Workaround for locked up AMLC lines

As it was in the real world, especially with dialup ports, it is possible
for an emulator AMLC line to get blocked by stray flow control characters.
The blocked port may appear dead to the next user to connect, if they are
not "serial savvy" enough to try sending an XON character.

A large number of vulnerability scanners have found and have been hitting
the public emulators, injecting HTTP transactions or worse into the AMLC
ports and often locking all of them daily.

This workaround injects an XON (DC1, 0221) and a line kill character as
extracted from the DEFKIL field in FIGCOM, into the AMLC line when a new
connection is received.

There is a -dolineclear command line switch to enable the behavior.

.gitignore

@@ -3,6 +3,7 @@
 *.log
 *.swp
 tags
+cmraw
 cscope.*
 em
 emlink

README.md

@@ -22,6 +22,9 @@ the host processor having a large set of general-purpose registers.
 Coming soon, we swear!  There is a unix man page included in this
 repository.
 
+Github discussions are now enabled for this repository, and can be
+used to ask for help.
+
 ## Public Systems
 
 There are a set of emulators available for public use.  These may be

devamlc.h

@@ -262,6 +262,7 @@ int devamlc (int class, int func, int device) {
     unsigned short ctinterrupt;         /* 1 bit per line */
     unsigned short dss;                 /* 1 bit per line */
     unsigned short connected;           /* 1 bit per line */
+    unsigned short dolineclear;         /* 1 bit per line */
     unsigned short serial;              /* true if any CT_SERIAL lines */
     unsigned short dsstime;             /* countdown to dss poll */
              short fd[16];              /* Unix fd, 1 per line */
@@ -329,6 +330,7 @@ int devamlc (int class, int func, int device) {
       for (dx=0; dx<MAXBOARDS; dx++) {
         dc[dx].deviceid = 0;
         dc[dx].connected = 0;
+        dc[dx].dolineclear = 0;
         dc[dx].serial = 0;
         for (lx = 0; lx < 16; lx++) {
           dc[dx].fd[lx] = -1;
@@ -885,6 +887,7 @@ int devamlc (int class, int func, int device) {
                   close(dc[i].fd[lx]);
                 dc[i].dss |= BITMASK16(lx+1);
                 dc[i].connected |= BITMASK16(lx+1);
+                dc[i].dolineclear |= BITMASK16(lx+1);
                 dc[i].fd[lx] = fd;
                 dc[i].tstate[lx] = TS_DATA;
                 //printf("em: AMLC connection, fd=%d, device='%o, line=%d\n", fd, dc[i].deviceid, lx);
@@ -911,10 +914,12 @@ int devamlc (int class, int func, int device) {
           optval = 1;
           if (setsockopt(fd, IPPROTO_TCP, TCP_NODELAY, &optval, sizeof(optval)) == -1)
             perror("unable to set TCP_NODELAY");
+#ifndef __APPLE__
           /* Set 600 second keepalive idle time for this socket */
           optval = 600;
-	  if (setsockopt(fd, 6 /* TCP */, TCP_KEEPIDLE, &optval, sizeof(optval)) == -1)
+          if (setsockopt(fd, IPPROTO_TCP, TCP_KEEPIDLE, &optval, sizeof(optval)) == -1)
             perror("unable to set TCP_KEEPIDLE");
+#endif
           /* ... and turn on keepalive */
           optval = 1;
           if (setsockopt(fd, SOL_SOCKET, SO_KEEPALIVE, &optval, sizeof(optval)) == -1)
@@ -1138,6 +1143,53 @@ dorecv:
       if (dc[dx].deviceid == 0 || dc[dx].connected == 0 || dc[dx].eor)
         continue;
 
