[FreeBSD] ptrace PT_SC_REMOTE missing argument validation: 32GiB memmove underflow + sysent out-of-bounds call

Summary A local unprivileged user can trigger a 32GiB memmove underflow via ptrace PTSCREMOTE with pscrnargs=0, and call arbitrary sysent function pointers due to missing syscall number bounds check in ptracesyscallreq. This allows kernel code execution under security.bsd.unprivilegedprocdebug=1...