How do I hook an interrupt handler in Watcom C? (under protected mode) - China DOS Union Forum

Under Watcom, hooking an interrupt in protected mode requires writing an interrupt wrapper yourself in assembly. In the Watcom installation directory\samples\goodies there are bimo.asm and bimodal.c, which are examples of setting protected-mode and real-mode interrupt service functions for the same interrupt vector. You can refer to them. The main thing is to consider protection of the data area and code segment under protected mode. If you want to simplify it, I tried using only int 31 to set the protected-mode interrupt, and on some machines it didn't work properly, though on some it did. You can give it a try.

void __interrupt __far (*oldISR)(void);
void __interrupt __far newISR(void)
{
....
outp(0x20, 0x20);
}

union REGS r;
void __far *fh;

/* get old isr pointer */
r.x.eax = 0x0204;
r.x.ebx = (unsigned long)vector;
int386(0x31, &r, &r);
oldISR = (void __interrupt *)MK_FP(r.x.ecx, r.x.edx);

/* set new isr */
fh = (void __far *)newISR;
r.x.eax = 0x0205;
r.x.ebx = (unsigned long)vector;
r.x.ecx = (unsigned long)FP_SEG(fh);
r.x.edx = (unsigned long)FP_OFF(fh);
int386(0x31, &r, &r);

Floor1　superham	Posted 2002-12-25 00:00
初级用户　Posts 2　Credits 112
Thanks

Floor2　hbnf	Posted 2003-09-04 00:00
初级用户　Posts 1　Credits 102
Same as BC, _setvect(int, void())

Floor3　lemonhall	Posted 2003-09-06 00:00
高级用户　Posts 183　Credits 639
Hmm, not sure. Under protected mode you can't use INT 24 anymore. There was discussion under DJGPP about files on how to hook a short program under DPMI0.9, not sure whether that helps you.

Floor4　ATLaS	Posted 2003-09-07 00:00
初级用户　Posts 29　Credits 169
Under Watcom, hooking an interrupt in protected mode requires writing an interrupt wrapper yourself in assembly. In the Watcom installation directory\samples\goodies there are bimo.asm and bimodal.c, which are examples of setting protected-mode and real-mode interrupt service functions for the same interrupt vector. You can refer to them. The main thing is to consider protection of the data area and code segment under protected mode. If you want to simplify it, I tried using only int 31 to set the protected-mode interrupt, and on some machines it didn't work properly, though on some it did. You can give it a try. void __interrupt __far (oldISR)(void); void __interrupt __far newISR(void) { .... outp(0x20, 0x20); } union REGS r; void __far fh; /* get old isr pointer / r.x.eax = 0x0204; r.x.ebx = (unsigned long)vector; int386(0x31, &r, &r); oldISR = (void __interrupt )MK_FP(r.x.ecx, r.x.edx); /* set new isr / fh = (void __far )newISR; r.x.eax = 0x0205; r.x.ebx = (unsigned long)vector; r.x.ecx = (unsigned long)FP_SEG(fh); r.x.edx = (unsigned long)FP_OFF(fh); int386(0x31, &r, &r);