[bootwrapper,00/13] Cleanups and improvements

Message

Mark Rutland Jan. 11, 2022, 1:06 p.m. UTC

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 in the next few days, I intend to apply these
patches by the end of the week. If people can provide Reviewed-by and
Tested-by tags, I'd be happy to apply this earlier.

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.

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               |  13 +--
 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               |   3 +
 arch/aarch64/utils.S              |   9 --
 common/boot.c                     |   4 -
 common/init.c                     |  60 +++++++++++
 common/platform.c                 |  46 +++++---
 common/psci.c                     |  22 +++-
 include/bits.h                    |  33 ++++++
 include/boot.h                    |   2 +
 include/platform.h                |  20 ++++
 model.lds.S                       |  20 ++--
 25 files changed, 621 insertions(+), 226 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