[Debuginfo][llvm-dwarfutil] Add check for unsupported debug sections.

[avl]

Summary

Current DWARFLinker implementation does not support some debug sections
(mainly DWARF v5 sections). This patch adds diagnostic for such sections.
The error would be displayed for critical(such that could not be removed)
sections and the source file would be skipped. Other unsupported sections
would be removed and warning message should be displayed. The zero exit
status would be returned for both cases.

Depends on D86539

[jhenderson]

The error would be displayed for critical(such that could not be removed) sections and the source file would be skipped. Other unsupported sections would be removed and warning message should be displayed

I have concerns about this difference in behaviour between "critical" and "non-critical" sections:

1. I assume this code has a DWARF version check, but if not, the assumption of what is "critical"/"non-critical" is going to fall down the next time a DWARF standard is published (potentially). Even then, developers of this tool will have to remember to update this list when adding DWARFv6 etc support. It feels fragile.
2. There's an assumption here that all .debug_* sections are part of the DWARF standard. I know of at least one downstream usage within my company where we've extended the DWARF spec by adding a new section. This was deliberately called .debug_* to ensure it got stripped by tools when stripping debug information, but is, if I'm not mistaken, otherwise independent of the debug information. By having a hard-coded list, we'll have to carry a private downstream patch around or anybody using this tool will end up having their debug data corrupted. Whilst I acknowledge that we don't need to worry about downstream users that much, I do think it's pointing to the fact that this is the wrong approach again, although I don't have a concrete answer to what the right approach should be.
3. What determines what is a "critical" versus a "non-critical" section? Surely that depends upon the consumer as well as the structure of the DWARF?

llvm/test/tools/llvm-dwarfutil/ELF/error-unsupported-types.test

4 ↗

(On Diff #422300)

Why does this use a canned binary rather than yaml2obj?

llvm/tools/llvm-dwarfutil/DebugInfoLinker.cpp

284

This comment needs reflowing too.

[avl]

In D123623#3447455, @jhenderson wrote:

The error would be displayed for critical(such that could not be removed) sections and the source file would be skipped. Other unsupported sections would be removed and warning message should be displayed

I have concerns about this difference in behaviour between "critical" and "non-critical" sections:

1. I assume this code has a DWARF version check, but if not, the assumption of what is "critical"/"non-critical" is going to fall down the next time a DWARF standard is published (potentially). Even then, developers of this tool will have to remember to update this list when adding DWARFv6 etc support. It feels fragile.

There is no check for DWARF version at the moment. I think it would be good to add.

At the moment DWARFLinker has partial support for DWARF v5 and partial support for DWARF v4 sections(it does not update .debug_macinfo, does not handle debug_types).

2. There's an assumption here that all .debug_* sections are part of the DWARF standard. I know of at least one downstream usage within my company where we've extended the DWARF spec by adding a new section. This was deliberately called .debug_* to ensure it got stripped by tools when stripping debug information, but is, if I'm not mistaken, otherwise independent of the debug information. By having a hard-coded list, we'll have to carry a private downstream patch around or anybody using this tool will end up having their debug data corrupted. Whilst I acknowledge that we don't need to worry about downstream users that much, I do think it's pointing to the fact that this is the wrong approach again, although I don't have a concrete answer to what the right approach should be.

The same assumption is used in other llvm parts f.e. ELFObjcopy.cpp:

static bool isDebugSection(const SectionBase &Sec) {
  return StringRef(Sec.Name).startswith(".debug") ||
         StringRef(Sec.Name).startswith(".zdebug") || Sec.Name == ".gdb_index";
}

To resolve that case with custom sections we can add option --keep-section=debug_custom.

3. What determines what is a "critical" versus a "non-critical" section? Surely that depends upon the consumer as well as the structure of the DWARF?

The difference is whether section might be safely dropped or not(in other words whether section is important for optimizations done by tool). f,e,

a) the tool need to handle address ranges for garbage collection. Since the tool does not able to process .debug_rnglists section then it could not do garbage collection at all. This is critical section.

b) .debug_cu_index is not used for garbage collection. But it references debug_info which rebuilt by tool. the tool does not update .debug_cu_index so it becomes invalid after garbage collection. Though it may be easily dropped. This is not critical section.

llvm/test/tools/llvm-dwarfutil/ELF/error-unsupported-types.test

4 ↗

(On Diff #422300)

yaml2obj does not support debug_types.

[jhenderson]

In D123623#3447631, @avl wrote:

To resolve that case with custom sections we can add option --keep-section=debug_custom.

I think this would be sensible. It would then be fairly easy to add downstream a more maintainable patch that always has that option enabled for the specific section.

3. What determines what is a "critical" versus a "non-critical" section? Surely that depends upon the consumer as well as the structure of the DWARF?

The difference is whether section might be safely dropped or not(in other words whether section is important for optimizations done by tool). f,e,

a) the tool need to handle address ranges for garbage collection. Since the tool does not able to process .debug_rnglists section then it could not do garbage collection at all. This is critical section.

b) .debug_cu_index is not used for garbage collection. But it references debug_info which rebuilt by tool. the tool does not update .debug_cu_index so it becomes invalid after garbage collection. Though it may be easily dropped. This is not critical section.

Thanks, I see.

llvm/test/tools/llvm-dwarfutil/ELF/error-unsupported-types.test

4 ↗

(On Diff #422300)

Do you need a fully fledged .debug_types though, or could you just use a regular section called .debug_types (containing either garbage or is empty etc)?

