Do not access device maps.
It's possible that a device map has memory controlled by a single entry
device driver. Thus, you can deadlock if a process is touching that
device memory and we try to unwind it and also touch that device memory.
Simply skip any attempts to step through, or get function names from
device memory maps.
Bug: 36130325
Test: Ran new unit tests, ran bionic unit tests, ran art ThreadStress.
Change-Id: Ibc62d7ec8106c619ee08968f05e04aea55d7cbfa
diff --git a/include/backtrace/Backtrace.h b/include/backtrace/Backtrace.h
index c896ab8..4f73a65 100644
--- a/include/backtrace/Backtrace.h
+++ b/include/backtrace/Backtrace.h
@@ -104,8 +104,10 @@
virtual bool Unwind(size_t num_ignore_frames, ucontext_t* context = NULL) = 0;
// Get the function name and offset into the function given the pc.
- // If the string is empty, then no valid function name was found.
- virtual std::string GetFunctionName(uintptr_t pc, uintptr_t* offset);
+ // If the string is empty, then no valid function name was found,
+ // or the pc is not in any valid map.
+ virtual std::string GetFunctionName(uintptr_t pc, uintptr_t* offset,
+ const backtrace_map_t* map = NULL);
// Fill in the map data associated with the given pc.
virtual void FillInMap(uintptr_t pc, backtrace_map_t* map);
diff --git a/include/backtrace/BacktraceMap.h b/include/backtrace/BacktraceMap.h
index df48dfe..8ab0dfa 100644
--- a/include/backtrace/BacktraceMap.h
+++ b/include/backtrace/BacktraceMap.h
@@ -33,6 +33,10 @@
#include <string>
#include <vector>
+// Special flag to indicate a map is in /dev/. However, a map in
+// /dev/ashmem/... does not set this flag.
+static constexpr int PROT_DEVICE_MAP = 0x8000;
+
struct backtrace_map_t {
uintptr_t start = 0;
uintptr_t end = 0;