vm86.c

内核linux2.4.20,可跟rtlinux3.2打补丁 组成实时linux系统,编译内核

	: "r" (base), "q" (val), "0" (ptr))

#define pushl(base, ptr, val) \
__asm__ __volatile__( \
	"decw %w0\n\t" \
	"rorl $16,%2\n\t" \
	"movb %h2,0(%1,%0)\n\t" \
	"decw %w0\n\t" \
	"movb %b2,0(%1,%0)\n\t" \
	"decw %w0\n\t" \
	"rorl $16,%2\n\t" \
	"movb %h2,0(%1,%0)\n\t" \
	"decw %w0\n\t" \
	"movb %b2,0(%1,%0)" \
	: "=r" (ptr) \
	: "r" (base), "q" (val), "0" (ptr))

#define popb(base, ptr) \
({ unsigned long __res; \
__asm__ __volatile__( \
	"movb 0(%1,%0),%b2\n\t" \
	"incw %w0" \
	: "=r" (ptr), "=r" (base), "=q" (__res) \
	: "0" (ptr), "1" (base), "2" (0)); \
__res; })

#define popw(base, ptr) \
({ unsigned long __res; \
__asm__ __volatile__( \
	"movb 0(%1,%0),%b2\n\t" \
	"incw %w0\n\t" \
	"movb 0(%1,%0),%h2\n\t" \
	"incw %w0" \
	: "=r" (ptr), "=r" (base), "=q" (__res) \
	: "0" (ptr), "1" (base), "2" (0)); \
__res; })

#define popl(base, ptr) \
({ unsigned long __res; \
__asm__ __volatile__( \
	"movb 0(%1,%0),%b2\n\t" \
	"incw %w0\n\t" \
	"movb 0(%1,%0),%h2\n\t" \
	"incw %w0\n\t" \
	"rorl $16,%2\n\t" \
	"movb 0(%1,%0),%b2\n\t" \
	"incw %w0\n\t" \
	"movb 0(%1,%0),%h2\n\t" \
	"incw %w0\n\t" \
	"rorl $16,%2" \
	: "=r" (ptr), "=r" (base), "=q" (__res) \
	: "0" (ptr), "1" (base)); \
__res; })

static void do_int(struct kernel_vm86_regs *regs, int i, unsigned char * ssp, unsigned long sp)
{
	unsigned long *intr_ptr, segoffs;

	if (regs->cs == BIOSSEG)
		goto cannot_handle;
	if (is_revectored(i, &KVM86->int_revectored))
		goto cannot_handle;
	if (i==0x21 && is_revectored(AH(regs),&KVM86->int21_revectored))
		goto cannot_handle;
	intr_ptr = (unsigned long *) (i << 2);
	if (get_user(segoffs, intr_ptr))
		goto cannot_handle;
	if ((segoffs >> 16) == BIOSSEG)
		goto cannot_handle;
	pushw(ssp, sp, get_vflags(regs));
	pushw(ssp, sp, regs->cs);
	pushw(ssp, sp, IP(regs));
	regs->cs = segoffs >> 16;
	SP(regs) -= 6;
	IP(regs) = segoffs & 0xffff;
	clear_TF(regs);
	clear_IF(regs);
	return;

cannot_handle:
	return_to_32bit(regs, VM86_INTx + (i << 8));
}

int handle_vm86_trap(struct kernel_vm86_regs * regs, long error_code, int trapno)
{
	if (VMPI.is_vm86pus) {
		if ( (trapno==3) || (trapno==1) )
			return_to_32bit(regs, VM86_TRAP + (trapno << 8));
		do_int(regs, trapno, (unsigned char *) (regs->ss << 4), SP(regs));
		return 0;
	}
	if (trapno !=1)
		return 1; /* we let this handle by the calling routine */
	if (current->ptrace & PT_PTRACED) {
		unsigned long flags;
		spin_lock_irqsave(&current->sigmask_lock, flags);
		sigdelset(&current->blocked, SIGTRAP);
		recalc_sigpending(current);
		spin_unlock_irqrestore(&current->sigmask_lock, flags);
	}
	send_sig(SIGTRAP, current, 1);
	current->thread.trap_no = trapno;
	current->thread.error_code = error_code;
	return 0;
}

void handle_vm86_fault(struct kernel_vm86_regs * regs, long error_code)
{
	unsigned char *csp, *ssp;
	unsigned long ip, sp;

