Lars, I misspoke. It's a stack error, not a stack overflow.
The kernel reports P1=00000008 in response to a stack fault trap 12 (0ch), If the trap 12 error code is non-zero, the error code is a segment selector which in this case was reported as P2=00004f34.
The gory details are at page 238 of my March, 2024 copy of the Intel IA64 and IA-32 SDM.
We still have no idea what triggered this exception.
Sigurd, what bldlevel does your copy of LANINST.PGM report?