Add support for reading msdos MZ executables.

See email thread starting here:  https://www.sourceware.org/ml/binutils/2018-01/msg00001.html

include	* coff/msdos.h: New header.
	* coff/pe.h: Move common defines to msdos.h.
	* coff/powerpc.h: Likewise.

bfd	* i386msdos.c (msdos_mkobject); New function.
	(msdos_object_p): New function.
	(i386_msdos_vec): Use msdos_object_p as the check_format
	function.
	* peicode.h: Rename external_PEI_DOS_hdr, DOSMAGIC, and
	NT_SIGNATURE to external_DOS_hdr, IMAGE_DOS_SIGNATURE, and
	IMAGE_NT_SIGNATURE.
	* peXXigen.c: Likewise.
	* coff-ia64.c: Likewise.

5 files changed, 105 insertions, 12 deletions

diff --git a/bfd/ChangeLog b/bfd/ChangeLog
index f147806..960e484 100644
--- a/bfd/ChangeLog
+++ b/bfd/ChangeLog
@@ -1,3 +1,15 @@
+2018-02-12  Zebediah Figura  <z.figura12@gmail.com>
+
+	* i386msdos.c (msdos_mkobject); New function.
+	(msdos_object_p): New function.
+	(i386_msdos_vec): Use msdos_object_p as the check_format
+	function.
+	* peicode.h: Rename external_PEI_DOS_hdr, DOSMAGIC, and
+	NT_SIGNATURE to external_DOS_hdr, IMAGE_DOS_SIGNATURE, and
+	IMAGE_NT_SIGNATURE.
+	* peXXigen.c: Likewise.
+	* coff-ia64.c: Likewise.
+
 2018-02-12  Nick Clifton  <nickc@redhat.com>
 
 	* elf32-nds32.c (nds32_elf_relax_longjump3): Remove redundant
diff --git a/bfd/coff-ia64.c b/bfd/coff-ia64.c
index 56100dd..270c959 100644
--- a/bfd/coff-ia64.c
+++ b/bfd/coff-ia64.c
@@ -72,7 +72,7 @@ ia64coff_object_p (bfd *abfd)
 {
 #ifdef COFF_IMAGE_WITH_PE
   {
-    struct external_PEI_DOS_hdr dos_hdr;
+    struct external_DOS_hdr dos_hdr;
     struct external_PEI_IMAGE_hdr image_hdr;
     file_ptr offset;
 
@@ -87,7 +87,7 @@ ia64coff_object_p (bfd *abfd)
 
     /* There are really two magic numbers involved; the magic number
        that says this is a NT executable (PEI) and the magic number
-       that determines the architecture.  The former is DOSMAGIC,
+       that determines the architecture.  The former is IMAGE_DOS_SIGNATURE,
        stored in the e_magic field.  The latter is stored in the
        f_magic field.  If the NT magic number isn't valid, the
        architecture magic number could be mimicked by some other
@@ -95,7 +95,7 @@ ia64coff_object_p (bfd *abfd)
        this routine can only be called correctly for a PEI file, check
        the e_magic number here, and, if it doesn't match, clobber the
        f_magic number so that we don't get a false match.  */
-    if (H_GET_16 (abfd, dos_hdr.e_magic) != DOSMAGIC)
+    if (H_GET_16 (abfd, dos_hdr.e_magic) != IMAGE_DOS_SIGNATURE)
       {
 	bfd_set_error (bfd_error_wrong_format);
 	return NULL;
diff --git a/bfd/i386msdos.c b/bfd/i386msdos.c
index c15707c..5437b16 100644
--- a/bfd/i386msdos.c
+++ b/bfd/i386msdos.c
@@ -27,12 +27,94 @@
 #include "bfd.h"
 #include "libbfd.h"
 #include "libaout.h"
+#include "coff/msdos.h"
 
-#define EXE_MAGIC	0x5a4d
 #define EXE_LOAD_HIGH	0x0000
 #define EXE_LOAD_LOW	0xffff
 #define EXE_PAGE_SIZE	512
 
