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authorMathieu Desnoyers <mathieu.desnoyers@efficios.com>2019-12-20 23:33:18 +0300
committerShuah Khan <skhan@linuxfoundation.org>2019-12-23 20:52:41 +0300
commit2a1f40adfb54ca65dc4c93bad444dd23b800a76e (patch)
tree284abbc081e5c549f99e3a1cec4eec74549ef8d5 /tools
parent8df34c56321479bfa1ec732c675b686c2b4df412 (diff)
downloadlinux-2a1f40adfb54ca65dc4c93bad444dd23b800a76e.tar.xz
rseq/selftests: Clarify rseq_prepare_unload() helper requirements
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> Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>
Diffstat (limited to 'tools')
-rw-r--r--tools/testing/selftests/rseq/rseq.h12
1 files 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)
{