Properly handle empty map after read-only map.
Recently, the maps for an elf in memory might show up looking like:
f0000-f1000 0 r-- /system/lib/libc.so
f1000-f2000 0 ---
f2000-f3000 1000 r-x /system/lib/libc.so
f3000-f4000 2000 rw- /system/lib/libc.so
The problem is that there is logic in the code that assumed that the
map before the execute map must be the read-only map. In the case
above, this is not true. Add a new prev_real_map that will point
to the previous map that is not one of these empty maps.
This will fix the backtraces that look like this:
#00 pc 0000000000050d58 /apex/com.android.runtime/lib64/bionic/libc.so!libc.so (offset 0x50000) (syscall+24) (BuildId: 5252408bf30e395d49ee270b54c77ca4)
To get rid of the !libc.so and the offset value, which is not correct.
Added new unit tests to verify this.
Added new offline test which an empty map between read-only and execute
map. Before this change, the backtraces had lines like
libc.so!libc.so (offset XXX) would be present.
Bug: 148075852
Test: Ran unit tests.
Change-Id: Ie04bfc96b8f91ed885cb1e655cf1e346efe48a45
diff --git a/libunwindstack/tests/MapInfoGetLoadBiasTest.cpp b/libunwindstack/tests/MapInfoGetLoadBiasTest.cpp
index da3dbf2..971d452 100644
--- a/libunwindstack/tests/MapInfoGetLoadBiasTest.cpp
+++ b/libunwindstack/tests/MapInfoGetLoadBiasTest.cpp
@@ -50,7 +50,7 @@
process_memory_.reset(memory_);
elf_ = new ElfFake(new MemoryFake);
elf_container_.reset(elf_);
- map_info_.reset(new MapInfo(nullptr, 0x1000, 0x20000, 0, PROT_READ | PROT_WRITE, ""));
+ map_info_.reset(new MapInfo(nullptr, nullptr, 0x1000, 0x20000, 0, PROT_READ | PROT_WRITE, ""));
}
void MultipleThreadTest(uint64_t expected_load_bias);
@@ -63,7 +63,7 @@
};
TEST_F(MapInfoGetLoadBiasTest, no_elf_and_no_valid_elf_in_memory) {
- MapInfo info(nullptr, 0x1000, 0x2000, 0, PROT_READ, "");
+ MapInfo info(nullptr, nullptr, 0x1000, 0x2000, 0, PROT_READ, "");
EXPECT_EQ(0U, info.GetLoadBias(process_memory_));
}