Fix getting elf file from JIT_SYMFILE maps.

For maps with MAPS_FLAGS_JIT_SYMFILE_MAP, the map range
is for a JIT function, which can be smaller than elf header size.
To get elf file from those maps, increase map_size to make sure
we can read elf header.

Bug: 215556268
Test: run libunwindstack_unit_test

Change-Id: Ib549f02c8ea806598ddb4319c655705227e36e16

1 files changed, 5 insertions, 1 deletions

diff --git a/libunwindstack/MapInfo.cpp b/libunwindstack/MapInfo.cpp
index 6193015..f19c6b7 100644
--- a/libunwindstack/MapInfo.cpp
+++ b/libunwindstack/MapInfo.cpp
@@ -120,7 +120,11 @@ Memory* MapInfo::GetFileMemory() {
   // and reinit to that size. This is needed because the dynamic linker
   // only maps in a portion of the original elf, and never the symbol
   // file data.
-  uint64_t map_size = end() - start();
+  //
+  // For maps with MAPS_FLAGS_JIT_SYMFILE_MAP, the map range is for a JIT function,
+  // which can be smaller than elf header size. So make sure map_size is large enough
+  // to read elf header.
+  uint64_t map_size = std::max<uint64_t>(end() - start(), sizeof(ElfTypes64::Ehdr));
   if (!memory->Init(name(), offset(), map_size)) {
     return nullptr;
   }