The framer's tests check its sites, stub bytes and moved displacements,
but nothing yet showed that framed code survives a write below rsp.
red_zone_framer_execution frames synthetic leaves with
FrameRedZoneFunctions in a writable and executable buffer, writes the
moved displacements and the stubs as Conversion.cpp and the trampoline
builders do, and calls each leaf with the trap flag set. A SIGTRAP
handler fills [rsp-0x80, rsp) of the interrupted context at every
instruction, as Windows exception dispatch may.
Five leaves each loop over slots they spilled, so a clobbered slot
changes the result: #5640's frameless shape, a leaf reaching 0x28 below
rsp, a leaf that also reads its saved rbx at +0x10 (moved in place), a
leaf that takes the address of a slot below rsp (shifted by the whole red
zone), and the inflate_fast-shaped leaf that allocates with sub after six
pushes. Each must return the right value unframed without the clobber
and a wrong one with it, and the right value framed with it.
The test is built and registered on Linux x86-64 only; elsewhere its main
returns 77.
