Hi Namhyung,
I'll certainly try to read (and even apply ;) this series carefully.
But let me make a couple of nits right now, even if I do not understand
this code yet.
On 11/27, Namhyung Kim wrote:
>
> + } else if (arg[1] == '+') {
> + struct file_offset_fetch_param *foprm;
> +
> + /* kprobes don't support file offsets */
> + if (is_kprobe)
> + return -EINVAL;
> +
> + ret = kstrtol(arg + 2, 0, &offset);
> + if (ret)
> + break;
> +
> + foprm = kzalloc(sizeof(*foprm), GFP_KERNEL);
> + if (!foprm)
> + return -ENOMEM;
> +
> + foprm->tu = priv;
> + foprm->offset = offset;
Hmm. I am not sure, but can't we simplify this?
Why do we need this foprm at all? To pass tu/offset obviously. But
why we need to store this info in fetch_param?
translate_user_vaddr() needs to access utask->vaddr anyway. It seems
to me it would be more clean to do the following:
1. Add
struct xxx {
struct trace_uprobe *tu;
unsigned long bp_addr;
};
in trace_uprobe.c.
2. Add
struct xxx info = {
.tu = tu,
.bp_addr = instruction_pointer(regs);
};
current->utask->vaddr = (long)&info;
into uprobe_dispatcher() and uretprobe_dispatcher() (the latter
should obviously use func instead of instruction_pointer).
3. FETCH_FUNC_NAME(file_offset, type) can do
struct xxx *info = (void*)current->utask->vaddr;
void *addr = data + info->bp_addr - info->tu->offset;
return FETCH_FUNC_NAME(memory, type)(regs, aaddr, dest);
4. Now, the only change we need in parse_probe_arg("@") is that
it should use either FETCH_MTD_memory or FETCH_MTD_file_offset
depending on arg[0] == '+'.
And we do not need to pass "void *prive" to parse_probe_arg().
What do you think? One again, I can be easily wrong, I didn't read the
code yet.
> static int uprobe_dispatcher(struct uprobe_consumer *con, struct pt_regs
> *regs)
> {
> struct trace_uprobe *tu;
> + struct uprobe_task *utask;
> int ret = 0;
>
> tu = container_of(con, struct trace_uprobe, consumer);
> tu->nhit++;
>
> + utask = current->utask;
> + if (utask == NULL)
> + return UPROBE_HANDLER_REMOVE;
Hmm, why? The previous change ensures ->utask is not NULL? If we hit
NULL we have a bug, we should not remove this uprobe.
Oleg.
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