Enable reading DWARF4 CIEs with 32 bit addresses.

- Reading DWARF4 CIEs was added in
https://chromium-review.googlesource.com/c/breakpad/breakpad/+/406012 but it
was only enabled for 64bit builds, since it would error out if the CIE
address size was not 8 bytes.
- Added a unit test to ensure that 32bit continues to work.

Change-Id: I824bb40cdf12056d39da335adb55ed315970fb88
Reviewed-on: https://chromium-review.googlesource.com/c/breakpad/breakpad/+/1941034
Reviewed-by: Ivan Penkov <ivanpe@chromium.org>
Reviewed-by: Mark Mentovai <mark@chromium.org>

1 files changed, 15 insertions, 12 deletions

diff --git a/src/common/dwarf/dwarf2reader.cc b/src/common/dwarf/dwarf2reader.cc
index 27f3a83e..3e6a3e89 100644
--- a/src/common/dwarf/dwarf2reader.cc
+++ b/src/common/dwarf/dwarf2reader.cc
@@ -2330,21 +2330,15 @@ bool CallFrameInfo::ReadCIEFields(CIE *cie) {
   }
 
   if (cie->version >= 4) {
-    uint8_t address_size = *cursor++;
-    if (address_size != 8) {
-      // TODO(scottmg): Only supporting x64 for now.
-      reporter_->UnexpectedAddressSize(cie->offset, address_size);
+    cie->address_size = *cursor++;
+    if (cie->address_size != 8 && cie->address_size != 4) {
+      reporter_->UnexpectedAddressSize(cie->offset, cie->address_size);
       return false;
     }
 
-    uint8_t segment_size = *cursor++;
-    if (segment_size != 0) {
-      // TODO(scottmg): Only supporting x64 for now.
-      // I would have perhaps expected 4 here, but LLVM emits a 0, near
-      // http://llvm.org/docs/doxygen/html/MCDwarf_8cpp_source.html#l00606. As
-      // we are not using the value, only succeed for now if it's the expected
-      // 0.
-      reporter_->UnexpectedSegmentSize(cie->offset, segment_size);
+    cie->segment_size = *cursor++;
+    if (cie->segment_size != 0) {
+      reporter_->UnexpectedSegmentSize(cie->offset, cie->segment_size);
       return false;
     }
   }
@@ -2606,6 +2600,15 @@ bool CallFrameInfo::Start() {
     if (!ReadCIEFields(&cie))
       continue;
 
+    // TODO(nbilling): This could lead to strange behavior if a single buffer
+    // contained a mixture of DWARF versions as well as address sizes. Not
+    // sure if it's worth handling such a case.
+
+    // DWARF4 CIE specifies address_size, so use it for this call frame.
+    if (cie.version >= 4) {
+      reader_->SetAddressSize(cie.address_size);
+    }
+
     // We now have the values that govern both the CIE and the FDE.
     cie.cie = &cie;
     fde.cie = &cie;