a.out is no longer the commonly encountered binary file format, the world has

moved to ELF.

Move the a.out specific defines and macros, but the MID_xxx values, from
<sys/exec.h> to <a.out.h>, and update the few userland binaries which really
need these defines (i.e. boot-related tools for old architectures) to
explicitly include <a.out.h> when needed.

"Fine" deraadt@

include/a.out.h

@@ -1,4 +1,4 @@
-/*	$OpenBSD: a.out.h,v 1.3 2003/06/02 19:34:12 millert Exp $	*/
+/*	$OpenBSD: a.out.h,v 1.4 2024/10/16 18:47:48 miod Exp $	*/
 /*	$NetBSD: a.out.h,v 1.15 1994/10/26 00:55:42 cgd Exp $	*/
 
 /*-
@@ -36,6 +36,118 @@
 #ifndef	_AOUT_H_
 #define	_AOUT_H_
 
+/*
+ * Legacy a.out structures and defines.
+ */
+
+/*
+ * Header prepended to each a.out file.
+ * only manipulate the a_midmag field via the
+ * N_SETMAGIC/N_GET{MAGIC,MID,FLAG} macros below.
+ */
+struct exec {
+	u_int32_t	a_midmag;	/* htonl(flags<<26|mid<<16|magic) */
+	u_int32_t	a_text;		/* text segment size */
+	u_int32_t	a_data;		/* initialized data size */
+	u_int32_t	a_bss;		/* uninitialized data size */
+	u_int32_t	a_syms;		/* symbol table size */
+	u_int32_t	a_entry;	/* entry point */
+	u_int32_t	a_trsize;	/* text relocation size */
+	u_int32_t	a_drsize;	/* data relocation size */
+};
+
+/* a_magic */
+#define	OMAGIC		0407	/* old impure format */
+#define	NMAGIC		0410	/* read-only text */
+#define	ZMAGIC		0413	/* demand load format */
+#define	QMAGIC		0314	/* "compact" demand load format; deprecated */
+
+/*
+ * a_flags
+ */
+#define EX_DYNAMIC	0x20
+#define EX_PIC		0x10
+#define EX_DPMASK	0x30
+/*
+ * Interpretation of the (a_flags & EX_DPMASK) bits:
+ *
+ *	00		traditional executable or object file
+ *	01		object file contains PIC code (set by `as -k')
+ *	10		dynamic executable
+ *	11		position independent executable image
+ * 			(eg. a shared library)
+ *
+ */
+
+/*
+ * The a.out structure's a_midmag field is a network-byteorder encoding
+ * of this int
+ *	FFFFFFmmmmmmmmmmMMMMMMMMMMMMMMMM
+ * Where `F' is 6 bits of flag like EX_DYNAMIC,
+ *       `m' is 10 bits of machine-id like MID_I386, and
+ *       `M' is 16 bits worth of magic number, ie. ZMAGIC.
+ * The macros below will set/get the needed fields.
+ */
+#define	N_GETMAGIC(ex) \
+    ( (((ex).a_midmag)&0xffff0000) ? (ntohl(((ex).a_midmag))&0xffff) : ((ex).a_midmag))
+#define	N_GETMAGIC2(ex) \
+    ( (((ex).a_midmag)&0xffff0000) ? (ntohl(((ex).a_midmag))&0xffff) : \
+    (((ex).a_midmag) | 0x10000) )
+#define	N_GETMID(ex) \
+    ( (((ex).a_midmag)&0xffff0000) ? ((ntohl(((ex).a_midmag))>>16)&0x03ff) : MID_ZERO )
+#define	N_GETFLAG(ex) \
+    ( (((ex).a_midmag)&0xffff0000) ? ((ntohl(((ex).a_midmag))>>26)&0x3f) : 0 )
+#define	N_SETMAGIC(ex,mag,mid,flag) \
+    ( (ex).a_midmag = htonl( (((flag)&0x3f)<<26) | (((mid)&0x03ff)<<16) | \
+    (((mag)&0xffff)) ) )
+
+#define	N_ALIGN(ex,x) \
+	(N_GETMAGIC(ex) == ZMAGIC || N_GETMAGIC(ex) == QMAGIC ? \
+	((x) + __LDPGSZ - 1) & ~(__LDPGSZ - 1) : (x))
+
+/* Valid magic number check. */
+#define	N_BADMAG(ex) \
+	(N_GETMAGIC(ex) != NMAGIC && N_GETMAGIC(ex) != OMAGIC && \
+	N_GETMAGIC(ex) != ZMAGIC && N_GETMAGIC(ex) != QMAGIC)
+
+/* Address of the bottom of the text segment. */
+#define	N_TXTADDR(ex)	(N_GETMAGIC2(ex) == (ZMAGIC|0x10000) ? 0 : __LDPGSZ)
+
+/* Address of the bottom of the data segment. */
+#define	N_DATADDR(ex) \
+	(N_GETMAGIC(ex) == OMAGIC ? N_TXTADDR(ex) + (ex).a_text : \
+	(N_TXTADDR(ex) + (ex).a_text + __LDPGSZ - 1) & ~(__LDPGSZ - 1))
+
+/* Address of the bottom of the bss segment. */
+#define	N_BSSADDR(ex) \
+	(N_DATADDR(ex) + (ex).a_data)
+
+/* Text segment offset. */
+#define	N_TXTOFF(ex) \
+	( N_GETMAGIC2(ex)==ZMAGIC || N_GETMAGIC2(ex)==(QMAGIC|0x10000) ? \
+	0 : (N_GETMAGIC2(ex)==(ZMAGIC|0x10000) ? __LDPGSZ : \
+	sizeof(struct exec)) )
+
+/* Data segment offset. */
+#define	N_DATOFF(ex) \
+	N_ALIGN(ex, N_TXTOFF(ex) + (ex).a_text)
+
+/* Text relocation table offset. */
+#define	N_TRELOFF(ex) \
+	(N_DATOFF(ex) + (ex).a_data)
+
+/* Data relocation table offset. */
+#define	N_DRELOFF(ex) \
+	(N_TRELOFF(ex) + (ex).a_trsize)
+
+/* Symbol table offset. */
+#define	N_SYMOFF(ex) \
+	(N_DRELOFF(ex) + (ex).a_drsize)
+
+/* String table offset. */
+#define	N_STROFF(ex) \
+	(N_SYMOFF(ex) + (ex).a_syms)
+
 #include <sys/exec.h>
 
 #define	_AOUT_INCLUDE_