feat(el3-runtime): translate EL3 handled exceptions to C and always call prepare_el3_entry

Exception handling in BL31 is tricky business and to satisfy the varying
requirements of the different code

feat(el3-runtime): translate EL3 handled exceptions to C and always call prepare_el3_entry

Exception handling in BL31 is tricky business and to satisfy the varying
requirements of the different code paths it has thus far largely been
written in assembly. However, assembly is extremely tedious to read and
modify. Similar to context management, it is desirable to have as much
as possible in C. C code is generally easier to follow and can enable
the compiler to do more optimisations on surrounding code.

Most exceptions that BL31 deals with are the synchronous exceptions and
those are processed within BL31. They already get prepared for EL3 entry
and after the initial dispatch end up in C. So the dispatch can also be
converted in C. Interrupt exceptions are very similar so are converted
too. Finally, asynchronous external aborts share some code with
synchronous external aborts and may end up being processed deeper in
BL31. So they can safely be prepared for EL3 entry too and converted to
C so that they can share code properly.

The IMP DEF exceptions are not part of this refactor as their speed may
be important. There is currently little that uses them, but they can be
converted to C too once their use expands and usage allows it.

This refactor allows to expand the responsibilities of
prepare_el3_entry(). Its role is already to prepare context for
executing within EL3 but with this patch EL3 execution is synonymous
with C runtime execution. So it's given the responsibility of saving
spsr and elr as well as putting the runtime stack in.

When a synchronous exception happens, the only possible paths are to
enter the C EL3 runtime, exiting via el3_exit(), or to panic. In the EL3
runtime case, we always need prepare_el3_entry() and the runtime stack,
whereas in the panic case, this doesn't matter as we will never return.
So hoist the prepare_el3_entry() call and the changing of the stacks as
early as possible and make the rest of the code agnostic of this.

This patch also gets rid of smc_prohibited. It is an optimisation by
skipping prepare_el3_entry() when a bad smc call happens. However, speed
doesn't matter in this case as this is an erroneous case.

Change-Id: I411af9d17ef4046a736b1f4f5f8fbc9c28e66106
Signed-off-by: Boyan Karatotev <boyan.karatotev@arm.com>

show more ...

refactor: unify blx_setup() and blx_main()

All BLs have a bl_setup() for things that need to happen early, a fall
back into assembly and then bl_main() for the main functionality. This
was necessary

refactor: unify blx_setup() and blx_main()

All BLs have a bl_setup() for things that need to happen early, a fall
back into assembly and then bl_main() for the main functionality. This
was necessary in order to fiddle with PAuth related things that tend to
break C calls. Since then PAuth's enablement has seen a lot of
refactoring and this is now worked around cleanly so the distinction can
be removed. The only tradeoff is that this requires pauth to not be used
for the top-level main function.

There are two main benefits to doing this: First, code is easier to
understand as it's all together and the entrypoint is smaller. Second,
the compiler gets to see more of the code and apply optimisations
(importantly LTO).

Change-Id: Iddb93551115a2048988017547eb7b8db441dbd37
Signed-off-by: Boyan Karatotev <boyan.karatotev@arm.com>

show more ...

refactor(bl1): clean up bl2 layout calculation

Layout calculation is spread out between core BL1 logic and common
platform code. Relocate these into common platform code so they are
organised logica

refactor(bl1): clean up bl2 layout calculation

Layout calculation is spread out between core BL1 logic and common
platform code. Relocate these into common platform code so they are
organised logically.

Change-Id: I8b05403e41b800957a0367316cecd373d10bb1a4
Signed-off-by: Harrison Mutai <harrison.mutai@arm.com>

show more ...