying the image which can lead to
|
|
unexpected and hard to debug issues with the firmware image. For example if the
|
|
ME region is defined at 6 MB in the IFD but the FMAP only allocates 4 MB for the
|
|
ME, then when the ME is added by the ifdtool 6 MB will be written which could
|
|
overwrite 2 MB of the BIOS.
|
|
|
|
In order to validate that the FMAP and the IFD are compatible the ifdtool
|
|
provides --validate (-t) option. `ifdtool -t` will read both the IFD and the
|
|
FMAP in the image and for every non empty region in the IFD if that region is
|
|
defined in the FMAP but the offset or size is different then the tool will
|
|
return an error.
|
|
|
|
Example:
|
|
|
|
```console
|
|
foo@bar:~$ ifdtool -t bad_image.bin
|
|
Region mismatch between bios and SI_BIOS
|
|
Descriptor region bios:
|
|
offset: 0x00400000
|
|
length: 0x01c00000
|
|
FMAP area SI_BIOS:
|
|
offset: 0x00800000
|
|
length: 0x01800000
|
|
Region mismatch between me and SI_ME
|
|
Descriptor region me:
|
|
offset: 0x00103000
|
|
length: 0x002f9000
|
|
FMAP area SI_ME:
|
|
offset: 0x00103000
|
|
length: 0x006f9000
|
|
Region mismatch between pd and SI_PDR
|
|
Descriptor region pd:
|
|
offset: 0x003fc000
|
|
length: 0x00004000
|
|
FMAP area SI_PDR:
|
|
offset: 0x007fc000
|
|
length: 0x00004000
|
|
``` |