[lldb] Fix lookup of .debug_loclists with split-dwarf

[kimanh]

Summary

This patch fixes the lookup of locations in
.debug_loclists, if they are split in a .dwp file.

Mainly, we need to consider the cu index offsets.

[jankratochvil]

LGTM with some those adjustments.

lldb/source/Plugins/SymbolFile/DWARF/DWARFUnit.cpp

460

There could be some ReportError.

480–482

loclists_base should be adjusted or printed also together with offset or so.

lldb/test/Shell/SymbolFile/DWARF/x86/debug_loclists-dwp.s

16–17

.Ltmp0 is not used.

56

Offsets not valid.

187

These offsets are no longer valid.

190

Likewise.

205

Likewise.

212–237

There could be the standard indentation.

[kimanh]

Address reviews:

• remove unused tmp label
• remove invalid offsets
• add ReportError when no loclist contribution was found
• adapt ReportError logging to include offset and loclist base

lldb/source/Plugins/SymbolFile/DWARF/DWARFUnit.cpp

ParseListTableHeader(const llvm::DWARFDataExtractor &data, uint64_t offset,
   }
   ListTableType Table;
   if (llvm::Error E = Table.extractHeaderAndOffsets(data, &offset))
     return std::move(E);
   return Table;
 }
 
 void DWARFUnit::SetLoclistsBase(dw_addr_t loclists_base) {
+  uint64_t offset = 0;
+  if (const llvm::DWARFUnitIndex::Entry *entry = m_header.GetIndexEntry()) {
+    const auto *contribution = entry->getContribution(llvm::DW_SECT_LOCLISTS);
+    if (!contribution) {
+      GetSymbolFileDWARF().GetObjectFile()->GetModule()->ReportError(
+          "Failed to find location list contribution for CU with DWO Id "
+          "0x%" PRIx64,
+          this->GetDWOId());
+      return;
+    }
+    offset += contribution->Offset;
+  }
   m_loclists_base = loclists_base;
 
   uint64_t header_size = llvm::DWARFListTableHeader::getHeaderSize(DWARF32);
   if (loclists_base < header_size)
     return;
 
   m_loclist_table_header.emplace(".debug_loclists", "locations");
-  uint64_t offset = loclists_base - header_size;
+  offset += loclists_base - header_size;
   if (llvm::Error E = m_loclist_table_header->extract(
           m_dwarf.GetDWARFContext().getOrLoadLocListsData().GetAsLLVM(),
           &offset)) {
     GetSymbolFileDWARF().GetObjectFile()->GetModule()->ReportError(
-        "Failed to extract location list table at offset 0x%" PRIx64 ": %s",
-        loclists_base, toString(std::move(E)).c_str());
+        "Failed to extract location list table at offset 0x%" PRIx64
+        " (location list base: 0x%" PRIx64 "): %s",
+        offset, loclists_base, toString(std::move(E)).c_str());
   }
 }
 
 std::unique_ptr<llvm::DWARFLocationTable>
 DWARFUnit::GetLocationTable(const DataExtractor &data) const {
   llvm::DWARFDataExtractor llvm_data(
       data.GetData(), data.GetByteOrder() == lldb::eByteOrderLittle,
       data.GetAddressByteSize());
 
   if (m_is_dwo || GetVersion() >= 5)
     return std::make_unique<llvm::DWARFDebugLoclists>(llvm_data, GetVersion());
   return std::make_unique<llvm::DWARFDebugLoc>(llvm_data);
 }
 
