[bootwrapper PATCH v2 00/13] Cleanups and improvements

Mark Rutland
2022-01-14T10:58:21Z

This series reworks the aarch64 boot-wrapper, moving a fair amount of
initialization code to C. This has a few benefits:

1) This makes the code more legible and easier to maintain.

Current feature detection and system register configuration is
written in assembly, requiring runs of *almost* identical blocks of
assembly to read ID registers and conditionally initialize register
values. This requires a bunch of labels (which are all named
numerically), and all the magic numbers are hard coded, so this gets
pretty painful to read:

| mrs x1, id_aa64isar0_el1
| ubfx x1, x1, #24, #4
| cbz x1, 1f
|
| orr x0, x0, #(1 << 34) // TME enable
|
| 1:

In C, it's much easier to add helpers which use mnemonics, which
makes the code much easier to read, and avoids the need to manually
allocate registers, etc:

| if (mrs_field(ID_AA64ISAR0_EL1, TME))
| scr |= SCR_EL3_TME;

This should make it easier to handle new architectural extensions
(and/or architecture variants such as ARMv8-R) in future.

2) This allows for better diagnostics.

Currently a mis-configured boot-wrapper is rather unforgiving, and
provides no indication as to what might have gone wrong. By moving
initialization to C, we can make use to the UART code to log
diagnostic information, and we can more easily add additional error
handling and conditional logic.

This series adds diagnostic information and error handling that can
be used to identify problems such as the boot-wrapper being launched
at the wrong exception level:

| Boot-wrapper v0.2
| Entered at EL2
| Memory layout:
| [0000000080000000..0000000080001f90] => boot-wrapper
| [000000008000fff8..0000000080010000] => mbox
| [0000000080200000..00000000822af200] => kernel
| [0000000088000000..0000000088002857] => dtb
|
| WARNING: PSCI could not be initialized. Boot may fail

Originally I had planned for this to be a more expansive set of changes,
unifying some early control-flow, fixing some latent bugs, and making
the boot-wrapper dynamically handle being entered at any of EL{3,2,1}
with automated selection of a suitable DT. As the series has already
become pretty long, I'd like to get this preparatory cleanup out of the
way first, and handle those cases with subsequent patches.

If there are no objections, I intend to apply these by the end of the
day.

I've pushed the series to the `cleanup` branch in the boot-wrapper repo:

https://git.kernel.org/pub/scm/linux/kernel/git/mark/boot-wrapper-aarch64.git/
git://git.kernel.org/pub/scm/linux/kernel/git/mark/boot-wrapper-aarch64.git

... and it should apply cleanup atop the `master` branch.

Since v1 [1]:
* Add comments for bit-field macros
* Use BIT() for *_RES1 definitions
* Complete start_el3/start_no_el3 cleanup
* Remove extraneous macro definition

[1] https://lore.kernel.org/r/20220111130653.2331827-1-mark.rutland@arm.com/

Thanks,
Mark.

Mark Rutland (13):
Document entry requirements
Add bit-field macros
aarch64: add system register accessors
aarch32: add coprocessor accessors
aarch64: add mov_64 macro
aarch64: initialize SCTLR_ELx for the boot-wrapper
Rework common init C code
Announce boot-wrapper mode / exception level
aarch64: move the bulk of EL3 initialization to C
aarch32: move the bulk of Secure PL1 initialization to C
Announce locations of memory objects
Rework bootmethod initialization
Unify start_el3 & start_no_el3

Makefile.am | 6 +-
arch/aarch32/boot.S | 33 +++---
arch/aarch32/include/asm/cpu.h | 62 ++++++++---
arch/aarch32/include/asm/gic-v3.h | 6 +-
arch/aarch32/include/asm/psci.h | 28 +++++
arch/aarch32/init.c | 42 ++++++++
arch/aarch32/psci.S | 16 +--
arch/aarch32/utils.S | 9 --
arch/aarch64/boot.S | 169 +++++++++++++-----------------
arch/aarch64/common.S | 10 +-
arch/aarch64/include/asm/cpu.h | 102 +++++++++++++++---
arch/aarch64/include/asm/gic-v3.h | 10 +-
arch/aarch64/include/asm/psci.h | 28 +++++
arch/aarch64/init.c | 88 ++++++++++++++++
arch/aarch64/psci.S | 22 +---
arch/aarch64/spin.S | 6 +-
arch/aarch64/utils.S | 9 --
common/boot.c | 4 -
common/init.c | 60 +++++++++++
common/platform.c | 45 +++++---
common/psci.c | 22 +++-
include/bits.h | 79 ++++++++++++++
include/boot.h | 2 +
include/platform.h | 20 ++++
model.lds.S | 20 ++--
25 files changed, 668 insertions(+), 230 deletions(-)
create mode 100644 arch/aarch32/include/asm/psci.h
create mode 100644 arch/aarch32/init.c
create mode 100644 arch/aarch64/include/asm/psci.h
create mode 100644 arch/aarch64/init.c
create mode 100644 common/init.c
create mode 100644 include/bits.h
create mode 100644 include/platform.h

--
2.30.2