kprobes.c

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         * kprobe_handler() that we have handled unlocking
         * and re-enabling preemption.
         */
        return 1;
}

void __kprobes arch_prepare_kretprobe(struct kretprobe *rp,
				      struct pt_regs *regs)
{
	struct kretprobe_instance *ri;

	if ((ri = get_free_rp_inst(rp)) != NULL) {
		ri->rp = rp;
		ri->task = current;
		ri->ret_addr = (kprobe_opcode_t *)regs->b0;

		/* Replace the return addr with trampoline addr */
		regs->b0 = ((struct fnptr *)kretprobe_trampoline)->ip;

		add_rp_inst(ri);
	} else {
		rp->nmissed++;
	}
}

int __kprobes arch_prepare_kprobe(struct kprobe *p)
{
	unsigned long addr = (unsigned long) p->addr;
	unsigned long *kprobe_addr = (unsigned long *)(addr & ~0xFULL);
	unsigned long kprobe_inst=0;
	unsigned int slot = addr & 0xf, template, major_opcode = 0;
	bundle_t *bundle = &p->ainsn.insn.bundle;

	memcpy(&p->opcode.bundle, kprobe_addr, sizeof(bundle_t));
	memcpy(&p->ainsn.insn.bundle, kprobe_addr, sizeof(bundle_t));

 	template = bundle->quad0.template;

	if(valid_kprobe_addr(template, slot, addr))
		return -EINVAL;

	/* Move to slot 2, if bundle is MLX type and kprobe slot is 1 */
 	if (slot == 1 && bundle_encoding[template][1] == L)
  		slot++;

	/* Get kprobe_inst and major_opcode from the bundle */
	get_kprobe_inst(bundle, slot, &kprobe_inst, &major_opcode);

	if (unsupported_inst(template, slot, major_opcode, kprobe_inst, p))
			return -EINVAL;

	prepare_break_inst(template, slot, major_opcode, kprobe_inst, p);

	return 0;
}

void __kprobes arch_arm_kprobe(struct kprobe *p)
{
	unsigned long addr = (unsigned long)p->addr;
	unsigned long arm_addr = addr & ~0xFULL;

	memcpy((char *)arm_addr, &p->ainsn.insn.bundle, sizeof(bundle_t));
	flush_icache_range(arm_addr, arm_addr + sizeof(bundle_t));
}

void __kprobes arch_disarm_kprobe(struct kprobe *p)
{
	unsigned long addr = (unsigned long)p->addr;
	unsigned long arm_addr = addr & ~0xFULL;

	/* p->opcode contains the original unaltered bundle */
	memcpy((char *) arm_addr, (char *) &p->opcode.bundle, sizeof(bundle_t));
	flush_icache_range(arm_addr, arm_addr + sizeof(bundle_t));
}

void __kprobes arch_remove_kprobe(struct kprobe *p)
{
}

/*
 * We are resuming execution after a single step fault, so the pt_regs
 * structure reflects the register state after we executed the instruction
 * located in the kprobe (p->ainsn.insn.bundle).  We still need to adjust
 * the ip to point back to the original stack address. To set the IP address
 * to original stack address, handle the case where we need to fixup the
 * relative IP address and/or fixup branch register.
 */
static void __kprobes resume_execution(struct kprobe *p, struct pt_regs *regs)
{
  	unsigned long bundle_addr = ((unsigned long) (&p->opcode.bundle)) & ~0xFULL;
  	unsigned long resume_addr = (unsigned long)p->addr & ~0xFULL;
 	unsigned long template;
 	int slot = ((unsigned long)p->addr & 0xf);

	template = p->opcode.bundle.quad0.template;

 	if (slot == 1 && bundle_encoding[template][1] == L)
 		slot = 2;

	if (p->ainsn.inst_flag) {

		if (p->ainsn.inst_flag & INST_FLAG_FIX_RELATIVE_IP_ADDR) {
			/* Fix relative IP address */
 			regs->cr_iip = (regs->cr_iip - bundle_addr) + resume_addr;
		}

