Re: [PATCH 3/7][RFC] powerpc64, tracing: add function graph tracer with dynamic tracing
From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Date: 2009-02-13 04:16:00
Also in:
lkml
quoted hunk ↗ jump to hunk
@@ -55,8 +56,9 @@ static unsigned char *ftrace_call_replace(unsignedlong 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.