Add the ability to the BFD library to read build-ids from core flies.

	* elf-bfd.h (elf_backend_data) <elf_backend_core_find_build_id>:
	New field.
	(_bfd_elf32_core_find_build_id, _bfd_elf64_core_find_build_id):
	New functions.
	(elf_read_notes): Add declaration.
	* elf.c (elf_read_notes): Move elf-bfd.h.
	(_bfd_elf_core_find_build_id): New function.
	(bfd_section_from_phdr): Scan core file PT_LOAD segments for
	build-id if none is known.
	(elf_parse_notes): For core files, scan for notes.
	* elfcore.h (elf_core_file_matches_executable_p): If both
	BFDs have identical build-ids, then they match.
	(_bfd_elf_core_find_build_id): New function.
	* elfxx-target.h (elf_backend_core_find_build_id): Define.
	(elfNN_bed): Add elf_backend_core_find_build_id.

5 files changed, 153 insertions, 5 deletions

diff --git a/bfd/ChangeLog b/bfd/ChangeLog
index 20d7d5a..78cbd51 100644
--- a/bfd/ChangeLog
+++ b/bfd/ChangeLog
@@ -1,3 +1,21 @@
+2019-10-30  Keith Seitz  <keiths@redhat.com>
+
+	* elf-bfd.h (elf_backend_data) <elf_backend_core_find_build_id>:
+	New field.
+	(_bfd_elf32_core_find_build_id, _bfd_elf64_core_find_build_id):
+	New functions.
+	(elf_read_notes): Add declaration.
+	* elf.c (elf_read_notes): Move elf-bfd.h.
+	(_bfd_elf_core_find_build_id): New function.
+	(bfd_section_from_phdr): Scan core file PT_LOAD segments for
+	build-id if none is known.
+	(elf_parse_notes): For core files, scan for notes.
+	* elfcore.h (elf_core_file_matches_executable_p): If both
+	BFDs have identical build-ids, then they match.
+	(_bfd_elf_core_find_build_id): New function.
+	* elfxx-target.h (elf_backend_core_find_build_id): Define.
+	(elfNN_bed): Add elf_backend_core_find_build_id.
+
 2019-10-29  Andrew Eikum  <aeikum@codeweavers.com>
 
 	* libcoff-in.h (struct pe_tdata): Add dos_message field.
diff --git a/bfd/elf-bfd.h b/bfd/elf-bfd.h
index ccd2c35..7309499 100644
--- a/bfd/elf-bfd.h
+++ b/bfd/elf-bfd.h
@@ -1377,6 +1377,8 @@ struct elf_backend_data
      int (*target_read_memory) (bfd_vma vma, bfd_byte *myaddr,
 				bfd_size_type len));
 
+  bfd_boolean (*elf_backend_core_find_build_id) (bfd *, bfd_vma);
+
   /* This function is used by `_bfd_elf_get_synthetic_symtab';
      see elf.c.  */
   bfd_vma (*plt_sym_val) (bfd_vma, const asection *, const arelent *);
@@ -2403,6 +2405,8 @@ extern bfd_boolean bfd_elf32_core_file_matches_executable_p
   (bfd *, bfd *);
 extern int bfd_elf32_core_file_pid
   (bfd *);
+extern bfd_boolean _bfd_elf32_core_find_build_id
+  (bfd *, bfd_vma);
 
 extern bfd_boolean bfd_elf32_swap_symbol_in
   (bfd *, const void *, const void *, Elf_Internal_Sym *);
@@ -2449,6 +2453,8 @@ extern bfd_boolean bfd_elf64_core_file_matches_executable_p
   (bfd *, bfd *);
 extern int bfd_elf64_core_file_pid
   (bfd *);
+extern bfd_boolean _bfd_elf64_core_find_build_id
+  (bfd *, bfd_vma);
 
 extern bfd_boolean bfd_elf64_swap_symbol_in
   (bfd *, const void *, const void *, Elf_Internal_Sym *);
@@ -2773,6 +2779,7 @@ extern bfd_boolean _bfd_elf_merge_object_attributes
 extern bfd_boolean _bfd_elf_merge_unknown_attribute_low (bfd *, bfd *, int);
 extern bfd_boolean _bfd_elf_merge_unknown_attribute_list (bfd *, bfd *);
 extern Elf_Internal_Shdr *_bfd_elf_single_rel_hdr (asection *sec);
+extern bfd_boolean elf_read_notes (bfd *, file_ptr, bfd_size_type, size_t);
 
