objtool: Validate IBT assumptions

objtool: Validate IBT assumptions

Intel IBT requires that every indirect JMP/CALL targets an ENDBR
instructions, failing this #CP happens and we die. Similarly, all
exception entries should be ENDBR.

Find all code relocations and ensure they're either an ENDBR
instruction or ANNOTATE_NOENDBR. For the exceptions look for
UNWIND_HINT_IRET_REGS at sym+0 not being ENDBR.

Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
Acked-by: Josh Poimboeuf <[email protected]>
Link: https://lore.kernel.org/r/[email protected]