[llvm-readelf/obj] - Stop printing invalid names for unnamed section symbols.

[grimar]

Summary

We have an issue with ELFDumper<ELFT>::getSymbolSectionName:

1. It is used deeply for both LLVM/GNU styles and might return LLVM-style only values to describe symbols: "Undefined", "Processor Specific", "Absolute", etc.

2. getSymbolSectionName is used by getFullSymbolName and these special values might appear instead of symbol names in many places. This occurs for unnamed section symbols currently.

This patch extracts the LLVM specific logic to LLVMStyle<ELFT>::printSymbolSection,
which seems to be the only place where we want to print the special values mentioned.

Depends on D87763

[jhenderson]

llvm/test/tools/llvm-readobj/ELF/dyn-symbols.test

338–340

Am I right in thinking these warnings are coming out because SHN_ABS isn't a valid section index? That doesn't seem right to me - a st_shndx of SHN_ABS is perfectly normal. You just wouldn't normally have a section symbol to them. What happens if there are many sections and section index 65521 is actually a valid section?

I'd be inclined to produce a warning saying "section symbols shouldn't be absolute" (or whatever), and then print <?>, in this case.

[MaskRay]

llvm/test/tools/llvm-readobj/ELF/dyn-symbols.test

338–340

"shouldn't be absolute" is too specific. Having a generic message for all these special indices should suffice.

[grimar]

• Addressed review comments.

llvm/test/tools/llvm-readobj/ELF/dyn-symbols.test

338–340

Am I right in thinking these warnings are coming out because SHN_ABS isn't a valid section index? That doesn't seem right to me - a st_shndx of SHN_ABS is perfectly normal

You are right, implementation was wrong. So, we should not be able to take a section index for symbols which have sh_shndx >= SHN_LORESERVE (SHN_XINDEX is an exception).

I've updated the logic and now reporting a better message.

[jhenderson]

llvm/test/tools/llvm-readobj/ELF/dyn-symbols.test

342

I'm thinking the warning/<?> output would probably make sense for undefined STT_SECTION symbols too. Those shouldn't really be a thing after all.

[grimar]

• Addressed review comment about SHN_UNDEF section symbols.

llvm/test/tools/llvm-readobj/ELF/dyn-symbols.test

342

Probably reasonable. Done.

[jhenderson]

LGTM, thanks!

llvm/test/tools/llvm-readobj/ELF/dyn-symbols.test

DynamicSymbols:
   - Name: foo
   - Name:  [[NAME=bar]]
     Type:  [[TYPE=STT_NOTYPE]]
     Index: [[INDEX=<none>]]
   - Name: [[NAME=zed]]
     Type: [[TYPE=STT_NOTYPE]]
 
 ## Check the behavior for unnamed versioned section symbols.
-## TODO: we should print proper symbol names instead of descriptions.
 # RUN: yaml2obj %s -DTYPE=STT_SECTION -DNAME="''" -DINDEX=SHN_ABS --docnum=6 -o %t6.sec.sym
-# RUN: llvm-readobj -V --dyn-symbols %t6.sec.sym | FileCheck %s --check-prefix=VERSIONED-SEC-SYM-LLVM
-# RUN: llvm-readelf -V --dyn-symbols %t6.sec.sym | FileCheck %s --check-prefix=VERSIONED-SEC-SYM-GNU
+# RUN: llvm-readobj -V --dyn-symbols %t6.sec.sym 2>&1 | \
+# RUN:   FileCheck %s -DFILE=%t6.sec.sym --check-prefix=VERSIONED-SEC-SYM-LLVM
+# RUN: llvm-readelf -V --dyn-symbols %t6.sec.sym 2>&1 | \
+# RUN:   FileCheck %s -DFILE=%t6.sec.sym --check-prefix=VERSIONED-SEC-SYM-GNU
 