[avl]

llvm/test/tools/llvm-dwarfutil/ELF/error-unsupported-types.test

4 ↗

(On Diff #422300)

yes, I do. If it is an empty .debug_types section or section filled with garbage then the error like "broken type unit" is displayed. It does not allow to get that: "type units are not currently supported" diagnostic.

[avl]

rebased.

[JDevlieghere]

llvm/lib/DWARFLinker/DWARFLinker.cpp

2427–2430

I generally expect errors to be fatal. Should this be a warning instead? Something like:

warning: .debug_rnglists is not currently supported: section will be skipped

llvm/tools/llvm-dwarfutil/DebugInfoLinker.cpp

215–221

This seems like a good candidate for a string switch.

[avl]

llvm/lib/DWARFLinker/DWARFLinker.cpp

2427–2430

I used error vs warning to differentiate a case when 'critical' or not 'critical' section is met. But I think it could be done by different message instead:

warning: .debug_rnglists is not currently supported: compile unit will be skipped

vs

warning: .gdb-index is not currently supported: section will be skipped

thus, will make both cases to be warning.

[avl]

llvm/lib/DWARFLinker/DWARFLinker.cpp

2427–2430

To make things explicit, after this patch is applied following messages would also be shown by dsymutil:

warning: type units are not currently supported: compile unit will be skipped
warning: .debug_rnglists is not currently supported: compile unit will be skipped
warning: .debug_loclists is not currently supported: compile unit will be skipped
warning: .debug_macinfo is not currently supported: compile unit will be skipped
warning: .debug_macro is not currently supported: compile unit will be skipped

[avl]

addressed comments.

[dblaikie]

llvm/test/tools/llvm-dwarfutil/ELF/X86/warning-skipped-loclists.test

9

Might be good to check these errors all include more info, like a file name - as it stands (what's actually FileCheck'd here) it'd be a pretty unactionable/opaque error message.

To do this you'd probably have to put the file in a particular location, like %t-filename.o then regex match in the CHECK line to skip the prefix and just look for erorr message {{.*}}-filename.o or the like.

Maybe it'd be simpler/more accurate for the error message to say "file will be skipped" - since I assume that's what's going to happen, yeah? Even if the file contains multiple units (could be multiple compile units from LTO, and/or multiple type units as well)

[jhenderson]

llvm/test/tools/llvm-dwarfutil/ELF/X86/warning-skipped-loclists.test

9

This check does check the filename though? That's what the [[FILE]] bit is doing...

[avl]

llvm/test/tools/llvm-dwarfutil/ELF/X86/warning-skipped-loclists.test

9

Might be good to check these errors all include more info, like a file name - as it stands (what's actually FileCheck'd here) it'd be a pretty unactionable/opaque error message.

To do this you'd probably have to put the file in a particular location, like %t-filename.o then regex match in the CHECK line to skip the prefix and just look for erorr message {{.*}}-filename.o or the like.

The error message already contains file name. [[FILE]] matches with file name.

Maybe it'd be simpler/more accurate for the error message to say "file will be skipped" - since I assume that's what's going to happen, yeah? Even if the file contains multiple units (could be multiple compile units from LTO, and/or multiple type units as well)

yes, I think that would be better message: "file will be skipped". Thanks.

[dblaikie]

llvm/test/tools/llvm-dwarfutil/ELF/X86/warning-skipped-loclists.test

9

Oh, right, sorry!

[JDevlieghere]

LGTM!

[avl]

changed text of warning message.

llvm/include/llvm/DWARFLinker/DWARFLinker.h

DWARFLinker(DwarfEmitter *Emitter,
               DwarfLinkerClient ClientID = DwarfLinkerClient::General)
       : TheDwarfEmitter(Emitter), DwarfLinkerClientID(ClientID) {}
 
   /// Add object file to be linked.
   void addObjectFile(DWARFFile &File);
 
   /// Link debug info for added objFiles. Object
   /// files are linked all together.
-  bool link();
+  Error link();
 
   /// A number of methods setting various linking options:
 
   /// Allows to generate log of linking process to the standard output.
   void setVerbosity(bool Verbose) { Options.Verbose = Verbose; }
 
   /// Print statistics to standard output.
   void setStatistics(bool Statistics) { Options.Statistics = Statistics; }

llvm/lib/DWARFLinker/DWARFLinker.cpp

 
 void DWARFLinker::addObjectFile(DWARFFile &File) {
   ObjectContexts.emplace_back(LinkContext(File));
 
   if (ObjectContexts.back().File.Dwarf)
     updateAccelKind(*ObjectContexts.back().File.Dwarf);
 }
 
-bool DWARFLinker::link() {
+Error DWARFLinker::link() {
   assert(Options.NoOutput || TheDwarfEmitter);
 
   // A unique ID that identifies each compile unit.
   unsigned UnitID = 0;
 
   // First populate the data structure we need for each iteration of the
   // parallel loop.
   unsigned NumObjects = ObjectContexts.size();
if (LLVM_LIKELY(!Options.Update) &&
       OptContext.Skip = true;
       continue;
     }
 
     // Setup access to the debug info.
     if (!OptContext.File.Dwarf)
       continue;
 
