6 Jan
2015
6 Jan
'15
9:33 p.m.
On Tue, Jan 6, 2015, at 15:20, Johnny Billquist wrote:
Later model PDP-11 processors had a hardware feature
called split I/D
space. This meant that you could have one 64Kb virtual memory space for
instructions, and one 64Kb virtual memory space for data.
Was it possible to read/write to the instruction space, or execute the
data space? From what I've seen, the calling convention for PDP-11 Unix
system calls read their arguments from directly after the trap
instruction (which would mean that the C wrappers for the system calls
would have to write their arguments there, even if assembly programs
could have them hardcoded.)