 # VERSIONED-SEC-SYM-LLVM: DynamicSymbols [
 # VERSIONED-SEC-SYM-LLVM:  Name: foo (12)
-# VERSIONED-SEC-SYM-LLVM:  Name: Absolute (0)
-# VERSIONED-SEC-SYM-LLVM:  Name: Undefined (0)
+# VERSIONED-SEC-SYM-LLVM: warning: '[[FILE]]': unable to get section index for symbol with st_shndx = 0xfff1 (SHN_ABS)
+# VERSIONED-SEC-SYM-LLVM:  Name: <?> (0)
+# VERSIONED-SEC-SYM-LLVM: warning: '[[FILE]]': unable to get section index for symbol with st_shndx = 0x0 (SHN_UNDEF)
+# VERSIONED-SEC-SYM-LLVM:  Name: <?> (0)
 # VERSIONED-SEC-SYM-LLVM: VersionSymbols [
 # VERSIONED-SEC-SYM-LLVM:  Name: foo
-# VERSIONED-SEC-SYM-LLVM:  Name: Absolute
-# VERSIONED-SEC-SYM-LLVM:  Name: Undefined
+# VERSIONED-SEC-SYM-LLVM:  Name: <?>
+# VERSIONED-SEC-SYM-LLVM:  Name: <?>
 
-# VERSIONED-SEC-SYM-GNU: Symbol table '.dynsym' contains 4 entries:
-# VERSIONED-SEC-SYM-GNU:    Num: {{.*}} Ndx Name
-# VERSIONED-SEC-SYM-GNU:      1: {{.*}} UND foo
-# VERSIONED-SEC-SYM-GNU-NEXT: 2: {{.*}} ABS Absolute
-# VERSIONED-SEC-SYM-GNU-NEXT: 3: {{.*}} UND Undefined
+# VERSIONED-SEC-SYM-GNU:     Symbol table '.dynsym' contains 4 entries:
+# VERSIONED-SEC-SYM-GNU:        Num: {{.*}} Ndx Name
+# VERSIONED-SEC-SYM-GNU:          1: {{.*}} UND foo
+# VERSIONED-SEC-SYM-GNU:      warning: '[[FILE]]': unable to get section index for symbol with st_shndx = 0xfff1 (SHN_ABS)
+# VERSIONED-SEC-SYM-GNU-NEXT:     2: {{.*}} ABS <?>
+# VERSIONED-SEC-SYM-GNU-NEXT: warning: '[[FILE]]': unable to get section index for symbol with st_shndx = 0x0 (SHN_UNDEF)
+# VERSIONED-SEC-SYM-GNU-NEXT:     3: {{.*}} UND <?>
 
 ## Case 8: Check what we print when:
 ## a) The dynamic symbol table does not exist.
 # RUN: yaml2obj %s --docnum=7 -o %t7
 # RUN: llvm-readobj --dyn-symbols %t7 | FileCheck %s --check-prefix=NO-DYNSYM-LLVM
 # RUN: llvm-readelf --dyn-symbols %t7 | count 0
 ## b) The dynamic symbol table has a size of 0.
 # RUN: yaml2obj %s --docnum=8 -o %t8

llvm/test/tools/llvm-readobj/ELF/hash-symbols.test

ProgramHeaders:
   - Type:  PT_LOAD
     Flags: [ PF_R, PF_X ]
     Sections:
       - Section: .hash
       - Section: .gnu.hash
       - Section: .dynamic
 
 ## Check what we print for unnamed section symbols.
-## TODO: we should print proper symbol names instead of descriptions.
 # RUN: yaml2obj --docnum=1 -DBITS=64 -DTYPE=STT_SECTION -DNAME="''" %s -o %t1-sec-syms.so
-# RUN: llvm-readelf --hash-symbols %t1-sec-syms.so | FileCheck %s --check-prefix=UNNAMED-SEC-SYMS
+# RUN: llvm-readelf --hash-symbols %t1-sec-syms.so 2>&1 | \
+# RUN:   FileCheck %s -DFILE=%t1-sec-syms.so --check-prefix=UNNAMED-SEC-SYMS
 
