On Fri, 2010-03-12 at 19:43 +0800, Wu Zhangjin wrote:
[...]
> Right, then, we can search the JAL or JALR, for kernel, will get it
> immediatly, for module, will only several instructions, we can do this
> searching in ftrace_make_nop and ftrace_make_call at run-time, but just
> found we can use the following function to do it in ftrace_init(), looks
> good.
>
> static inline int is_call_mcount(unsigned int insn)
> {
> return ((insn & JAL) == JAL) || (insn == JALR_V1);
> }
>
> static inline unsinged long mcount_callsite(unsigned long addr)
> {
> unsigned int insn;
>
> insn = *(unsigned int *)addr; /*need safe_load_code*/
> if (is_call_mcount(insn))
> return addr;
>
> do {
> addr += 4; /* what about big endian? */
> insn = *(unsigned int *)addr; /*need safe_load_code*/
> } while (!is_call_mcount(insn));
>
This is not possible for modules, for currently, the modules are not
loaded yet.
Regards,
Wu Zhangjin
