Use zero offset when getting bias from memory.nougat-dev

The code to get the bias was incorrectly using the passed in map offset
when reading it from memory. This doesn't work since the offset is the
offset into the apk. Change to always check for a zero in this case.

Bug: 28685297
Change-Id: I9ab2a89401429c4bcf4faa510b1b619be70318ab

1 files changed, 5 insertions, 1 deletions

diff --git a/src/elfxx.c b/src/elfxx.c
index 7fda0b72..057a3baf 100644
--- a/src/elfxx.c
+++ b/src/elfxx.c
@@ -635,7 +635,11 @@ HIDDEN bool elf_w (get_load_base) (struct elf_image* ei, unw_word_t mapoff, unw_
       Elf_W(Phdr) phdr;
       GET_PHDR_FIELD(ei, offset, &phdr, p_type);
       GET_PHDR_FIELD(ei, offset, &phdr, p_offset);
-      if (phdr.p_type == PT_LOAD && phdr.p_offset == mapoff) {
+      // Always use zero as the map offset for in memory maps.
+      // The dlopen of a shared library from an APK will result in a
+      // non-zero map offset which would mean we would never find the
+      // correct program header using the passed in map offset.
+      if (phdr.p_type == PT_LOAD && phdr.p_offset == 0) {
         GET_PHDR_FIELD(ei, offset, &phdr, p_vaddr);
         *load_base = phdr.p_vaddr;
         return true;