 # UNNAMED-SEC-SYMS:      Symbol table of .hash for image:
 # UNNAMED-SEC-SYMS-NEXT:  Num   {{.*}} Ndx Name
-# UNNAMED-SEC-SYMS-NEXT:    1   {{.*}} UND Undefined
+# UNNAMED-SEC-SYMS-NEXT: warning: '[[FILE]]': unable to get section index for symbol with st_shndx = 0x0 (SHN_UNDEF)
+# UNNAMED-SEC-SYMS-NEXT:    1   {{.*}} UND <?>
 # UNNAMED-SEC-SYMS-NEXT:    5   {{.*}}   1 .hash
-# UNNAMED-SEC-SYMS-NEXT:    3   {{.*}} ABS Absolute
+# UNNAMED-SEC-SYMS-NEXT: warning: '[[FILE]]': unable to get section index for symbol with st_shndx = 0xfff1 (SHN_ABS)
+# UNNAMED-SEC-SYMS-NEXT:    3   {{.*}} ABS <?>
 # UNNAMED-SEC-SYMS-NEXT:    2   {{.*}}   1 .hash
 # UNNAMED-SEC-SYMS-NEXT:    4   {{.*}}   2 .gnu.hash
 # UNNAMED-SEC-SYMS-EMPTY:
 # UNNAMED-SEC-SYMS:      Symbol table of .gnu.hash for image:
 # UNNAMED-SEC-SYMS-NEXT:  Num {{.*}} Ndx Name
 # UNNAMED-SEC-SYMS-NEXT:    2 {{.*}}   1 .hash
-# UNNAMED-SEC-SYMS-NEXT:    3 {{.*}} ABS Absolute
+# UNNAMED-SEC-SYMS-NEXT:    3 {{.*}} ABS <?>
 # UNNAMED-SEC-SYMS-NEXT:    4 {{.*}}   2 .gnu.hash
 # UNNAMED-SEC-SYMS-NEXT:    5 {{.*}}   1 .hash
 
 ## Check the output when only .hash section is present.
 
 # RUN: yaml2obj --docnum=2 %s -o %t2-32.so
 # RUN: llvm-readelf --hash-symbols %t2-32.so \
 # RUN:   | FileCheck %s --strict-whitespace --match-full-lines --check-prefix ONLY-HASH-32

llvm/test/tools/llvm-readobj/ELF/mips-got.test

Entries:
       - Tag:   DT_MIPS_GOTSYM
         Value: 1
       - Tag:   DT_PLTGOT
         Value: 0x1122
 DynamicSymbols:
   - Name: foo
 
 ## Check how we print global GOT entries when they are unnamed section symbols.
-## TODO: we should print proper symbol names instead of descriptions.
 # RUN: yaml2obj --docnum=5 %s -o %t.err8.o
 # RUN: llvm-readobj -A %t.err8.o 2>&1 | FileCheck %s -DFILE=%t.err8.o --check-prefix=SEC-SYMS-LLVM
 # RUN: llvm-readelf -A %t.err8.o 2>&1 | FileCheck %s -DFILE=%t.err8.o --check-prefix=SEC-SYMS-GNU
 
 # SEC-SYMS-LLVM:      Global entries [
 # SEC-SYMS-LLVM-NEXT:   Entry {
 # SEC-SYMS-LLVM:          Section: Absolute (0xFFF1)
-# SEC-SYMS-LLVM-NEXT:     Name: Absolute (0)
+# SEC-SYMS-LLVM-NEXT: warning: '[[FILE]]': unable to get section index for symbol with st_shndx = 0xfff1 (SHN_ABS)
+# SEC-SYMS-LLVM-NEXT:     Name: <?> (0)
 # SEC-SYMS-LLVM-NEXT:   }
 # SEC-SYMS-LLVM-NEXT:   Entry {
 # SEC-SYMS-LLVM:          Section: .got (0x1)
 # SEC-SYMS-LLVM-NEXT:     Name: .got (0)
 # SEC-SYMS-LLVM-NEXT:   }
 # SEC-SYMS-LLVM-NEXT:   Entry {
 # SEC-SYMS-LLVM:          Section: Common (0xFFF2)
-# SEC-SYMS-LLVM-NEXT:     Name: Common (0)
+# SEC-SYMS-LLVM-NEXT: warning: '[[FILE]]': unable to get section index for symbol with st_shndx = 0xfff2 (SHN_COMMON)
+# SEC-SYMS-LLVM-NEXT:     Name: <?> (0)
 # SEC-SYMS-LLVM-NEXT:   }
 # SEC-SYMS-LLVM-NEXT: ]
 
