[PATCH 3/7][RFC] powerpc64, tracing: add function graph tracer with dynamic tracing
Benjamin Herrenschmidt
benh at kernel.crashing.org
Fri Feb 13 15:15:09 EST 2009
> @@ -55,8 +56,9 @@ static unsigned char *ftrace_call_replace(unsigned
> long ip, unsigned long addr)
> */
> addr = GET_ADDR(addr);
>
> - /* Set to "bl addr" */
> - op = 0x48000001 | (ftrace_calc_offset(ip, addr) & 0x03fffffc);
> + /* if (link) set op to 'bl' else 'b' */
> + op = 0x48000000 | (link ? 1 : 0);
> + op |= (ftrace_calc_offset(ip, addr) & 0x03fffffc);
Any reason why you aren't using the code in
arch/powerpc/lib/code-patching.c here ?
> new = ftrace_call_replace(ip, stub, 0);
> + memcpy(old, new, MCOUNT_INSN_SIZE);
> + new = ftrace_call_replace(ip, addr, 0);
> +
> + return ftrace_modify_code(ip, old, new);
> +}
Heh, memcpy of 4 bytes :-) I hope gcc is smart enough to turn that into
a simple load/store ..
Cheers,
Ben.
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