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Re: [PATCH] jprobes: Ensure that the probepoint is at function entry

From Ingo Molnar <mingo@kernel.org>
Newsgroups linux.kernel
Subject Re: [PATCH] jprobes: Ensure that the probepoint is at function entry
Date 2017-07-06 14:20 +0200
Message-ID <u0dVf-4cO-7@gated-at.bofh.it> (permalink)
References <tXJ5h-qk-25@gated-at.bofh.it> <tZQ2B-56s-7@gated-at.bofh.it> <u0bTt-2TC-27@gated-at.bofh.it>
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* Masami Hiramatsu <mhiramat@kernel.org> wrote:

> > Also, 'function_offset_within_entry' is way too long a name, and it's also a 
> > minomer I think. The purpose of this function is to enforce that the relative 
> > 'offset' of a new probe is at the standard function entry offset: i.e. 0 on most 
> > architectures, and some ABI dependent constant on PowerPC, right?
> > 
> > That's not at all clear from that name, plus it's a global namespace symbol, yet 
> > has no 'kprobes' prefix. So it should be named something like 
> > 'kprobe_offset_valid()' or such, with an arch_kprobe_offset_valid() counterpart.
> 
> Hmm, I would rather like kprobe_within_entry(), since offset != 0 is
> actually valid for normal kprobe, that is kretprobe and jprobe limitation.

But what entry? That it's within a range or that offset is always 0 is really an 
implementational detail: depending on what type of kprobe it is, it is either 
validly within the confines of the specified function symbol or not.

What _really_ matters to callers is whether it's a valid kprobe to be inserted 
into that function, right?

I.e. the long name came from over-specifying what is done by the function - while 
simplifying makes it actually more meaningful to read.

Thanks,

	Ingo

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Thread

Re: [PATCH] jprobes: Ensure that the probepoint is at function entry Ingo Molnar <mingo@kernel.org> - 2017-07-05 12:50 +0200
  Re: [PATCH] jprobes: Ensure that the probepoint is at function  entry Masami Hiramatsu <mhiramat@kernel.org> - 2017-07-06 12:10 +0200
    Re: [PATCH] jprobes: Ensure that the probepoint is at function entry Ingo Molnar <mingo@kernel.org> - 2017-07-06 14:20 +0200
      Re: [PATCH] jprobes: Ensure that the probepoint is at function  entry Masami Hiramatsu <mhiramat@kernel.org> - 2017-07-07 03:10 +0200
        Re: [PATCH] jprobes: Ensure that the probepoint is at function entry Ingo Molnar <mingo@kernel.org> - 2017-07-07 12:50 +0200
          Re: [PATCH] jprobes: Ensure that the probepoint is at function entry "Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com> - 2017-07-07 13:30 +0200

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