ELF loader: use only symbol table if unique

Some firmware images may present as EXEC but only have a static symbol
table.

Drop the now unused `GetSectionByType` helper function.

PiperOrigin-RevId: 572916484
Change-Id: I28ab0881ee536a7e1ddec6cb8e7126ee6e422e7c

1 files changed, 21 insertions, 16 deletions

diff --git a/elf_loader.cc b/elf_loader.cc
index 5b9a864..6575b17 100644
--- a/elf_loader.cc
+++ b/elf_loader.cc
@@ -218,12 +218,6 @@ Elf_Scn* MaybeGetSectionByType(Elf* elf, Elf64_Word type) {
   return sections[0];
 }
 
-Elf_Scn* GetSectionByType(Elf* elf, Elf64_Word type) {
-  Elf_Scn* section = MaybeGetSectionByType(elf, type);
-  Check(section != nullptr) << "no section found with type " << type;
-  return section;
-}
-
 Elf_Scn* GetSectionByIndex(Elf* elf, size_t index) {
   Elf_Scn* section = elf_getscn(elf, index);
   Check(section != nullptr) << "no section found with index " << index;
@@ -270,17 +264,28 @@ Elf_Scn* GetSymbolTableSection(Elf* elf, bool is_linux_kernel_binary,
     std::cout << "ELF type: " << ElfHeaderTypeToString(elf_header.e_type)
               << '\n';
   }
-  // Relocatable ELF binaries, Linux kernel and modules have their exported
-  // symbols in .symtab, all other ELF types have their exported symbols in
-  // .dynsym.
-  if (elf_header.e_type == ET_REL || is_linux_kernel_binary) {
-    return GetSectionByType(elf, SHT_SYMTAB);
-  }
-  if (elf_header.e_type == ET_DYN || elf_header.e_type == ET_EXEC) {
-    return GetSectionByType(elf, SHT_DYNSYM);
+
+  Elf_Scn* symtab = MaybeGetSectionByType(elf, SHT_SYMTAB);
+  Elf_Scn* dynsym = MaybeGetSectionByType(elf, SHT_DYNSYM);
+  if (symtab != nullptr && dynsym != nullptr) {
+    // Relocatable ELF binaries, Linux kernel and modules have their
+    // exported symbols in .symtab, all other ELF types have their
+    // exported symbols in .dynsym.
+    if (elf_header.e_type == ET_REL || is_linux_kernel_binary) {
+      return symtab;
+    }
+    if (elf_header.e_type == ET_DYN || elf_header.e_type == ET_EXEC) {
+      return dynsym;
+    }
+    Die() << "unsupported ELF type: '"
+          << ElfHeaderTypeToString(elf_header.e_type) << "'";
+  } else if (symtab != nullptr) {
+    return symtab;
+  } else if (dynsym != nullptr) {
+    return dynsym;
+  } else {
+    Die() << "no ELF symbol table found";
   }
-  Die() << "unsupported ELF type: '" << ElfHeaderTypeToString(elf_header.e_type)
-        << "'";
 }