Fix MIPS breakage introduced when adding support for arm64.

MIPS shared libraries lack a DT_PLTREL, but current code insists on
seeing either DT_REL or DT_RELA.  This stops the crazy linker from
working correctly on MIPS:

  /LibraryLoader( 4421): Loading: chromium_android_linker
  I/LibraryLoader( 4421): Loading: chrome.2056.0
  E/chromium_android_linker( 4421): LoadLibrary: Could not open
  libchrome.2056.0.so: Unsupported or missing DT_PLTREL in dynamic section

Remove the requirement for relocations_type_ to be set by DT_PLTREL.
If not set by DT_PLTREL then assign based on the presence of either
DT_REL or DT_RELA.

BUG=386594

Review URL: https://codereview.chromium.org/343933002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@279134 0039d316-1c4b-4281-b951-d872f2087c98

2 files changed, 35 insertions, 18 deletions

diff --git a/third_party/android_crazy_linker/README.chromium b/third_party/android_crazy_linker/README.chromium
index e843964..ad87dc6 100644
--- a/third_party/android_crazy_linker/README.chromium
+++ b/third_party/android_crazy_linker/README.chromium
@@ -30,3 +30,5 @@ index 5fa16df..bc03739 100644
   (Re-add license header to crazy_linker_elf_view.cpp)
 
 - Fix for crbug/373695 (NDK crazy linker: Bug in library file name handling)
+
+- Fix for crbug/386594 (Crazy linker fails to load a browser on MIPS)
diff --git a/third_party/android_crazy_linker/src/src/crazy_linker_elf_relocations.cpp b/third_party/android_crazy_linker/src/src/crazy_linker_elf_relocations.cpp
index 591a1fd..a8d1629 100644
--- a/third_party/android_crazy_linker/src/src/crazy_linker_elf_relocations.cpp
+++ b/third_party/android_crazy_linker/src/src/crazy_linker_elf_relocations.cpp
@@ -242,11 +242,20 @@ bool ElfRelocations::Init(const ElfView* view, Error* error) {
     }
   }
 
-  if (relocations_type_ != DT_REL && relocations_type_ != DT_RELA) {
-    *error = "Unsupported or missing DT_PLTREL in dynamic section";
+  if (has_rel_relocations && has_rela_relocations) {
+    *error = "Combining DT_REL and DT_RELA is not currently supported";
     return false;
   }
 
+  // If DT_PLTREL did not explicitly assign relocations_type_, set it
+  // here based on the type of relocations found.
+  if (relocations_type_ != DT_REL && relocations_type_ != DT_RELA) {
+    if (has_rel_relocations)
+      relocations_type_ = DT_REL;
+    else if (has_rela_relocations)
+      relocations_type_ = DT_RELA;
+  }
+
   if (relocations_type_ == DT_REL && has_rela_relocations) {
     *error = "Found DT_RELA in dyn section, but DT_PLTREL is DT_REL";
     return false;
@@ -286,7 +295,7 @@ bool ElfRelocations::ApplyAll(const ElfSymbols* symbols,
       return false;
   }
 
-  else if (relocations_type_ == DT_RELA) {
+  if (relocations_type_ == DT_RELA) {
     if (!ApplyRelaRelocs(reinterpret_cast<ELF::Rela*>(plt_relocations_),
                          plt_relocations_size_ / sizeof(ELF::Rela),
                          symbols,
@@ -578,13 +587,16 @@ bool ElfRelocations::ApplyRelRelocs(const ELF::Rel* rel,
 
     // If this is a symbolic relocation, compute the symbol's address.
     if (__builtin_expect(rel_symbol != 0, 0)) {
-      resolved = ResolveSymbol(rel_type,
-                               rel_symbol,
-                               symbols,
-                               resolver,
-                               reloc,
-                               &sym_addr,
-                               error);
+      if (!ResolveSymbol(rel_type,
+                         rel_symbol,
+                         symbols,
+                         resolver,
+                         reloc,
+                         &sym_addr,
+                         error)) {
+        return false;
+      }
+      resolved = true;
     }
 
     if (!ApplyRelReloc(rel, sym_addr, resolved, error))
@@ -625,13 +637,16 @@ bool ElfRelocations::ApplyRelaRelocs(const ELF::Rela* rela,
 
     // If this is a symbolic relocation, compute the symbol's address.
     if (__builtin_expect(rel_symbol != 0, 0)) {
-      resolved = ResolveSymbol(rel_type,
-                               rel_symbol,
-                               symbols,
-                               resolver,
-                               reloc,
-                               &sym_addr,
-                               error);
+      if (!ResolveSymbol(rel_type,
+                         rel_symbol,
+                         symbols,
+                         resolver,
+                         reloc,
+                         &sym_addr,
+                         error)) {
+        return false;
+      }
+      resolved = true;
     }
 
     if (!ApplyRelaReloc(rela, sym_addr, resolved, error))
@@ -803,7 +818,7 @@ void ElfRelocations::CopyAndRelocate(size_t src_addr,
   if (relocations_type_ == DT_REL)
     RelocateRel(src_addr, dst_addr, map_addr, size);
 
-  else if (relocations_type_ == DT_RELA)
+  if (relocations_type_ == DT_RELA)
     RelocateRela(src_addr, dst_addr, map_addr, size);
 
 #ifdef __mips__