Fix unwinding on arm64 kernel v6.18-rc1 and newer

[fabled]

Some fields of the arm64 pt_regs were removed recently (the last two fields, see commit torvalds/linux@ee776d6).

This caused attempt to read beyond the stack page. Let's remove the fields we don't need to reduce data read, and similar issues if additional kernel internals are removed from this struct. But keep the struct size multiple of 8 for fast memory copy.

fixes #1054

[bobrik]

Is there a way to detect this sort of a regression with integration checks that would run the latest kernel?

[fabled]

Is there a way to detect this sort of a regression with integration checks that would run the latest kernel?

I believe this would have been caught by the integration tests if new enough kernel was included in the kernel versions to test matrix. The latest kernel it does currently is 6.16. They way the test matrix is setup, adding new kernels requires a manual update to the github ci/cd yml.

[florianl]

Just created #1103 to add more recent kernels to our CI. For background information, there was an issue that prevented earlier use of new kernels - see cilium/ci-kernels#84.