From: Ingo Molnar <mingo@kernel.org>
To: "Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com>
Cc: Masami Hiramatsu <mhiramat@kernel.org>,
Ananth N Mavinakayanahalli <ananth@linux.vnet.ibm.com>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] jprobes: Ensure that the probepoint is at function entry
Date: Wed, 5 Jul 2017 12:42:16 +0200 [thread overview]
Message-ID: <20170705104216.674ejyueqquctsn5@gmail.com> (raw)
In-Reply-To: <20170629145655.5282-1-naveen.n.rao@linux.vnet.ibm.com>
* Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com> wrote:
> Similar to commit 90ec5e89e393c ("kretprobes: Ensure probe location is
> at function entry"), ensure that the jprobe probepoint is at function
> entry.
>
> Signed-off-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
> ---
> kernel/kprobes.c | 9 +++++++--
> 1 file changed, 7 insertions(+), 2 deletions(-)
>
> diff --git a/kernel/kprobes.c b/kernel/kprobes.c
> index adfe3b4cfe05..950018609339 100644
> --- a/kernel/kprobes.c
> +++ b/kernel/kprobes.c
> @@ -1776,9 +1776,14 @@ int register_jprobes(struct jprobe **jps, int num)
> jp = jps[i];
> addr = arch_deref_entry_point(jp->entry);
>
> - /* Verify probepoint is a function entry point */
> + /*
> + * Verify probepoint as well as the jprobe handler are
> + * function entry points.
> + */
> if (kallsyms_lookup_size_offset(addr, NULL, &offset) &&
> - offset == 0) {
> + offset == 0 &&
> + function_offset_within_entry(jp->kp.addr,
> + jp->kp.symbol_name, jp->kp.offset)) {
> jp->kp.pre_handler = setjmp_pre_handler;
> jp->kp.break_handler = longjmp_break_handler;
> ret = register_kprobe(&jp->kp);
Yeah, so I agree with the fix, but the line breaks there are disgusting.
One solution would be to split out the iterator into a register_jprobe() function.
Also, introduce a 'kp' temporary variable to simplify and shorten usage.
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.
All of these cleanups should be in separate patches - with the fix in the end.
Thanks,
Ingo
next prev parent reply other threads:[~2017-07-05 10:42 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-06-29 14:56 [PATCH] jprobes: Ensure that the probepoint is at function entry Naveen N. Rao
2017-07-05 10:42 ` Ingo Molnar [this message]
2017-07-06 10:03 ` Masami Hiramatsu
2017-07-06 12:15 ` Ingo Molnar
2017-07-07 1:02 ` Masami Hiramatsu
2017-07-07 10:49 ` Ingo Molnar
2017-07-07 11:26 ` Naveen N. Rao
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