		if (p->ainsn.inst_flag & INST_FLAG_FIX_BRANCH_REG) {
		/*
		 * Fix target branch register, software convention is
		 * to use either b0 or b6 or b7, so just checking
		 * only those registers
		 */
			switch (p->ainsn.target_br_reg) {
			case 0:
				if ((regs->b0 == bundle_addr) ||
					(regs->b0 == bundle_addr + 0x10)) {
					regs->b0 = (regs->b0 - bundle_addr) +
						resume_addr;
				}
				break;
			case 6:
				if ((regs->b6 == bundle_addr) ||
					(regs->b6 == bundle_addr + 0x10)) {
					regs->b6 = (regs->b6 - bundle_addr) +
						resume_addr;
				}
				break;
			case 7:
				if ((regs->b7 == bundle_addr) ||
					(regs->b7 == bundle_addr + 0x10)) {
					regs->b7 = (regs->b7 - bundle_addr) +
						resume_addr;
				}
				break;
			} /* end switch */
		}
		goto turn_ss_off;
	}

	if (slot == 2) {
 		if (regs->cr_iip == bundle_addr + 0x10) {
 			regs->cr_iip = resume_addr + 0x10;
 		}
 	} else {
 		if (regs->cr_iip == bundle_addr) {
 			regs->cr_iip = resume_addr;
 		}
	}

turn_ss_off:
  	/* Turn off Single Step bit */
  	ia64_psr(regs)->ss = 0;
}

static void __kprobes prepare_ss(struct kprobe *p, struct pt_regs *regs)
{
	unsigned long bundle_addr = (unsigned long) &p->opcode.bundle;
	unsigned long slot = (unsigned long)p->addr & 0xf;

	/* single step inline if break instruction */
	if (p->ainsn.inst_flag == INST_FLAG_BREAK_INST)
		regs->cr_iip = (unsigned long)p->addr & ~0xFULL;
	else
		regs->cr_iip = bundle_addr & ~0xFULL;

	if (slot > 2)
		slot = 0;

	ia64_psr(regs)->ri = slot;

	/* turn on single stepping */
	ia64_psr(regs)->ss = 1;
}

static int __kprobes is_ia64_break_inst(struct pt_regs *regs)
{
	unsigned int slot = ia64_psr(regs)->ri;
	unsigned int template, major_opcode;
	unsigned long kprobe_inst;
	unsigned long *kprobe_addr = (unsigned long *)regs->cr_iip;
	bundle_t bundle;

	memcpy(&bundle, kprobe_addr, sizeof(bundle_t));
	template = bundle.quad0.template;

	/* Move to slot 2, if bundle is MLX type and kprobe slot is 1 */
	if (slot == 1 && bundle_encoding[template][1] == L)
  		slot++;

	/* Get Kprobe probe instruction at given slot*/
	get_kprobe_inst(&bundle, slot, &kprobe_inst, &major_opcode);

	/* For break instruction,
	 * Bits 37:40 Major opcode to be zero
	 * Bits 27:32 X6 to be zero
	 * Bits 32:35 X3 to be zero
	 */
	if (major_opcode || ((kprobe_inst >> 27) & 0x1FF) ) {
		/* Not a break instruction */
		return 0;
	}

	/* Is a break instruction */
	return 1;
}

static int __kprobes pre_kprobes_handler(struct die_args *args)
{
	struct kprobe *p;
	int ret = 0;
	struct pt_regs *regs = args->regs;
	kprobe_opcode_t *addr = (kprobe_opcode_t *)instruction_pointer(regs);

	preempt_disable();

	/* Handle recursion cases */
	if (kprobe_running()) {
		p = get_kprobe(addr);
		if (p) {
			if ( (kprobe_status == KPROBE_HIT_SS) &&
	 		     (p->ainsn.inst_flag == INST_FLAG_BREAK_INST)) {
  				ia64_psr(regs)->ss = 0;
				unlock_kprobes();
				goto no_kprobe;
			}
			/* We have reentered the pre_kprobe_handler(), since
			 * another probe was hit while within the handler.
			 * We here save the original kprobes variables and
			 * just single step on the instruction of the new probe
			 * without calling any user handlers.
			 */
			save_previous_kprobe();
			set_current_kprobe(p);
			p->nmissed++;
			prepare_ss(p, regs);
			kprobe_status = KPROBE_REENTER;
			return 1;
		} else if (args->err == __IA64_BREAK_JPROBE) {
			/*
			 * jprobe instrumented function just completed
			 */
			p = current_kprobe;
			if (p->break_handler && p->break_handler(p, regs)) {
				goto ss_probe;
			}
		} else {
			/* Not our break */
			goto no_kprobe;
		}
	}