+    // Check whether type units are presented.
+    if (!OptContext.File.Dwarf->types_section_units().empty()) {
+      reportWarning("type units are not currently supported: file will "
+                    "be skipped",
+                    OptContext.File);
+      OptContext.Skip = true;
+      continue;
+    }
+
+    // Check for unsupported sections. Following sections can be referenced
+    // from .debug_info section. Current DWARFLinker implementation does not
+    // support or update references to these tables. Thus we report warning
+    // and skip corresponding object file.
+    if (!OptContext.File.Dwarf->getDWARFObj()
+             .getRnglistsSection()
+             .Data.empty()) {
+      reportWarning("'.debug_rnglists' is not currently supported: file "
+                    "will be skipped",
+                    OptContext.File);
+      OptContext.Skip = true;
+      continue;
+    }
+
+    if (!OptContext.File.Dwarf->getDWARFObj()
+             .getLoclistsSection()
+             .Data.empty()) {
+      reportWarning("'.debug_loclists' is not currently supported: file "
+                    "will be skipped",
+                    OptContext.File);
+      OptContext.Skip = true;
+      continue;
+    }
+
+    if (!OptContext.File.Dwarf->getDWARFObj().getMacroSection().Data.empty()) {
+      reportWarning("'.debug_macro' is not currently supported: file "
+                    "will be skipped",
+                    OptContext.File);
+      OptContext.Skip = true;
+      continue;
+    }
+
+    if (OptContext.File.Dwarf->getDWARFObj().getMacinfoSection().size() > 1) {
+      reportWarning("'.debug_macinfo' is not currently supported: file "
+                    "will be skipped",
+                    OptContext.File);
+      OptContext.Skip = true;
+      continue;
+    }
+
     // In a first phase, just read in the debug info and load all clang modules.
     OptContext.CompileUnits.reserve(
         OptContext.File.Dwarf->getNumCompileUnits());
 
     for (const auto &CU : OptContext.File.Dwarf->compile_units()) {
       updateDwarfVersion(CU->getVersion());
       auto CUDie = CU->getUnitDIE(false);
       if (Options.Verbose) {
if (Options.Statistics) {
     outs() << "----------------------------------------------------------------"
               "---------------\n";
     llvm::outs() << formatv(FormatStr, "Total", InputTotal, OutputTotal,
                             ComputePercentange(InputTotal, OutputTotal));
     outs() << "----------------------------------------------------------------"
               "---------------\n\n";
   }
 
-  return true;
+  return Error::success();
 }
 
 bool DWARFLinker::verify(const DWARFFile &File) {
   assert(File.Dwarf);
 
   DIDumpOptions DumpOpts;
   if (!File.Dwarf->verify(llvm::outs(), DumpOpts.noImplicitRecursion())) {
     reportWarning("input verification failed", File);
     return false;
   }
   return true;
 }
 
 } // namespace llvm

llvm/test/tools/llvm-dwarfutil/ELF/X86/warning-skipped-cu-index.test

+## This test checks the warning message displayed if input file
+## contains .debug_cu_index section.
+
+# RUN: yaml2obj %s -o %t.o
+
+# RUN: llvm-dwarfutil --garbage-collection %t.o %t1 2>&1 | FileCheck %s -DFILE=%t.o
+
+# CHECK: [[FILE]]: warning: '.debug_cu_index' is not currently supported: section will be skipped
+
+--- !ELF
+FileHeader:
+  Class:    ELFCLASS64
+  Data:     ELFDATA2LSB
+  Type:     ET_REL
+  Machine:  EM_X86_64
+Sections:
+  - Name:            .text
+    Type:            SHT_PROGBITS
+    Flags:           [ SHF_ALLOC, SHF_EXECINSTR ]
+    Address:         0x1000
+    AddressAlign:    0x0000000000000010
+    Content:         "FFFFFFFF"
+  - Name:            .debug_cu_index
+    Type:            SHT_PROGBITS
+    Flags:           [  ]
+    Content:         "0000"
+DWARF:
+  debug_abbrev:
+    - Table:
+      - Tag:      DW_TAG_compile_unit
+        Children: DW_CHILDREN_yes
+        Attributes:
+          - Attribute: DW_AT_producer
+            Form:      DW_FORM_string
+          - Attribute: DW_AT_language
+            Form:      DW_FORM_data2
+          - Attribute: DW_AT_name
+            Form:      DW_FORM_string
+          - Attribute: DW_AT_low_pc
+            Form:      DW_FORM_addr
+          - Attribute: DW_AT_high_pc
+            Form:      DW_FORM_data8
+  debug_info:
+    - Version: 4
+      Entries:
+        - AbbrCode: 1
+          Values:
+            - CStr: by_hand
+            - Value:  0x04
+            - CStr: CU1
+            - Value:  0x1000
+            - Value:  0x4
+        - AbbrCode: 0
+...

