[LLDB] - Add support for DW_FORM_rnglistx and relative DW_RLE_* entries.

[grimar]

Summary

This adds support for DW_RLE_base_addressx, DW_RLE_startx_endx,
DW_RLE_startx_length, DW_FORM_rnglistx.

[clayborg]

Just one question about extracting the value for DW_AT_ranges. It would be nice if we just took care of extracting the value so the form value was more useful

source/Plugins/SymbolFile/DWARF/DWARFDebugInfoEntry.cpp

1072–1079

Can/should we do all this work when we extract the form value so that "form_value.Unsigned()" just returns the right thing? If not, every place that gets DW_AT_ranges attribute would need to do this.

[grimar]

• Addressed review comments.

source/Plugins/SymbolFile/DWARF/DWARFDebugInfoEntry.cpp

1072–1079

Doing everything inside DWARFFormValue::ExtractValue would make the callers code simpler indeed,
but my concern is that it would mean that instead of the attribute value requested it would return the offset value read from .debug_rnglists section. I am not sure it is good idea to read any debug section content at that low level.

I think 'ExtractValue` ideally should not know about the debug sections. And also that would not be consistent with the other forms it reads. I am not sure if we might want to know the raw value of the DW_FORM_rnglistx one day, but with such change, we will lose such possibility.

I would suggest making a helper function instead, so all the callers can use it. I did it in this patch, what do you think?

[clayborg]

Solution is fine. As long as we don't have to duplicate the work everywhere that needs a ranges offset.

lit/Breakpoint/Inputs/debug_rnglistx_rlex.yaml

+--- !ELF
+FileHeader:      
+  Class:           ELFCLASS64
+  Data:            ELFDATA2LSB
+  Type:            ET_EXEC
+  Machine:         EM_X86_64
+  Entry:           0x0000000000201000
+Sections:        
+  - Name:            .text
+    Type:            SHT_PROGBITS
+    Flags:           [ SHF_ALLOC, SHF_EXECINSTR ]
+    Address:         0x0000000000201000
+    AddressAlign:    0x0000000000000010
+    Content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
+  - Name:            .debug_str_offsets
+    Type:            SHT_PROGBITS
+    AddressAlign:    0x0000000000000001
+    Content:         28000000050000003000000067000000000000002800000076000000240000006F0000007400000022000000
+  - Name:            .debug_str
+    Type:            SHT_PROGBITS
+    Flags:           [ SHF_MERGE, SHF_STRINGS ]
+    AddressAlign:    0x0000000000000001
+    Content:         2F686F6D652F756D622F74657374735F323031382F3131345F726E676C69737473007900696E74005F5A336261726900636C616E672076657273696F6E20382E302E3020287472756E6B203334353639392920286C6C766D2F7472756E6B203334353530362900746573742E6363006D61696E00780062617200
+  - Name:            .debug_loclists
+    Type:            SHT_PROGBITS
+    AddressAlign:    0x0000000000000001
+    Content:         '15000000050008000000000003000301005503020101005000'
+  - Name:            .debug_abbrev
+    Type:            SHT_PROGBITS
+    AddressAlign:    0x0000000000000001
+    Content:         011101252513050325721710171B2573171101552374178C01170000022E01111B120640187A196E2503253A0B3B0B49133F190000030500021703253A0B3B0B49130000042E01111B120640187A1903253A0B3B0B49133F1900000534001C0D03253A0B3B0B4913000006240003253E0B0B0B000000
+  - Name:            .debug_info
+    Type:            SHT_PROGBITS
+    AddressAlign:    0x0000000000000001
+    Content:         6600000005000108000000000100040001080000000000000002080000000000000000000000000C0000000C00000002000400000001570304010365000000030C0000000701036500000000040106000000015706010765000000050108010865000000000605050400
+  - Name:            .debug_rnglists
+    Type:            SHT_PROGBITS
+    AddressAlign:    0x0000000000000001
+    Content:         '1300000005000800010000000400000003000403010600'
+  - Name:            .debug_macinfo
+    Type:            SHT_PROGBITS
+    AddressAlign:    0x0000000000000001
+    Content:         '00'
+  - Name:            .debug_addr
+    Type:            SHT_PROGBITS
+    AddressAlign:    0x0000000000000001
+    Content:         1C00000005000800E010200000000000F010200000000000E310200000000000
+  - Name:            .debug_line
+    Type:            SHT_PROGBITS
+    AddressAlign:    0x0000000000000001
+    Content:         82000000050008004C000000010101FB0E0D00010101010000000100000101011F010000000003011F020F051E022200000000FC42F1EAF1396417A8FBE442FBADC7032200000000FC42F1EAF1396417A8FBE442FBADC703000902E01020000000000014050B0A130504063C0201000101000902F0102000000000001805030A140206000101
+  - Name:            .debug_line_str
+    Type:            SHT_PROGBITS
+    Flags:           [ SHF_MERGE, SHF_STRINGS ]
+    AddressAlign:    0x0000000000000001
+    Content:         2F686F6D652F756D622F74657374735F323031382F3131345F726E676C6973747300746573742E636300
+Symbols:

lit/Breakpoint/debug_rnglistx_rlex.test

+# RUN: yaml2obj %p/Inputs/debug_rnglistx_rlex.yaml > %ttest
+# RUN: lldb-test breakpoints %ttest %s | FileCheck %s
+
+# The following code and invocation were used.
+# clang -gdwarf-5 test.cc -o test_v5 -fuse-ld=lld -fno-rtti -O2 -ffunction-sections
+# Then output was converted to yaml and reduced.
+#
+# int bar(int x) {
+#    return ++x;
+# }
+# 
+# int main() {
+#   int y = 1;
+#   return bar(y);
+# }
+#
+# clang and LLD versions were 8.0.0 (trunk 345699)
+#
+# Output file contains DW_FORM_rnglistx and DW_RLE_startx_length.
+
+b bar
+b main
+
+# CHECK-LABEL: b bar
+# CHECK: Address: {{.*}}`bar(int) at test.cc:4:11
+
+# CHECK-LABEL: b main
+# CHECK: Address: {{.*}}`main at test.cc:9:3

source/Plugins/SymbolFile/DWARF/DWARFDebugInfoEntry.cpp

for (i = 0; i < numAttributes; ++i) {
           case DW_FORM_data8:
           case DW_FORM_ref8:
           case DW_FORM_ref_sig8:
             form_size = 8;
             break;
 
           // signed or unsigned LEB 128 values
           case DW_FORM_addrx:
+          case DW_FORM_rnglistx:
           case DW_FORM_sdata:
           case DW_FORM_udata:
           case DW_FORM_ref_udata:
           case DW_FORM_GNU_addr_index:
           case DW_FORM_GNU_str_index:
           case DW_FORM_strx:
             debug_info_data.Skip_LEB128(&offset);
             break;

 }
 
 size_t DWARFDebugInfoEntry::GetAttributeAddressRanges(
     SymbolFileDWARF *dwarf2Data, const DWARFUnit *cu,
     DWARFRangeList &ranges, bool check_hi_lo_pc,
     bool check_specification_or_abstract_origin) const {
   ranges.Clear();
 
