commit 568f196756ad9fe2b49c46bbf6a9de1b190438b4
author Peter Zijlstra <peterz@infradead.org> Mon Jan 28 17:21:52 2019 -0800
committer Daniel Borkmann <daniel@iogearbox.net> Tue Feb 19 21:53:07 2019 +0100
tree a8c84a1e56786296cd005d6c7ca7ad741c2367ea
parent a5d9265e017f081f0dc133c0e2f45103d027b874

bpf: check that BPF programs run with preemption disabled

Introduce cant_sleep() macro for annotation of functions that
cannot sleep.

Use it in BPF_PROG_RUN to catch execution of BPF programs in
preemptable context.

Suggested-by: Jann Horn <jannh@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

include/linux/kernel.h

diff --git a/include/linux/kernel.h b/include/linux/kernel.h
index 8f0e68e..a8868a3 100644
--- a/include/linux/kernel.h
+++ b/include/linux/kernel.h
@@ -245,8 +245,10 @@ extern int _cond_resched(void);
 #endif
 
 #ifdef CONFIG_DEBUG_ATOMIC_SLEEP
-  void ___might_sleep(const char *file, int line, int preempt_offset);
-  void __might_sleep(const char *file, int line, int preempt_offset);
+extern void ___might_sleep(const char *file, int line, int preempt_offset);
+extern void __might_sleep(const char *file, int line, int preempt_offset);
+extern void __cant_sleep(const char *file, int line, int preempt_offset);
+
 /**
  * might_sleep - annotation for functions that can sleep
  *
@@ -259,6 +261,13 @@ extern int _cond_resched(void);
  */
 # define might_sleep() \
 	do { __might_sleep(__FILE__, __LINE__, 0); might_resched(); } while (0)
+/**
+ * cant_sleep - annotation for functions that cannot sleep
+ *
+ * this macro will print a stack trace if it is executed with preemption enabled
+ */
+# define cant_sleep() \
+	do { __cant_sleep(__FILE__, __LINE__, 0); } while (0)
 # define sched_annotate_sleep()	(current->task_state_change = 0)
 #else
   static inline void ___might_sleep(const char *file, int line,
@@ -266,6 +275,7 @@ extern int _cond_resched(void);
   static inline void __might_sleep(const char *file, int line,
 				   int preempt_offset) { }
 # define might_sleep() do { might_resched(); } while (0)
+# define cant_sleep() do { } while (0)
 # define sched_annotate_sleep() do { } while (0)
 #endif