Fix issues with ARM Processor CPER records

This is needed for both kernelspace and userspace properly handle ARM processor CPER events.

Patch 1 of this series fix the UEFI 2.6+ implementation of the ARM trace event, as the original implementation was incomplete. Changeset e9279e83ad1f ("trace, ras: add ARM processor error trace event") added such event, but it reports only some fields of the CPER record defined on UEFI 2.6+ appendix N, table N.16. Those are not enough actually parse such events on userspace, as not even the event type is exported.

Patch 2 fixes a compilation breakage when W=1;

Patch 3 adds a new helper function to be used by cper and ghes drivers to display CPER bitmaps;

Patch 4 fixes CPER logic according with UEFI 2.9A errata. Before it, there was no description about how processor type field was encoded. The errata defines it as a bitmask, and provides the information about how it should be encoded.

Patch 5 adds CPER functions to Kernel-doc.

This series was validated with the help of an ARM EINJ code for QEMU:

https://gitlab.com/mchehab_kernel/qemu/-/tree/qemu_submission

$ scripts/ghes_inject.py -d arm -p 0xdeadbeef -t cache,bus,micro-arch

[   11.094205] {1}[Hardware Error]: Hardware error from APEI Generic Hardware Error Source: 0
[   11.095009] {1}[Hardware Error]: event severity: recoverable
[   11.095486] {1}[Hardware Error]:  Error 0, type: recoverable
[   11.096090] {1}[Hardware Error]:   section_type: ARM processor error
[   11.096399] {1}[Hardware Error]:   MIDR: 0x00000000000f0510
[   11.097135] {1}[Hardware Error]:   Multiprocessor Affinity Register (MPIDR): 0x0000000080000000
[   11.097811] {1}[Hardware Error]:   running state: 0x0
[   11.098193] {1}[Hardware Error]:   Power State Coordination Interface state: 0
[   11.098699] {1}[Hardware Error]:   Error info structure 0:
[   11.099174] {1}[Hardware Error]:   num errors: 2
[   11.099682] {1}[Hardware Error]:    error_type: 0x1a: cache error|bus error|micro-architectural error
[   11.100150] {1}[Hardware Error]:    physical fault address: 0x00000000deadbeef
[   11.111214] Memory failure: 0xdeadb: recovery action for free buddy page: Recovered

-

I also tested the ghes and cper reports both with and without this change, using different versions of rasdaemon, with and without support for the extended trace event. Those are a summary of the test results:

- adding more fields to the trace events didn't break userspace API:
both versions of rasdaemon handled it;

- the rasdaemon patches to handle the new trace report was missing a backward-compatibility logic. I fixed already. So, rasdaemon can now handle both old and new trace events.

Btw, rasdaemon has gained support for the extended trace since its version 0.5.8 (released in 2021). I didn't saw any issues there complain about troubles on it, so either distros used on ARM servers are using an old version of rasdaemon, or they're carrying on the trace event changes as well.

---

v3:
- history of patch 1 improved with a chain of co-developed-by;
- add a better description and an example on patch 3;
- use BIT_ULL() on patch 3;
- add a missing include on patch 4.

v2:
- removed an uneeded patch adding #ifdef for CONFIG_ARM/ARM64;
- cper_bits_to_str() now returns the number of chars filled at the buffer;
- did a cosmetic (blank lines) improvement at include/linux/ras.h;
- arm_event trace dynamic arrays renamed to pei_buf/ctx_buf/oem_buf.

Jason Tian (1):
RAS: Report all ARM processor CPER information to userspace

Mauro Carvalho Chehab (4):
efi/cper: Adjust infopfx size to accept an extra space efi/cper: Add a new helper function to print bitmasks efi/cper: align ARM CPER type with UEFI 2.9A/2.10 specs
docs: efi: add CPER functions to driver-api

 .../driver-api/firmware/efi/index.rst         | 11 +++-
 drivers/acpi/apei/ghes.c                      | 27 ++++----
 drivers/firmware/efi/cper-arm.c               | 52 ++++++++--------
 drivers/firmware/efi/cper.c                   | 62 ++++++++++++++++++-
 drivers/ras/ras.c                             | 41 +++++++++++-
 include/linux/cper.h                          | 12 ++--
 include/linux/ras.h                           | 16 ++++-
 include/ras/ras_event.h                       | 48 ++++++++++++--
 8 files changed, 210 insertions(+), 59 deletions(-)

2.46.0