llvm/test/tools/llvm-dwarfutil/ELF/X86/warning-skipped-gdb-index.test

+## This test checks the warning message displayed if input file
+## contains .gdb_index section.
+
+# RUN: yaml2obj %s -o %t.o
+
+# RUN: llvm-dwarfutil --garbage-collection %t.o %t1 2>&1 | FileCheck %s -DFILE=%t.o
+
+# CHECK: [[FILE]]: warning: '.gdb_index' is not currently supported: section will be skipped
+
+--- !ELF
+FileHeader:
+  Class:    ELFCLASS64
+  Data:     ELFDATA2LSB
+  Type:     ET_REL
+  Machine:  EM_X86_64
+Sections:
+  - Name:            .text
+    Type:            SHT_PROGBITS
+    Flags:           [ SHF_ALLOC, SHF_EXECINSTR ]
+    Address:         0x1000
+    AddressAlign:    0x0000000000000010
+    Content:         "FFFFFFFF"
+  - Name:            .gdb_index
+    Type:            SHT_PROGBITS
+    Flags:           [  ]
+    Content:         "0000"
+DWARF:
+  debug_abbrev:
+    - Table:
+      - Tag:      DW_TAG_compile_unit
+        Children: DW_CHILDREN_yes
+        Attributes:
+          - Attribute: DW_AT_producer
+            Form:      DW_FORM_string
+          - Attribute: DW_AT_language
+            Form:      DW_FORM_data2
+          - Attribute: DW_AT_name
+            Form:      DW_FORM_string
+          - Attribute: DW_AT_low_pc
+            Form:      DW_FORM_addr
+          - Attribute: DW_AT_high_pc
+            Form:      DW_FORM_data8
+  debug_info:
+    - Version: 4
+      Entries:
+        - AbbrCode: 1
+          Values:
+            - CStr: by_hand
+            - Value:  0x04
+            - CStr: CU1
+            - Value:  0x1000
+            - Value:  0x4
+        - AbbrCode: 0
+...

llvm/test/tools/llvm-dwarfutil/ELF/X86/warning-skipped-gnu-pubnames.test

+## This test checks the warning message displayed if input file
+## contains .debug_pubnames section.
+
+# RUN: yaml2obj %s -o %t.o
+
+# RUN: llvm-dwarfutil --garbage-collection %t.o %t1 2>&1 | FileCheck %s -DFILE=%t.o
+
+# CHECK: [[FILE]]: warning: '.debug_gnu_pubnames' is not currently supported: section will be skipped
+
+--- !ELF
+FileHeader:
+  Class:    ELFCLASS64
+  Data:     ELFDATA2LSB
+  Type:     ET_REL
+  Machine:  EM_X86_64
+Sections:
+  - Name:            .text
+    Type:            SHT_PROGBITS
+    Flags:           [ SHF_ALLOC, SHF_EXECINSTR ]
+    Address:         0x1000
+    AddressAlign:    0x0000000000000010
+    Content:         "FFFFFFFF"
+  - Name:            .debug_gnu_pubnames
+    Type:            SHT_PROGBITS
+    Flags:           [  ]
+    Content:         "0000"
+DWARF:
+  debug_abbrev:
+    - Table:
+      - Tag:      DW_TAG_compile_unit
+        Children: DW_CHILDREN_yes
+        Attributes:
+          - Attribute: DW_AT_producer
+            Form:      DW_FORM_string
+          - Attribute: DW_AT_language
+            Form:      DW_FORM_data2
+          - Attribute: DW_AT_name
+            Form:      DW_FORM_string
+          - Attribute: DW_AT_low_pc
+            Form:      DW_FORM_addr
+          - Attribute: DW_AT_high_pc
+            Form:      DW_FORM_data8
+  debug_info:
+    - Version: 4
+      Entries:
+        - AbbrCode: 1
+          Values:
+            - CStr: by_hand
+            - Value:  0x04
+            - CStr: CU1
+            - Value:  0x1000
+            - Value:  0x4
+        - AbbrCode: 0
+...

llvm/test/tools/llvm-dwarfutil/ELF/X86/warning-skipped-gnu-pubtypes.test

+## This test checks the warning message displayed if input file
+## contains .debug_gnu_pubtypes section.
+
+# RUN: yaml2obj %s -o %t.o
+
+# RUN: llvm-dwarfutil --garbage-collection %t.o %t1 2>&1 | FileCheck %s -DFILE=%t.o
+
+# CHECK: [[FILE]]: warning: '.debug_gnu_pubtypes' is not currently supported: section will be skipped
+
+--- !ELF
+FileHeader:
+  Class:    ELFCLASS64
+  Data:     ELFDATA2LSB
+  Type:     ET_REL
+  Machine:  EM_X86_64
+Sections:
+  - Name:            .text
+    Type:            SHT_PROGBITS
+    Flags:           [ SHF_ALLOC, SHF_EXECINSTR ]
+    Address:         0x1000
+    AddressAlign:    0x0000000000000010
+    Content:         "FFFFFFFF"
+  - Name:            .debug_gnu_pubtypes
+    Type:            SHT_PROGBITS
+    Flags:           [  ]
+    Content:         "0000"
+DWARF:
+  debug_abbrev:
+    - Table:
+      - Tag:      DW_TAG_compile_unit
+        Children: DW_CHILDREN_yes
+        Attributes:
+          - Attribute: DW_AT_producer
+            Form:      DW_FORM_string
+          - Attribute: DW_AT_language
+            Form:      DW_FORM_data2
+          - Attribute: DW_AT_name
+            Form:      DW_FORM_string
+          - Attribute: DW_AT_low_pc
+            Form:      DW_FORM_addr
+          - Attribute: DW_AT_high_pc
+            Form:      DW_FORM_data8
+  debug_info:
+    - Version: 4
+      Entries:
+        - AbbrCode: 1
+          Values:
+            - CStr: by_hand
+            - Value:  0x04
+            - CStr: CU1
+            - Value:  0x1000
+            - Value:  0x4
+        - AbbrCode: 0
+...