-  dw_offset_t debug_ranges_offset = GetAttributeValueAsUnsigned(
-      dwarf2Data, cu, DW_AT_ranges, DW_INVALID_OFFSET,
-      check_specification_or_abstract_origin);
-  if (debug_ranges_offset != DW_INVALID_OFFSET) {
-    if (DWARFDebugRangesBase *debug_ranges = dwarf2Data->DebugRanges())
+  dw_offset_t at_ranges_val = DW_INVALID_OFFSET;
+  DWARFFormValue form_value;
+  if (GetAttributeValue(dwarf2Data, cu, DW_AT_ranges, form_value, nullptr,
+                        check_specification_or_abstract_origin))
+    at_ranges_val = form_value.Unsigned();
+
+  if (at_ranges_val != DW_INVALID_OFFSET) {
+    if (DWARFDebugRangesBase *debug_ranges = dwarf2Data->DebugRanges()) {
+
+      dw_offset_t debug_ranges_offset;
+      if (form_value.Form() == DW_FORM_rnglistx)
+        debug_ranges_offset = debug_ranges->GetOffset(at_ranges_val);
+      else
+        debug_ranges_offset = at_ranges_val;
+
       debug_ranges->FindRanges(cu, debug_ranges_offset, ranges);
+    }
   } else if (check_hi_lo_pc) {
     dw_addr_t lo_pc = LLDB_INVALID_ADDRESS;
     dw_addr_t hi_pc = LLDB_INVALID_ADDRESS;
     if (GetAttributeAddressRange(dwarf2Data, cu, lo_pc, hi_pc,
                                  LLDB_INVALID_ADDRESS,
                                  check_specification_or_abstract_origin)) {
       if (lo_pc < hi_pc)
         ranges.Append(DWARFRangeList::Entry(lo_pc, hi_pc - lo_pc));

source/Plugins/SymbolFile/DWARF/DWARFDebugRanges.h

 
 class DWARFDebugRangesBase {
 public:
   virtual ~DWARFDebugRangesBase(){};
 
   virtual void Extract(SymbolFileDWARF *dwarf2Data) = 0;
   virtual bool FindRanges(const DWARFUnit *cu, dw_offset_t debug_ranges_offset,
                           DWARFRangeList &range_list) const = 0;
+  virtual uint64_t GetOffset(size_t Index) = 0;
 };
 
 class DWARFDebugRanges final : public DWARFDebugRangesBase {
 public:
   DWARFDebugRanges();
 
-  virtual void Extract(SymbolFileDWARF *dwarf2Data) override;
-  virtual bool FindRanges(const DWARFUnit *cu, dw_offset_t debug_ranges_offset,
-                          DWARFRangeList &range_list) const override;
+  void Extract(SymbolFileDWARF *dwarf2Data) override;
+  bool FindRanges(const DWARFUnit *cu, dw_offset_t debug_ranges_offset,
+  uint64_t GetOffset(size_t Index) override;
 
   static void Dump(lldb_private::Stream &s,
                    const lldb_private::DWARFDataExtractor &debug_ranges_data,
                    lldb::offset_t *offset_ptr, dw_addr_t cu_base_addr);
 
 protected:
   bool Extract(SymbolFileDWARF *dwarf2Data, lldb::offset_t *offset_ptr,
                DWARFRangeList &range_list);
struct RngListEntry {
     uint64_t value0;
     uint64_t value1;
   };
 
 public:
   void Extract(SymbolFileDWARF *dwarf2Data) override;
   bool FindRanges(const DWARFUnit *cu, dw_offset_t debug_ranges_offset,
                   DWARFRangeList &range_list) const override;
+  uint64_t GetOffset(size_t Index) override;
 
 protected:
   bool ExtractRangeList(const lldb_private::DWARFDataExtractor &data,
                         uint8_t addrSize, lldb::offset_t *offset_ptr,
                         std::vector<RngListEntry> &list);
 
   std::vector<uint64_t> Offsets;
   std::map<dw_offset_t, std::vector<RngListEntry>> m_range_map;
 };
 
 #endif // SymbolFileDWARF_DWARFDebugRanges_h_

source/Plugins/SymbolFile/DWARF/DWARFDebugRanges.cpp

if (pos != m_range_map.end()) {
     // unit. We add the compile unit base address to make sure all the
     // addresses are properly fixed up.
     range_list.Slide(cu->GetBaseAddress());
     return true;
   }
   return false;
 }
 
