llvm-nm: Print correct symbol types for init and fini sections

[meadori]

Summary

This patch fixes a small bug where symbols defined in the INIT
and FINI sections were incorrectly getting a type of 'n'.

[MaskRay]

This copied a bug from GNU nm.

static const struct section_to_type stt[] =
{
  {".bss", 'b'},
  {"code", 't'},		/* MRI .text */
  {".data", 'd'},
  {"*DEBUG*", 'N'},
  {".debug", 'N'},		/* MSVC's .debug (non-standard debug syms) */
  {".drectve", 'i'},		/* MSVC's .drective section */
  {".edata", 'e'},		/* MSVC's .edata (export) section */
  {".fini", 't'},		/* ELF fini section */
  {".idata", 'i'},		/* MSVC's .idata (import) section */
  {".init", 't'},		/* ELF init section */
  {".pdata", 'p'},		/* MSVC's .pdata (stack unwind) section */
  {".rdata", 'r'},		/* Read only data.  */
  {".rodata", 'r'},		/* Read only data.  */
  {".sbss", 's'},		/* Small BSS (uninitialized data).  */
  {".scommon", 'c'},		/* Small common.  */
  {".sdata", 'g'},		/* Small initialized data.  */
  {".text", 't'},
  {"vars", 'd'},		/* MRI .data */
  {"zerovars", 'b'},		/* MRI .bss */
  {0, 0}
};

/* Return the single-character symbol type corresponding to
   section S, or '?' for an unknown COFF section.

   Check for any leading string which matches, so .text5 returns
   't' as well as .text */

static char
coff_section_type (const char *s)
{
  const struct section_to_type *t;

  for (t = &stt[0]; t->section; t++)
    if (!strncmp (s, t->section, strlen (t->section))) ///////// symbols in ".init_array" are incorrectly marked "t"
      return t->type;

  return '?';
}

The behavior is not consistent with a symbol defined in .preinit_array, e.g.

d __preinit_array_start
t __init_array_start

The more sensible choice is probably to mark both as d.

Filed https://sourceware.org/bugzilla/show_bug.cgi?id=24511

llvm/trunk/test/tools/llvm-nm/X86/init-fini.test

+# RUN: llvm-nm -B -S %p/Inputs/init-fini.out.elf-x86_64 | FileCheck --match-full-lines %s
+
+CHECK: 00000000006000c2 0000000000000000 T __bss_start
+CHECK: 00000000006000c2 0000000000000000 t __init_array_end
+CHECK: 00000000006000ba 0000000000000000 t __init_array_start
+CHECK: 00000000006000c2 0000000000000000 T _edata
+CHECK: 00000000006000c8 0000000000000000 T _end
+CHECK: 00000000004000b0 0000000000000000 T _start

llvm/trunk/tools/llvm-nm/llvm-nm.cpp

case ELF::SHT_DYNAMIC:
       case ELF::SHF_ALLOC:
       case (ELF::SHF_ALLOC | ELF::SHF_MERGE):
       case (ELF::SHF_ALLOC | ELF::SHF_MERGE | ELF::SHF_STRINGS):
         return 'r';
       }
       break;
     case ELF::SHT_NOBITS:
       return 'b';
+    case ELF::SHT_INIT_ARRAY:
+    case ELF::SHT_FINI_ARRAY:
+      return 't';
     }
   }
 
   if (SymI->getELFType() == ELF::STT_SECTION) {
     Expected<StringRef> Name = SymI->getName();
     if (!Name) {
       consumeError(Name.takeError());
       return '?';