llvm/test/tools/llvm-dwarfutil/ELF/X86/warning-skipped-loclists.test

+## This test checks the warning message displayed if input file
+## contains .debug_loclists section.
+
+# RUN: yaml2obj %s -o %t.o
+
+# RUN: llvm-dwarfutil --garbage-collection %t.o %t1 2>&1 | FileCheck %s -DFILE=%t.o
+
+# CHECK: [[FILE]]: warning: '.debug_loclists' is not currently supported: file will be skipped
+
+--- !ELF
+FileHeader:
+  Class:    ELFCLASS64
+  Data:     ELFDATA2LSB
+  Type:     ET_REL
+  Machine:  EM_X86_64
+Sections:
+  - Name:            .text
+    Type:            SHT_PROGBITS
+    Flags:           [ SHF_ALLOC, SHF_EXECINSTR ]
+    Address:         0x1000
+    AddressAlign:    0x0000000000000010
+    Content:        "FFFFFFFF"
+  - Name:            .debug_loclists
+    Type:            SHT_PROGBITS
+    Flags:           [  ]
+    Content:        "0000000000000000000000"
+DWARF:
+  debug_abbrev:
+    - Table:
+      - Tag:      DW_TAG_compile_unit
+        Children: DW_CHILDREN_yes
+        Attributes:
+          - Attribute: DW_AT_producer
+            Form:      DW_FORM_string
+          - Attribute: DW_AT_language
+            Form:      DW_FORM_data2
+          - Attribute: DW_AT_name
+            Form:      DW_FORM_string
+          - Attribute: DW_AT_low_pc
+            Form:      DW_FORM_addr
+          - Attribute: DW_AT_high_pc
+            Form:      DW_FORM_data8
+  debug_info:
+    - Version: 4
+      Entries:
+        - AbbrCode: 1
+          Values:
+            - CStr: by_hand
+            - Value:  0x04
+            - CStr: CU1
+            - Value:  0x1000
+            - Value:  0x4
+        - AbbrCode: 0
+...

llvm/test/tools/llvm-dwarfutil/ELF/X86/warning-skipped-macinfo.test

+## This test checks the warning message displayed if input file
+## contains .debug_macinfo section.
+
+# RUN: yaml2obj %s -o %t.o
+
+# RUN: llvm-dwarfutil --garbage-collection %t.o %t1 2>&1 | FileCheck %s -DFILE=%t.o
+
+# CHECK: [[FILE]]: warning: '.debug_macinfo' is not currently supported: file will be skipped
+
+--- !ELF
+FileHeader:
+  Class:    ELFCLASS64
+  Data:     ELFDATA2LSB
+  Type:     ET_REL
+  Machine:  EM_X86_64
+Sections:
+  - Name:            .text
+    Type:            SHT_PROGBITS
+    Flags:           [ SHF_ALLOC, SHF_EXECINSTR ]
+    Address:         0x1000
+    AddressAlign:    0x0000000000000010
+    Content:        "FFFFFFFF"
+  - Name:            .debug_macinfo
+    Type:            SHT_PROGBITS
+    Flags:           [  ]
+    Content:        "0000"
+DWARF:
+  debug_abbrev:
+    - Table:
+      - Tag:      DW_TAG_compile_unit
+        Children: DW_CHILDREN_yes
+        Attributes:
+          - Attribute: DW_AT_producer
+            Form:      DW_FORM_string
+          - Attribute: DW_AT_language
+            Form:      DW_FORM_data2
+          - Attribute: DW_AT_name
+            Form:      DW_FORM_string
+          - Attribute: DW_AT_low_pc
+            Form:      DW_FORM_addr
+          - Attribute: DW_AT_high_pc
+            Form:      DW_FORM_data8
+  debug_info:
+    - Version: 4
+      Entries:
+        - AbbrCode: 1
+          Values:
+            - CStr: by_hand
+            - Value:  0x04
+            - CStr: CU1
+            - Value:  0x1000
+            - Value:  0x4
+        - AbbrCode: 0
+...

llvm/test/tools/llvm-dwarfutil/ELF/X86/warning-skipped-macro.test

+## This test checks the warning message displayed if input file
+## contains .debug_macro section.
+
+# RUN: yaml2obj %s -o %t.o
+
+# RUN: llvm-dwarfutil --garbage-collection %t.o %t1 2>&1 | FileCheck %s -DFILE=%t.o
+
+# CHECK: [[FILE]]: warning: '.debug_macro' is not currently supported: file will be skipped
+
+--- !ELF
+FileHeader:
+  Class:    ELFCLASS64
+  Data:     ELFDATA2LSB
+  Type:     ET_REL
+  Machine:  EM_X86_64
+Sections:
+  - Name:            .text
+    Type:            SHT_PROGBITS
+    Flags:           [ SHF_ALLOC, SHF_EXECINSTR ]
+    Address:         0x1000
+    AddressAlign:    0x0000000000000010
+    Content:        "FFFFFFFF"
+  - Name:            .debug_macro
+    Type:            SHT_PROGBITS
+    Flags:           [  ]
+    Content:        "0000"
+DWARF:
+  debug_abbrev:
+    - Table:
+      - Tag:      DW_TAG_compile_unit
+        Children: DW_CHILDREN_yes
+        Attributes:
+          - Attribute: DW_AT_producer
+            Form:      DW_FORM_string
+          - Attribute: DW_AT_language
+            Form:      DW_FORM_data2
+          - Attribute: DW_AT_name
+            Form:      DW_FORM_string
+          - Attribute: DW_AT_low_pc
+            Form:      DW_FORM_addr
+          - Attribute: DW_AT_high_pc
+            Form:      DW_FORM_data8
+  debug_info:
+    - Version: 4
+      Entries:
+        - AbbrCode: 1
+          Values:
+            - CStr: by_hand
+            - Value:  0x04
+            - CStr: CU1
+            - Value:  0x1000
+            - Value:  0x4
+        - AbbrCode: 0
+...

