implement (partially) int21/8Ch call

hdr/sig.h

@@ -0,0 +1,29 @@
+/*
+ *  FDPP - freedos port to modern C++
+ *  Copyright (C) 2017-2026  @stsp
+ *
+ *  This program is free software: you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation, either version 3 of the License, or
+ *  (at your option) any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+typedef struct {
+  UWORD sig_off;
+  UWORD sig_seg;
+  UBYTE sig_num;
+  UBYTE sig_action;
+} sigact;
+ANNOTATE_SIZE(sigact, 6);
+
+enum { _SIG_DFL, _SIG_IGN, _SIG_GET };
+enum { _SIGINTR = 1, _SIGHUP, _SIGTERM = 8, _SIGPIPE, _SIGUSER1 = 0xd,
+       _SIGUSER2 };

kernel/break.c

@@ -96,3 +96,26 @@ void handle_break(struct dhdr FAR *pdev)
 
   spawn_int23();                /* invoke user INT-23 and never come back */
 }
+
+void handle_sig(int signum)
+{
+  if (signum != sig_act.sig_num)
+    return;
+  switch (sig_act.sig_action) {
+    case _SIG_DFL:
+      return_code = 0x400 | signum;
+      return_user();
+      /* no break */
+    case _SIG_IGN:
+      return;
+  }
+  if (!ErrorMode) {             /* within int21_handler, InDOS is not incremented */
+    if (InDOS)
+      --InDOS;                  /* fail-safe */
+    else
+      panic("Signal not in DOS");
+  }
+
+  /* TODO: if more signals implemented, copy sa to sig_act here */
+  dispatch_sig();
+}

kernel/chario.c

@@ -311,8 +311,10 @@ long cooked_read(struct dhdr FAR *pdev, size_t n, char FAR *bp,
     c = raw_get_char(pdev, check_break);
     if (c < 0)
       return c;
-    if (c == 256)
+    if (c == 256) {
+      handle_sig(_SIGHUP);
       break;
+    }
     *bp++ = c;
     xfer++;
     if ((unsigned char)c == CTL_Z)
@@ -346,7 +348,7 @@ STATIC unsigned do_read_char_dev(struct dhdr FAR *pdev, BOOL check_break)
       else
       {
         unsigned char c1 = ndread(syscon);
-        if (c1 == CTL_C)
+        if (!c1 || c1 == CTL_C)
         {
           con_flush(syscon);
           c = 256;  // EOF
@@ -421,6 +423,7 @@ static unsigned int do_read_line(int sft_in, kbd0a FAR *kp, BOOL check_break,
     {
       case 0:
       case 256:
+        handle_sig(_SIGHUP);
         return c;
       case LF:
         /* show LF if it's not the first character. Never store it */

kernel/entry.asm

@@ -324,6 +324,8 @@ int21_reentry:
                 je      int21_user
                 cmp     ah,51h
                 je      int21_user
+                cmp     ah,8ch
+                je      int21_user
                 cmp     ah,62h
                 jne     int21_1
 

kernel/glob_asm.h

@@ -29,6 +29,7 @@ __ASM(dmatch, sda_tmp_dm_ren) SEMIC   /* 2nd Temporary directory match buffer */
 __ASM(dmatch, dmatch_ff) SEMIC        /* directory match buffer for fcb */
 __ASM_FAR(void, dta) SEMIC
 __ASM(UWORD, cu_psp) SEMIC            /* current psp segment                  */
+__ASM(sigact, sig_act) SEMIC
 __ASM_FAR(iregs, user_r) SEMIC      /* User registers for int 21h call      */
 __ASM_FAR(fcb, sda_lpFcb) SEMIC     /* Pointer to users fcb                 */
 __ASM_FAR(sft, lpCurSft) SEMIC

kernel/globals.h

@@ -63,6 +63,7 @@ static BYTE *Globals_hRcsId =
 #include "nls.h"
 #include "dyn.h"
 #include "memtype.h"
+#include "sig.h"
 #include "glob_fd.h"
 #include "debug.h"
 

kernel/inthndlr.c

@@ -167,6 +167,26 @@ VOID ASMCFUNC int21_syscall(iregs FAR * irp)
     case 0x62:
       irp->BX = cu_psp;
 
+    /* it must be here and not in int21_service() to not overwrite user_r */
+    case 0x8c: {
+      sigact old = sig_act, n;
+      if (irp->AL != _SIGHUP) {
+        irp->AX = 1;
+        irp->FLAGS |= FLG_CARRY;
+        break;
+      }
+      n.sig_num = irp->AL;
+      n.sig_action = irp->BL;
+      n.sig_seg = irp->DS;
+      n.sig_off = irp->DX;
+      n_fmemcpy(&sig_act, &n, sizeof(n));
+      irp->AX = old.sig_action;
+      irp->ES = old.sig_seg;
+      irp->BX = old.sig_off;
+      irp->FLAGS &= ~FLG_CARRY;
+      break;
+    }
+
       /* Normal DOS function - DO NOT ARRIVE HERE          */
  /* default: */
   }
@@ -1079,7 +1099,7 @@ VOID ASMCFUNC int21_service(iregs FAR * r)
 