+      /* Inject xon / kill if dolineclear is true */
+
+      if (dolinecleararg)
+        for (lx = 0; lx < 16; lx++)
+          if (dc[dx].dolineclear & BITMASK16(lx+1))
+          {
+            unsigned char ch;
+            unsigned short utemp;
+            int dmcpair, lcount;
+            ea_t dmcea, dmcbufbegea, dmcbufendea;
+            unsigned short dmcnw;
+
+            if (dc[dx].bufnum)
+              dmcea = dc[dx].dmcchan + 2;
+            else
+              dmcea = dc[dx].dmcchan;
+            dmcpair = get32io(dmcea);
+            dmcbufbegea = dmcpair>>16;
+            dmcbufendea = dmcpair & 0xffff;
+            dmcnw = dmcbufendea - dmcbufbegea + 1;
+
+            if (dmcnw < 2)
+              continue;
+
+            utemp = lx<<12 | 0x0200 | 0221; /* dc1/xon */
+            put16io(utemp, dmcbufbegea);
+            dmcbufbegea = INCVA(dmcbufbegea, 1);
+
+            ch = (unsigned char)get16(MAKEVA(014, 0705));
+            utemp = lx<<12 | 0x0200 | ch; /* kill */
+            put16io(utemp, dmcbufbegea);
+            dmcbufbegea = INCVA(dmcbufbegea, 1);
+
+            dc[dx].recvlx = lx;
+            if (dmcbufbegea-1 > dmcbufendea)
+              fatal("AMLC tumble table overflowed?");
+            put16io(dmcbufbegea, dmcea);
+            if (dmcbufbegea > dmcbufendea) {          /* end of range has occurred */
+              dc[dx].bufnum = 1-dc[dx].bufnum;
+              dc[dx].eor = 1;
+              neweor = 1;
+              anyeor = 1;
+            }
+
+            dc[dx].dolineclear &= ~BITMASK16(lx+1);
+          }
+
       /* select to see which lines have data to be read */
 
       FD_ZERO(&readfds);

em.1

@@ -2,7 +2,7 @@
 .\" em.1, Boone, 03/13/20
 .\" Man page for Jim Wilcoxson's Prime 50-Series emulator
 .\" ---------------------------------------------------------------------------
-.TH em 1 "2020-03-14" "Jim Wilcoxson" "50-Series Emulator"
+.TH em 1 "2020-06-23" "Jim Wilcoxson" "50-Series Emulator"
 .\" ---------------------------------------------------------------------------
 .SH NAME
 em \- Emulator for Prime 50-Series systems
@@ -35,6 +35,8 @@ a tape controller, 4 drives, using the .TAP format
 .IP \(bu
 a PNC controller emulating RingNet over TCP/IP
 .IP \(bu
+two sync serial controllers supporting up to 8 lines
+.IP \(bu
 a bypass for Primos system serial number checks
 .IP \(bu
 Unix utilities to read/write physical tapes & Magsav tapes
@@ -143,6 +145,15 @@ on the host.  Multiple trace types may be listed, separated by
 spaces.  Tracing may be initially turned off by including the
 .I off
 trace type.
+.PP
+\fB-dolineclear\fR
+.IP
+Inject an XON (DC1, 0221) character and a line kill character into the
+input buffers each time an AMLC line receives an incoming connection.
+The system's configured line kill character is fetched from the
+DEFKIL field of FIGCOM, at address 14(0)/705.  This behavior helps
+counteract lines which have been blocked by internet vulnerability
+scanners injecting non-telnet data streams.
 .\" ---------------------------------------------------------------------------
 .SH FILES
 .TP
@@ -163,6 +174,18 @@ Example:
 8 192.168.10.4:9000  # Outbound socket connection e.g. for spooler
 .EE
 .TP
+smlc.cfg
+Used to associate outbound sync serial (MDLC or HSSMLC) lines with destination
+IP addresses and port numbers, or to associate inbound sync serial lines
+with port numbers.  An outbound line corresponds to an RJE site defined as a
+SLAVE site, and an inbound line corresponds to an RJE site defined as a MASTER
+site.  Optional.  Comments work the same as amlc.cfg.  Example:
+
+.EX
+0 10.1.1.3:2554      # Connect to TCP port 2554 of host 10.1.1.3 for outbound line 0
+1 9951               # Listen on TCP port 9951 for inbound line 1
+.EE
+.TP
 console.log
 All console output is also written to this file.  It is overwritten
 at each invocation.  Created by
@@ -274,9 +297,12 @@ off|Start with tracing disabled
 all|Everything
 flush|Flush trace file after each write
 tlb|STLB and IOTLB changes
+smlc|MDLC/HSSMLC device I/O
 OWNERL|Execution of this PCB
-instruction count|Begin after specified number of instructions
+#instruction count|Begin after specified number of instructions
+|(the leading # is literal)
 octal segno|Execution in the given segment number
+|(may interact poorly with "off")
 process number|Execution of this user number
 .TE
 .\" ---------------------------------------------------------------------------
@@ -360,7 +386,8 @@ CMD,1/3/5+1,Cartridge Module 32/64/96 MB
 .\" ---------------------------------------------------------------------------
 .SH AUTHOR
 .PP
-This emulator was written by Jim Wilcoxson.  Man page by Dennis Boone.
+This emulator was written by Jim Wilcoxson.  MDLC/HSSMLC support by
+Kevin Jordan.  Man page by Dennis Boone.
 .\" ---------------------------------------------------------------------------
 .SH SEE ALSO
 This project is hosted at

