Add some more detail on how to handle system firmware. I'm still undecided about this, so this patch is more of an RFC discussion than a serious patch. Please comment.
Cc: Daniel Thompson <daniel.thomp...@linaro.org> Signed-off-by: Grant Likely <grant.lik...@arm.com> --- source/ebbr.rst | 58 ++++++++++++++++++++++++++++++++++++++++++++++++++++----- 1 file changed, 53 insertions(+), 5 deletions(-) diff --git a/source/ebbr.rst b/source/ebbr.rst index 3998397..c24cef5 100644 --- a/source/ebbr.rst +++ b/source/ebbr.rst @@ -200,16 +200,64 @@ System Volume Format The system firmware must support all partitioning standards required by the UEFI specification. -On systems where the system firmware binaries reside on the System Volume then -the System Volume must be pre-configured with a partition table and include -protective partitions to reduce risk of accidental destruction of the system -firmware. - All pre-installed partition tables must use GPT partitioning unless some immutable feature of the platform (such as a mask programmed boot ROM) makes this impossible; on such platforms MBR partitioning may be used as an alternative. +System Firmware Partitions +^^^^^^^^^^^^^^^^^^^^^^^^^^ +On systems where the system firmware binaries reside on the System Volume then +the System Volume must be pre-configured with a partition table and system +firmware binaries. + +When system firmware is located at a fixed offset, It is strongly recommended +for the partition table to include protective partitions covering the location +of firmware to reduce risk of accidental destruction of the system firmware. + +System boot ROM should obtain the system firmware partition location +by reading the partition table. +Using a fixed offset into the storage media is deprecated and should +not be used for new SoC designs. +Future issues of this specification will disallow the use of fixed offsets. + +A system firmware partition should not also be used as a EFI System +Partition (ESP). +Pre-installed system firmware partitions must not use the ESP GUID, +and OS installation tools should not install EFI executables in a system +firmware partition. + +.. todo:: + + I'm not sure if this is a good idea. It might be that EBBR should define a + common GUID for system firmware partitions. It also might be that I'm worrying + too much and it is fine to use the ESP as a system firmware partition. + This TODO note is a bit of a discussion of the options. + + Options: + + - Require ESP and SFPs to be separate + - Should a common SFP GUID be defined so a single image can hold firmware + for multiple platforms? + - Don't have to repartition to add additional platforms. + - Yet repartitioning required to add the *first* platform + - Require FAT formatting? + - Probably also requires a vendor/soc/file pathname spec to avoid + conflicts. + - OS can mount the ESP without touching SFPs. This means firmware could + perform (mediated) operations on the SPF (ex. to update variables) + without unmounting the ESP. + - Downside: Requries at least two fixed sized partitions to boot the + platform: a SFP, and the ESP. A single combined SFP+ESP would be more + efficient on space. + - Allow ESP to be used as an SFP + - Downside: Partitioning/Install tools can't simply blank the ESP to reset + to scratch + - Upside: platform firmware can be added by simply dropping files + in the ESP + - Using the ESP filesystem is a more efficient use of space. + - Still need to define pathname spec to avoid conflicts + GPT partitioning ^^^^^^^^^^^^^^^^ -- 2.13.0 _______________________________________________ boot-architecture mailing list boot-architecture@lists.linaro.org https://lists.linaro.org/mailman/listinfo/boot-architecture
