Add original unix v6
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memnoth
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#
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#include "../param.h"
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#include "../systm.h"
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#include "../user.h"
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#include "../proc.h"
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#include "../reg.h"
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#include "../seg.h"
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#define EBIT 1 /* user error bit in PS: C-bit */
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#define UMODE 0170000 /* user-mode bits in PS word */
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#define SETD 0170011 /* SETD instruction */
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#define SYS 0104400 /* sys (trap) instruction */
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#define USER 020 /* user-mode flag added to dev */
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/*
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* structure of the system entry table (sysent.c)
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*/
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struct sysent {
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int count; /* argument count */
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int (*call)(); /* name of handler */
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} sysent[64];
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/*
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* Offsets of the user's registers relative to
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* the saved r0. See reg.h
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*/
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char regloc[9]
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{
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R0, R1, R2, R3, R4, R5, R6, R7, RPS
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};
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/*
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* Called from l40.s or l45.s when a processor trap occurs.
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* The arguments are the words saved on the system stack
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* by the hardware and software during the trap processing.
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* Their order is dictated by the hardware and the details
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* of C's calling sequence. They are peculiar in that
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* this call is not 'by value' and changed user registers
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* get copied back on return.
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* dev is the kind of trap that occurred.
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*/
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trap(dev, sp, r1, nps, r0, pc, ps)
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{
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register i, a;
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register struct sysent *callp;
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savfp();
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if ((ps&UMODE) == UMODE)
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dev =| USER;
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u.u_ar0 = &r0;
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switch(dev) {
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/*
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* Trap not expected.
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* Usually a kernel mode bus error.
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* The numbers printed are used to
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* find the hardware PS/PC as follows.
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* (all numbers in octal 18 bits)
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* address_of_saved_ps =
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* (ka6*0100) + aps - 0140000;
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* address_of_saved_pc =
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* address_of_saved_ps - 2;
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*/
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default:
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printf("ka6 = %o\n", *ka6);
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printf("aps = %o\n", &ps);
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printf("trap type %o\n", dev);
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panic("trap");
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case 0+USER: /* bus error */
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i = SIGBUS;
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break;
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/*
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* If illegal instructions are not
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* being caught and the offending instruction
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* is a SETD, the trap is ignored.
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* This is because C produces a SETD at
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* the beginning of every program which
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* will trap on CPUs without 11/45 FPU.
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*/
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case 1+USER: /* illegal instruction */
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if(fuiword(pc-2) == SETD && u.u_signal[SIGINS] == 0)
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goto out;
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i = SIGINS;
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break;
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case 2+USER: /* bpt or trace */
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i = SIGTRC;
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break;
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case 3+USER: /* iot */
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i = SIGIOT;
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break;
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case 5+USER: /* emt */
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i = SIGEMT;
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break;
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case 6+USER: /* sys call */
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u.u_error = 0;
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ps =& ~EBIT;
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callp = &sysent[fuiword(pc-2)&077];
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if (callp == sysent) { /* indirect */
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a = fuiword(pc);
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pc =+ 2;
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i = fuword(a);
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if ((i & ~077) != SYS)
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i = 077; /* illegal */
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callp = &sysent[i&077];
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for(i=0; i<callp->count; i++)
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u.u_arg[i] = fuword(a =+ 2);
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} else {
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for(i=0; i<callp->count; i++) {
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u.u_arg[i] = fuiword(pc);
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pc =+ 2;
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}
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}
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u.u_dirp = u.u_arg[0];
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trap1(callp->call);
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if(u.u_intflg)
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u.u_error = EINTR;
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if(u.u_error < 100) {
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if(u.u_error) {
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ps =| EBIT;
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r0 = u.u_error;
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}
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goto out;
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}
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i = SIGSYS;
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break;
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/*
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* Since the floating exception is an
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* imprecise trap, a user generated
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* trap may actually come from kernel
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* mode. In this case, a signal is sent
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* to the current process to be picked
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* up later.
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*/
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case 8: /* floating exception */
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psignal(u.u_procp, SIGFPT);
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return;
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case 8+USER:
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i = SIGFPT;
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break;
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/*
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* If the user SP is below the stack segment,
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* grow the stack automatically.
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* This relies on the ability of the hardware
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* to restart a half executed instruction.
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* On the 11/40 this is not the case and
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* the routine backup/l40.s may fail.
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* The classic example is on the instruction
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* cmp -(sp),-(sp)
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*/
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case 9+USER: /* segmentation exception */
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a = sp;
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if(backup(u.u_ar0) == 0)
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if(grow(a))
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goto out;
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i = SIGSEG;
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break;
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}
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psignal(u.u_procp, i);
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out:
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if(issig())
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psig();
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setpri(u.u_procp);
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}
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/*
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* Call the system-entry routine f (out of the
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* sysent table). This is a subroutine for trap, and
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* not in-line, because if a signal occurs
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* during processing, an (abnormal) return is simulated from
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* the last caller to savu(qsav); if this took place
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* inside of trap, it wouldn't have a chance to clean up.
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*
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* If this occurs, the return takes place without
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* clearing u_intflg; if it's still set, trap
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* marks an error which means that a system
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* call (like read on a typewriter) got interrupted
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* by a signal.
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*/
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trap1(f)
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int (*f)();
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{
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u.u_intflg = 1;
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savu(u.u_qsav);
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(*f)();
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u.u_intflg = 0;
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}
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/*
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* nonexistent system call-- set fatal error code.
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*/
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nosys()
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{
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u.u_error = 100;
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}
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/*
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* Ignored system call
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*/
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nullsys()
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{
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}
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