#define CHECK_IF_IN_TRAP \
	if (VMPI.vm86dbg_active && VMPI.vm86dbg_TFpendig) \
		pushw(ssp,sp,popw(ssp,sp) | TF_MASK);
#define VM86_FAULT_RETURN \
	if (VMPI.force_return_for_pic  && (VEFLAGS & (IF_MASK | VIF_MASK))) \
		return_to_32bit(regs, VM86_PICRETURN); \
	return;
	                                   
	csp = (unsigned char *) (regs->cs << 4);
	ssp = (unsigned char *) (regs->ss << 4);
	sp = SP(regs);
	ip = IP(regs);

	switch (popb(csp, ip)) {

	/* operand size override */
	case 0x66:
		switch (popb(csp, ip)) {

		/* pushfd */
		case 0x9c:
			SP(regs) -= 4;
			IP(regs) += 2;
			pushl(ssp, sp, get_vflags(regs));
			VM86_FAULT_RETURN;

		/* popfd */
		case 0x9d:
			SP(regs) += 4;
			IP(regs) += 2;
			CHECK_IF_IN_TRAP
			set_vflags_long(popl(ssp, sp), regs);
			VM86_FAULT_RETURN;

		/* iretd */
		case 0xcf:
			SP(regs) += 12;
			IP(regs) = (unsigned short)popl(ssp, sp);
			regs->cs = (unsigned short)popl(ssp, sp);
			CHECK_IF_IN_TRAP
			set_vflags_long(popl(ssp, sp), regs);
			VM86_FAULT_RETURN;
		/* need this to avoid a fallthrough */
		default:
			return_to_32bit(regs, VM86_UNKNOWN);
		}

	/* pushf */
	case 0x9c:
		SP(regs) -= 2;
		IP(regs)++;
		pushw(ssp, sp, get_vflags(regs));
		VM86_FAULT_RETURN;

	/* popf */
	case 0x9d:
		SP(regs) += 2;
		IP(regs)++;
		CHECK_IF_IN_TRAP
		set_vflags_short(popw(ssp, sp), regs);
		VM86_FAULT_RETURN;

	/* int xx */
	case 0xcd: {
	        int intno=popb(csp, ip);
		IP(regs) += 2;
		if (VMPI.vm86dbg_active) {
			if ( (1 << (intno &7)) & VMPI.vm86dbg_intxxtab[intno >> 3] )
				return_to_32bit(regs, VM86_INTx + (intno << 8));
		}
		do_int(regs, intno, ssp, sp);
		return;
	}

	/* iret */
	case 0xcf:
		SP(regs) += 6;
		IP(regs) = popw(ssp, sp);
		regs->cs = popw(ssp, sp);
		CHECK_IF_IN_TRAP
		set_vflags_short(popw(ssp, sp), regs);
		VM86_FAULT_RETURN;

	/* cli */
	case 0xfa:
		IP(regs)++;
		clear_IF(regs);
		VM86_FAULT_RETURN;

	/* sti */
	/*
	 * Damn. This is incorrect: the 'sti' instruction should actually
	 * enable interrupts after the /next/ instruction. Not good.
	 *
	 * Probably needs some horsing around with the TF flag. Aiee..
	 */
	case 0xfb:
		IP(regs)++;
		set_IF(regs);
		VM86_FAULT_RETURN;

	default:
		return_to_32bit(regs, VM86_UNKNOWN);
	}
}

/* ---------------- vm86 special IRQ passing stuff ----------------- */

#define VM86_IRQNAME		"vm86irq"

static struct vm86_irqs {
	struct task_struct *tsk;
	int sig;
} vm86_irqs[16];
static int irqbits;

