Bug 1593966 - Add minimal support for the DW_FORM_GNU_ref_alt and DW_…

…FORM_GNU_strp_alt operand forms in dump_syms r=froydnj

Differential Revision: https://phabricator.services.mozilla.com/D51801

--HG--
extra : moz-landing-system : lando

toolkit/crashreporter/breakpad-patches/09-gnu-alt-form-minimal-support.patch

@@ -0,0 +1,85 @@
+# HG changeset patch
+# User Gabriele Svelto <[email protected]>
+# Date 1572953718 -3600
+#      Tue Nov 05 12:35:18 2019 +0100
+# Node ID 229ab2882283fb1a080486bceda9db729525e78c
+# Parent  53ebedebdb63ded40f5f3fef677ccc60fa6deeac
+Bug 1593966 - Add minimal support for the DW_FORM_GNU_ref_alt and DW_FORM_GNU_strp_alt operand forms in dump_syms
+
+diff --git a/src/common/dwarf/dwarf2enums.h b/src/common/dwarf/dwarf2enums.h
+--- a/src/common/dwarf/dwarf2enums.h
++++ b/src/common/dwarf/dwarf2enums.h
+@@ -147,17 +147,22 @@ enum DwarfForm {
+
+   // Added in DWARF 4:
+   DW_FORM_sec_offset = 0x17,
+   DW_FORM_exprloc = 0x18,
+   DW_FORM_flag_present = 0x19,
+   DW_FORM_ref_sig8 = 0x20,
+   // Extensions for Fission.  See http://gcc.gnu.org/wiki/DebugFission.
+   DW_FORM_GNU_addr_index = 0x1f01,
+-  DW_FORM_GNU_str_index = 0x1f02
++  DW_FORM_GNU_str_index = 0x1f02,
++
++  // Extensions introduced for the dwz compression tool. See
++  // https://fedoraproject.org/wiki/Features/DwarfCompressor
++  DW_FORM_GNU_ref_alt = 0x1f20,
++  DW_FORM_GNU_strp_alt = 0x1f21,
+ };
+
+ // Attribute names and codes
+ enum DwarfAttribute {
+   DW_AT_sibling = 0x01,
+   DW_AT_location = 0x02,
+   DW_AT_name = 0x03,
+   DW_AT_ordering = 0x09,
+diff --git a/src/common/dwarf/dwarf2reader.cc b/src/common/dwarf/dwarf2reader.cc
+--- a/src/common/dwarf/dwarf2reader.cc
++++ b/src/common/dwarf/dwarf2reader.cc
+@@ -219,16 +219,21 @@ const uint8_t *CompilationUnit::SkipAttr
+       assert(header_.version >= 2);
+       if (header_.version == 2) {
+         return start + reader_->AddressSize();
+       } else if (header_.version >= 3) {
+         return start + reader_->OffsetSize();
+       }
+       break;
+
++    case DW_FORM_GNU_ref_alt:
++    case DW_FORM_GNU_strp_alt:
++      return start + reader_->OffsetSize();
++      break;
++
+     case DW_FORM_block1:
+       return start + 1 + reader_->ReadOneByte(start);
+     case DW_FORM_block2:
+       return start + 2 + reader_->ReadTwoBytes(start);
+     case DW_FORM_block4:
+       return start + 4 + reader_->ReadFourBytes(start);
+     case DW_FORM_block:
+     case DW_FORM_exprloc: {
+@@ -515,16 +520,24 @@ const uint8_t *CompilationUnit::ProcessA
+     case DW_FORM_GNU_addr_index: {
+       uint64 addr_index = reader_->ReadUnsignedLEB128(start, &len);
+       const uint8_t* addr_ptr =
+           addr_buffer_ + addr_base_ + addr_index * reader_->AddressSize();
+       ProcessAttributeUnsigned(dieoffset, attr, form,
+                                reader_->ReadAddress(addr_ptr));
+       return start + len;
+     }
++    case DW_FORM_GNU_ref_alt: {
++      // TODO: This effectively ignores attributes stored in alternate object
++      // files. We should process them properly instead.
++      return start + reader_->OffsetSize();
++    }
++    case DW_FORM_GNU_strp_alt: {
++      return start + reader_->OffsetSize();
++    }
+   }
+   fprintf(stderr, "Unhandled form type\n");
+   return NULL;
+ }
+
+ const uint8_t *CompilationUnit::ProcessDIE(uint64 dieoffset,
+                                            const uint8_t *start,
+                                            const Abbrev& abbrev) {

toolkit/crashreporter/google-breakpad/src/common/dwarf/dwarf2enums.h

@@ -152,7 +152,12 @@ enum DwarfForm {
   DW_FORM_ref_sig8 = 0x20,
   // Extensions for Fission.  See http://gcc.gnu.org/wiki/DebugFission.
   DW_FORM_GNU_addr_index = 0x1f01,
-  DW_FORM_GNU_str_index = 0x1f02
+  DW_FORM_GNU_str_index = 0x1f02,
+
+  // Extensions introduced for the dwz compression tool. See
+  // https://fedoraproject.org/wiki/Features/DwarfCompressor
+  DW_FORM_GNU_ref_alt = 0x1f20,
+  DW_FORM_GNU_strp_alt = 0x1f21,
 };
 
 // Attribute names and codes

toolkit/crashreporter/google-breakpad/src/common/dwarf/dwarf2reader.cc

@@ -224,6 +224,11 @@ const uint8_t *CompilationUnit::SkipAttribute(const uint8_t *start,
       }
       break;
 
+    case DW_FORM_GNU_ref_alt:
+    case DW_FORM_GNU_strp_alt:
+      return start + reader_->OffsetSize();
+      break;
+
     case DW_FORM_block1:
       return start + 1 + reader_->ReadOneByte(start);
     case DW_FORM_block2:
@@ -520,6 +525,14 @@ const uint8_t *CompilationUnit::ProcessAttribute(
                                reader_->ReadAddress(addr_ptr));
       return start + len;
     }
+    case DW_FORM_GNU_ref_alt: {
+      // TODO: This effectively ignores attributes stored in alternate object
+      // files. We should process them properly instead.
+      return start + reader_->OffsetSize();
+    }
+    case DW_FORM_GNU_strp_alt: {
+      return start + reader_->OffsetSize();
+    }
   }
   fprintf(stderr, "Unhandled form type\n");
   return NULL;