Re: [PATCHSET 00/13] tracing/uprobes: Add support for more fetchmethods (v6)

From: Oleg Nesterov
Date: Tue Nov 05 2013 - 14:22:49 EST

On 11/05, Oleg Nesterov wrote:
> As for "-= tu->offset"... Can't we avoid it? User-space needs to calculate
> the "@" argument anyway, why it can't also substruct this offset?
> Or perhaps we can change parse_probe_arg("@") to update "param" ? Yes,
> in this case it needs another argument, not sure...


> + if (is_ret_probe(tu)) {
> + saved_ip = instruction_pointer(regs);
> + instruction_pointer_set(func);
> + }
> store_trace_args(...);
> + if (is_ret_probe(tu))
> + instruction_pointer_set(saved_ip);

we can put "-= tu->offset" here.

> although not pretty.


Or. Perhaps we can leave "case '@'" in parse_probe_arg() and
FETCH_MTD_memory alone. You seem to agree that "absolute address"
can be useful anyway.

Instead, perhaps we can add FETCH_MTD_memory_do_fancy_addr_translation,
and, say, the new "case '*'" in parse_probe_arg() should add all the
neccessary info as f->data (like, say, FETCH_MTD_symbol).

But, just in case, I do not have a strong opinion. Just I think it
is better to discuss every choice we have.


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