+uint64_t DWARFDebugRanges::GetOffset(size_t Index) {
+  lldbassert(false && "DW_FORM_rnglistx is not present before DWARF5");
+  return 0;
+}
+
 bool DWARFDebugRngLists::ExtractRangeList(
     const DWARFDataExtractor &data, uint8_t addrSize,
     lldb::offset_t *offset_ptr, std::vector<RngListEntry> &rangeList) {
   rangeList.clear();
 
   bool error = false;
   while (!error) {
     switch (data.GetU8(offset_ptr)) {
while (!error) {
 
     case DW_RLE_offset_pair: {
       dw_addr_t begin = data.GetULEB128(offset_ptr);
       dw_addr_t end = data.GetULEB128(offset_ptr);
       rangeList.push_back({DW_RLE_offset_pair, begin, end});
       break;
     }
 
+    case DW_RLE_base_addressx: {
+      dw_addr_t base = data.GetULEB128(offset_ptr);
+      rangeList.push_back({DW_RLE_base_addressx, base, 0});
+      break;
+    }
+
+    case DW_RLE_startx_endx: {
+      dw_addr_t start = data.GetULEB128(offset_ptr);
+      dw_addr_t end = data.GetULEB128(offset_ptr);
+      rangeList.push_back({DW_RLE_startx_endx, start, end});
+      break;
+    }
+
+    case DW_RLE_startx_length: {
+      dw_addr_t start = data.GetULEB128(offset_ptr);
+      dw_addr_t length = data.GetULEB128(offset_ptr);
+      rangeList.push_back({DW_RLE_startx_length, start, length});
+      break;
+    }
+
     default:
-      // Next encodings are not yet supported:
-      // DW_RLE_base_addressx, DW_RLE_startx_endx, DW_RLE_startx_length.
       lldbassert(0 && "unknown range list entry encoding");
       error = true;
     }
   }
 
   return false;
 }
 
+static uint64_t ReadAddressFromDebugAddrSection(const DWARFUnit *cu,
+                                                uint32_t index) {
+  uint32_t index_size = cu->GetAddressByteSize();
+  dw_offset_t addr_base = cu->GetAddrBase();
+  lldb::offset_t offset = addr_base + index * index_size;
+  return cu->GetSymbolFileDWARF()->get_debug_addr_data().GetMaxU64(&offset,
+                                                                   index_size);
+}
+
 bool DWARFDebugRngLists::FindRanges(const DWARFUnit *cu,
                                     dw_offset_t debug_ranges_offset,
                                     DWARFRangeList &range_list) const {
   range_list.Clear();
   dw_addr_t debug_ranges_address = cu->GetRangesBase() + debug_ranges_offset;
   auto pos = m_range_map.find(debug_ranges_address);
   if (pos != m_range_map.end()) {
     dw_addr_t BaseAddr = cu->GetBaseAddress();
     for (const RngListEntry &E : pos->second) {
       switch (E.encoding) {
       case DW_RLE_start_length:
         range_list.Append(DWARFRangeList::Entry(E.value0, E.value1));
         break;
       case DW_RLE_base_address:
         BaseAddr = E.value0;
         break;
       case DW_RLE_start_end:
         range_list.Append(DWARFRangeList::Entry(E.value0, E.value1 - E.value0));
         break;
       case DW_RLE_offset_pair:
         range_list.Append(
             DWARFRangeList::Entry(BaseAddr + E.value0, E.value1 - E.value0));
         break;
+      case DW_RLE_base_addressx: {
+        BaseAddr = ReadAddressFromDebugAddrSection(cu, E.value0);
+        break;
+      }
+      case DW_RLE_startx_endx: {
+        dw_addr_t start = ReadAddressFromDebugAddrSection(cu, E.value0);
+        dw_addr_t end = ReadAddressFromDebugAddrSection(cu, E.value1);
+        range_list.Append(DWARFRangeList::Entry(start, end - start));
+        break;
+      }
+      case DW_RLE_startx_length: {
+        dw_addr_t start = ReadAddressFromDebugAddrSection(cu, E.value0);
+        range_list.Append(DWARFRangeList::Entry(start, E.value1));
+        break;
+      }
       default:
         llvm_unreachable("unexpected encoding");
       }
     }
     return true;
   }
   return false;
 }
void DWARFDebugRngLists::Extract(SymbolFileDWARF *dwarf2Data) {
   // We do not support non-zero segment selector size.
   if (data.GetU8(&offset) != 0) {
     lldbassert(0 && "not implemented");
     return;
   }
 
