Re: [PATCH v5 0/2] Return EADDRNOTAVAIL when func matches several symbols during kprobe creation

[Masami Hiramatsu (Google) <mhiramat@kernel.org>]

On Wed, 18 Oct 2023 13:00:42 -0400
Steven Rostedt <rostedt@goodmis.org> wrote:

> On Wed, 18 Oct 2023 17:40:28 +0300
> Francis Laniel <flaniel@linux.microsoft.com> wrote:
> 
> > Changes since:
> >  v1:
> >   * Use EADDRNOTAVAIL instead of adding a new error code.
> >   * Correct also this behavior for sysfs kprobe.
> >  v2:
> >   * Count the number of symbols corresponding to function name and return
> >   EADDRNOTAVAIL if higher than 1.
> >   * Return ENOENT if above count is 0, as it would be returned later by while
> >   registering the kprobe.
> >  v3:
> >   * Check symbol does not contain ':' before testing its uniqueness.
> >   * Add a selftest to check this is not possible to install a kprobe for a non
> >   unique symbol.
> >  v5:
> >   * No changes, just add linux-stable as recipient.
> 
> So why is this adding stable? (and as Greg's form letter states, that's not
> how you do that)
> 
> I don't see this as a fix but a new feature.

I asked him to make this a fix since the current kprobe event' behavior is
somewhat strange. It puts the probe on only the "first symbol" if user
specifies a symbol name which has multiple instances. In this case, the
actual probe address can not be solved by name. User must specify the
probe address by unique name + offset. Unless, it can put a probe on
unexpected address, especially if it specifies non-unique symbol + offset,
the address may NOT be the instruction boundary.
To avoid this issue, it should check the given symbol is unique.

Thank you,

> 
> -- Steve


-- 
Masami Hiramatsu (Google) <mhiramat@kernel.org>