static void __kprobes setup_singlestep()

in kernel/kprobes.c [125:191]

• 41 lines of code
• 5 McCabe index (conditional complexity)

static void __kprobes setup_singlestep(struct kprobe *p, struct pt_regs *regs)
{
	unsigned long next_pc;
	unsigned long tgt_if_br = 0;
	int is_branch;
	unsigned long bta;

	/* Copy the opcode back to the kprobe location and execute the
	 * instruction. Because of this we will not be able to get into the
	 * same kprobe until this kprobe is done
	 */
	*(p->addr) = p->opcode;

	flush_icache_range((unsigned long)p->addr,
			   (unsigned long)p->addr + sizeof(kprobe_opcode_t));

	/* Now we insert the trap at the next location after this instruction to
	 * single step. If it is a branch we insert the trap at possible branch
	 * targets
	 */

	bta = regs->bta;

	if (regs->status32 & 0x40) {
		/* We are in a delay slot with the branch taken */

		next_pc = bta & ~0x01;

		if (!p->ainsn.is_short) {
			if (bta & 0x01)
				regs->blink += 2;
			else {
				/* Branch not taken */
				next_pc += 2;

				/* next pc is taken from bta after executing the
				 * delay slot instruction
				 */
				regs->bta += 2;
			}
		}

		is_branch = 0;
	} else
		is_branch =
		    disasm_next_pc((unsigned long)p->addr, regs,
			(struct callee_regs *) current->thread.callee_reg,
			&next_pc, &tgt_if_br);

	p->ainsn.t1_addr = (kprobe_opcode_t *) next_pc;
	p->ainsn.t1_opcode = *(p->ainsn.t1_addr);
	*(p->ainsn.t1_addr) = TRAP_S_2_INSTRUCTION;

	flush_icache_range((unsigned long)p->ainsn.t1_addr,
			   (unsigned long)p->ainsn.t1_addr +
			   sizeof(kprobe_opcode_t));

	if (is_branch) {
		p->ainsn.t2_addr = (kprobe_opcode_t *) tgt_if_br;
		p->ainsn.t2_opcode = *(p->ainsn.t2_addr);
		*(p->ainsn.t2_addr) = TRAP_S_2_INSTRUCTION;

		flush_icache_range((unsigned long)p->ainsn.t2_addr,
				   (unsigned long)p->ainsn.t2_addr +
				   sizeof(kprobe_opcode_t));
	}
}