       /* Load and Execute Program */
     case 0x4b:
-      break_flg = FALSE;
+      break_flg = 0;
       rc = DosExec(lr.AL, MK_FP(lr.ES, lr.BX), FP_DS_DX);
       goto short_check;
 
@@ -1098,8 +1118,8 @@ VOID ASMCFUNC int21_service(iregs FAR * r)
       }
       else if (break_flg)
       {
-        break_flg = FALSE;
-        rc = 0x100;
+        rc = break_flg << 8;
+        break_flg = 0;
       }
       return_code = lr.AL | rc;
       if (DosMemCheck() != SUCCESS)

kernel/kernel.asm

@@ -610,7 +610,14 @@ int21regs_seg   dw      0
                 global  critical_sp
 critical_sp     dw      0               ;268 - critical error internal stack
                 global  current_ddsc
-current_ddsc    times 2 dw 0
+current_ddsc    times 2 dw 0            ;26a
+                global  _sig_act
+_sig_act:
+sig_off         dw      0               ;26e
+sig_seg         dw      0               ;270
+                global  sig_num
+sig_num         db      0               ;272
+sig_act         db      0               ;273
 
                 ; Pad to 027ah
                 times (27ah - ($ - _internal_data)) db 0

kernel/procsupt.asm

@@ -35,6 +35,8 @@
 
                 extern  _break_flg     ; break detected flag
                 extern  _int21_handler
+                extern  _sig_act
+                extern  sig_num
 
                 %include "stacks.inc"
 
@@ -131,6 +133,50 @@ _spawn_int23:
 ??int23_respawn:
 		jmp DGROUP:_int21_handler
 
+; void ASMFUNC NORETURN dispatch_sig(void);
+                global  _dispatch_sig
+_dispatch_sig:
+		mov ds, [cs:_DGROUP_]		;; Make sure DS is OK
+		mov bp, [_user_r]
+		cli
+		mov ss, [_user_r+2]
+		RestoreSP
+		sti
+		; get all the user registers back
+		Restore386Registers
+		POP$ALL
+		push ds
+		push bp
+		mov bp, sp
+		clc
+		pushf
+		mov ds, [cs:_DGROUP_]
+		call far [ds:_sig_act]
+		mov sp, bp
+		pop bp
+		pop ds
+		jc ??sig_term
+		jz ??sig_err
+??sig_respawn:
+		jmp DGROUP:_int21_handler
+??sig_term:
+		;; The user returned via RETF 0, Carry is set
+		;; --> terminate program
+		;; This is done by set the _break_flg and modify the
+		;; AH value, which is passed to the _respawn_ call
+		;; into 0, which is "Terminate program".
+		push ds                 ;; we need DGROUP
+		mov ds, [cs:_DGROUP_]
+		mov byte [_break_flg], 4
+		mov al, byte [sig_num]
+		pop ds
+		mov ah, 4ch		;; terminate
+		jmp ??sig_respawn
+??sig_err:
+		mov ax, 5fh  ; interrupted
+		stc
+		retf 2
+
 ;
 ; interrupt enable and disable routines
 ;

kernel/proto.h

@@ -54,6 +54,7 @@ unsigned char ctrl_break_pressed(void);
 unsigned char check_handle_break(__FAR(struct dhdr) pdev);
 void handle_break(__FAR(struct dhdr) pdev);
 void clear_break(void);
+void handle_sig(int signum);
 #ifdef __WATCOMC__
 #pragma aux handle_break aborts;
 #endif
@@ -551,5 +552,6 @@ WORD ASMPASCAL INITTEXT init_switchar(WORD chr);
 COUNT ASMPASCAL INITTEXT UMB_get_largest(__FAR(void) driverAddress, UDWORD * __seg, UCOUNT * size);
 VOID ASMFUNC INITTEXT init_stacks(__FAR(VOID) stack_base, COUNT nStacks, WORD stackSize);
 void ASMFUNC NORETURN spawn_int23(void);        /* procsupt.asm */
+void ASMFUNC NORETURN dispatch_sig(void);       /* procsupt.asm */
 /* kernel.asm */
 VOID ASMFUNC FAR NORETURN call_p_0(__FAR(const struct config)Config); /* P_0, actually */

kernel/task.c

@@ -974,7 +974,7 @@ VOID ASMCFUNC P_0(const struct config FAR *Config)
 
 VOID ASMCFUNC P_0_exit(unsigned short retcode)
 {
-  if ((retcode & 0xff) == 0) {
+  if ((retcode & 0xff) == 0 || (retcode >> 8)) {
     switch (retcode >> 8) {
       case 0:
         _printf("\nShell %s exited, press any key...\n", GET_PTR(Shell));
@@ -985,6 +985,10 @@ VOID ASMCFUNC P_0_exit(unsigned short retcode)
       case 2:
         _printf("\nShell %s aborted due to critical error, press any key...\n", GET_PTR(Shell));
         break;
+      case 4:
+        _printf("\nShell %s aborted by signal %i, press any key...\n",
+            GET_PTR(Shell), retcode & 0xff);
+        break;
     }
     con_flush_stdin();
     read_char_stdin(0);