llvm/test/tools/llvm-dwarfutil/ELF/X86/warning-skipped-names.test

+## This test checks the warning message displayed if input file
+## contains .debug_names section.
+
+# RUN: yaml2obj %s -o %t.o
+
+# RUN: llvm-dwarfutil --garbage-collection %t.o %t1 2>&1 | FileCheck %s -DFILE=%t.o
+
+# CHECK: [[FILE]]: warning: '.debug_names' is not currently supported: section will be skipped
+
+--- !ELF
+FileHeader:
+  Class:    ELFCLASS64
+  Data:     ELFDATA2LSB
+  Type:     ET_REL
+  Machine:  EM_X86_64
+Sections:
+  - Name:            .text
+    Type:            SHT_PROGBITS
+    Flags:           [ SHF_ALLOC, SHF_EXECINSTR ]
+    Address:         0x1000
+    AddressAlign:    0x0000000000000010
+    Content:         "FFFFFFFF"
+  - Name:            .debug_names
+    Type:            SHT_PROGBITS
+    Flags:           [  ]
+    Content:         "0000"
+DWARF:
+  debug_abbrev:
+    - Table:
+      - Tag:      DW_TAG_compile_unit
+        Children: DW_CHILDREN_yes
+        Attributes:
+          - Attribute: DW_AT_producer
+            Form:      DW_FORM_string
+          - Attribute: DW_AT_language
+            Form:      DW_FORM_data2
+          - Attribute: DW_AT_name
+            Form:      DW_FORM_string
+          - Attribute: DW_AT_low_pc
+            Form:      DW_FORM_addr
+          - Attribute: DW_AT_high_pc
+            Form:      DW_FORM_data8
+  debug_info:
+    - Version: 4
+      Entries:
+        - AbbrCode: 1
+          Values:
+            - CStr: by_hand
+            - Value:  0x04
+            - CStr: CU1
+            - Value:  0x1000
+            - Value:  0x4
+        - AbbrCode: 0
+...

llvm/test/tools/llvm-dwarfutil/ELF/X86/warning-skipped-pubnames.test

+## This test checks the warning message displayed if input file
+## contains .debug_pubnames section.
+
+# RUN: yaml2obj %s -o %t.o
+
+# RUN: llvm-dwarfutil --garbage-collection %t.o %t1 2>&1 | FileCheck %s -DFILE=%t.o
+
+# CHECK: [[FILE]]: warning: '.debug_pubnames' is not currently supported: section will be skipped
+
+--- !ELF
+FileHeader:
+  Class:    ELFCLASS64
+  Data:     ELFDATA2LSB
+  Type:     ET_REL
+  Machine:  EM_X86_64
+Sections:
+  - Name:            .text
+    Type:            SHT_PROGBITS
+    Flags:           [ SHF_ALLOC, SHF_EXECINSTR ]
+    Address:         0x1000
+    AddressAlign:    0x0000000000000010
+    Content:         "FFFFFFFF"
+  - Name:            .debug_pubnames
+    Type:            SHT_PROGBITS
+    Flags:           [  ]
+    Content:         "0000"
+DWARF:
+  debug_abbrev:
+    - Table:
+      - Tag:      DW_TAG_compile_unit
+        Children: DW_CHILDREN_yes
+        Attributes:
+          - Attribute: DW_AT_producer
+            Form:      DW_FORM_string
+          - Attribute: DW_AT_language
+            Form:      DW_FORM_data2
+          - Attribute: DW_AT_name
+            Form:      DW_FORM_string
+          - Attribute: DW_AT_low_pc
+            Form:      DW_FORM_addr
+          - Attribute: DW_AT_high_pc
+            Form:      DW_FORM_data8
+  debug_info:
+    - Version: 4
+      Entries:
+        - AbbrCode: 1
+          Values:
+            - CStr: by_hand
+            - Value:  0x04
+            - CStr: CU1
+            - Value:  0x1000
+            - Value:  0x4
+        - AbbrCode: 0
+...

llvm/test/tools/llvm-dwarfutil/ELF/X86/warning-skipped-pubtypes.test

+## This test checks the warning message displayed if input file
+## contains .debug_pubtypes section.
+
+# RUN: yaml2obj %s -o %t.o
+
+# RUN: llvm-dwarfutil --garbage-collection %t.o %t1 2>&1 | FileCheck %s -DFILE=%t.o
+
+# CHECK: [[FILE]]: warning: '.debug_pubtypes' is not currently supported: section will be skipped
+
+--- !ELF
+FileHeader:
+  Class:    ELFCLASS64
+  Data:     ELFDATA2LSB
+  Type:     ET_REL
+  Machine:  EM_X86_64
+Sections:
+  - Name:            .text
+    Type:            SHT_PROGBITS
+    Flags:           [ SHF_ALLOC, SHF_EXECINSTR ]
+    Address:         0x1000
+    AddressAlign:    0x0000000000000010
+    Content:         "FFFFFFFF"
+  - Name:            .debug_pubtypes
+    Type:            SHT_PROGBITS
+    Flags:           [  ]
+    Content:         "0000"
+DWARF:
+  debug_abbrev:
+    - Table:
+      - Tag:      DW_TAG_compile_unit
+        Children: DW_CHILDREN_yes
+        Attributes:
+          - Attribute: DW_AT_producer
+            Form:      DW_FORM_string
+          - Attribute: DW_AT_language
+            Form:      DW_FORM_data2
+          - Attribute: DW_AT_name
+            Form:      DW_FORM_string
+          - Attribute: DW_AT_low_pc
+            Form:      DW_FORM_addr
+          - Attribute: DW_AT_high_pc
+            Form:      DW_FORM_data8
+  debug_info:
+    - Version: 4
+      Entries:
+        - AbbrCode: 1
+          Values:
+            - CStr: by_hand
+            - Value:  0x04
+            - CStr: CU1
+            - Value:  0x1000
+            - Value:  0x4
+        - AbbrCode: 0
+...