 DWARFDataExtractor DWARFUnit::GetLocationData() const {
   DWARFContext &Ctx = GetSymbolFileDWARF().GetDWARFContext();
   const DWARFDataExtractor &data =
       GetVersion() >= 5 ? Ctx.getOrLoadLocListsData() : Ctx.getOrLoadLocData();
   if (const llvm::DWARFUnitIndex::Entry *entry = m_header.GetIndexEntry()) {
-    if (const auto *contribution = entry->getContribution(llvm::DW_SECT_EXT_LOC))
+    if (const auto *contribution = entry->getContribution(
+            GetVersion() >= 5 ? llvm::DW_SECT_LOCLISTS : llvm::DW_SECT_EXT_LOC))
       return DWARFDataExtractor(data, contribution->Offset,
                                 contribution->Length);
     return DWARFDataExtractor();
   }
   return data;
 }
 
 void DWARFUnit::SetRangesBase(dw_addr_t ranges_base) {

lldb/test/Shell/SymbolFile/DWARF/x86/debug_loclists-dwp.s

+## This tests if .debug_loclists.dwo are correctly read if they are part
+## of a dwp file.
+
+# RUN: llvm-mc -triple=x86_64-pc-linux -filetype=obj %s --defsym MAIN=0 > %t
+# RUN: llvm-mc -triple=x86_64-pc-linux -filetype=obj %s > %t.dwp
+# RUN: %lldb %t -o "image lookup -v -s lookup_loclists" -o exit | FileCheck %s
+
+# CHECK-LABEL: image lookup -v -s lookup_loclists
+# CHECK: Variable: id = {{.*}}, name = "x0", type = "int", location = DW_OP_reg0 RAX,
+# CHECK: Variable: id = {{.*}}, name = "x1", type = "int", location = DW_OP_reg1 RDX,
+
+## This part is kept in both the main and the dwp file to be able to reference the offsets.
+loclists:
+        nop
+        nop
+.Ltmp1:
+lookup_loclists:
+        nop
+.Ltmp2:
+        nop
+.Ltmp3:
+        nop
+.Lloclists_end:
+
+## The main file.
+.ifdef MAIN
+        .section        .debug_abbrev,"",@progbits
+        .byte   1                       # Abbreviation Code
+        .byte   74                      # DW_TAG_compile_unit
+        .byte   0                       # DW_CHILDREN_no
+        .byte   0x76                    # DW_AT_dwo_name
+        .byte   8                       # DW_FORM_string
+        .byte   115                     # DW_AT_addr_base
+        .byte   23                      # DW_FORM_sec_offset
+        .byte   17                      # DW_AT_low_pc
+        .byte   1                       # DW_FORM_addr
+        .byte   85                      # DW_AT_ranges
+        .byte   35                      # DW_FORM_rnglistx
+        .byte   116                     # DW_AT_rnglists_base
+        .byte   23                      # DW_FORM_sec_offset
+        .byte   0                       # EOM(1)
+        .byte   0                       # EOM(2)
+        .byte   0                       # EOM(3)
+
+        .section        .debug_info,"",@progbits
+.Lcu_begin0:
+        .long   .Ldebug_info_end0-.Ldebug_info_start0 # Length of Unit
+.Ldebug_info_start0:
+        .short  5                       # DWARF version number
+        .byte   4                       # DWARF Unit Type
+        .byte   8                       # Address Size (in bytes)
+        .long   .debug_abbrev           # Offset Into Abbrev. Section
+        .quad   1026699901672188186      # DWO id
+        .byte   1                       # Abbrev [1] DW_TAG_compile_unit
+        .asciz  "debug_loclists-dwp.dwo"  # DW_AT_dwo_name
+        .long   .Laddr_table_base0      # DW_AT_addr_base
+        .quad   loclists                # DW_AT_low_pc
+        .byte   0                       # DW_AT_ranges
+        .long   .Lskel_rnglists_table_base # DW_AT_rnglists_base
+.Ldebug_info_end0:
+        .section        .debug_rnglists,"",@progbits
+        .long   .Lskel_rnglist_table_end-.Lskel_rnglist_table_start # Length
+.Lskel_rnglist_table_start:
+        .short  5                       # Version
+        .byte   8                       # Address size
+        .byte   0                       # Segment selector size
+        .long   1                       # Offset entry count
+.Lskel_rnglists_table_base:
+        .long   .Lskel_ranges0-.Lskel_rnglists_table_base
+.Lskel_ranges0:
+        .byte   7                       # DW_RLE_start_length
