Messages in this thread Patch in this message | | | Date | Mon, 6 Jan 2020 14:10:37 -0500 (EST) | From | Mathieu Desnoyers <> | Subject | Re: [PATCH for 5.5 1/2 v2] rseq: Fix: Clarify rseq.h UAPI rseq_cs memory reclaim requirements |
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----- On Dec 20, 2019, at 3:33 PM, Mathieu Desnoyers mathieu.desnoyers@efficios.com wrote:
> The rseq.h UAPI documents that the rseq_cs field must be cleared > before reclaiming memory that contains the targeted struct rseq_cs. > > We should extend this comment to also dictate that the rseq_cs field > must be cleared before reclaiming memory of the code pointed to by > the rseq_cs start_ip and post_commit_offset fields. > > While we can expect that use of dlclose(3) will typically unmap > both struct rseq_cs and its associated code at once, nothing would > theoretically prevent a JIT from reclaiming the code without > reclaiming the struct rseq_cs, which would erroneously allow the > kernel to consider new code which is not a rseq critical section > as a rseq critical section following a code reclaim.
Hi Peter,
Is there anything preventing this rseq UAPI documentation fix from being merged ?
Thanks,
Mathieu
> > Suggested-by: Florian Weimer <fw@deneb.enyo.de> > Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> > Cc: Florian Weimer <fw@deneb.enyo.de> > Cc: Thomas Gleixner <tglx@linutronix.de> > Cc: Peter Zijlstra (Intel) <peterz@infradead.org> > Cc: "Paul E. McKenney" <paulmck@linux.ibm.com> > Cc: Boqun Feng <boqun.feng@gmail.com> > Cc: "H . Peter Anvin" <hpa@zytor.com> > Cc: Paul Turner <pjt@google.com> > Cc: Dmitry Vyukov <dvyukov@google.com> > Cc: Neel Natu <neelnatu@google.com> > Cc: linux-api@vger.kernel.org > --- > include/uapi/linux/rseq.h | 4 +++- > 1 file changed, 3 insertions(+), 1 deletion(-) > > diff --git a/include/uapi/linux/rseq.h b/include/uapi/linux/rseq.h > index 9a402fdb60e9..d94afdfc4b7c 100644 > --- a/include/uapi/linux/rseq.h > +++ b/include/uapi/linux/rseq.h > @@ -100,7 +100,9 @@ struct rseq { > * instruction sequence block, as well as when the kernel detects that > * it is preempting or delivering a signal outside of the range > * targeted by the rseq_cs. Also needs to be set to NULL by user-space > - * before reclaiming memory that contains the targeted struct rseq_cs. > + * before reclaiming memory that contains the targeted struct rseq_cs > + * or reclaiming memory that contains the code referred to by the > + * start_ip and post_commit_offset fields of struct rseq_cs. > * > * Read and set by the kernel. Set by user-space with single-copy > * atomicity semantics. This field should only be updated by the > -- > 2.17.1
-- Mathieu Desnoyers EfficiOS Inc. http://www.efficios.com
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