llvm/test/tools/llvm-dwarfutil/ELF/X86/warning-skipped-rnglists.test

+## This test checks the warning message displayed if input file
+## contains .debug_rnglists section.
+
+# RUN: yaml2obj %s -o %t.o
+
+# RUN: llvm-dwarfutil --garbage-collection %t.o %t1 2>&1 | FileCheck %s -DFILE=%t.o
+
+# CHECK: [[FILE]]: warning: '.debug_rnglists' is not currently supported: file will be skipped
+
+--- !ELF
+FileHeader:
+  Class:    ELFCLASS64
+  Data:     ELFDATA2LSB
+  Type:     ET_REL
+  Machine:  EM_X86_64
+Sections:
+  - Name:            .text
+    Type:            SHT_PROGBITS
+    Flags:           [ SHF_ALLOC, SHF_EXECINSTR ]
+    Address:         0x1000
+    AddressAlign:    0x0000000000000010
+    Content:        "FFFFFFFF"
+  - Name:            .debug_rnglists
+    Type:            SHT_PROGBITS
+    Flags:           [  ]
+    Content:        "0000"
+DWARF:
+  debug_abbrev:
+    - Table:
+      - Tag:      DW_TAG_compile_unit
+        Children: DW_CHILDREN_yes
+        Attributes:
+          - Attribute: DW_AT_producer
+            Form:      DW_FORM_string
+          - Attribute: DW_AT_language
+            Form:      DW_FORM_data2
+          - Attribute: DW_AT_name
+            Form:      DW_FORM_string
+          - Attribute: DW_AT_low_pc
+            Form:      DW_FORM_addr
+          - Attribute: DW_AT_high_pc
+            Form:      DW_FORM_data8
+  debug_info:
+    - Version: 4
+      Entries:
+        - AbbrCode: 1
+          Values:
+            - CStr: by_hand
+            - Value:  0x04
+            - CStr: CU1
+            - Value:  0x1000
+            - Value:  0x4
+        - AbbrCode: 0
+...

llvm/test/tools/llvm-dwarfutil/ELF/X86/warning-skipped-types.test

+## This test checks the warning message displayed if input file
+## contains type units.
+
+# RUN: llvm-dwarfutil --garbage-collection --tombstone=maxpc %p/Inputs/type-units.o %t1 2>&1 | FileCheck %s -DFILE=%p/Inputs/type-units.o
+
+# CHECK: [[FILE]]: warning: type units are not currently supported: file will be skipped

llvm/tools/dsymutil/DwarfLinkerForBinary.cpp

else {
       ObjectsForLinking.push_back(std::make_unique<DWARFFile>(
           Obj->getObjectFilename(), nullptr, nullptr,
           Obj->empty() ? Obj->getWarnings() : EmptyWarnings));
       GeneralLinker.addObjectFile(*ObjectsForLinking.back());
     }
   }
 
   // link debug info for loaded object files.
-  GeneralLinker.link();
+  if (Error E = GeneralLinker.link())
+    return error(toString(std::move(E)));
 
   StringRef ArchName = Map.getTriple().getArchName();
   if (Error E = emitRemarks(Options, Map.getBinaryPath(), ArchName, RL))
     return error(toString(std::move(E)));
 
   if (Options.NoOutput)
     return true;
 

llvm/tools/llvm-dwarfutil/DebugInfoLinker.h

 namespace llvm {
 namespace dwarfutil {
 
 inline bool isDebugSection(StringRef SecName) {
   return SecName.startswith(".debug") || SecName.startswith(".zdebug") ||
          SecName == ".gdb_index";
 }
 
-bool linkDebugInfo(object::ObjectFile &file, const Options &Options,
+Error linkDebugInfo(object::ObjectFile &file, const Options &Options,
                     raw_pwrite_stream &OutStream);
 
 } // end of namespace dwarfutil
 } // end of namespace llvm
 
 #endif // LLVM_TOOLS_LLVM_DWARFUTIL_DEBUGINFOLINKER_H

llvm/tools/llvm-dwarfutil/DebugInfoLinker.cpp

 //=== DebugInfoLinker.cpp -------------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
 #include "DebugInfoLinker.h"
 #include "Error.h"
+#include "llvm/ADT/StringSwitch.h"
 #include "llvm/DWARFLinker/DWARFLinker.h"
 #include "llvm/DWARFLinker/DWARFStreamer.h"
 #include "llvm/DebugInfo/DWARF/DWARFContext.h"
 #include "llvm/DebugInfo/DWARF/DWARFExpression.h"
 #include "llvm/Object/ObjectFile.h"
 #include <memory>
 #include <vector>
 
protected:
   }
 
 private:
   RangesTy DWARFAddressRanges;
   AddressRanges TextAddressRanges;
   const Options &Opts;
 };
 