 # SEC-SYMS-GNU:      Global entries:
 # SEC-SYMS-GNU-NEXT:  {{.*}} Ndx Name
-# SEC-SYMS-GNU-NEXT:  {{.*}} ABS Absolute
+# SEC-SYMS-GNU-NEXT: warning: '[[FILE]]': unable to get section index for symbol with st_shndx = 0xfff1 (SHN_ABS)
+# SEC-SYMS-GNU-NEXT:  {{.*}} ABS <?>
 # SEC-SYMS-GNU-NEXT:  {{.*}}   1 .got
-# SEC-SYMS-GNU-NEXT:  {{.*}} COM Common
+# SEC-SYMS-GNU-NEXT: warning: '[[FILE]]': unable to get section index for symbol with st_shndx = 0xfff2 (SHN_COMMON)
+# SEC-SYMS-GNU-NEXT:  {{.*}} COM <?>
 
 --- !ELF
 FileHeader:
   Class:   ELFCLASS64
   Data:    ELFDATA2LSB
   Type:    ET_REL
   Machine: EM_MIPS
 Sections:

llvm/test/tools/llvm-readobj/ELF/mips-plt.test

 # ERR6: error: '[[FILE]]': unable to get a symbol table linked to the SHT_PROGBITS section with index 2: invalid section index: 2863311530
 
 # RUN: yaml2obj --docnum=2 -DVAL2=0x100 %s -o %t.err7.o
 # RUN: not llvm-readobj -A %t.err7.o 2>&1 | FileCheck %s -DFILE=%t.err7.o -check-prefix ERR7
 
 # ERR7: error: '[[FILE]]': unable to get a string table for the SHT_DYNAMIC section with index 1: invalid sh_type for symbol table, expected SHT_SYMTAB or SHT_DYNSYM
 
 ## Check how we print PLT entries when they are unnamed section symbols.
-## TODO: we should print proper symbol names instead of descriptions.
-# RUN: yaml2obj --docnum=3 %s -o %t.3
-# RUN: llvm-readobj -A %t.3 2>&1 | FileCheck %s -DFILE=%t.err8.o --check-prefix=SEC-SYMS-LLVM
-# RUN: llvm-readelf -A %t.3 2>&1 | FileCheck %s -DFILE=%t.err8.o --check-prefix=SEC-SYMS-GNU
+# RUN: yaml2obj --docnum=3 %s -o %t3
+# RUN: llvm-readobj -A %t3 2>&1 | FileCheck %s -DFILE=%t3 --check-prefix=SEC-SYMS-LLVM
+# RUN: llvm-readelf -A %t3 2>&1 | FileCheck %s -DFILE=%t3 --check-prefix=SEC-SYMS-GNU
 
 # SEC-SYMS-LLVM:      PLT GOT {
 # SEC-SYMS-LLVM:        Entries [
 # SEC-SYMS-LLVM:          Entry {
 # SEC-SYMS-LLVM:            Section: Absolute (0xFFF1)
-# SEC-SYMS-LLVM-NEXT:       Name: Absolute (0)
+# SEC-SYMS-LLVM-NEXT: warning: '[[FILE]]': unable to get section index for symbol with st_shndx = 0xfff1 (SHN_ABS)
+# SEC-SYMS-LLVM-NEXT:       Name: <?> (0)
 # SEC-SYMS-LLVM-NEXT:     }
 # SEC-SYMS-LLVM-NEXT:     Entry {
 # SEC-SYMS-LLVM:            Section: .got.plt (0x2)
 # SEC-SYMS-LLVM-NEXT:       Name: .got.plt (0)
 # SEC-SYMS-LLVM-NEXT:     }
 # SEC-SYMS-LLVM-NEXT:     Entry {
 # SEC-SYMS-LLVM:            Section: Common (0xFFF2)
-# SEC-SYMS-LLVM-NEXT:       Name: Common (0)
+# SEC-SYMS-LLVM-NEXT: warning: '[[FILE]]': unable to get section index for symbol with st_shndx = 0xfff2 (SHN_COMMON)
+# SEC-SYMS-LLVM-NEXT:       Name: <?> (0)
 # SEC-SYMS-LLVM-NEXT:     }
 # SEC-SYMS-LLVM-NEXT:   ]
 # SEC-SYMS-LLVM-NEXT: }
 
