Currently EBBR contains nothing describing how systems that share storage media between firmware and OS behave. Add a description of how such as system can be robustly pre-partitioned.

Fixes: #3 Fixed: #8 Signed-off-by: Daniel Thompson daniel.thompson@linaro.org ---

Notes: v2: * Added patch description. * Don't explicitly enumerate supported partitioning standards, defer to UEFI instead (this implicitly adds MBR and el-torito support). * Forbid hybrid GPT/MBR partitioning. * Require that pre-configured protective partitions using GPT to set the Platform Require Attribute Flag. * Improve documentation the 1MB threshold for MBR

source/ebbr.rst | 47 ++++++++++++++++++++++++++++++++++++++++++++++- 1 file changed, 46 insertions(+), 1 deletion(-)

diff --git a/source/ebbr.rst b/source/ebbr.rst index b6e48d6ac67d..39983974b1c1 100644 --- a/source/ebbr.rst +++ b/source/ebbr.rst @@ -197,7 +197,52 @@ virtualized service, by the hypervisor and not as part of the host firmware. System Volume Format --------------------

-The system firmware must support GPT partitioning. +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. + +GPT partitioning +^^^^^^^^^^^^^^^^ + +Any pre-installed partition table must strictly conform to the UEFI +specification and include a protective MBR authored exactly as +described in UEFI specification (hybrid partitioning schemes are not +permitted). + +Pre-installed protective partitions must have the Platform Required +Attribute Flag set. + +It is recommended that automatic system disk partitioning utilities +preserve Platform Required partitions as is, and that manual disk +partitioning utilities provide warnings and/or other safe guards to +reduce risk of accidental removal. + +MBR partitioning +^^^^^^^^^^^^^^^^ + +Pre-installed protective partitions should have a partition type of 0xF8 +unless some immutable feature of the platform makes this impossible. + +It is recommended that disk partitioning utilities treat such +partitions in the same manner as GPT partitions with the Platform +Required Attribute Flag set. + +It is recommended that pre-installed protective partitions that are not +type 0xF8 be located wholly within 1MB of the start of the disk. + +Automatic disk partitioning utilities shall not create partitions +within 1MB of the start of the disk. Manual disk partitioning +utilities should avoid recommending that partitions start within +1MB of the start of the disk.

UEFI Boot Services ================== -- 2.17.0