kinst(4): search for push rbp anywhere in the function

[christos]

Summary

This patch fixes kinst ignoring functions that push %rbp
after the first instruction.

[christos]

Mention leaf function with rbp omitted.

[markj]

sys/cddl/dev/kinst/amd64/kinst_isa.c

555

Let's put this in its own function, something like bool kinst_can_trace_func(uint8_t *instr, uint8_t *limit);. kinst_make_probe() has too many local vars otherwise, and we might want to add/change the checks over time, so a separate function is a bit neater.

[christos]

Put it in its own function.

[christos]

Abandoning this one since we no longer search for push %rbp, instead we
exclude just the exception handlers (see D39229).