-bool linkDebugInfo(object::ObjectFile &File, const Options &Options,
+static bool knownByDWARFUtil(StringRef SecName) {
+  return llvm::StringSwitch<bool>(SecName)
+      .Case(".debug_info", true)
+      .Case(".debug_types", true)
+      .Case(".debug_abbrev", true)
+      .Case(".debug_loc", true)
+      .Case(".debug_loclists", true)
+      .Case(".debug_frame", true)
+      .Case(".debug_aranges", true)
+      .Case(".debug_ranges", true)
+      .Case(".debug_rnglists", true)
+      .Case(".debug_line", true)
+      .Case(".debug_line_str", true)
+      .Case(".debug_addr", true)
+      .Case(".debug_macro", true)
+      .Case(".debug_macinfo", true)
+      .Case(".debug_str", true)
+      .Case(".debug_str_offsets", true)
+      .Default(false);
+}
+
+Error linkDebugInfo(object::ObjectFile &File, const Options &Options,
                     raw_pwrite_stream &OutStream) {
 
   auto ReportWarn = [&](const Twine &Message, StringRef Context,
                         const DWARFDie *Die) {
     warning(Message, Context);
 
     if (!Options.Verbose || !Die)
       return;
 
     DIDumpOptions DumpOpts;
     DumpOpts.ChildRecurseDepth = 0;
     DumpOpts.Verbose = Options.Verbose;
 
     WithColor::note() << "    in DIE:\n";
     Die->dump(errs(), /*Indent=*/6, DumpOpts);
   };
   auto ReportErr = [&](const Twine &Message, StringRef Context,
                        const DWARFDie *) {
     WithColor::error(errs(), Context) << Message << '\n';
   };
 
   // Create output streamer.
   DwarfStreamer OutStreamer(OutputFileType::Object, OutStream, nullptr,
                             ReportWarn, ReportWarn);
-  if (!OutStreamer.init(File.makeTriple(), ""))
-    return false;
+  Triple TargetTriple = File.makeTriple();
+  if (!OutStreamer.init(TargetTriple, formatv("cannot create a stream for {0}",
+                                              TargetTriple.getTriple())
+                                          .str()))
+    return createStringError(std::errc::invalid_argument, "");
 
   // Create DWARF linker.
   DWARFLinker DebugInfoLinker(&OutStreamer, DwarfLinkerClient::LLD);
 
   DebugInfoLinker.setEstimatedObjfilesAmount(1);
   DebugInfoLinker.setAccelTableKind(DwarfLinkerAccelTableKind::None);
   DebugInfoLinker.setErrorHandler(ReportErr);
   DebugInfoLinker.setWarningHandler(ReportWarn);
   DebugInfoLinker.setNumThreads(Options.NumThreads);
   DebugInfoLinker.setNoODR(!Options.DoODRDeduplication);
   DebugInfoLinker.setVerbosity(Options.Verbose);
   DebugInfoLinker.setUpdate(!Options.DoGarbageCollection);
 
   std::vector<std::unique_ptr<DWARFFile>> ObjectsForLinking(1);
   std::vector<std::unique_ptr<AddressesMap>> AddresssMapForLinking(1);
   std::vector<std::string> EmptyWarnings;
 
   std::unique_ptr<DWARFContext> Context = DWARFContext::create(File);
 
+  // Unknown debug sections would be removed. Display warning
+  // for such sections.
+  for (SectionName Sec : Context->getDWARFObj().getSectionNames()) {
+    if (isDebugSection(Sec.Name) && !knownByDWARFUtil(Sec.Name))
+      warning(
+          formatv("'{0}' is not currently supported: section will be skipped",
+                  Sec.Name),
+          Options.InputFileName);
+  }
+
   // Add object files to the DWARFLinker.
   AddresssMapForLinking[0] =
       std::make_unique<ObjFileAddressMap>(*Context, Options, File);
 
   ObjectsForLinking[0] = std::make_unique<DWARFFile>(
       File.getFileName(), &*Context, AddresssMapForLinking[0].get(),
       EmptyWarnings);
 
   for (size_t I = 0; I < ObjectsForLinking.size(); I++)
     DebugInfoLinker.addObjectFile(*ObjectsForLinking[I]);
 
   // Link debug info.
-  DebugInfoLinker.link();
+  if (Error Err = DebugInfoLinker.link())
+    return Err;
+
   OutStreamer.finish();
-  return true;
+  return Error::success();
 }
 
 } // end of namespace dwarfutil
 } // end of namespace llvm

llvm/tools/llvm-dwarfutil/llvm-dwarfutil.cpp

 
 static Error applyCLOptions(const struct Options &Opts, ObjectFile &InputFile) {
   if (Opts.DoGarbageCollection) {
     verbose("Do garbage collection for debug info ...", Opts.Verbose);
 
     DebugInfoBits LinkedDebugInfo;
     raw_svector_ostream OutStream(LinkedDebugInfo);
 
-    if (linkDebugInfo(InputFile, Opts, OutStream)) {
-      if (Error Err =
-              saveLinkedDebugInfo(Opts, InputFile, std::move(LinkedDebugInfo)))
-        return Err;
+    if (Error Err = linkDebugInfo(InputFile, Opts, OutStream))
+      return Err;
+
 
-      return Error::success();
-    }
-
-    return createStringError(std::errc::invalid_argument,
-                             "possible broken debug info");
   } else if (Opts.BuildSeparateDebugFile) {
     if (Error Err = splitDebugIntoSeparateFile(Opts, InputFile))
       return Err;
   } else {
     if (Error Err = saveCopyOfFile(Opts, InputFile))
       return Err;
   }