commit 819f13116e25c2724a7daeed9afb3adb2d027f5b
author Christopher Ferris <cferris@google.com> Thu Oct 03 13:35:48 2019 -0700
committer Christopher Ferris <cferris@google.com> Tue Oct 08 17:36:06 2019 +0000
tree 85e5d2e80bb63bf0bdaef49823079b9323268572
parent 6c1668d6600da00aefabd245430d68c395e4b207

Handle when bias is different in elf headers.

The original code assumed that the load bias in the program headers
would be exactly the same as in eh_frame/eh_frame_hdr/debug_frame.

This isn't guaranteed, so add a section bias for use when creating
a DwarfSection. In addtion, make the load bias and section bias
a signed value. There is no reason that this value needs to be positive,
so don't force it to be.

Add a new offline test that has a different load bias in eh_frame than
in the executable load.

Add additional unit tests to verify the load bias values are set properly.

Clean up the tests in ElfInterfaceTest, making all tests names follow the
same convention.

Bug: 141888859
Bug: 142094469

Test: New units and old unit tests pass on host and taimen.
Change-Id: Ib878123ab5545f0f315c749cfe0d27b012d873ee

libunwindstack/Elf.cpp

diff --git a/libunwindstack/Elf.cpp b/libunwindstack/Elf.cpp
index 3454913..c141b2e 100644
--- a/libunwindstack/Elf.cpp
+++ b/libunwindstack/Elf.cpp
@@ -53,7 +53,7 @@
 
   valid_ = interface_->Init(&load_bias_);
   if (valid_) {
-    interface_->InitHeaders(load_bias_);
+    interface_->InitHeaders();
     InitGnuDebugdata();
   } else {
     interface_.reset(nullptr);
@@ -77,9 +77,9 @@
 
   // Ignore the load_bias from the compressed section, the correct load bias
   // is in the uncompressed data.
-  uint64_t load_bias;
+  int64_t load_bias;
   if (gnu->Init(&load_bias)) {
-    gnu->InitHeaders(load_bias);
+    gnu->InitHeaders();
     interface_->SetGnuDebugdataInterface(gnu);
   } else {
     // Free all of the memory associated with the gnu_debugdata section.
@@ -124,7 +124,7 @@
   }
 
   // Adjust by the load bias.
-  if (*memory_address < load_bias_) {
+  if (load_bias_ > 0 && *memory_address < static_cast<uint64_t>(load_bias_)) {
     return false;
   }
 
@@ -229,7 +229,7 @@
 }
 
 bool Elf::IsValidPc(uint64_t pc) {
-  if (!valid_ || pc < load_bias_) {
+  if (!valid_ || (load_bias_ > 0 && pc < static_cast<uint64_t>(load_bias_))) {
     return false;
   }
 
@@ -299,7 +299,7 @@
   return interface.release();
 }
 
-uint64_t Elf::GetLoadBias(Memory* memory) {
+int64_t Elf::GetLoadBias(Memory* memory) {
   if (!IsValidElf(memory)) {
     return 0;
   }