 extern bfd_boolean _bfd_elf_parse_gnu_properties
   (bfd *, Elf_Internal_Note *);
diff --git a/bfd/elf.c b/bfd/elf.c
index 38872d7..be060d5 100644
--- a/bfd/elf.c
+++ b/bfd/elf.c
@@ -53,8 +53,6 @@ static int elf_sort_sections (const void *, const void *);
 static bfd_boolean assign_file_positions_except_relocs (bfd *, struct bfd_link_info *);
 static bfd_boolean prep_headers (bfd *);
 static bfd_boolean swap_out_syms (bfd *, struct elf_strtab_hash **, int) ;
-static bfd_boolean elf_read_notes (bfd *, file_ptr, bfd_size_type,
-				   size_t align) ;
 static bfd_boolean elf_parse_notes (bfd *abfd, char *buf, size_t size,
 				    file_ptr offset, size_t align);
 
@@ -3061,6 +3059,16 @@ _bfd_elf_make_section_from_phdr (bfd *abfd,
   return TRUE;
 }
 
+static bfd_boolean
+_bfd_elf_core_find_build_id (bfd *templ, bfd_vma offset)
+{
+  /* The return value is ignored.  Build-ids are considered optional.  */
+  if (templ->xvec->flavour == bfd_target_elf_flavour)
+    return (*get_elf_backend_data (templ)->elf_backend_core_find_build_id)
+      (templ, offset);
+  return FALSE;
+}
+
 bfd_boolean
 bfd_section_from_phdr (bfd *abfd, Elf_Internal_Phdr *hdr, int hdr_index)
 {
@@ -3072,7 +3080,11 @@ bfd_section_from_phdr (bfd *abfd, Elf_Internal_Phdr *hdr, int hdr_index)
       return _bfd_elf_make_section_from_phdr (abfd, hdr, hdr_index, "null");
 
     case PT_LOAD:
-      return _bfd_elf_make_section_from_phdr (abfd, hdr, hdr_index, "load");
+      if (! _bfd_elf_make_section_from_phdr (abfd, hdr, hdr_index, "load"))
+	return FALSE;
+      if (bfd_get_format (abfd) == bfd_core && abfd->build_id == NULL)
+	_bfd_elf_core_find_build_id (abfd, hdr->p_offset);
+      return TRUE;
 
     case PT_DYNAMIC:
       return _bfd_elf_make_section_from_phdr (abfd, hdr, hdr_index, "dynamic");
@@ -11838,7 +11850,8 @@ elf_parse_notes (bfd *abfd, char *buf, size_t size, file_ptr offset,
 	      GROKER_ELEMENT ("NetBSD-CORE", elfcore_grok_netbsd_note),
 	      GROKER_ELEMENT ( "OpenBSD", elfcore_grok_openbsd_note),
 	      GROKER_ELEMENT ("QNX", elfcore_grok_nto_note),
-	      GROKER_ELEMENT ("SPU/", elfcore_grok_spu_note)
+	      GROKER_ELEMENT ("SPU/", elfcore_grok_spu_note),
+	      GROKER_ELEMENT ("GNU", elfobj_grok_gnu_note)
 	    };
 #undef GROKER_ELEMENT
 	    int i;
@@ -11878,7 +11891,7 @@ elf_parse_notes (bfd *abfd, char *buf, size_t size, file_ptr offset,
   return TRUE;
 }
 
-static bfd_boolean
+bfd_boolean
 elf_read_notes (bfd *abfd, file_ptr offset, bfd_size_type size,
 		size_t align)
 {
diff --git a/bfd/elfcore.h b/bfd/elfcore.h
index 3550eaa..1279327 100644
--- a/bfd/elfcore.h
+++ b/bfd/elfcore.h
@@ -49,6 +49,14 @@ elf_core_file_matches_executable_p (bfd *core_bfd, bfd *exec_bfd)
       return FALSE;
     }
 