 # SEC-SYMS-GNU:      PLT GOT:
 # SEC-SYMS-GNU:       Entries:
 # SEC-SYMS-GNU-NEXT:   Address          {{.*}} Ndx Name
-# SEC-SYMS-GNU-NEXT:   0000000000002010 {{.*}} ABS Absolute
+# SEC-SYMS-GNU-NEXT: warning: '[[FILE]]': unable to get section index for symbol with st_shndx = 0xfff1 (SHN_ABS)
+# SEC-SYMS-GNU-NEXT:   0000000000002010 {{.*}} ABS <?>
 # SEC-SYMS-GNU-NEXT:   0000000000002018 {{.*}}   2 .got.plt
-# SEC-SYMS-GNU-NEXT:   0000000000002020 {{.*}} COM Common
+# SEC-SYMS-GNU-NEXT: warning: '[[FILE]]': unable to get section index for symbol with st_shndx = 0xfff2 (SHN_COMMON)
+# SEC-SYMS-GNU-NEXT:   0000000000002020 {{.*}} COM <?>
 
 --- !ELF
 FileHeader:
   Class:   ELFCLASS64
   Data:    ELFDATA2LSB
   Type:    ET_REL
   Machine: EM_MIPS
 Sections:

llvm/test/tools/llvm-readobj/ELF/symbol-shndx.test

- Name:    [[NAME=xindex]]
     Type:    [[TYPE=STT_NOTYPE]]
 
 ## Check the behavior for section symbols.
 # RUN: yaml2obj --docnum=1 -DTYPE=STT_SECTION %s -o %t1-sec
 # RUN: llvm-readobj --symbols %t1-sec | FileCheck %s --check-prefix=LLVM1
 # RUN: llvm-readelf --symbols %t1-sec | FileCheck %s --check-prefix=GNU1
 
 ## Check the behavior for unnamed section symbols.
-## TODO: we should print proper symbol names instead of descriptions.
 # RUN: yaml2obj --docnum=1 -DTYPE=STT_SECTION -DNAME="''" %s -o %t1-sec-unnamed
-# RUN: llvm-readobj --symbols %t1-sec-unnamed | FileCheck %s --check-prefix=LLVM1-SEC-SYMS
-# RUN: llvm-readelf --symbols %t1-sec-unnamed | FileCheck %s --check-prefix=GNU1-SEC-SYMS
+# RUN: llvm-readobj --symbols %t1-sec-unnamed 2>&1 | \
+# RUN:   FileCheck %s -DFILE=%t1-sec-unnamed --check-prefix=LLVM1-SEC-SYMS
+# RUN: llvm-readelf --symbols %t1-sec-unnamed 2>&1 | \
+# RUN:   FileCheck %s -DFILE=%t1-sec-unnamed --check-prefix=GNU1-SEC-SYMS
 
