[PATCH] D76081: [Object] object::ELFObjectFile::dynamic_symbol_begin(): skip symbol index 0

[Xing GUO via Phabricator via llvm-commits]

Higuoxing updated this revision to Diff 255018.
Higuoxing added a comment.

Remove last test case. We will add it in a follow up patch.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D76081/new/

https://reviews.llvm.org/D76081

Files:
  llvm/include/llvm/Object/ELFObjectFile.h
  llvm/test/tools/llvm-nm/dynamic.test


Index: llvm/test/tools/llvm-nm/dynamic.test
===================================================================
--- /dev/null
+++ llvm/test/tools/llvm-nm/dynamic.test
@@ -0,0 +1,62 @@
+## This is a test for --dynamic/-D option.
+
+## Test llvm-nm dumping ELF file with valid .dynsym section.
+# RUN: yaml2obj --docnum=1 %s -o %t1.o
+# RUN: llvm-nm --dynamic %t1.o | \
+# RUN:   FileCheck %s --match-full-lines --strict-whitespace --check-prefix DYNSYM
+# RUN: llvm-nm -D %t1.o | \
+# RUN:   FileCheck %s --match-full-lines --strict-whitespace --check-prefix DYNSYM
+
+#       DYNSYM:                 U globalsym
+#  DYNSYM-NEXT:                 U localsym1
+#  DYNSYM-NEXT:0000000000000000 n localsym2
+# DYNSYM-EMPTY:
+
+--- !ELF
+FileHeader:
+  Class:   ELFCLASS64
+  Data:    ELFDATA2LSB
+  Type:    ET_DYN
+  Machine: EM_X86_64
+Sections:
+  - Name: section
+    Type: SHT_PROGBITS
+DynamicSymbols:
+  - Name:    localsym1
+    Type:    STT_OBJECT
+  - Name:    localsym2
+    Section: section
+  - Name:    globalsym
+    Type:    STT_OBJECT
+    Binding: STB_GLOBAL
+
+## Test llvm-nm dumping ELF file without a .dynsym section.
+# RUN: yaml2obj --docnum=2 %s -o %t2.o
+# RUN: llvm-nm --dynamic %t2.o 2>&1 | \
+# RUN:   FileCheck %s --match-full-lines --strict-whitespace -DFILE=%t2.o --check-prefix NO-SYMS
+
+#       NO-SYMS:[[FILE]]: no symbols
+# NO-SYMS-EMPTY:
+
+--- !ELF
+FileHeader:
+  Class:   ELFCLASS64
+  Data:    ELFDATA2LSB
+  Type:    ET_DYN
+  Machine: EM_X86_64
+
+## Test llvm-nm dumping ELF file with an empty .dynsym section.
+# RUN: yaml2obj --docnum=3 %s -o %t3.o
+# RUN: llvm-nm --dynamic %t3.o 2>&1 | \
+# RUN:   FileCheck %s --match-full-lines --strict-whitespace -DFILE=%t3.o --check-prefix NO-SYMS
+
+--- !ELF
+FileHeader:
+  Class:   ELFCLASS64
+  Data:    ELFDATA2LSB
+  Type:    ET_DYN
+  Machine: EM_X86_64
+Sections:
+  - Name: .dynsym
+    Type: SHT_DYNSYM
+    Size: 0
Index: llvm/include/llvm/Object/ELFObjectFile.h
===================================================================
--- llvm/include/llvm/Object/ELFObjectFile.h
+++ llvm/include/llvm/Object/ELFObjectFile.h
@@ -1019,8 +1019,12 @@
 
 template <class ELFT>
 elf_symbol_iterator ELFObjectFile<ELFT>::dynamic_symbol_begin() const {
-  DataRefImpl Sym = toDRI(DotDynSymSec, 0);
-  return symbol_iterator(SymbolRef(Sym, this));
+  if (!DotDynSymSec || DotDynSymSec->sh_size < sizeof(Elf_Sym))
+    // Ignore errors here where the dynsym is empty or sh_size less than the
+    // size of one symbol. These should be handled elsewhere.
+    return symbol_iterator(SymbolRef(toDRI(DotDynSymSec, 0), this));
+  // Skip 0-index NULL symbol.
+  return symbol_iterator(SymbolRef(toDRI(DotDynSymSec, 1), this));
 }
 
 template <class ELFT>


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