[TUHS] pdp11 UNIX memory allocation.
random832 at fastmail.us
random832 at fastmail.us
Wed Jan 7 06:33:53 AEST 2015
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.)
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