em.c

@@ -1,5 +1,5 @@
 /* Pr1me Computer emulator, Jim Wilcoxson (prirun@gmail.com), April 4, 2005
-   Copyright (C) 2005-2019, Jim Wilcoxson.  All Rights Reserved.
+   Copyright (C) 2005-2021, Jim Wilcoxson.  All Rights Reserved.
 
    Emulates a Prime Computer system by:
    - booting from a Prime disk image (normal usage)
@@ -287,6 +287,7 @@ static void macheck (unsigned short p300vec, unsigned short chkvec, unsigned int
    T_PX         Process exchange
    T_LM         License manager
    T_TLB        STLB and IOTLB changes
+   T_SMLC       SMLC device I/O
 */
 
 #define T_EAR   0x00000001
@@ -309,6 +310,7 @@ static void macheck (unsigned short p300vec, unsigned short chkvec, unsigned int
 #define T_GET   0x00020000
 #define T_EAS   0x00040000
 #define T_TLB   0x00080000
+#define T_SMLC  0x00100000
 
 #define BITMASK16(b) (0x8000 >> ((b)-1))
 #define BITMASK32(b) ((unsigned int)(0x80000000) >> ((b)-1))
@@ -656,6 +658,7 @@ static unsigned short *physmem = NULL; /* system's physical memory */
 
 //static ea_t tnoua_ea=0, tnou_ea=0, tsrc_ea=0;
 static int domemdump;                       /* -memdump arg */
+static int dolinecleararg;                  /* -dolineclear arg */
 
 static int tport;                           /* -tport option (incoming terminals) */
 static int nport;                           /* -nport option (PNC/Ringnet) */
@@ -1689,6 +1692,8 @@ static int devpoll[64] = {0};
    '35 = devamlc: 4th AMLC (16 lines)
    '45 = devdisk: 7th disk controller (8 drives)
    '46 = devdisk: 8th disk controller (8 drives)
+   '50 = devsmlc: 1st HSSMLC/MDLC (4 lines)
+   '51 = devsmlc: 2nd HSSMLC/MDLC (4 lines)
    '52 = devamlc: 3rd AMLC (16 lines)
    '53 = devamlc: 2nd AMLC (16 lines)
    '54 = devamlc: 1st AMLC (16 lines)
@@ -1700,7 +1705,7 @@ static int (*devmap[64])(int, int, int) = {
   /* '2x */ devcp,devnone,devdisk,devdisk,devdisk,devdisk,devdisk,devdisk,
   /* '3x */ devnone,devnone,devamlc,devnone,devnone,devamlc,devnone,devnone,
   /* '4x */ devnone,devnone,devnone,devnone,devnone,devdisk,devdisk,devnone,
-  /* '5x */ devnone,devnone,devamlc,devamlc,devamlc,devnone,devnone,devnone,
+  /* '5x */ devsmlc,devsmlc,devamlc,devamlc,devamlc,devnone,devnone,devnone,
   /* '6x */ devnone,devnone,devnone,devnone,devnone,devnone,devnone,devnone,
   /* '7x */ devnone,devnone,devnone,devnone,devnone,devnone,devnone,devnone};
 