+static bfd_boolean
+msdos_mkobject (bfd *abfd)
+{
+  bfd_default_set_arch_mach (abfd, bfd_arch_i386, bfd_mach_i386_i8086);
+
+  return aout_32_mkobject (abfd);
+}
+
+static const bfd_target *
+msdos_object_p (bfd *abfd)
+{
+  struct external_DOS_hdr hdr;
+  bfd_byte buffer[2];
+  asection *section;
+  unsigned int size;
+
+  if (bfd_seek (abfd, (file_ptr) 0, SEEK_SET) != 0
+      || bfd_bread (&hdr, (bfd_size_type) sizeof (hdr), abfd) < DOS_HDR_SIZE)
+    {
+      if (bfd_get_error () != bfd_error_system_call)
+	bfd_set_error (bfd_error_wrong_format);
+      return NULL;
+    }
+
+  if (H_GET_16 (abfd, hdr.e_magic) != IMAGE_DOS_SIGNATURE)
+    {
+      bfd_set_error (bfd_error_wrong_format);
+      return NULL;
+    }
+
+  /* Check that this isn't actually a PE, NE, or LE file. If it is, the
+     e_lfanew field will be valid and point to a header beginning with one of
+     the relevant signatures.  If not, e_lfanew might point to anything, so
+     don't bail if we can't read there.  */
+  if (H_GET_16 (abfd, hdr.e_cparhdr) < 4
+      || bfd_seek (abfd, (file_ptr) H_GET_32 (abfd, hdr.e_lfanew), SEEK_SET) != 0
+      || bfd_bread (buffer, (bfd_size_type) 2, abfd) != 2)
+    {
+      if (bfd_get_error () == bfd_error_system_call)
+	return NULL;
+    }
+  else
+    {
+      if (H_GET_16 (abfd, buffer) == IMAGE_NT_SIGNATURE
+	  || H_GET_16 (abfd, buffer) == IMAGE_OS2_SIGNATURE
+	  || H_GET_16 (abfd, buffer) == IMAGE_OS2_SIGNATURE_LE
+	  || H_GET_16 (abfd, buffer) == IMAGE_OS2_SIGNATURE_LX)
+	{
+	  bfd_set_error (bfd_error_wrong_format);
+	  return NULL;
+	}
+    }
+
+  if (!msdos_mkobject (abfd))
+    return NULL;
+
+  abfd->flags = EXEC_P;
+  abfd->start_address = H_GET_16 (abfd, hdr.e_ip);
+
+  section = bfd_make_section (abfd, ".text");
+  if (section == NULL)
+    return NULL;
+
+  section->flags = (SEC_ALLOC | SEC_LOAD | SEC_CODE | SEC_HAS_CONTENTS);
+  section->filepos = H_GET_16 (abfd, hdr.e_cparhdr) * 16;
+  size = (H_GET_16 (abfd, hdr.e_cp) - 1) * EXE_PAGE_SIZE - section->filepos;
+  size += H_GET_16 (abfd, hdr.e_cblp);
+
+  /* Check that the size is valid.  */
+  if (bfd_seek (abfd, (file_ptr) (section->filepos + size), SEEK_SET) != 0)
+    {
+      if (bfd_get_error () != bfd_error_system_call)
+	bfd_set_error (bfd_error_wrong_format);
+      return NULL;
+    }
+
+  bfd_set_section_size (abfd, section, size);
+  section->alignment_power = 4;
+
+  return abfd->xvec;
+}
+
 static int
 msdos_sizeof_headers (bfd *abfd ATTRIBUTE_UNUSED,
 		      struct bfd_link_info *info ATTRIBUTE_UNUSED)
@@ -77,7 +159,7 @@ msdos_write_object_contents (bfd *abfd)
     }
 
   /* Constants.  */
-  H_PUT_16 (abfd, EXE_MAGIC, &hdr[0]);
+  H_PUT_16 (abfd, IMAGE_DOS_SIGNATURE, &hdr[0]);
   H_PUT_16 (abfd, EXE_PAGE_SIZE / 16, &hdr[8]);
   H_PUT_16 (abfd, EXE_LOAD_LOW, &hdr[12]);
   H_PUT_16 (abfd, 0x3e, &hdr[24]);
@@ -127,7 +209,6 @@ msdos_set_section_contents (bfd *abfd,
 
