* [PATCH for 5.5 1/2 v2] rseq: Fix: Clarify rseq.h UAPI rseq_cs memory reclaim requirements
@ 2019-12-20 20:33 Mathieu Desnoyers
2019-12-20 20:33 ` [PATCH for 5.5 2/2 v2] rseq/selftests: Clarify rseq_prepare_unload() helper requirements Mathieu Desnoyers
2020-01-06 19:10 ` [PATCH for 5.5 1/2 v2] rseq: Fix: Clarify rseq.h UAPI rseq_cs memory reclaim requirements Mathieu Desnoyers
0 siblings, 2 replies; 3+ messages in thread
From: Mathieu Desnoyers @ 2019-12-20 20:33 UTC (permalink / raw)
To: Thomas Gleixner
Cc: linux-kernel, Peter Zijlstra, Paul E . McKenney, Boqun Feng,
H . Peter Anvin, Paul Turner, linux-api, stable,
Mathieu Desnoyers, Florian Weimer, Dmitry Vyukov, Neel Natu
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.
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
^ permalink raw reply related [flat|nested] 3+ messages in thread
* [PATCH for 5.5 2/2 v2] rseq/selftests: Clarify rseq_prepare_unload() helper requirements
2019-12-20 20:33 [PATCH for 5.5 1/2 v2] rseq: Fix: Clarify rseq.h UAPI rseq_cs memory reclaim requirements Mathieu Desnoyers
@ 2019-12-20 20:33 ` Mathieu Desnoyers
2020-01-06 19:10 ` [PATCH for 5.5 1/2 v2] rseq: Fix: Clarify rseq.h UAPI rseq_cs memory reclaim requirements Mathieu Desnoyers
1 sibling, 0 replies; 3+ messages in thread
From: Mathieu Desnoyers @ 2019-12-20 20:33 UTC (permalink / raw)
To: Thomas Gleixner
Cc: linux-kernel, Peter Zijlstra, Paul E . McKenney, Boqun Feng,
H . Peter Anvin, Paul Turner, linux-api, stable,
Mathieu Desnoyers, Shuah Khan, Florian Weimer, Dmitry Vyukov
The rseq.h UAPI now documents that the rseq_cs field must be cleared
before reclaiming memory that contains the targeted struct rseq_cs, but
also 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.
Suggested-by: Florian Weimer <fw@deneb.enyo.de>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Shuah Khan <skhan@linuxfoundation.org>
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>
---
tools/testing/selftests/rseq/rseq.h | 12 +++++++-----
1 file changed, 7 insertions(+), 5 deletions(-)
diff --git a/tools/testing/selftests/rseq/rseq.h b/tools/testing/selftests/rseq/rseq.h
index d40d60e7499e..3f63eb362b92 100644
--- a/tools/testing/selftests/rseq/rseq.h
+++ b/tools/testing/selftests/rseq/rseq.h
@@ -149,11 +149,13 @@ static inline void rseq_clear_rseq_cs(void)
/*
* rseq_prepare_unload() should be invoked by each thread executing a rseq
* critical section at least once between their last critical section and
- * library unload of the library defining the rseq critical section
- * (struct rseq_cs). This also applies to use of rseq in code generated by
- * JIT: rseq_prepare_unload() should be invoked at least once by each
- * thread executing a rseq critical section before reclaim of the memory
- * holding the struct rseq_cs.
+ * library unload of the library defining the rseq critical section (struct
+ * rseq_cs) or the code referred to by the struct rseq_cs start_ip and
+ * post_commit_offset fields. This also applies to use of rseq in code
+ * generated by JIT: rseq_prepare_unload() should be invoked at least once by
+ * each thread executing a rseq critical section before reclaim of the memory
+ * holding the struct rseq_cs or reclaim of the code pointed to by struct
+ * rseq_cs start_ip and post_commit_offset fields.
*/
static inline void rseq_prepare_unload(void)
{
--
2.17.1
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH for 5.5 1/2 v2] rseq: Fix: Clarify rseq.h UAPI rseq_cs memory reclaim requirements
2019-12-20 20:33 [PATCH for 5.5 1/2 v2] rseq: Fix: Clarify rseq.h UAPI rseq_cs memory reclaim requirements Mathieu Desnoyers
2019-12-20 20:33 ` [PATCH for 5.5 2/2 v2] rseq/selftests: Clarify rseq_prepare_unload() helper requirements Mathieu Desnoyers
@ 2020-01-06 19:10 ` Mathieu Desnoyers
1 sibling, 0 replies; 3+ messages in thread
From: Mathieu Desnoyers @ 2020-01-06 19:10 UTC (permalink / raw)
To: Peter Zijlstra
Cc: linux-kernel, paulmck, Boqun Feng, H. Peter Anvin, Paul Turner,
linux-api, stable, Florian Weimer, Dmitry Vyukov, Neel Natu,
Thomas Gleixner
----- 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
^ permalink raw reply [flat|nested] 3+ messages in thread
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