	lock_kprobes();
	p = get_kprobe(addr);
	if (!p) {
		unlock_kprobes();
		if (!is_ia64_break_inst(regs)) {
			/*
			 * The breakpoint instruction was removed right
			 * after we hit it.  Another cpu has removed
			 * either a probepoint or a debugger breakpoint
			 * at this address.  In either case, no further
			 * handling of this interrupt is appropriate.
			 */
			ret = 1;

		}

		/* Not one of our break, let kernel handle it */
		goto no_kprobe;
	}

	kprobe_status = KPROBE_HIT_ACTIVE;
	set_current_kprobe(p);

	if (p->pre_handler && p->pre_handler(p, regs))
		/*
		 * Our pre-handler is specifically requesting that we just
		 * do a return.  This is used for both the jprobe pre-handler
		 * and the kretprobe trampoline
		 */
		return 1;

ss_probe:
	prepare_ss(p, regs);
	kprobe_status = KPROBE_HIT_SS;
	return 1;

no_kprobe:
	preempt_enable_no_resched();
	return ret;
}

static int __kprobes post_kprobes_handler(struct pt_regs *regs)
{
	if (!kprobe_running())
		return 0;

	if ((kprobe_status != KPROBE_REENTER) && current_kprobe->post_handler) {
		kprobe_status = KPROBE_HIT_SSDONE;
		current_kprobe->post_handler(current_kprobe, regs, 0);
	}

	resume_execution(current_kprobe, regs);

	/*Restore back the original saved kprobes variables and continue. */
	if (kprobe_status == KPROBE_REENTER) {
		restore_previous_kprobe();
		goto out;
	}

	unlock_kprobes();

out:
	preempt_enable_no_resched();
	return 1;
}

static int __kprobes kprobes_fault_handler(struct pt_regs *regs, int trapnr)
{
	if (!kprobe_running())
		return 0;

	if (current_kprobe->fault_handler &&
	    current_kprobe->fault_handler(current_kprobe, regs, trapnr))
		return 1;

	if (kprobe_status & KPROBE_HIT_SS) {
		resume_execution(current_kprobe, regs);
		unlock_kprobes();
		preempt_enable_no_resched();
	}

	return 0;
}

int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
				       unsigned long val, void *data)
{
	struct die_args *args = (struct die_args *)data;
	switch(val) {
	case DIE_BREAK:
		if (pre_kprobes_handler(args))
			return NOTIFY_STOP;
		break;
	case DIE_SS:
		if (post_kprobes_handler(args->regs))
			return NOTIFY_STOP;
		break;
	case DIE_PAGE_FAULT:
		if (kprobes_fault_handler(args->regs, args->trapnr))
			return NOTIFY_STOP;
	default:
		break;
	}
	return NOTIFY_DONE;
}

int __kprobes setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs)
{
	struct jprobe *jp = container_of(p, struct jprobe, kp);
	unsigned long addr = ((struct fnptr *)(jp->entry))->ip;

	/* save architectural state */
	jprobe_saved_regs = *regs;

	/* after rfi, execute the jprobe instrumented function */
	regs->cr_iip = addr & ~0xFULL;
	ia64_psr(regs)->ri = addr & 0xf;
	regs->r1 = ((struct fnptr *)(jp->entry))->gp;

	/*
	 * fix the return address to our jprobe_inst_return() function
	 * in the jprobes.S file
	 */
 	regs->b0 = ((struct fnptr *)(jprobe_inst_return))->ip;

	return 1;
}

int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
{
	*regs = jprobe_saved_regs;
	return 1;
}

static struct kprobe trampoline_p = {
	.pre_handler = trampoline_probe_handler
};

int __init arch_init_kprobes(void)
{
	trampoline_p.addr =
		(kprobe_opcode_t *)((struct fnptr *)kretprobe_trampoline)->ip;
	return register_kprobe(&trampoline_p);
}