On 6/10/20 10:17 AM, Ard Biesheuvel wrote:
It is not always possible to deploy the standalone MM core in a way where
the runtime address is known at build time. This does not matter for most
modules, since they are relocated at dispatch time. However, for the MM
core itself, it means we need to do some extra work to relocate the image
in place if it ends up at a different offset than expected.
On AARCH64, the standalone MM stack is deployed inside a non-privileged
secure world container which only has limited control over its memory
mappings, and so we need to ensure that the executable code itself is
free of absolute quantities that need to be fixed up. This is very similar
to how shared libraries are constructed, given that pages can only be
shared between processes if they are not modified, even by the dynamic
loader. So we can use this support to emit the standaline MM core in a
way that guarantees that the executable code does not need to modify
itself (patch #4)
Patch #5 adds the actual code to perform the self relocation after the
.data section has been made writable and non-executable. Note that the
PE/COFF library code modifies the header in place, and so in the case
where we need to perform the runtime relocation, we need to remap the
header page writable and non-executable as well.
The remaining patches are optimizations and fixes I picked up along
the way.
Cc: Michael D Kinney <michael.d.kin...@intel.com>
Cc: Liming Gao <liming....@intel.com>
Cc: Jiewen Yao <jiewen....@intel.com>
Cc: Sami Mujawar <sami.muja...@arm.com>
Cc: Ilias Apalodimas <ilias.apalodi...@linaro.org>
Any thoughts from the StandaloneMmPkg co-maintainers?
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