 # LLVM1-SEC-SYMS:      Symbols [
 # LLVM1-SEC-SYMS-NEXT:   Symbol {
 # LLVM1-SEC-SYMS-NEXT:     Name:  (0)
 # LLVM1-SEC-SYMS:          Section: Undefined (0x0)
-# LLVM1-SEC-SYMS:        Symbol {
-# LLVM1-SEC-SYMS-NEXT:     Name: Undefined (0)
+# LLVM1-SEC-SYMS: warning: '[[FILE]]': unable to get section index for symbol with st_shndx = 0x0 (SHN_UNDEF)
+# LLVM1-SEC-SYMS-NEXT:   Symbol {
+# LLVM1-SEC-SYMS-NEXT:     Name: <?> (0)
 # LLVM1-SEC-SYMS:          Section: Undefined (0x0)
 # LLVM1-SEC-SYMS:        Symbol {
 # LLVM1-SEC-SYMS-NEXT:     Name: .text (0)
 # LLVM1-SEC-SYMS:          Section: .text (0x1)
-# LLVM1-SEC-SYMS:        Symbol {
-# LLVM1-SEC-SYMS-NEXT:     Name: Common (0)
+# LLVM1-SEC-SYMS: warning: '[[FILE]]': unable to get section index for symbol with st_shndx = 0xfff2 (SHN_COMMON)
+# LLVM1-SEC-SYMS-NEXT:   Symbol {
+# LLVM1-SEC-SYMS-NEXT:     Name: <?> (0)
 # LLVM1-SEC-SYMS:          Section: Common (0xFFF2)
-# LLVM1-SEC-SYMS:        Symbol {
-# LLVM1-SEC-SYMS-NEXT:     Name: Absolute (0)
+# LLVM1-SEC-SYMS: warning: '[[FILE]]': unable to get section index for symbol with st_shndx = 0xfff1 (SHN_ABS)
+# LLVM1-SEC-SYMS-NEXT:   Symbol {
+# LLVM1-SEC-SYMS-NEXT:     Name: <?> (0)
 # LLVM1-SEC-SYMS:          Section: Absolute (0xFFF1)
-# LLVM1-SEC-SYMS:        Symbol {
-# LLVM1-SEC-SYMS-NEXT:     Name: Processor Specific (0)
+# LLVM1-SEC-SYMS: warning: '[[FILE]]': unable to get section index for symbol with st_shndx = 0xff01 (SHN_LOPROC+0x1)
+# LLVM1-SEC-SYMS-NEXT:   Symbol {
+# LLVM1-SEC-SYMS-NEXT:     Name: <?> (0)
 # LLVM1-SEC-SYMS:          Section: Processor Specific (0xFF01)
-# LLVM1-SEC-SYMS:        Symbol {
-# LLVM1-SEC-SYMS-NEXT:     Name: Operating System Specific (0)
+# LLVM1-SEC-SYMS: warning: '[[FILE]]': unable to get section index for symbol with st_shndx = 0xff21 (SHN_LOOS+0x1)
+# LLVM1-SEC-SYMS-NEXT:   Symbol {
+# LLVM1-SEC-SYMS-NEXT:     Name: <?> (0)
 # LLVM1-SEC-SYMS:          Section: Operating System Specific (0xFF21)
-# LLVM1-SEC-SYMS:        Symbol {
-# LLVM1-SEC-SYMS-NEXT:     Name: Reserved (0)
+# LLVM1-SEC-SYMS: warning: '[[FILE]]': unable to get section index for symbol with st_shndx = 0xfffe (SHN_LORESERVE+0xfe)
+# LLVM1-SEC-SYMS-NEXT:   Symbol {
+# LLVM1-SEC-SYMS-NEXT:     Name: <?> (0)
 # LLVM1-SEC-SYMS:          Section: Reserved (0xFFFE)
 # LLVM1-SEC-SYMS:        Symbol {
 # LLVM1-SEC-SYMS-NEXT:     Name: .text (0)
 # LLVM1-SEC-SYMS:          Section: .text (0x1)
 
