[v5,0/4] fix CPER issues related to UEFI 2.9A Errata

The UEFI 2.9A errata makes clear how ARM processor type encoding should
be done: it is meant to be equal to Generic processor, using a bitmask.

The current code assumes, for both generic and ARM processor types
that this is an integer, which is an incorrect assumption.

Fix it. While here, also fix a compilation issue when using W=1.

After the change, Kernel will properly decode receiving two errors at the same
message, as defined at UEFI spec:

[   75.282430] Memory failure: 0x5cdfd: recovery action for free buddy page: Recovered
[   94.973081] {2}[Hardware Error]: Hardware error from APEI Generic Hardware Error Source: 1
[   94.973770] {2}[Hardware Error]: event severity: recoverable
[   94.974334] {2}[Hardware Error]:  Error 0, type: recoverable
[   94.974962] {2}[Hardware Error]:   section_type: ARM processor error
[   94.975586] {2}[Hardware Error]:   MIDR: 0x000000000000cd24
[   94.976202] {2}[Hardware Error]:   Multiprocessor Affinity Register (MPIDR): 0x000000000000ab12
[   94.977011] {2}[Hardware Error]:   error affinity level: 2
[   94.977593] {2}[Hardware Error]:   running state: 0x1
[   94.978135] {2}[Hardware Error]:   Power State Coordination Interface state: 4660
[   94.978884] {2}[Hardware Error]:   Error info structure 0:
[   94.979463] {2}[Hardware Error]:   num errors: 3
[   94.979971] {2}[Hardware Error]:    first error captured
[   94.980523] {2}[Hardware Error]:    propagated error captured
[   94.981110] {2}[Hardware Error]:    overflow occurred, error info is incomplete
[   94.981893] {2}[Hardware Error]:    error_type: 0x0006: cache error|TLB error
[   94.982606] {2}[Hardware Error]:    error_info: 0x000000000091000f
[   94.983249] {2}[Hardware Error]:     transaction type: Data Access
[   94.983891] {2}[Hardware Error]:     cache error, operation type: Data write
[   94.984559] {2}[Hardware Error]:     TLB error, operation type: Data write
[   94.985215] {2}[Hardware Error]:     cache level: 2
[   94.985749] {2}[Hardware Error]:     TLB level: 2
[   94.986277] {2}[Hardware Error]:     processor context not corrupted

And the error code is properly decoded according with table N.17 from UEFI 2.10
spec:

	[   94.981893] {2}[Hardware Error]:    error_type: 0x0006: cache error|TLB error

The error injection logic was checked via QEMU using this patch:
https://lore.kernel.org/all/20240621165115.336-1-shiju.jose@huawei.com/

v5:
- Do some cleanups and minor fixes as suggested by Jonathan and Tony:
  - check errors at strscpy();
  - simplify cper_bits_to_str() function;
  - use FIELD_GET() and for_each_set_bit();
  - use ARRAY_SIZE() on infofx to let it clear that it should be size of newpfx + 1;
  - fix kernel-doc warning with W=1;
  - use kernel-doc for two exported functions at cper.c.

v4:
- The print function had some bugs on it, which was discovered with
  the help of an error injection tool I'm now using.

v3:
- It adds a helper function to produce a buffer describing the
  error bits at cper's printk and ghes pr_warn_bitrated. It also
  fixes a W=1 error while building cper.

v2:
- It fixes the way printks are handled on both cper_arm and ghes
  drivers.

v1: 
- (tagged as RFC) was mostly to give a heads up that the current 
  implementation is not following the spec. It also touches
  only cper code.




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                      | 15 +++---
 drivers/firmware/efi/cper-arm.c               | 52 +++++++++----------
 drivers/firmware/efi/cper.c                   | 41 ++++++++++++++-
 include/linux/cper.h                          | 12 +++--
 5 files changed, 89 insertions(+), 42 deletions(-)