#define ALLOWED_SIGS ( 1 /* 0 = don't send a signal */ \
	| (1 << SIGUSR1) | (1 << SIGUSR2) | (1 << SIGIO)  | (1 << SIGURG) \
	| (1 << SIGUNUSED) )
	
static void irq_handler(int intno, void *dev_id, struct pt_regs * regs) {
	int irq_bit;
	unsigned long flags;
	
	save_flags(flags);
	cli();
	irq_bit = 1 << intno;
	if ((irqbits & irq_bit) || ! vm86_irqs[intno].tsk)
		goto out;
	irqbits |= irq_bit;
	if (vm86_irqs[intno].sig)
		send_sig(vm86_irqs[intno].sig, vm86_irqs[intno].tsk, 1);
	/* else user will poll for IRQs */
out:
	restore_flags(flags);
}

static inline void free_vm86_irq(int irqnumber)
{
	free_irq(irqnumber,0);
	vm86_irqs[irqnumber].tsk = 0;
	irqbits &= ~(1 << irqnumber);
}

static inline int task_valid(struct task_struct *tsk)
{
	struct task_struct *p;
	int ret = 0;

	read_lock(&tasklist_lock);
	for_each_task(p) {
		if ((p == tsk) && (p->sig)) {
			ret = 1;
			break;
		}
	}
	read_unlock(&tasklist_lock);
	return ret;
}

void release_x86_irqs(struct task_struct *task)
{
	int i;
	for (i=3; i<16; i++)
	    if (vm86_irqs[i].tsk == task)
		free_vm86_irq(i);
}

static inline void handle_irq_zombies(void)
{
	int i;
	for (i=3; i<16; i++) {
		if (vm86_irqs[i].tsk) {
			if (task_valid(vm86_irqs[i].tsk)) continue;
			free_vm86_irq(i);
		}
	}
}

static inline int get_and_reset_irq(int irqnumber)
{
	int bit;
	unsigned long flags;
	
	if ( (irqnumber<3) || (irqnumber>15) ) return 0;
	if (vm86_irqs[irqnumber].tsk != current) return 0;
	save_flags(flags);
	cli();
	bit = irqbits & (1 << irqnumber);
	irqbits &= ~bit;
	restore_flags(flags);
	return bit;
}


static int do_vm86_irq_handling(int subfunction, int irqnumber)
{
	int ret;
	switch (subfunction) {
		case VM86_GET_AND_RESET_IRQ: {
			return get_and_reset_irq(irqnumber);
		}
		case VM86_GET_IRQ_BITS: {
			return irqbits;
		}
		case VM86_REQUEST_IRQ: {
			int sig = irqnumber >> 8;
			int irq = irqnumber & 255;
			handle_irq_zombies();
			if (!capable(CAP_SYS_ADMIN)) return -EPERM;
			if (!((1 << sig) & ALLOWED_SIGS)) return -EPERM;
			if ( (irq<3) || (irq>15) ) return -EPERM;
			if (vm86_irqs[irq].tsk) return -EPERM;
			ret = request_irq(irq, &irq_handler, 0, VM86_IRQNAME, 0);
			if (ret) return ret;
			vm86_irqs[irq].sig = sig;
			vm86_irqs[irq].tsk = current;
			return irq;
		}
		case  VM86_FREE_IRQ: {
			handle_irq_zombies();
			if ( (irqnumber<3) || (irqnumber>15) ) return -EPERM;
			if (!vm86_irqs[irqnumber].tsk) return 0;
			if (vm86_irqs[irqnumber].tsk != current) return -EPERM;
			free_vm86_irq(irqnumber);
			return 0;
		}
	}
	return -EINVAL;
}