[LLD][ELF] - Improve the DWARF v5 suport for building .gdb_index.

[grimar]

Summary

Now LLD might build the broken/incomplete .gdb_index when some DWARF v5
sections (like .debug_rnglists and .debug_addr) are used.

Particularly, for the case above, we emit an empty address area.
A test case is provided and patch fixes the issue.

[ruiu]

LGTM

ELF/DWARF.h

void forEachInfoSections(
       llvm::function_ref<void(const llvm::DWARFSection &)> F) const override {
     F(InfoSection);
   }
 
   const llvm::DWARFSection &getRangeSection() const override {
     return RangeSection;
   }
 
+  const llvm::DWARFSection &getRnglistsSection() const override {
+    return RngListsSection;
+  }
+
   const llvm::DWARFSection &getLineSection() const override {
     return LineSection;
   }
 
+  const llvm::DWARFSection &getAddrSection() const override {
+    return AddrSection;
+  }
+
   const llvm::DWARFSection &getGnuPubNamesSection() const override {
     return GnuPubNamesSection;
   }
 
   const llvm::DWARFSection &getGnuPubTypesSection() const override {
     return GnuPubTypesSection;
   }
 
private:
   llvm::Optional<llvm::RelocAddrEntry> findAux(const InputSectionBase &Sec,
                                                uint64_t Pos,
                                                ArrayRef<RelTy> Rels) const;
 
   LLDDWARFSection GnuPubNamesSection;
   LLDDWARFSection GnuPubTypesSection;
   LLDDWARFSection InfoSection;
   LLDDWARFSection RangeSection;
+  LLDDWARFSection RngListsSection;
   LLDDWARFSection LineSection;
-
+  LLDDWARFSection AddrSection;
   StringRef AbbrevSection;
   StringRef StrSection;
   StringRef LineStringSection;
 };
 
 } // namespace elf
 } // namespace lld
 
 #endif

ELF/DWARF.cpp

 
 template <class ELFT> LLDDwarfObj<ELFT>::LLDDwarfObj(ObjFile<ELFT> *Obj) {
   for (InputSectionBase *Sec : Obj->getSections()) {
     if (!Sec)
       continue;
 
     if (LLDDWARFSection *M =
             StringSwitch<LLDDWARFSection *>(Sec->Name)
+                .Case(".debug_addr", &AddrSection)
                 .Case(".debug_gnu_pubnames", &GnuPubNamesSection)
                 .Case(".debug_gnu_pubtypes", &GnuPubTypesSection)
                 .Case(".debug_info", &InfoSection)
                 .Case(".debug_ranges", &RangeSection)
+                .Case(".debug_rnglists", &RngListsSection)
                 .Case(".debug_line", &LineSection)
                 .Default(nullptr)) {
       M->Data = toStringRef(Sec->data());
       M->Sec = Sec;
       continue;
     }
 
     if (Sec->Name == ".debug_abbrev")