+        .quad   loclists
+        .uleb128   .Lloclists_end-loclists
+        .byte   0                       # DW_RLE_end_of_list
+.Lskel_rnglist_table_end:
+        .section        .debug_addr,"",@progbits
+        .long   .Ldebug_addr_end0-.Ldebug_addr_start0 # Length of contribution
+.Ldebug_addr_start0:
+        .short  5                       # DWARF version number
+        .byte   8                       # Address size
+        .byte   0                       # Segment selector size
+.Laddr_table_base0:
+        .quad   loclists
+        .quad   .Ltmp1
+.Ldebug_addr_end0:
+
+.else
+## DWP file starts here.
+
+        .section        .debug_loclists.dwo,"e",@progbits
+## Start the section with an unused table to check that the reading offset
+## of the real table is correctly adjusted.
+        .long .LLLDummyEnd-.LLLDummyVersion # Length of Unit
+.LLLDummyVersion:
+        .short 5                            # Version
+        .byte 8                             # Address size
+        .byte 0                             # Segment selector size
+        .long 0                             # Offset entry count
+        .byte 0                             # DW_LLE_end_of_list
+.LLLDummyEnd:
+.LLLBegin:
+        .long   .Ldebug_loclist_table_end0-.Ldebug_loclist_table_start0 # Length
+.Ldebug_loclist_table_start0:
+        .short  5                       # Version
+        .byte   8                       # Address size
+        .byte   0                       # Segment selector size
+        .long   2                       # Offset entry count
+.Lloclists_table_base:
+        .long   .Ldebug_loc0-.Lloclists_table_base
+        .long   .Ldebug_loc1-.Lloclists_table_base
+.Ldebug_loc0:
+        .byte   4                       # DW_LLE_offset_pair
+        .uleb128 loclists-loclists
+        .uleb128  .Ltmp2-loclists
+        .uleb128 1                      # Expression size
+        .byte   80                      # super-register DW_OP_reg0
+        .byte   0                       # DW_LLE_end_of_list
+.Ldebug_loc1:
+        .byte   3                       # DW_LLE_startx_length
+        .uleb128 1
+        .uleb128  .Ltmp3-.Ltmp1
+        .uleb128 1                      # Expression size
+        .byte   81                      # super-register DW_OP_reg1
+        .byte   0                       # DW_LLE_end_of_list
+.Ldebug_loclist_table_end0:
+.LLLEnd:
+        .section        .debug_abbrev.dwo,"e",@progbits
+.LAbbrevBegin:
+        .byte   1                       # Abbreviation Code
+        .byte   17                      # DW_TAG_compile_unit
+        .byte   1                       # DW_CHILDREN_yes
+        .byte   37                      # DW_AT_producer
+        .byte   8                       # DW_FORM_string
+        .byte   19                      # DW_AT_language
+        .byte   5                       # DW_FORM_data2
+        .byte   0                       # EOM(1)
+        .byte   0                       # EOM(2)
+        .byte   2                       # Abbreviation Code
+        .byte   46                      # DW_TAG_subprogram
+        .byte   1                       # DW_CHILDREN_yes
+        .byte   17                      # DW_AT_low_pc
+        .byte   27                      # DW_FORM_addrx
+        .byte   18                      # DW_AT_high_pc
+        .byte   6                       # DW_FORM_data4
+        .byte   3                       # DW_AT_name
+        .byte   8                       # DW_FORM_string
+        .byte   73                      # DW_AT_type
+        .byte   19                      # DW_FORM_ref4
+        .byte   0                       # EOM(1)
+        .byte   0                       # EOM(2)
+        .byte   3                       # Abbreviation Code
+        .byte   5                       # DW_TAG_formal_parameter
+        .byte   0                       # DW_CHILDREN_no
+        .byte   2                       # DW_AT_location
+        .byte   0x22                    # DW_FORM_loclistx
