[Courgette] Fix AssemblyProgram parsing for ELF-ARM.

courgette/disassembler_elf_32.cc

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "courgette/disassembler_elf_32.h"
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include <algorithm>
@@ skipping 144 matching lines @@
     Elf32_Addr begin = segment_header->p_vaddr;
     Elf32_Addr end = segment_header->p_vaddr + segment_header->p_memsz;
 
     if (rva >= begin && rva < end)
       return true;
   }
 
   return false;
 }
 
-// Returns RVA for an in memory address, or NULL.
-CheckBool DisassemblerElf32::RVAToFileOffset(Elf32_Addr addr,
-                                                size_t* result) const {
+CheckBool DisassemblerElf32::RVAToFileOffset(RVA rva,
+                                             size_t* result) const {
+  for (int i = 0; i < SectionHeaderCount(); i++) {
+    const Elf32_Shdr *section_header = SectionHeader(i);
+    // These can appear to have a size in the file, but don't.
+    if (section_header->sh_type == SHT_NOBITS)
+      continue;
+    Elf32_Addr begin = section_header->sh_addr;
+    Elf32_Addr end = begin + section_header->sh_size;
 
-  for (int i = 0; i < ProgramSegmentHeaderCount(); i++) {
-    Elf32_Addr begin = ProgramSegmentMemoryBegin(i);
-    Elf32_Addr end = begin + ProgramSegmentMemorySize(i);
-
-    if (addr >= begin  && addr < end) {
-      Elf32_Addr offset = addr - begin;
-
-      if (offset < ProgramSegmentFileSize(i)) {
-        *result = ProgramSegmentFileOffset(i) + offset;
-        return true;
-      }
+    if (rva >= begin && rva < end) {
+      *result = section_header->sh_offset + (rva - begin);
+      return true;
     }
   }
-
   return false;
 }
 
 RVA DisassemblerElf32::FileOffsetToRVA(size_t offset) const {
   // File offsets can be 64 bit values, but we are dealing with 32
   // bit executables and so only need to support 32bit file sizes.
   uint32_t offset32 = (uint32_t)offset;
 
   for (int i = 0; i < SectionHeaderCount(); i++) {
 
@@ skipping 291 matching lines @@
 
   rel32_locations_.clear();
 
   // Loop through sections for relocation sections
   for (int section_id = 0;
        section_id < SectionHeaderCount();
        section_id++) {
 
     const Elf32_Shdr *section_header = SectionHeader(section_id);
 
-    if (section_header->sh_type != SHT_PROGBITS)
+    // Some debug sections can have sh_type=SHT_PROGBITS but sh_addr=0.
+    if (section_header->sh_type != SHT_PROGBITS ||
+        section_header->sh_addr == 0)
       continue;
 
     if (!ParseRel32RelocsFromSection(section_header))
       return false;
   }
 
   std::sort(rel32_locations_.begin(),
             rel32_locations_.end(),
             TypedRVA::IsLessThan);
   DCHECK(rel32_locations_.empty() ||
          rel32_locations_.back()->rva() != kUnassignedRVA);
   return true;
 }
 
 }  // namespace courgette