Hi Mathieu,
On 12/20/19 1:12 PM, Mathieu Desnoyers wrote:
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..15cbd51d0818 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 refered to by the struct rseq_cs start_ip and
Nit: referred instead of refered
- 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
*/ static inline void rseq_prepare_unload(void) {
- rseq_cs start_ip and post_commit_offset fields.
thanks, -- Shuah