include/bout.h

   1 /*
   2  * This file is a modified version of 'a.out.h'.  It is to be used in all
   3  * GNU tools modified to support the i80960 (or tools that operate on
   4  * object files created by such tools).
   5  *
   6  * All i80960 development is done in a CROSS-DEVELOPMENT environment.  I.e.,
   7  * object code is generated on, and executed under the direction of a symbolic
   8  * debugger running on, a host system.  We do not want to be subject to the
   9  * vagaries of which host it is or whether it supports COFF or a.out format,
  10  * or anything else.  We DO want to:
  11  *
  12  *      o always generate the same format object files, regardless of host.
  13  *
  14  *      o have an 'a.out' header that we can modify for our own purposes
  15  *        (the 80960 is typically an embedded processor and may require
  16  *        enhanced linker support that the normal a.out.h header can't
  17  *        accommodate).
  18  *
  19  * As for byte-ordering, the following rules apply:
  20  *
  21  *      o Text and data that is actually downloaded to the target is always
  22  *        in i80960 (little-endian) order.
  23  *
  24  *      o All other numbers (in the header, symbols, relocation directives)
  25  *        are in host byte-order:  object files CANNOT be lifted from a
  26  *        little-end host and used on a big-endian (or vice versa) without
  27  *        modification.
  28  * ==> THIS IS NO LONGER TRUE USING BFD.  WE CAN GENERATE ANY BYTE ORDER
  29  *     FOR THE HEADER, AND READ ANY BYTE ORDER.  PREFERENCE WOULD BE TO
  30  *     USE LITTLE-ENDIAN BYTE ORDER THROUGHOUT, REGARDLESS OF HOST.  <==
  31  *
  32  *      o The downloader ('comm960') takes care to generate a pseudo-header
  33  *        with correct (i80960) byte-ordering before shipping text and data
  34  *        off to the NINDY monitor in the target systems.  Symbols and
  35  *        relocation info are never sent to the target.
  36  */
  37
  38
  39 #define BMAGIC  0415
  40 /* We don't accept the following (see N_BADMAG macro).
  41  * They're just here so GNU code will compile.
  42  */
  43 #define OMAGIC  0407            /* old impure format */
  44 #define NMAGIC  0410            /* read-only text */
  45 #define ZMAGIC  0413            /* demand load format */
  46
  47 /* FILE HEADER
  48  *      All 'lengths' are given as a number of bytes.
  49  *      All 'alignments' are for relinkable files only;  an alignment of
  50  *              'n' indicates the corresponding segment must begin at an
  51  *              address that is a multiple of (2**n).
  52  */
  53 struct exec {
  54         /* Standard stuff */
  55         unsigned long a_magic;  /* Identifies this as a b.out file      */
  56         unsigned long a_text;   /* Length of text                       */
  57         unsigned long a_data;   /* Length of data                       */
  58         unsigned long a_bss;    /* Length of runtime uninitialized data area */
  59         unsigned long a_syms;   /* Length of symbol table               */
  60         unsigned long a_entry;  /* Runtime start address                */
  61         unsigned long a_trsize; /* Length of text relocation info       */
  62         unsigned long a_drsize; /* Length of data relocation info       */
  63
  64         /* Added for i960 */
  65         unsigned long a_tload;  /* Text runtime load address            */
  66         unsigned long a_dload;  /* Data runtime load address            */
  67         unsigned char a_talign; /* Alignment of text segment            */
  68         unsigned char a_dalign; /* Alignment of data segment            */
  69         unsigned char a_balign; /* Alignment of bss segment             */
  70         unsigned char unused;   /* (Just to make struct size a multiple of 4) */
  71 };
  72
  73 #define N_BADMAG(x)     (((x).a_magic)!=BMAGIC)
  74 #define N_TXTOFF(x)     ( sizeof(struct exec) )
  75 #define N_DATOFF(x)     ( N_TXTOFF(x) + (x).a_text )
  76 #define N_TROFF(x)      ( N_DATOFF(x) + (x).a_data )
  77 #define N_DROFF(x)      ( N_TROFF(x) + (x).a_trsize )
  78 #define N_SYMOFF(x)     ( N_DROFF(x) + (x).a_drsize )
  79 #define N_STROFF(x)     ( N_SYMOFF(x) + (x).a_syms )
  80
  81 /* A single entry in the symbol table
  82  */
  83 struct nlist {
