Re: [RFC PATCH v1 06/25] unwind_user: Enable archs that define CFA = SP_callsite + offset

Most architectures define their CFA as the value of the stack pointer
(SP) at the call site in the previous frame, as suggested by the DWARF
standard.  Therefore the SP at call site can be unwound using an
implicitly assumed value offset from CFA rule with an offset of zero:

  .cfi_val_offset <SP>, 0

As a result the SP at call site computes as follows:

  SP = CFA

Enable unwinding of user space for architectures, such as s390, which
define their CFA as the value of the SP at the call site in the previous
frame with an offset.  Do so by enabling architectures to override the
default SP value offset from CFA of zero with an architecture-specific
one:

  .cfi_val_offset <SP>, offset

So that the SP at call site computes as follows:

  SP = CFA + offset

Signed-off-by: Jens Remus <redacted>

Sashiko has reviewed this patch and found no issues. It looks great!

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Sashiko AI review · https://sashiko.dev/#/patchset/20260818144954.2320378-1-jremus@linux.ibm.com?part=6