 # GNU1-SEC-SYMS:      Num: {{.*}} Ndx Name
-# GNU1-SEC-SYMS-NEXT:   0: {{.*}} UND
-# GNU1-SEC-SYMS-NEXT:   1: {{.*}} UND Undefined
+# GNU1-SEC-SYMS-NEXT:   0: {{.*}} UND {{$}}
+# GNU1-SEC-SYMS-NEXT: warning: '[[FILE]]': unable to get section index for symbol with st_shndx = 0x0 (SHN_UNDEF)
+# GNU1-SEC-SYMS-NEXT:   1: {{.*}} UND <?>
 # GNU1-SEC-SYMS-NEXT:   2: {{.*}}   1 .text
-# GNU1-SEC-SYMS-NEXT:   3: {{.*}} COM Common
-# GNU1-SEC-SYMS-NEXT:   4: {{.*}} ABS Absolute
-# GNU1-SEC-SYMS-NEXT:   5: {{.*}} PRC[0xff01] Processor Specific
-# GNU1-SEC-SYMS-NEXT:   6: {{.*}} OS[0xff21] Operating System Specific
-# GNU1-SEC-SYMS-NEXT:   7: {{.*}} RSV[0xfffe] Reserved
+# GNU1-SEC-SYMS-NEXT: warning: '[[FILE]]': unable to get section index for symbol with st_shndx = 0xfff2 (SHN_COMMON)
+# GNU1-SEC-SYMS-NEXT:   3: {{.*}} COM <?>
+# GNU1-SEC-SYMS-NEXT: warning: '[[FILE]]': unable to get section index for symbol with st_shndx = 0xfff1 (SHN_ABS)
+# GNU1-SEC-SYMS-NEXT:   4: {{.*}} ABS <?>
+# GNU1-SEC-SYMS-NEXT: warning: '[[FILE]]': unable to get section index for symbol with st_shndx = 0xff01 (SHN_LOPROC+0x1)
+# GNU1-SEC-SYMS-NEXT:   5: {{.*}} PRC[0xff01] <?>
+# GNU1-SEC-SYMS-NEXT: warning: '[[FILE]]': unable to get section index for symbol with st_shndx = 0xff21 (SHN_LOOS+0x1)
+# GNU1-SEC-SYMS-NEXT:   6: {{.*}} OS[0xff21] <?>
+# GNU1-SEC-SYMS-NEXT: warning: '[[FILE]]': unable to get section index for symbol with st_shndx = 0xfffe (SHN_LORESERVE+0xfe)
+# GNU1-SEC-SYMS-NEXT:   7: {{.*}} RSV[0xfffe] <?>
 # GNU1-SEC-SYMS-NEXT:   8: {{.*}}   1 .text
 
 ## In this case, the index does not correspond to a real section. Check that GNU
 ## style just prints the section index as normal and LLVM style prints a warning
 ## (but only once for each warning).
 # RUN: yaml2obj --docnum=2 %s -o %t2
 # RUN: llvm-readobj --symbols %t2 2> %t2.llvm.err | FileCheck %s --check-prefix=LLVM2
 # RUN: FileCheck %s --input-file=%t2.llvm.err --check-prefix=BAD-SHNDX --implicit-check-not=warning

llvm/tools/llvm-readobj/ELFDumper.cpp

std::string ELFDumper<ELFT>::getFullSymbolName(const Elf_Sym *Symbol,
   }
   return SymbolName;
 }
 
 template <typename ELFT>
 Expected<unsigned>
 ELFDumper<ELFT>::getSymbolSectionIndex(const Elf_Sym *Symbol,
                                        const Elf_Sym *FirstSym) const {
-  return Symbol->st_shndx == SHN_XINDEX
-             ? object::getExtendedSymbolTableIndex<ELFT>(*Symbol, *FirstSym,
-                                                         ShndxTable)
-             : Symbol->st_shndx;
+  unsigned Ndx = Symbol->st_shndx;
+  if (Ndx == SHN_XINDEX)
+    return object::getExtendedSymbolTableIndex<ELFT>(*Symbol, *FirstSym,
+                                                     ShndxTable);
+  if (Ndx != SHN_UNDEF && Ndx < SHN_LORESERVE)
+    return Ndx;
+
+  auto CreateErr = [&](const Twine &Name, Optional<unsigned> Offset = None) {
+    std::string Desc;
+    if (Offset)
+      Desc = (Name + "+0x" + Twine::utohexstr(*Offset)).str();
+    else
+      Desc = Name.str();
+    return createError(
+        "unable to get section index for symbol with st_shndx = 0x" +
+        Twine::utohexstr(Ndx) + " (" + Desc + ")");
+  };
+
+  if (Ndx >= ELF::SHN_LOPROC && Ndx <= ELF::SHN_HIPROC)
+    return CreateErr("SHN_LOPROC", Ndx - ELF::SHN_LOPROC);
+  if (Ndx >= ELF::SHN_LOOS && Ndx <= ELF::SHN_HIOS)
+    return CreateErr("SHN_LOOS", Ndx - ELF::SHN_LOOS);
+  if (Ndx == ELF::SHN_UNDEF)
+    return CreateErr("SHN_UNDEF");
+  if (Ndx == ELF::SHN_ABS)
+    return CreateErr("SHN_ABS");
+  if (Ndx == ELF::SHN_COMMON)
+    return CreateErr("SHN_COMMON");
+  return CreateErr("SHN_LORESERVE", Ndx - SHN_LORESERVE);
 }
 
