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authorJohn Gilmore <gnu@cygnus>1991-04-25 04:20:11 +0000
committerJohn Gilmore <gnu@cygnus>1991-04-25 04:20:11 +0000
commita07cc61341225966fd714e8715aeca6c558b5b8e (patch)
tree4619bd0c087f07b5b8cd155e1bf34ecdce2dbf0e /include/bout.h
parenta6ac0c5998db0fb3b89c11800507b7307dba692b (diff)
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Initial revision
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+/* $Id$
+ *
+ * This file is a modified version of 'a.out.h'. It is to be used in all
+ * GNU tools modified to support the i80960 (or tools that operate on
+ * object files created by such tools).
+ *
+ * All i80960 development is done in a CROSS-DEVELOPMENT environment. I.e.,
+ * object code is generated on, and executed under the direction of a symbolic
+ * debugger running on, a host system. We do not want to be subject to the
+ * vagaries of which host it is or whether it supports COFF or a.out format,
+ * or anything else. We DO want to:
+ *
+ * o always generate the same format object files, regardless of host.
+ *
+ * o have an 'a.out' header that we can modify for our own purposes
+ * (the 80960 is typically an embedded processor and may require
+ * enhanced linker support that the normal a.out.h header can't
+ * accommodate).
+ *
+ * As for byte-ordering, the following rules apply:
+ *
+ * o Text and data that is actually downloaded to the target is always
+ * in i80960 (little-endian) order.
+ *
+ * o All other numbers (in the header, symbols, relocation directives)
+ * are in host byte-order: object files CANNOT be lifted from a
+ * little-end host and used on a big-endian (or vice versa) without
+ * modification.
+ * ==> THIS IS NO LONGER TRUE USING BFD. WE CAN GENERATE ANY BYTE ORDER
+ * FOR THE HEADER, AND READ ANY BYTE ORDER. PREFERENCE WOULD BE TO
+ * USE LITTLE-ENDIAN BYTE ORDER THROUGHOUT, REGARDLESS OF HOST. <==
+ *
+ * o The downloader ('comm960') takes care to generate a pseudo-header
+ * with correct (i80960) byte-ordering before shipping text and data
+ * off to the NINDY monitor in the target systems. Symbols and
+ * relocation info are never sent to the target.
+ */
+
+
+#define BMAGIC 0415
+/* We don't accept the following (see N_BADMAG macro).
+ * They're just here so GNU code will compile.
+ */
+#define OMAGIC 0407 /* old impure format */
+#define NMAGIC 0410 /* read-only text */
+#define ZMAGIC 0413 /* demand load format */
+
+/* FILE HEADER
+ * All 'lengths' are given as a number of bytes.
+ * All 'alignments' are for relinkable files only; an alignment of
+ * 'n' indicates the corresponding segment must begin at an
+ * address that is a multiple of (2**n).