@@ -1714,6 +1719,7 @@ static int (*devmap[64])(int, int, int) = {
    '20 = devcp: clock / VCP / SOC
    '26 = devdisk: 1st disk controller (8 drives)
    '27 = devdisk: 2nd disk controller (8 drives)
+   '50 = devsmlc: 1st HSSMLC/MDLC (4 lines)
    '54 = 1st amlc (terminal) controller (16 lines)
    '53 = devamlc: 2nd AMLC (16 lines)
 */
@@ -1724,7 +1730,7 @@ static int (*devmap[64])(int, int, int) = {
   /* '2x */ devcp,devnone,devnone,devnone,devnone,devnone,devdisk,devdisk,
   /* '3x */ devnone,devnone,devnone,devnone,devnone,devnone,devnone,devnone,
   /* '4x */ devnone,devnone,devnone,devnone,devnone,devnone,devnone,devnone,
-  /* '5x */ devnone,devnone,devnone,devamlc,devamlc,devnone,devnone,devnone,
+  /* '5x */ devsmlc,devnone,devnone,devamlc,devamlc,devnone,devnone,devnone,
   /* '6x */ devnone,devnone,devnone,devnone,devnone,devnone,devnone,devnone,
   /* '7x */ devnone,devnone,devnone,devnone,devnone,devnone,devnone,devnone};
 #endif
@@ -4363,7 +4369,7 @@ int main (int argc, char **argv) {
 #define XRBRACE 0375
 
   printf("[Prime Emulator ver %s %s]\n", REV, __DATE__);
-  printf("[Copyright (C) 2005-2019 Jim Wilcoxson prirun@gmail.com]\n");
+  printf("[Copyright (C) 2005-2021 Jim Wilcoxson prirun@gmail.com]\n");
   if (argc > 1 && (strcmp(argv[1],"--version") == 0)) {
     exit(0);
   }
@@ -4446,6 +4452,7 @@ int main (int argc, char **argv) {
 #include "dispatch.h"
 
   domemdump = 0;
+  dolinecleararg = 0;
   bootarg = NULL;
   bootfile[0] = 0;
   gv.pmap32bits = 0;
@@ -4465,6 +4472,9 @@ int main (int argc, char **argv) {
     } else if (strcmp(argv[i],"-memdump") == 0) {
       domemdump = 1;
 
+    } else if (strcmp(argv[i],"-dolineclear") == 0) {
+      dolinecleararg = 1;
+
     } else if (strcmp(argv[i],"-ss") == 0) {
       if (i+1 < argc && argv[i+1][0] != '-') {
         sscanf(argv[++i],"%o", &templ);
@@ -4603,14 +4613,16 @@ int main (int argc, char **argv) {
           setlinebuf(gv.tracefile);
         else if (strcmp(argv[i],"tlb") == 0)
           gv.traceflags |= T_TLB;
+        else if (strcmp(argv[i],"smlc") == 0)
+          gv.traceflags |= T_SMLC;
         else if (isdigit(argv[i][0]) && strlen(argv[i]) <= 3 && sscanf(argv[i],"%d", &templ) == 1)
           gv.traceuser = 0100000 | (templ<<6);   /* form OWNERL for user # */
-	else if (isdigit(argv[i][0]) && sscanf(argv[i],"%d", &templ) == 1)
-	  gv.traceinstcount = templ;
         else if (strlen(argv[i]) == 6 && sscanf(argv[i],"%o", &templ) == 1)
           gv.traceuser = templ;                  /* specify OWNERL directly */
         else if (strlen(argv[i]) == 4 && sscanf(argv[i],"%o", &templ) == 1)
           gv.traceseg = templ;                   /* specify RPH segno */
+        else if (argv[i][0] == '#' && sscanf(argv[i]+1,"%d", &templ) == 1)
+          gv.traceinstcount = templ;
         else if (strlen(argv[i]) <= 8 && argv[i][0] != '-') {
           if (gv.numtraceprocs >= MAXTRACEPROCS)
             fprintf(stderr,"Only %d trace procs are allowed\n", MAXTRACEPROCS);
@@ -4701,6 +4713,7 @@ int main (int argc, char **argv) {
   /* finish setting up tracing after all options are read, ie, maps */
 
