int ftrace_make_nop()

in kernel/ftrace.c [112:150]

• 21 lines of code
• 2 McCabe index (conditional complexity)

int ftrace_make_nop(struct module *mod,
			struct dyn_ftrace *rec, unsigned long addr)
{
	/* we have this part of code which we are working with
	 * b000c000        imm     -16384
	 * b9fc8e30        bralid  r15, -29136     // c0008e30 <_mcount>
	 * 80000000        or      r0, r0, r0
	 *
	 * The first solution (!USE_FTRACE_NOP-could be called branch solution)
	 * b000c000        bri	12 (0xC - jump to any other instruction)
	 * b9fc8e30        bralid  r15, -29136     // c0008e30 <_mcount>
	 * 80000000        or      r0, r0, r0
	 * any other instruction
	 *
	 * The second solution (USE_FTRACE_NOP) - no jump just nops
	 * 80000000        or      r0, r0, r0
	 * 80000000        or      r0, r0, r0
	 * 80000000        or      r0, r0, r0
	 */
	int ret = 0;

	if (recorded == 0) {
		recorded = 1;
		imm = *(unsigned int *)rec->ip;
		pr_debug("%s: imm:0x%x\n", __func__, imm);
#ifdef USE_FTRACE_NOP
		bralid = *(unsigned int *)(rec->ip + 4);
		pr_debug("%s: bralid 0x%x\n", __func__, bralid);
#endif /* USE_FTRACE_NOP */
	}

#ifdef USE_FTRACE_NOP
	ret = ftrace_modify_code(rec->ip, MICROBLAZE_NOP);
	ret += ftrace_modify_code(rec->ip + 4, MICROBLAZE_NOP);
#else /* USE_FTRACE_NOP */
	ret = ftrace_modify_code(rec->ip, MICROBLAZE_BRI);
#endif /* USE_FTRACE_NOP */
	return ret;
}