Messages in this thread | | | Date | Mon, 7 Aug 2006 10:22:13 +0530 | From | Ananth N Mavinakayanahalli <> | Subject | Re: [PATCH] module interface improvement for kprobes |
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On Fri, Aug 04, 2006 at 04:57:11PM +0100, Christoph Hellwig wrote: > > { > > /* grab the module, making sure it won't get unloaded until > > * we're done */ > > const char *mod_name = "joydev"; > > if (module_get_byname(mod_name, &mod) != 0) > > return 1; > > > > /* Specify the address/offset where you want to insert > > * probe. If this were a real kprobe module, we'd "relocate" > > * our probe address based on the load address of the module > > * we're interested in. */ > > kp.addr = (kprobe_opcode_t *) mod->module_core + 0; > > > > /* All set to register with Kprobes */ > > register_kprobe(&kp); > > return 0; > > } > > This interface is horrible. You actual patch looks good to me, but it > I can't see why you would need it. kallsyms_lookup_name deals with modules > transparently and you shouldn't put a probe at a relative offset into a > module but only at a symbol you could find with kallsys. > > That beeing said we should probably change the kprobes interface to > automatically do the kallsysms name lookup for the caller. It would simplify > the kprobes interface and allow us to get rid of the kallsyms_lookup_name > export that doesn't have a valid use except for kprobes. With > that change the example kprobe would look like:
This sounds like a good idea. How about we still allow .addr atleast for users who know what they are doing and would want to just specify a text addr?
> static struct kprobe kp = { .addr = <addr>
> .pre_handler = handler_pre, > .post_handler = handler_post, > .fault_handler = handler_fault, > .symbol_name = "do_fork", > };
The symbol_name lookup can then be done when only when .addr is non-NULL.
That said, I have a working patch I was planning to post today that introduces the KPROBE_ADDR macro that abstracts out the architecture-specific artefacts of getting the actual text address to probe, so kprobe modules can be made more portable. I was envisaging this to be used by the module writer, but with your idea, this could live in-kernel itself.
I'll cook up a patch for this in a short while.
Ananth
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