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| author | Patrick Rudolph <patrick.rudolph@9elements.com> | 2019-04-15 16:17:59 +0200 |
|---|---|---|
| committer | Patrick Rudolph <siro@das-labor.org> | 2019-04-30 08:18:57 +0000 |
| commit | 345d202d662fae57ab7a13432f213cd4109e5e3c (patch) | |
| tree | f836cd16b6228914a28b69e4a5485ade7fea4ce7 /Documentation/soc/intel/fit.md | |
| parent | 46c5807d29a1fae542d22c82f6c07955f0296f78 (diff) | |
| download | coreboot-345d202d662fae57ab7a13432f213cd4109e5e3c.tar.xz | |
Documentation: Add FIT
Describe the Firmware Interface Table and reference useful documentation.
Change-Id: I00abc1fd13be7b48d56ba8cb65d2542ed07f9017
Signed-off-by: Patrick Rudolph <patrick.rudolph@9elements.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/32325
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>
Diffstat (limited to 'Documentation/soc/intel/fit.md')
| -rw-r--r-- | Documentation/soc/intel/fit.md | 60 |
1 files changed, 60 insertions, 0 deletions
diff --git a/Documentation/soc/intel/fit.md b/Documentation/soc/intel/fit.md new file mode 100644 index 0000000000..8b638f0433 --- /dev/null +++ b/Documentation/soc/intel/fit.md @@ -0,0 +1,60 @@ +# Intel Firmware Interface Table + +The FIT allows to run code before the actual IA32 reset vector is executed +by the CPU. The FIT resides in the BIOS region (usually near the reset vector) +and is pointed to by the FIT pointer residing at `0xFFFFFFC0`. + +## Table layout +The table consists of blocks each 16 bytes in size. +The first is called *FIT header* the other are called *FIT entry*. + +![FIT in x86 memory map][fit] + +[fit]: fit.svg + +## Fit types + +Each entry has a *type* that give the other bits in the entry a different +meaning. The following types are known: + +```eval_rst ++-----------+------------------------------------------------------------------+ +| no. | Description | ++===========+==================================================================+ +| 0x0 | HEADER. | ++-----------+------------------------------------------------------------------+ +| 0x1 | MICROCODE. | ++-----------+------------------------------------------------------------------+ +| 0x2 | STARTUP_ACM. | ++-----------+------------------------------------------------------------------+ +| 0x7 | BIOS_STARTUP_MODULE. | ++-----------+------------------------------------------------------------------+ +| 0x8 | TPM_POLICY. | ++-----------+------------------------------------------------------------------+ +| 0x9 | BIOS_POLICY. | ++-----------+------------------------------------------------------------------+ +| 0xa | TXT_POLICY. | ++-----------+------------------------------------------------------------------+ +| 0xb | KEY_MANIFEST. | ++-----------+------------------------------------------------------------------+ +| 0xc | BOOT_POLICY_MANIFEST. | ++-----------+------------------------------------------------------------------+ +| 0x10 | CSE_SECURE_BOOT. | ++-----------+------------------------------------------------------------------+ +| 0x2d | TXTSX_POLICY. | ++-----------+------------------------------------------------------------------+ +| 0x2f | JMP_DEBUG_POLICY. | ++-----------+------------------------------------------------------------------+ +| 0x7f | SKIP. | ++-----------+------------------------------------------------------------------+ +``` + +## Usage in coreboot + +The most common usage of FIT is to use *Type1* to update microcode before +execution of the IA32 reset vector happens. + +## References + +* [Intel TXT LAB handout](https://downloadmirror.intel.com/18931/eng/Intel%20TXT%20LAB%20Handout.pdf) +* [FIT bios specification](https://www.intel.com/content/dam/www/public/us/en/documents/guides/fit-bios-specification.pdf) |