linux-kernel - [PATCH 0/2] kprobes: Remove kprobe::fault

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Message-ID: <20210525072518.791889911@infradead.org>
Date:   Tue, 25 May 2021 09:25:18 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     mhiramat@...nel.org
Cc:     linux-kernel@...r.kernel.org, peterz@...radead.org,
        mingo@...nel.org, rostedt@...dmis.org,
        naveen.n.rao@...ux.vnet.ibm.com, ananth@...ux.ibm.com,
        x86@...nel.org
Subject: [PATCH 0/2] kprobes: Remove kprobe::fault_handler

The reason for kprobe::fault_handler(), as given by their comment:

* We come here because instructions in the pre/post
* handler caused the page_fault, this could happen
* if handler tries to access user space by
* copy_from_user(), get_user() etc. Let the
* user-specified handler try to fix it first.

Is just plain bad. Those other handlers are ran from non-preemptible
context and had better use _nofault() functions. Also, there is no
upstream usage of this.

The corollary of this change is that no tracing/probing/whatever can consume
faults.