 #ifndef NOTRACE
+  TRACEA("Trace file initialized\n");
   TRACEA("Trace flags = 0x%x\n", gv.traceflags);
   gv.savetraceflags = gv.traceflags;
   gv.traceflags = 0;
@@ -4710,6 +4723,14 @@ int main (int argc, char **argv) {
     TRACEA("Tracing enabled for all users\n");
   if (gv.traceinstcount != 0)
     TRACEA("Tracing enabled after instruction %u\n", gv.traceinstcount);
+  if (gv.traceseg != 0)
+  {
+    TRACEA("Tracing enabled for segment %04o\n", gv.traceseg);
+    /* This could be splattering other settings that aren't really
+       compatible with RPH trace.  C'est la vie? */
+    gv.savetraceflags |= T_FLOW;
+    gv.tracetriggered = 0;
+  }
   for (i=0; i<gv.numtraceprocs; i++) {
     for (j=0; j<numsyms; j++) {
       if (strcasecmp(mapsym[j].symname, traceprocs[i].name) == 0 && mapsym[j].symtype == 'e') {
@@ -4936,6 +4957,11 @@ fetch:
 #endif
 
 #ifndef NOTRACE
+  if (gv.traceseg != 0)
+    if (gv.traceseg == (RPH & 0xFFF))
+      gv.tracetriggered = 1;
+    else
+      gv.tracetriggered = 0;
     gv.traceflags = 0;
   if (gv.tracetriggered &&
       (gv.instcount >= gv.traceinstcount) &&
@@ -6276,15 +6302,33 @@ d_hlt:  /* 000000 */
   if (bootarg) {
     printf("\nCPU halt, instruction #%u at %o/%o %s: %o %o ^%06o^\nA='%o/%d  B='%o/%d  L='%o/%d  X=%o/%d", gv.instcount, RPH, RPL, searchloadmap(gv.prevpc,' '), get16t(gv.prevpc), get16t(gv.prevpc+1), lights, getcrs16(A), getcrs16s(A), getcrs16(B), getcrs16s(B), getcrs32(A), getcrs32s(A), getcrs16(X), getcrs16s(X));
     while (1) {
+      int n;
+      static int ttydev;
+      ttydev = open("/dev/tty", O_RDWR, 0);
+      if (ttydev < 0) {
+        perror(" error opening /dev/tty");
+        fatal(NULL);
+      }
       printf("\nPress Enter to continue, h to halt... ");
-      utempa = getchar();
+      fflush(stdout);
+      utempa = ' ';
+      n = 0;
+      while (n == 0)
+        n = read(ttydev, &utempa, 1);
+/*    utempa = getchar(); */
       printf("\n");
       if (utempa == '\r' || utempa == '\n')
+      {
+        close(ttydev);
         goto fetch;
+      }
       if (utempa == 'h')
+      {
+        close(ttydev);
         break;
       }
     }
+  }
   fatal("CPU halt");
 
 d_pim:  /* 000205 (R-mode) */

emdev.h

@@ -2224,3 +2224,5 @@ int devdisk (int class, int func, int device) {
 #include "devpnc.h"
 
 #include "devamlc.h"
+
+#include "devsmlc.h"

makefile

@@ -7,7 +7,7 @@ all_deps = makefile
 em_objs = em.o em
 em_deps = \
   em.c regs.h emdev.h ea64v.h ea32i.h fp.h dispatch.h geom.h \
-  devpnc.h devamlc.h swap.h
+  devpnc.h devamlc.h devsmlc.h swap.h
 
 CFLAGS =
 # Uncomment for building on SmartOS/Solaris:

util/cmraw.c

@@ -0,0 +1,35 @@
+/* Show approximate minimum clock resolution
+   Derived from the example in the linux man page for clock_gettime() */
+
+#define _XOPEN_SOURCE 600
+#include <time.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdbool.h>
+#include <unistd.h>
+
+static void displayClock(clockid_t clock, char *name)
+{
+   struct timespec ts;
+   time_t oldsec;
+   long oldnsec;
+
+   clock_gettime(clock, &ts);
+   oldsec = ts.tv_sec;
+   oldnsec = ts.tv_nsec;
+   while (ts.tv_sec == oldsec && ts.tv_nsec == oldnsec)
+   {
+      if (clock_gettime(clock, &ts) == -1) {
+         perror("clock_gettime");
+         exit(EXIT_FAILURE);
+      }
+   }
+   printf("%-15s: %10ld sec %09ld nsec\n", name,
+      (long) ts.tv_sec - oldsec, ts.tv_nsec - oldnsec);
+}
+
+int main(int argc, char *argv[])
+{
+   displayClock(CLOCK_MONOTONIC_RAW, "CLOCK_MONOTONIC_RAW");
+   exit(0);
+}