test/ELF/gdb-index-rng-lists.s

+# REQUIRES: x86
+# RUN: llvm-mc -filetype=obj -triple=x86_64-pc-linux %s -o %t1.o
+# RUN: ld.lld --gdb-index %t1.o -o %t
+# RUN: llvm-dwarfdump -gdb-index %t | FileCheck %s
+
+## The code contains DWARF v5 sections .debug_rnglists and .debug_addr.
+## Check we are able to build the correct address
+## area using address range lists.
+
+# CHECK:      .gdb_index contents:
+# CHECK:      Address area offset = 0x28, has 2 entries:
+# CHECK-NEXT:  Low/High address = [0x201000, 0x201001) (Size: 0x1), CU id = 0
+# CHECK-NEXT:  Low/High address = [0x201001, 0x201003) (Size: 0x2), CU id = 0
+
+.text
+.section .text._Z3zedv,"ax",@progbits
+.Lfunc_begin0:
+  retq
+.Lfunc_end0:
+
+.section .text.main,"ax",@progbits
+.Lfunc_begin1:
+ retq
+ retq
+.Lfunc_end1:
+
+.section .debug_str_offsets,"",@progbits
+.long 32
+.short 5
+.short 0
+.Lstr_offsets_base0:
+ .long .Linfo_string0
+ .long .Linfo_string0
+ .long .Linfo_string0
+ .long .Linfo_string0
+ .long .Linfo_string0
+ .long .Linfo_string0
+ .long .Linfo_string0
+
+.section .debug_str,"MS",@progbits,1
+.Linfo_string0:
+ .asciz "stub"
+
+.section .debug_abbrev,"",@progbits
+  .byte  1                           # Abbreviation Code
+  .byte  17                          # DW_TAG_compile_unit
+  .byte  1                           # DW_CHILDREN_yes
+  .byte  37                          # DW_AT_producer
+  .byte  37                          # DW_FORM_strx1
+  .byte  19                          # DW_AT_language
+  .byte  5                           # DW_FORM_data2
+  .byte  3                           # DW_AT_name
+  .byte  37                          # DW_FORM_strx1
+  .byte  114                         # DW_AT_str_offsets_base
+  .byte  23                          # DW_FORM_sec_offset
+  .byte  16                          # DW_AT_stmt_list
+  .byte  23                          # DW_FORM_sec_offset
+  .byte  27                          # DW_AT_comp_dir
+  .byte  37                          # DW_FORM_strx1
+  .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  2                           # Abbreviation Code
+  .byte  46                          # DW_TAG_subprogram
+  .byte  0                           # DW_CHILDREN_no
+  .byte  17                          # DW_AT_low_pc
+  .byte  27                          # DW_FORM_addrx
+  .byte  18                          # DW_AT_high_pc
+  .byte  6                           # DW_FORM_data4
+  .byte  64                          # DW_AT_frame_base
+  .byte  24                          # DW_FORM_exprloc
+  .byte  110                         # DW_AT_linkage_name
+  .byte  37                          # DW_FORM_strx1
+  .byte  3                           # DW_AT_name
+  .byte  37                          # DW_FORM_strx1
+  .byte  58                          # DW_AT_decl_file
+  .byte  11                          # DW_FORM_data1
+  .byte  59                          # DW_AT_decl_line
+  .byte  11                          # DW_FORM_data1
+  .byte  73                          # DW_AT_type
+  .byte  19                          # DW_FORM_ref4
+  .byte  63                          # DW_AT_external
+  .byte  25                          # DW_FORM_flag_present
+  .byte  0                           # EOM(1)
+  .byte  0                           # EOM(2)
+  .byte  3                           # Abbreviation Code
+  .byte  46                          # DW_TAG_subprogram
+  .byte  0                           # DW_CHILDREN_no
+  .byte  17                          # DW_AT_low_pc
+  .byte  27                          # DW_FORM_addrx
+  .byte  18                          # DW_AT_high_pc
+  .byte  6                           # DW_FORM_data4
+  .byte  64                          # DW_AT_frame_base
+  .byte  24                          # DW_FORM_exprloc
+  .byte  3                           # DW_AT_name
+  .byte  37                          # DW_FORM_strx1
+  .byte  58                          # DW_AT_decl_file
+  .byte  11                          # DW_FORM_data1
+  .byte  59                          # DW_AT_decl_line
+  .byte  11                          # DW_FORM_data1
+  .byte  73                          # DW_AT_type
+  .byte  19                          # DW_FORM_ref4
+  .byte  63                          # DW_AT_external
+  .byte  25                          # DW_FORM_flag_present
+  .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  37                          # DW_FORM_strx1
+  .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)
+
+.section .debug_info,"",@progbits
+.Lcu_begin0:
+  .long  75                          # Length of Unit
+  .short 5                           # DWARF version number
+  .byte  1                           # DWARF Unit Type
+  .byte  8                           # Address Size (in bytes)
+  .long  .debug_abbrev               # Offset Into Abbrev. Section
+  
+  .byte  1                           # Abbrev [1] 0xc:0x43 DW_TAG_compile_unit
+  .byte  0                           # DW_AT_producer
+  .short 4                           # DW_AT_language
+  .byte  1                           # DW_AT_name
+  .long  .Lstr_offsets_base0         # DW_AT_str_offsets_base
+  .long  0                           # DW_AT_stmt_list
+  .byte  2                           # DW_AT_comp_dir
+  .long  .Laddr_table_base0          # DW_AT_addr_base
+  .quad  0                           # DW_AT_low_pc
+  .byte  0                           # DW_AT_ranges
+  .long  .Lrnglists_table_base0      # DW_AT_rnglists_base
+
+  .byte 2                            # Abbrev [2] 0x2b:0x10 DW_TAG_subprogram
+  .byte 0                            # DW_AT_low_pc
+  .long .Lfunc_end0-.Lfunc_begin0    # DW_AT_high_pc
+  .byte 1                            # DW_AT_frame_base
+  .byte 86
+  .byte 3                            # DW_AT_linkage_name
+  .byte 4                            # DW_AT_name
+  .byte 1                            # DW_AT_decl_file
+  .byte 1                            # DW_AT_decl_line
+  .long 74                           # DW_AT_type
+                                     # DW_AT_external
+
+  .byte  3                           # Abbrev [3] 0x3b:0xf DW_TAG_subprogram
+  .byte  1                           # DW_AT_low_pc
+  .long  .Lfunc_end1-.Lfunc_begin1   # DW_AT_high_pc
+  .byte  1                           # DW_AT_frame_base
+  .byte  86
+  .byte  6                           # DW_AT_name
+  .byte  1                           # DW_AT_decl_file
+  .byte  5                           # DW_AT_decl_line
+  .long  74                          # DW_AT_type
+                                     # DW_AT_external
+
+  .byte  4                           # Abbrev [4] 0x4a:0x4 DW_TAG_base_type
+  .byte  5                           # DW_AT_name
+  .byte  5                           # DW_AT_encoding
+  .byte  4                           # DW_AT_byte_size
+  .byte  0                           # End Of Children Mark
+
+.section .debug_rnglists,"",@progbits
+.long .Ldebug_rnglist_table_end0-.Ldebug_rnglist_table_start0 # Length
+.Ldebug_rnglist_table_start0:        
+  .short 5                           # Version
+  .byte  8                           # Address size
+  .byte  0                           # Segment selector size
+  .long  1                           # Offset entry count
+.Lrnglists_table_base0:
+  .long .Ldebug_ranges0-.Lrnglists_table_base0
+.Ldebug_ranges0:
+  .byte 3                            # DW_RLE_startx_length
+  .byte 0                            #   start index
+  .uleb128 .Lfunc_end0-.Lfunc_begin0 #   length
+  .byte 3                            # DW_RLE_startx_length
+  .byte 1                            #   start index
+  .uleb128 .Lfunc_end1-.Lfunc_begin1 #   length
+  .byte 0                            # DW_RLE_end_of_list
+.Ldebug_rnglist_table_end0:
+
+.section .debug_addr,"",@progbits
+  .long  20
+  .short 5
+  .byte  8
+  .byte  0
+.Laddr_table_base0:
+  .quad .Lfunc_begin0
+  .quad .Lfunc_begin1