On Wed, 10 Jan 2018 15:38:10 +0800
Alan Kao <noner...@gmail.com> wrote:
> +static int ftrace_check_current_call(unsigned long hook_pos,
> + unsigned int *expected)
> +{
> + unsigned int replaced[2];
> + unsigned int nops[2] = {NOP4, NOP4};
> +
> + /* we expect nops at the hook position */
> + if (!expected)
> + expected = nops;
> +
> + /* read the text we want to modify */
> + if (probe_kernel_read(replaced, (void *)hook_pos, MCOUNT_INSN_SIZE))
> + return -EFAULT;
> +
> + /* Make sure it is what we expect it to be */
> + if (replaced[0] != expected[0] || replaced[1] != expected[1]) {
I wonder if we can have a slight enhancement by doing:
if (memcmp(replaced, expected, sizeof(replaced)) != 0) {
-- Steve
> + pr_err("%p: expected (%08x %08x) but get (%08x %08x)",
> + (void *)hook_pos, expected[0], expected[1], replaced[0],
> + replaced[1]);
> + return -EINVAL;
> + }
> +
> + return 0;
> +}
