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Require FMP and "on disk" OsIndicationsSupported bits when supported #137

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Require FMP and "on disk" OsIndicationsSupported bits when supported #137

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fe73130
trivial: add in-band firmware update section anchor
vstehle Jan 14, 2025
eba89b8
chapter2: adjust fmp format wording
vstehle Jan 14, 2025
8d93999
chapter2: require fmp and on-disk indications when supported
vstehle Jan 14, 2025
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12 changes: 10 additions & 2 deletions source/chapter2-uefi.rst
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Original file line number Diff line number Diff line change
Expand Up @@ -206,6 +206,7 @@ Variables as found in :UEFI:`3.3`.
- Method for OS to request features from firmware.
* - `OsIndicationsSupported`
- Variable for firmware to indicate which features can be enabled.
See section :ref:`section-in-band-fw-update` for additional requirements.

.. _section-required-vars-for-on-disk:

Expand Down Expand Up @@ -615,13 +616,15 @@ secure platforms.
EBBR platforms are required to implement either an in-band or an out-of-band
firmware update mechanism.

.. _section-in-band-fw-update:

In-band firmware update
^^^^^^^^^^^^^^^^^^^^^^^

If firmware update is performed in-band (firmware on the application processor
updates itself), then the firmware shall implement the `UpdateCapsule()` runtime
service and accept only authenticated updates in the "Firmware Management
Protocol Data Capsule Structure" format as described in :UEFI:`23.3`, with
service and accept only authenticated updates in the Firmware Management
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@xypron xypron Jan 14, 2025 •
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UpdateCapsule() expects a scatter list. From that scatter list a capsule can be reconstructed as described in "23.3.2 DEFINED FIRMWARE MANAGEMENT PROTOCOL DATA CAPSULE STRUCTURE". The capsule consists of a EFI_FIRMWARE_MANAGEMENT_CAPSULE_IMAGE_HEADER and a capsule body. The body starts with an EFI_FIRMWARE_MANAGEMENT_CAPSULE_HEADER.

The term "Firmware Management Protocol Format" would not catch the existence of a scatter list and an EFI_FIRMWARE_MANAGEMENT_CAPSULE_IMAGE_HEADER.

Protocol (FMP) format as described in :UEFI:`23.3`, with
`IMAGE_ATTRIBUTE_AUTHENTICATION_REQUIRED` set. [#FMPNote]_
`UpdateCapsule()` is only required before `ExitBootServices()` is called.

Expand Down Expand Up @@ -650,6 +653,11 @@ Firmware must support the delivery of capsules via file on mass storage device
.. [#VarNote] Some Variables are required to support capsule "on disk".
See section :ref:`section-required-vars-for-on-disk`.

The `OsIndicationsSupported` Variable bits
`EFI_OS_INDICATIONS_FMP_CAPSULE_SUPPORTED` and
`EFI_OS_INDICATIONS_FILE_CAPSULE_DELIVERY_SUPPORTED` must be set to indicate
support of capsules in FMP format and "on disk" delivery.

.. note::
It is recommended that firmware implementing the `UpdateCapsule()` runtime
service and an ESRT also implement the `EFI_FIRMWARE_MANAGEMENT_PROTOCOL`
Expand Down