Account for padding in FreeBSD/mipsn32 NT_PRSTATUS notes.

Add a new ELF backend method to grok FreeBSD NT_PRSTATUS core dump
notes.  Define a method for MIPS N32 to override the default
elfcore_grok_freebsd_prstatus that accounts for additional padding
between pr_pid and pr_reg that is not present in other 32-bit FreeBSD
platforms.

	* elf-bfd.h (struct elf_backend_data): Add
	`elf_backend_grok_freebsd_prstatus'.
	* elf.c (elfcore_grok_freebsd_note): Call
	`elf_backend_grok_freebsd_prstatus' to handle NT_PRSTATUS if
	present.
	* elfn32-mips.c (elf_n32_mips_grok_freebsd_prstatus): New
	function.
	(elf_backend_grok_freebsd_prstatus): Define.
	* elfxx-target.h (elf_backend_grok_freebsd_prstatus): Define.
	(elfNN_bed): Initialize `elf_backend_grok_freebsd_prstatus'.

bfd/ChangeLog

@@ -1,3 +1,16 @@
+2017-10-06  John Baldwin  <jhb@FreeBSD.org>
+
+	* elf-bfd.h (struct elf_backend_data): Add
+	`elf_backend_grok_freebsd_prstatus'.
+	* elf.c (elfcore_grok_freebsd_note): Call
+	`elf_backend_grok_freebsd_prstatus' to handle NT_PRSTATUS if
+	present.
+	* elfn32-mips.c (elf_n32_mips_grok_freebsd_prstatus): New
+	function.
+	(elf_backend_grok_freebsd_prstatus): Define.
+	* elfxx-target.h (elf_backend_grok_freebsd_prstatus): Define.
+	(elfNN_bed): Initialize `elf_backend_grok_freebsd_prstatus'.
+
 2017-10-06  H.J. Lu  <hongjiu.lu@intel.com>
 
 	* elfxx-x86.h (COPY_INPUT_RELOC_P): Add "do/while(0);".

bfd/elf-bfd.h

@@ -1270,6 +1270,11 @@ struct elf_backend_data
   bfd_boolean (*elf_backend_grok_psinfo)
     (bfd *, Elf_Internal_Note *);
 
+  /* This function, if defined, is called when a "FreeBSD" NT_PRSTATUS
+     note is found in a core file.  */
+  bfd_boolean (*elf_backend_grok_freebsd_prstatus)
+    (bfd *, Elf_Internal_Note *);
+
   /* This function, if defined, is called to write a note to a corefile.  */
   char *(*elf_backend_write_core_note)
     (bfd *abfd, char *buf, int *bufsiz, int note_type, ...);

bfd/elf.c

@@ -9981,9 +9981,14 @@ elfcore_grok_freebsd_prstatus (bfd *abfd, Elf_Internal_Note *note)
 static bfd_boolean
 elfcore_grok_freebsd_note (bfd *abfd, Elf_Internal_Note *note)
 {
+  const struct elf_backend_data *bed = get_elf_backend_data (abfd);
+
   switch (note->type)
     {
     case NT_PRSTATUS:
+      if (bed->elf_backend_grok_freebsd_prstatus)
+	if ((*bed->elf_backend_grok_freebsd_prstatus) (abfd, note))
+	  return TRUE;
       return elfcore_grok_freebsd_prstatus (abfd, note);
 
     case NT_FPREGSET:

bfd/elfn32-mips.c

@@ -80,6 +80,8 @@ static bfd_boolean elf32_mips_grok_prstatus
   (bfd *, Elf_Internal_Note *);
 static bfd_boolean elf32_mips_grok_psinfo
   (bfd *, Elf_Internal_Note *);
+static bfd_boolean elf_n32_mips_grok_freebsd_prstatus
+  (bfd *, Elf_Internal_Note *);
 static irix_compat_t elf_n32_mips_irix_compat
   (bfd *);
 
@@ -3578,6 +3580,56 @@ elf32_mips_grok_psinfo (bfd *abfd, Elf_Internal_Note *note)
 
   return TRUE;
 }
+
+static bfd_boolean
+elf_n32_mips_grok_freebsd_prstatus (bfd *abfd, Elf_Internal_Note *note)
+{
+  size_t offset;
+  size_t size;
+  size_t min_size;
+
+  /* Compute offset of pr_getregsz, skipping over pr_statussz.
+     Also compute minimum size of this note.  */
+  offset = 4 + 4;
+  min_size = offset + 4 * 2 + 4 + 4 + 4;
+
+  if (note->descsz < min_size)
+    return FALSE;
+
+  /* Check for version 1 in pr_version.  */
+  if (bfd_h_get_32 (abfd, (bfd_byte *) note->descdata) != 1)
+    return FALSE;
+
+  /* Extract size of pr_reg from pr_gregsetsz.  */
+  /* Skip over pr_gregsetsz and pr_fpregsetsz.  */
+  size = bfd_h_get_32 (abfd, (bfd_byte *) note->descdata + offset);
+  offset += 4 * 2;
+
+  /* Skip over pr_osreldate.  */
+  offset += 4;
+
+  /* Read signal from pr_cursig.  */
+  if (elf_tdata (abfd)->core->signal == 0)
+    elf_tdata (abfd)->core->signal
+      = bfd_h_get_32 (abfd, (bfd_byte *) note->descdata + offset);
+  offset += 4;
+
+  /* Read TID from pr_pid.  */
+  elf_tdata (abfd)->core->lwpid
+      = bfd_h_get_32 (abfd, (bfd_byte *) note->descdata + offset);
+  offset += 4;
+
+  /* Padding before pr_reg.  */
+  offset += 4;
+
+  /* Make sure that there is enough data remaining in the note.  */
+  if (note->descsz - offset < size)
+    return FALSE;
+
+  /* Make a ".reg/999" section and a ".reg" section.  */
+  return _bfd_elfcore_make_pseudosection (abfd, ".reg",
+					  size, note->descpos + offset);
+}
 
 /* Depending on the target vector we generate some version of Irix
    executables or "normal" MIPS ELF ABI executables.  */
@@ -3684,6 +3736,8 @@ static const struct ecoff_debug_swap mips_elf32_ecoff_debug_swap = {
 					_bfd_mips_elf_copy_indirect_symbol
 #define elf_backend_grok_prstatus	elf32_mips_grok_prstatus
 #define elf_backend_grok_psinfo		elf32_mips_grok_psinfo
+#define elf_backend_grok_freebsd_prstatus \
+					elf_n32_mips_grok_freebsd_prstatus
 #define elf_backend_ecoff_debug_swap	&mips_elf32_ecoff_debug_swap
 
 #define elf_backend_got_header_size	(4 * MIPS_RESERVED_GOTNO)

bfd/elfxx-target.h

@@ -597,6 +597,9 @@
 #ifndef elf_backend_grok_psinfo
 #define elf_backend_grok_psinfo			NULL
 #endif
+#ifndef elf_backend_grok_freebsd_prstatus
+#define elf_backend_grok_freebsd_prstatus	NULL
+#endif
 #ifndef elf_backend_write_core_note
 #define elf_backend_write_core_note		NULL
 #endif
@@ -820,6 +823,7 @@ static struct elf_backend_data elfNN_bed =
   elf_backend_sort_relocs_p,
   elf_backend_grok_prstatus,
   elf_backend_grok_psinfo,
+  elf_backend_grok_freebsd_prstatus,
   elf_backend_write_core_note,
   elf_backend_lookup_section_flags_hook,
   elf_backend_reloc_type_class,