+ */
+struct exec {
+ /* Standard stuff */
+ unsigned long a_magic; /* Identifies this as a b.out file */
+ unsigned long a_text; /* Length of text */
+ unsigned long a_data; /* Length of data */
+ unsigned long a_bss; /* Length of runtime uninitialized data area */
+ unsigned long a_syms; /* Length of symbol table */
+ unsigned long a_entry; /* Runtime start address */
+ unsigned long a_trsize; /* Length of text relocation info */
+ unsigned long a_drsize; /* Length of data relocation info */
+
+ /* Added for i960 */
+ unsigned long a_tload; /* Text runtime load address */
+ unsigned long a_dload; /* Data runtime load address */
+ unsigned char a_talign; /* Alignment of text segment */
+ unsigned char a_dalign; /* Alignment of data segment */
+ unsigned char a_balign; /* Alignment of bss segment */
+ unsigned char unused; /* (Just to make struct size a multiple of 4) */
+};
+
+#define N_BADMAG(x) (((x).a_magic)!=BMAGIC)
+#define N_TXTOFF(x) ( sizeof(struct exec) )
+#define N_DATOFF(x) ( N_TXTOFF(x) + (x).a_text )
+#define N_TROFF(x) ( N_DATOFF(x) + (x).a_data )
+#define N_DROFF(x) ( N_TROFF(x) + (x).a_trsize )
+#define N_SYMOFF(x) ( N_DROFF(x) + (x).a_drsize )
+#define N_STROFF(x) ( N_SYMOFF(x) + (x).a_syms )
+
+/* A single entry in the symbol table
+ */
+struct nlist {
+ union {
+ char *n_name;
+ struct nlist *n_next;
+ long n_strx; /* Index into string table */
+ } n_un;
+ unsigned char n_type; /* See below */
+ char n_other; /* Used in i80960 support -- see below */
+ short n_desc;
+ unsigned long n_value;
+};
+
+
+/* Legal values of n_type
+ */
+#define N_UNDF 0 /* Undefined symbol */
+#define N_ABS 2 /* Absolute symbol */
+#define N_TEXT 4 /* Text symbol */
+#define N_DATA 6 /* Data symbol */
+#define N_BSS 8 /* BSS symbol */
+#define N_FN 31 /* Filename symbol */
+
+#define N_EXT 1 /* External symbol (OR'd in with one of above) */
+#define N_TYPE 036 /* Mask for all the type bits */
+#define N_STAB 0340 /* Mask for all bits used for SDB entries */
+
+/* MEANING OF 'n_other'
+ *
+ * If non-zero, the 'n_other' fields indicates either a leaf procedure or
+ * a system procedure, as follows:
+ *
+ * 1 <= n_other <= 32 :
+ * The symbol is the entry point to a system procedure.
+ * 'n_value' is the address of the entry, as for any other
+ * procedure. The system procedure number (which can be used in
+ * a 'calls' instruction) is (n_other-1). These entries come from
+ * '.sysproc' directives.
+ *
+ * n_other == N_CALLNAME
+ * the symbol is the 'call' entry point to a leaf procedure.
+ * The *next* symbol in the symbol table must be the corresponding
+ * 'bal' entry point to the procedure (see following). These
+ * entries come from '.leafproc' directives in which two different
+ * symbols are specified (the first one is represented here).
+ *
+ *
+ * n_other == N_BALNAME
+ * the symbol is the 'bal' entry point to a leaf procedure.
+ * These entries result from '.leafproc' directives in which only
+ * one symbol is specified, or in which the same symbol is
+ * specified twice.
+ *
+ * Note that an N_CALLNAME entry *must* have a corresponding N_BALNAME entry,
+ * but not every N_BALNAME entry must have an N_CALLNAME entry.
+ */
+#define N_CALLNAME (-1)
+#define N_BALNAME (-2)
+#define IS_CALLNAME(x) (N_CALLNAME == (int)(x))
+#define IS_BALNAME(x) (N_BALNAME == (int)(x))
+#define IS_OTHER(x) ((x)>0 && (x) <=32)
+
+struct relocation_info {
+ int r_address; /* File address of item to be relocated */
+ unsigned
+ r_symbolnum:24,/* Index of symbol on which relocation is based,
+ * if r_extern is set. Otherwise set to
+ * either N_TEXT, N_DATA, or N_BSS to
+ * indicate section on which relocation is
+ * based.
+ */
+ r_pcrel:1, /* 1 => relocate PC-relative; else absolute
+ * On i960, pc-relative implies 24-bit
+ * address, absolute implies 32-bit.
+ */
+ r_length:2, /* Number of bytes to relocate:
+ * 0 => 1 byte
+ * 1 => 2 bytes
+ * 2 => 4 bytes -- only value used for i960
+ */
+ r_extern:1,
+ r_bsr:1, /* Something for the GNU NS32K assembler */
+ r_disp:1, /* Something for the GNU NS32K assembler */
+ r_callj:1, /* 1 if relocation target is an i960 'callj' */
+ nuthin:1; /* Unused */
+};