[PATCH v4 0/2] Create UART DebugLib implementation for runtime drivers

[Ard Biesheuvel <ard.biesheuvel@linaro.org>]

Commit 4bf95a9f361e ("MdeModulePkg/ResetSystemRuntimeDxe: Add more debug
message") broke the DEBUG build for systems using a MMIO mapped UART for
DEBUG output. In other words, it broke the build for all ARM and AARCH64
systems, given that port I/O does not exist on those architectures.

Instead of patching it up locally, let's fix this issue once and for all,
by creating a UART DebugLib implementation for DXE_RUNTIME_DRIVER modules
that does the right thing by default.

v4:
- add Laszlo's R-b
- keep ASSERT() message in local buffer even it is not printed to the serial
  port, to allow it to be accessed via the debugger

v3:
- revert PCD changes, as they are unnecessary for the PCDs in question (since
  they are fixed or patchable only)
- drop redundant mEfiAtRuntime checks around ASSERT()s
- revert whitespace cleanup, i.e., move back to BaseDebugLibSerialPort origin
  for most of the file

v2:
- incorporate Laszlo's feedback into patch #1
- add Laszlo's R-b to patch #2
- dropped patch #3 that blacklists the original BASE implementation for
  DXE_RUNTIME_DRIVER modules

Note that I retained the deadloop/breakpoint code for ASSERT()s at runtime.
I think it is perfectly reasonable behavior for a DEBUG build at runtime,
even if other cores may be up and running as well: the purpose of these
facilities is to allow a debugger to attach to the CPU to figure out what
has happened, and both deadloops and breakpoints can achieve that just
fine even at runtime.


Ard Biesheuvel (2):
  MdePkg: introduce DxeRuntimeDebugLibSerialPort
  ArmVirtPkg: switch to DXE runtime version of DebugLib where
    appropriate

 ArmVirtPkg/ArmVirt.dsc.inc                                                   |   3 +
 MdePkg/Library/DxeRuntimeDebugLibSerialPort/DebugLib.c                       | 346 ++++++++++++++++++++
 MdePkg/Library/DxeRuntimeDebugLibSerialPort/DxeRuntimeDebugLibSerialPort.inf |  55 ++++
 MdePkg/Library/DxeRuntimeDebugLibSerialPort/DxeRuntimeDebugLibSerialPort.uni |  21 ++
 4 files changed, 425 insertions(+)
 create mode 100644 MdePkg/Library/DxeRuntimeDebugLibSerialPort/DebugLib.c
 create mode 100644 MdePkg/Library/DxeRuntimeDebugLibSerialPort/DxeRuntimeDebugLibSerialPort.inf
 create mode 100644 MdePkg/Library/DxeRuntimeDebugLibSerialPort/DxeRuntimeDebugLibSerialPort.uni

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2.11.0