   uint32_t offsetsAmount = data.GetU32(&offset);
   for (uint32_t i = 0; i < offsetsAmount; ++i)
-    Offsets.push_back(data.GetPointer(&offset));
+    Offsets.push_back(data.GetMaxU64(&offset, isDwarf64 ? 8 : 4));
 
   lldb::offset_t listOffset = offset;
   std::vector<RngListEntry> rangeList;
   while (offset < end && ExtractRangeList(data, addrSize, &offset, rangeList)) {
     m_range_map[listOffset] = rangeList;
     listOffset = offset;
   }
 }
+
+uint64_t DWARFDebugRngLists::GetOffset(size_t Index) { return Offsets[Index]; }

source/Plugins/SymbolFile/DWARF/DWARFFormValue.cpp

case DW_FORM_sdata:
       break;
     case DW_FORM_strp:
     case DW_FORM_line_strp:
       assert(m_cu);
       m_value.value.uval =
           data.GetMaxU64(offset_ptr, DWARFUnit::IsDWARF64(m_cu) ? 8 : 4);
       break;
     case DW_FORM_addrx:
+    case DW_FORM_rnglistx:
     case DW_FORM_strx:
       m_value.value.uval = data.GetULEB128(offset_ptr);
       break;
     case DW_FORM_addrx1:
     case DW_FORM_strx1:
       m_value.value.uval = data.GetU8(offset_ptr);
       break;
     case DW_FORM_addrx2:
case DW_FORM_implicit_const:
     case DW_FORM_data8:
     case DW_FORM_ref8:
     case DW_FORM_ref_sig8:
       *offset_ptr += 8;
       return true;
 
     // signed or unsigned LEB 128 values
     case DW_FORM_addrx:
+    case DW_FORM_rnglistx:
     case DW_FORM_sdata:
     case DW_FORM_udata:
     case DW_FORM_ref_udata:
     case DW_FORM_GNU_addr_index:
     case DW_FORM_GNU_str_index:
     case DW_FORM_strx:
       debug_info_data.Skip_LEB128(offset_ptr);
       return true;
int DWARFFormValue::Compare(const DWARFFormValue &a_value,
   }
   return -1;
 }
 
 bool DWARFFormValue::FormIsSupported(dw_form_t form) {
   switch (form) {
     case DW_FORM_addr:
     case DW_FORM_addrx:
+    case DW_FORM_rnglistx:
     case DW_FORM_block2:
     case DW_FORM_block4:
     case DW_FORM_data2:
     case DW_FORM_data4:
     case DW_FORM_data8:
     case DW_FORM_string:
     case DW_FORM_block:
     case DW_FORM_block1:

source/Plugins/SymbolFile/DWARF/DWARFUnit.cpp

if (log && log->GetVerbose()) {
     log->PutString(strm.GetString());
   }
 }
 
 // m_die_array_mutex must be already held as read/write.
 void DWARFUnit::AddUnitDIE(const DWARFDebugInfoEntry &cu_die) {
   SetAddrBase(
       cu_die.GetAttributeValueAsUnsigned(m_dwarf, this, DW_AT_addr_base, 0));
+  SetRangesBase(cu_die.GetAttributeValueAsUnsigned(m_dwarf, this,
+                                                   DW_AT_rnglists_base, 0));
 
   uint64_t base_addr = cu_die.GetAttributeValueAsAddress(
       m_dwarf, this, DW_AT_low_pc, LLDB_INVALID_ADDRESS);
   if (base_addr == LLDB_INVALID_ADDRESS)
     base_addr = cu_die.GetAttributeValueAsAddress(
         m_dwarf, this, DW_AT_entry_pc, 0);
   SetBaseAddress(base_addr);