 
 
-#define msdos_mkobject aout_32_mkobject
 #define msdos_make_empty_symbol aout_32_make_empty_symbol
 #define msdos_bfd_reloc_type_lookup aout_32_reloc_type_lookup
 #define msdos_bfd_reloc_name_lookup aout_32_reloc_name_lookup
@@ -203,7 +284,7 @@ const bfd_target i386_msdos_vec =
 
     {
       _bfd_dummy_target,
-      _bfd_dummy_target,		/* bfd_check_format */
+      msdos_object_p,		/* bfd_check_format */
       _bfd_dummy_target,
       _bfd_dummy_target,
     },
diff --git a/bfd/peXXigen.c b/bfd/peXXigen.c
index 679dabf..6caca17 100644
--- a/bfd/peXXigen.c
+++ b/bfd/peXXigen.c
@@ -828,7 +828,7 @@ _bfd_XXi_only_swap_filehdr_out (bfd * abfd, void * in, void * out)
   if (pe_data (abfd)->dll)
     filehdr_in->f_flags |= F_DLL;
 
-  filehdr_in->pe.e_magic    = DOSMAGIC;
+  filehdr_in->pe.e_magic    = IMAGE_DOS_SIGNATURE;
   filehdr_in->pe.e_cblp     = 0x90;
   filehdr_in->pe.e_cp       = 0x3;
   filehdr_in->pe.e_crlc     = 0x0;
@@ -872,7 +872,7 @@ _bfd_XXi_only_swap_filehdr_out (bfd * abfd, void * in, void * out)
   filehdr_in->pe.dos_message[13] = 0x0a0d0d2e;
   filehdr_in->pe.dos_message[14] = 0x24;
   filehdr_in->pe.dos_message[15] = 0x0;
-  filehdr_in->pe.nt_signature = NT_SIGNATURE;
+  filehdr_in->pe.nt_signature = IMAGE_NT_SIGNATURE;
 
   H_PUT_16 (abfd, filehdr_in->f_magic, filehdr_out->f_magic);
   H_PUT_16 (abfd, filehdr_in->f_nscns, filehdr_out->f_nscns);
diff --git a/bfd/peicode.h b/bfd/peicode.h
index 94dd861..30dc08b 100644
--- a/bfd/peicode.h
+++ b/bfd/peicode.h
@@ -1386,7 +1386,7 @@ static const bfd_target *
 pe_bfd_object_p (bfd * abfd)
 {
   bfd_byte buffer[6];
-  struct external_PEI_DOS_hdr dos_hdr;
+  struct external_DOS_hdr dos_hdr;
   struct external_PEI_IMAGE_hdr image_hdr;
   struct internal_filehdr internal_f;
   struct internal_aouthdr internal_a;
@@ -1420,7 +1420,7 @@ pe_bfd_object_p (bfd * abfd)
 
   /* There are really two magic numbers involved; the magic number
      that says this is a NT executable (PEI) and the magic number that
-     determines the architecture.  The former is DOSMAGIC, stored in
+     determines the architecture.  The former is IMAGE_DOS_SIGNATURE, stored in
      the e_magic field.  The latter is stored in the f_magic field.
      If the NT magic number isn't valid, the architecture magic number
      could be mimicked by some other field (specifically, the number
@@ -1428,7 +1428,7 @@ pe_bfd_object_p (bfd * abfd)
      correctly for a PEI file, check the e_magic number here, and, if
      it doesn't match, clobber the f_magic number so that we don't get
      a false match.  */
-  if (H_GET_16 (abfd, dos_hdr.e_magic) != DOSMAGIC)
+  if (H_GET_16 (abfd, dos_hdr.e_magic) != IMAGE_DOS_SIGNATURE)
     {
       bfd_set_error (bfd_error_wrong_format);
       return NULL;