+        .byte   3                       # DW_AT_name
+        .byte   8                       # DW_FORM_string
+        .byte   73                      # DW_AT_type
+        .byte   19                      # DW_FORM_ref4
+        .byte   0                       # EOM(1)
+        .byte   0                       # EOM(2)
+        .byte   4                       # Abbreviation Code
+        .byte   36                      # DW_TAG_base_type
+        .byte   0                       # DW_CHILDREN_no
+        .byte   3                       # DW_AT_name
+        .byte   8                       # DW_FORM_string
+        .byte   62                      # DW_AT_encoding
+        .byte   11                      # DW_FORM_data1
+        .byte   11                      # DW_AT_byte_size
+        .byte   11                      # DW_FORM_data1
+        .byte   0                       # EOM(1)
+        .byte   0                       # EOM(2)
+        .byte   0                       # EOM(3)
+.LAbbrevEnd:
+        .section        .debug_info.dwo,"e",@progbits
+.LCUBegin:
+.Lcu_begin1:
+        .long   .Ldebug_info_end1-.Ldebug_info_start1 # Length of Unit
+.Ldebug_info_start1:
+        .short  5                       # DWARF version number
+        .byte   5                       # DWARF Unit Type
+        .byte   8                       # Address Size (in bytes)
+        .long   0                       # Offset Into Abbrev. Section
+        .quad   1026699901672188186      # DWO id
+        .byte   1                       # Abbrev [1] DW_TAG_compile_unit
+        .asciz  "Hand-written DWARF"    # DW_AT_producer
+        .short  12                      # DW_AT_language
+        .byte   2                       # Abbrev [2] DW_TAG_subprogram
+        .byte   0                       # DW_AT_low_pc
+        .long   .Lloclists_end-loclists # DW_AT_high_pc
+        .asciz  "loclists"              # DW_AT_name
+        .long   .Lint                   # DW_AT_type
+        .byte   3                       # Abbrev [3] DW_TAG_formal_parameter
+        .uleb128 0                      # DW_AT_location
+        .asciz  "x0"                    # DW_AT_name
+        .long   .Lint                   # DW_AT_type
+        .byte   3                       # Abbrev [3] DW_TAG_formal_parameter
+        .uleb128 1                      # DW_AT_location
+        .asciz  "x1"                    # DW_AT_name
+        .long   .Lint                   # DW_AT_type
+        .byte   0                       # End Of Children Mark
+.Lint:
+        .byte   4                       # Abbrev [4] DW_TAG_base_type
+        .asciz  "int"                   # DW_AT_name
+        .byte   5                       # DW_AT_encoding
+        .byte   4                       # DW_AT_byte_size
+        .byte   0                       # End Of Children Mark
+.Ldebug_info_end1:
+.LCUEnd:
+        .section .debug_cu_index, "", @progbits
+## Header:
+        .short 5                        # Version
+        .short 0                        # Padding
+        .long 3                         # Section count
+        .long 1                         # Unit count
+        .long 2                         # Slot count
+## Hash Table of Signatures:
+        .quad 1026699901672188186
+        .quad 0
+## Parallel Table of Indexes:
+        .long 1
+        .long 0
+## Table of Section Offsets:
+## Row 0:
+        .long 1                         # DW_SECT_INFO
+        .long 3                         # DW_SECT_ABBREV
+        .long 5                         # DW_SECT_LOCLISTS
+## Row 1:
+        .long 0                         # Offset in .debug_info.dwo
+        .long 0                         # Offset in .debug_abbrev.dwo
+        .long .LLLBegin-.debug_loclists.dwo # Offset in .debug_loclists.dwo
+## Table of Section Sizes:
+        .long .LCUEnd-.LCUBegin         # Size in .debug_info.dwo
+        .long .LAbbrevEnd-.LAbbrevBegin # Size in .debug_abbrev.dwo
+        .long .LLLEnd-.LLLBegin         # Size in .debug_loclists.dwo
+.endif