+  /* If both BFDs have identical build-ids, then they match.  */
+  if (core_bfd->build_id != NULL
+      && exec_bfd->build_id != NULL
+      && core_bfd->build_id->size == exec_bfd->build_id->size
+      && memcmp (core_bfd->build_id->data, exec_bfd->build_id->data,
+		 core_bfd->build_id->size) == 0)
+    return TRUE;
+
   /* See if the name in the corefile matches the executable name.  */
   corename = elf_tdata (core_bfd)->core->program;
   if (corename != NULL)
@@ -313,3 +321,101 @@ wrong:
 fail:
   return NULL;
 }
+
+/* Attempt to find a build-id in a core file from the core file BFD.
+   OFFSET is the file offset to a PT_LOAD segment that may contain
+   the build-id note.  Returns TRUE upon success, FALSE otherwise.  */
+
+bfd_boolean
+NAME(_bfd_elf, core_find_build_id)
+  (bfd *abfd,
+   bfd_vma offset)
+{
+  Elf_External_Ehdr x_ehdr;	/* Elf file header, external form.   */
+  Elf_Internal_Ehdr i_ehdr;	/* Elf file header, internal form.   */
+  Elf_Internal_Phdr *i_phdr;
+  unsigned int i;
+
+  /* Seek to the position of the segment at OFFSET.  */
+  if (bfd_seek (abfd, offset, SEEK_SET) != 0)
+    goto fail;
+
+  /* Read in the ELF header in external format.  */
+  if (bfd_bread (&x_ehdr, sizeof (x_ehdr), abfd) != sizeof (x_ehdr))
+    {
+      if (bfd_get_error () != bfd_error_system_call)
+	goto wrong;
+      else
+	goto fail;
+    }
+
+  /* Now check to see if we have a valid ELF file, and one that BFD can
+     make use of.  The magic number must match, the address size ('class')
+     and byte-swapping must match our XVEC entry, and it must have a
+     section header table (FIXME: See comments re sections at top of this
+     file).  */
+  if (! elf_file_p (&x_ehdr)
+      || x_ehdr.e_ident[EI_VERSION] != EV_CURRENT
+      || x_ehdr.e_ident[EI_CLASS] != ELFCLASS)
+    goto wrong;
+
+  /* Check that file's byte order matches xvec's.  */
+  switch (x_ehdr.e_ident[EI_DATA])
+    {
+    case ELFDATA2MSB:		/* Big-endian.  */
+      if (! bfd_header_big_endian (abfd))
+	goto wrong;
+      break;
+    case ELFDATA2LSB:		/* Little-endian.  */
+      if (! bfd_header_little_endian (abfd))
+	goto wrong;
+      break;
+    case ELFDATANONE:		/* No data encoding specified.  */
+    default:			/* Unknown data encoding specified . */
+      goto wrong;
+    }
+
+  elf_swap_ehdr_in (abfd, &x_ehdr, &i_ehdr);
+#if DEBUG
+  elf_debug_file (&i_ehdr);
+#endif
+
+  if (i_ehdr.e_phentsize != sizeof (Elf_External_Phdr) || i_ehdr.e_phnum == 0)
+    goto fail;
+
+  /* Read in program headers.  */
+  i_phdr = (Elf_Internal_Phdr *) bfd_alloc2 (abfd, i_ehdr.e_phnum,
+					     sizeof (*i_phdr));
+  if (i_phdr == NULL)
+    goto fail;
+
+  if (bfd_seek (abfd, (file_ptr) (offset + i_ehdr.e_phoff), SEEK_SET) != 0)
+    goto fail;
+
+  /* Read in program headers and parse notes.  */
+  for (i = 0; i < i_ehdr.e_phnum; ++i, ++i_phdr)
+    {
+      Elf_External_Phdr x_phdr;
+
+      if (bfd_bread (&x_phdr, sizeof (x_phdr), abfd) != sizeof (x_phdr))
+	goto fail;
+      elf_swap_phdr_in (abfd, &x_phdr, i_phdr);
+
+      if (i_phdr->p_type == PT_NOTE && i_phdr->p_filesz > 0)
+	{
+	  elf_read_notes (abfd, offset + i_phdr->p_offset,
+			  i_phdr->p_filesz, i_phdr->p_align);
+	  if (abfd->build_id != NULL)
+	    return TRUE;
+	}
+    }
+
+  /* Having gotten this far, we have a valid ELF section, but no
+     build-id was found.  */
+  goto fail;
+
+wrong:
+  bfd_set_error (bfd_error_wrong_format);
+fail:
+  return FALSE;
+}
diff --git a/bfd/elfxx-target.h b/bfd/elfxx-target.h
index 78a1f63..29ad2e8 100644
--- a/bfd/elfxx-target.h
+++ b/bfd/elfxx-target.h
@@ -521,6 +521,9 @@
 #ifndef elf_backend_bfd_from_remote_memory
 #define elf_backend_bfd_from_remote_memory _bfd_elfNN_bfd_from_remote_memory
 #endif
+#ifndef elf_backend_core_find_build_id
+#define elf_backend_core_find_build_id _bfd_elfNN_core_find_build_id
+#endif
 #ifndef elf_backend_got_header_size
 #define elf_backend_got_header_size	0
 #endif
@@ -860,6 +863,7 @@ static struct elf_backend_data elfNN_bed =
   elf_backend_mips_rtype_to_howto,
   elf_backend_ecoff_debug_swap,
   elf_backend_bfd_from_remote_memory,
+  elf_backend_core_find_build_id,
   elf_backend_plt_sym_val,
   elf_backend_common_definition,
   elf_backend_common_section_index,