int ftrace_make_call()

in kernel/ftrace.c [113:182]

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

int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
{
	u32 insn[FTRACE_PATCHABLE_FUNCTION_SIZE];
	u32 *tramp;
	int size, ret, i;
	void *ip;

#ifdef CONFIG_64BIT
	unsigned long addr2 =
		(unsigned long)dereference_function_descriptor((void *)addr);

	u32 ftrace_trampoline[] = {
		0x73c10208, /* std,ma r1,100(sp) */
		0x0c2110c1, /* ldd -10(r1),r1 */
		0xe820d002, /* bve,n (r1) */
		addr2 >> 32,
		addr2 & 0xffffffff,
		0xe83f1fd7, /* b,l,n .-14,r1 */
	};

	u32 ftrace_trampoline_unaligned[] = {
		addr2 >> 32,
		addr2 & 0xffffffff,
		0x37de0200, /* ldo 100(sp),sp */
		0x73c13e01, /* std r1,-100(sp) */
		0x34213ff9, /* ldo -4(r1),r1 */
		0x50213fc1, /* ldd -20(r1),r1 */
		0xe820d002, /* bve,n (r1) */
		0xe83f1fcf, /* b,l,n .-20,r1 */
	};

	BUILD_BUG_ON(ARRAY_SIZE(ftrace_trampoline_unaligned) >
				FTRACE_PATCHABLE_FUNCTION_SIZE);
#else
	u32 ftrace_trampoline[] = {
		(u32)addr,
		0x6fc10080, /* stw,ma r1,40(sp) */
		0x48213fd1, /* ldw -18(r1),r1 */
		0xe820c002, /* bv,n r0(r1) */
		0xe83f1fdf, /* b,l,n .-c,r1 */
	};
#endif

	BUILD_BUG_ON(ARRAY_SIZE(ftrace_trampoline) >
				FTRACE_PATCHABLE_FUNCTION_SIZE);

	size = sizeof(ftrace_trampoline);
	tramp = ftrace_trampoline;

#ifdef CONFIG_64BIT
	if (rec->ip & 0x4) {
		size = sizeof(ftrace_trampoline_unaligned);
		tramp = ftrace_trampoline_unaligned;
	}
#endif

	ip = (void *)(rec->ip + 4 - size);

	ret = copy_from_kernel_nofault(insn, ip, size);
	if (ret)
		return ret;

	for (i = 0; i < size / 4; i++) {
		if (insn[i] != INSN_NOP)
			return -EINVAL;
	}

	__patch_text_multiple(ip, tramp, size);
	return 0;
}