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#ifndef __MSDOS__
#ifdef __AS386_16__
#include <errno.h>
#include <signal.h>
typedef __sighandler_t Sig;
extern int __signal __P((int, __sighandler_t));
static Sig system_signal();
Sig __sigtable[_NSIG-1];
/*
* Signal handler.
*
*/
/*
* KERNEL INTERFACE:
* It is assumed the kernel will never give us a signal we haven't
* _explicitly_ asked for!
*
* The Kernel need only save space for _one_ function pointer
* (to system_signal) and must deal with SIG_DFL and SIG_IGN
* in kernel space.
*
* When a signal is required the kernel must set all the registers as if
* returning from a interrupt normally then push the number of the signal
* to be generated, push the current pc value, then set the pc to the
* address of the 'system_signal' function.
*/
Sig
signal(number, pointer)
int number;
Sig pointer;
{
Sig old_sig;
int rv;
if( number < 1 || number >= _NSIG ) { errno=EINVAL; return SIG_ERR; }
if( pointer == SIG_DFL || pointer == SIG_IGN )
rv = __signal(number, pointer);
else
rv = __signal(number, (__sighandler_t) system_signal);
if( rv < 0 ) return SIG_ERR;
old_sig = __sigtable[number-1];
__sigtable[number-1] = pointer;
switch(rv)
{
case 0: return SIG_DFL;
case 1: return SIG_IGN;
return old_sig;
}
}
#asm
.text
_system_signal: ! When this is called by the kernel the stack contains
pushf ! in order:
push ax !
push bx ! The signal number, (NOS)
push cx ! The program counter, (TOS)
push dx !
push si ! It does NOT contain the CS register or the flags.
push di ! This means it cannot be unraveled by an iret.
push bp
push es ! Note also only ES segment register is saved.
mov bx,sp ! Unlike minix the rv from a system call is in AX.
mov bx,[bx+20]
#if __FIRST_ARG_IN_AX__
mov ax,bx
#else
push bx ! NB this is _unchecked_, do we want to ?
#endif
add bx,bx
mov bx,[bx+___sigtable-2] ! Offset by 2 cause no entry for signal 0
call bx ! Do we want to check BX for 0 or 1 ?
inc sp
inc sp
pop es
pop bp
pop di
pop si
pop dx
pop cx
pop bx
pop ax
popf
ret #2 ! Get rid of the signum too.
#endasm
#endif /* __AS386_16__ */
#endif /* __MSDOS__ */
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