  84         union {
  85                 char    *n_name;
  86                 struct nlist *n_next;
  87                 long    n_strx;         /* Index into string table      */
  88         } n_un;
  89         unsigned char n_type;   /* See below                            */
  90         char    n_other;        /* Used in i80960 support -- see below  */
  91         short   n_desc;
  92         unsigned long n_value;
  93 };
  94
  95
  96 /* Legal values of n_type
  97  */
  98 #define N_UNDF  0       /* Undefined symbol     */
  99 #define N_ABS   2       /* Absolute symbol      */
 100 #define N_TEXT  4       /* Text symbol          */
 101 #define N_DATA  6       /* Data symbol          */
 102 #define N_BSS   8       /* BSS symbol           */
 103 #define N_FN    31      /* Filename symbol      */
 104
 105 #define N_EXT   1       /* External symbol (OR'd in with one of above)  */
 106 #define N_TYPE  036     /* Mask for all the type bits                   */
 107 #define N_STAB  0340    /* Mask for all bits used for SDB entries       */
 108
 109 /* MEANING OF 'n_other'
 110  *
 111  * If non-zero, the 'n_other' fields indicates either a leaf procedure or
 112  * a system procedure, as follows:
 113  *
 114  *      1 <= n_other <= 32 :
 115  *              The symbol is the entry point to a system procedure.
 116  *              'n_value' is the address of the entry, as for any other
 117  *              procedure.  The system procedure number (which can be used in
 118  *              a 'calls' instruction) is (n_other-1).  These entries come from
 119  *              '.sysproc' directives.
 120  *
 121  *      n_other == N_CALLNAME
 122  *              the symbol is the 'call' entry point to a leaf procedure.
 123  *              The *next* symbol in the symbol table must be the corresponding
 124  *              'bal' entry point to the procedure (see following).  These
 125  *              entries come from '.leafproc' directives in which two different
 126  *              symbols are specified (the first one is represented here).
 127  *
 128  *
 129  *      n_other == N_BALNAME
 130  *              the symbol is the 'bal' entry point to a leaf procedure.
 131  *              These entries result from '.leafproc' directives in which only
 132  *              one symbol is specified, or in which the same symbol is
 133  *              specified twice.
 134  *
 135  * Note that an N_CALLNAME entry *must* have a corresponding N_BALNAME entry,
 136  * but not every N_BALNAME entry must have an N_CALLNAME entry.
 137  */
 138 #define N_CALLNAME      (-1)
 139 #define N_BALNAME       (-2)
 140 #define IS_CALLNAME(x)  (N_CALLNAME == (int)(x))
 141 #define IS_BALNAME(x)   (N_BALNAME == (int)(x))
 142 #define IS_OTHER(x)     ((x)>0 && (x) <=32)
 143
 144 struct relocation_info {
 145         int      r_address;     /* File address of item to be relocated */
 146         unsigned
 147                 r_symbolnum:24,/* Index of symbol on which relocation is based,
 148                                 *       if r_extern is set.  Otherwise set to
 149                                 *       either N_TEXT, N_DATA, or N_BSS to
 150                                 *       indicate section on which relocation is
 151                                 *       based.
 152                                 */
 153                 r_pcrel:1,      /* 1 => relocate PC-relative; else absolute
 154                                  *      On i960, pc-relative implies 24-bit
 155                                  *      address, absolute implies 32-bit.
 156                                  */
 157                 r_length:2,     /* Number of bytes to relocate:
 158                                  *      0 => 1 byte
 159                                  *      1 => 2 bytes
 160                                  *      2 => 4 bytes -- only value used for i960
 161                                  */
 162                 r_extern:1,
 163                 r_bsr:1,        /* Something for the GNU NS32K assembler */
 164                 r_disp:1,       /* Something for the GNU NS32K assembler */
 165                 r_callj:1,      /* 1 if relocation target is an i960 'callj' */
 166                 nuthin:1;       /* Unused                               */
 167 };