-// If the Symbol has a reserved st_shndx other than SHN_XINDEX, return a
-// descriptive interpretation of the st_shndx value. Otherwise, return the name
-// of the section with index SectionIndex. This function assumes that if the
-// Symbol has st_shndx == SHN_XINDEX the SectionIndex will be the value derived
-// from the SHT_SYMTAB_SHNDX section.
 template <typename ELFT>
 Expected<StringRef>
 ELFDumper<ELFT>::getSymbolSectionName(const Elf_Sym *Symbol,
                                       unsigned SectionIndex) const {
-  if (Symbol->isUndefined())
-    return "Undefined";
-  if (Symbol->isProcessorSpecific())
-    return "Processor Specific";
-  if (Symbol->isOSSpecific())
-    return "Operating System Specific";
-  if (Symbol->isAbsolute())
-    return "Absolute";
-  if (Symbol->isCommon())
-    return "Common";
-  if (Symbol->isReserved() && Symbol->st_shndx != SHN_XINDEX)
-    return "Reserved";
-
   const ELFFile<ELFT> *Obj = ObjF->getELFFile();
-  Expected<const Elf_Shdr *> SecOrErr =
-      Obj->getSection(SectionIndex);
+  Expected<const Elf_Shdr *> SecOrErr = Obj->getSection(SectionIndex);
   if (!SecOrErr)
     return SecOrErr.takeError();
   return Obj->getSectionName(**SecOrErr);
 }
 
 template <class ELFO>
 static const typename ELFO::Elf_Shdr *
 findNotEmptySectionByAddress(const ELFO *Obj, StringRef FileName,
case ELF::SHN_ABS:
     return "ABS";
   case ELF::SHN_COMMON:
     return "COM";
   case ELF::SHN_XINDEX: {
     Expected<uint32_t> IndexOrErr = object::getExtendedSymbolTableIndex<ELFT>(
         *Symbol, *FirstSym, this->dumper()->getShndxTable());
     if (!IndexOrErr) {
       assert(Symbol->st_shndx == SHN_XINDEX &&
-             "getSymbolSectionIndex should only fail due to an invalid "
+             "getExtendedSymbolTableIndex should only fail due to an invalid "
              "SHT_SYMTAB_SHNDX table/reference");
       this->reportUniqueWarning(IndexOrErr.takeError());
       return "RSV[0xffff]";
     }
     return to_string(format_decimal(*IndexOrErr, 3));
   }
   default:
     // Find if:
if (opts::SectionData && Sec.sh_type != ELF::SHT_NOBITS) {
           StringRef(reinterpret_cast<const char *>(Data.data()), Data.size()));
     }
   }
 }
 
 template <class ELFT>
 void LLVMStyle<ELFT>::printSymbolSection(const Elf_Sym *Symbol,
                                          const Elf_Sym *First) {
+  auto GetSectionSpecialType = [&]() -> Optional<StringRef> {
+    if (Symbol->isUndefined())
+      return StringRef("Undefined");
+    if (Symbol->isProcessorSpecific())
+      return StringRef("Processor Specific");
+    if (Symbol->isOSSpecific())
+      return StringRef("Operating System Specific");
+    if (Symbol->isAbsolute())
+      return StringRef("Absolute");
+    if (Symbol->isCommon())
+      return StringRef("Common");
+    if (Symbol->isReserved() && Symbol->st_shndx != SHN_XINDEX)
+      return StringRef("Reserved");
+    return None;
+  };
+
+  if (Optional<StringRef> Type = GetSectionSpecialType()) {
+    W.printHex("Section", *Type, Symbol->st_shndx);
+    return;
+  }
+
   Expected<unsigned> SectionIndex =
       this->dumper()->getSymbolSectionIndex(Symbol, First);
   if (!SectionIndex) {
     assert(Symbol->st_shndx == SHN_XINDEX &&
            "getSymbolSectionIndex should only fail due to an invalid "
            "SHT_SYMTAB_SHNDX table/reference");
     this->reportUniqueWarning(SectionIndex.takeError());
     W.printHex("Section", "Reserved", SHN_XINDEX);