pdp11: initial low level bits (incomplete)

diff --git a/Kernel/lowlevel-pdp11.S b/Kernel/lowlevel-pdp11.S
new file mode 100644 (file)
index 0000000..38491f3
--- /dev/null
+++ b/Kernel/lowlevel-pdp11.S
@@ -0,0 +1,91 @@
+#include "kernel-pdp11.def"
+
+       .globl _di
+       .globl _ei
+       .globl _irqrestore
+       .globl _doexec
+       .globl ___udivhi3
+       .globl ___umodhi3
+       .globl _abort
+       .globl outr0hex
+       .globl outstring
+
+/*     Probably should go to ipl6 not ipl7 to allow profiling ?
+
+       This is slightly odd compared with most machines. Rather than
+       having special move to/from control register instructions the
+       status register actually lives at the very top of the unibus device
+       address space - for now 077776 and the other control registers work
+       in a very similar way */
+
+_di:
+       mov 0177776,r0
+       bis 0340,0177776
+       rts pc
+_ei:
+       mov 0177776,r0
+       bic 0340,0177776
+       rts pc
+_irqrestore:
+       mov 2(sp),0177776
+       rts pc
+
+
+/*     FIXME: need correct code for MMU supervisor/user case */
+
+_doexec:
+#if CONFIG_PDP11_04
+       mov 2(sp),r0                    /* Jump address */
+       mov $_udata+U_DATA__U_ISP,sp    /* user stack = kernel for simple */
+       clr -(sp)
+       move r0,-(sp)
+       clr r0
+       clr r1
+       clr r2
+       clr r3
+       clr r4
+       clr r5
+       rtt
+#else
+       mov 2(sp),r0
+       mov $_udata+U_DATA__U_ISP,r1
+       mov r1,0177717          /* user mode stack pointer */
+       mov $_udata+512,sp      /* rewind to the top of kernel stack */
+
+       /* PSW is
+          [mode.2][prevmode.2][grs][revid.2][cissusp][pri.3][flags]
+          00: kernel 01: supervisor, 11 user*/
+
+       /* Make a trap frame */
+       mov $0xC000,-(sp)       /* user, was kernel */
+       mov r0,-(sp)
+       clr r0                  /* no leaks */
+       clr r1
+       clr r2
+       clr r3
+       clr r4
+       clr r5
+       rtt                     /* IRQ on, user space return */
+#endif
+       
+
+___udivhi3:
+___umodhi3:
+_abort:
+       rts pc
+
+outr0hex:
+       rts pc
+
+outstring:
+       mov r1,-(sp)
+       mov r0,r1
+1:
+       movb (r1)+,r0
+       tstb r0
+       beq 2f
+       jsr pc,outchar
+       jmp 1
+2:
+       mov (sp)+,r1
+       rts pc