lib/libexec/exec_aout.c

   1 #define _SYSTEM 1
   2
   3 #include <minix/type.h>
   4 #include <minix/const.h>
   5 #include <a.out.h>
   6 #include <assert.h>
   7 #include <unistd.h>
   8 #include <errno.h>
   9 #include <libexec.h>
  10
  11 int read_header_aout(
  12   const char *exec_hdr,         /* executable header */
  13   size_t exec_len,              /* executable file size */
  14   int *sep_id,                  /* true iff sep I&D */
  15   vir_bytes *text_bytes,        /* place to return text size */
  16   vir_bytes *data_bytes,        /* place to return initialized data size */
  17   vir_bytes *bss_bytes,         /* place to return bss size */
  18   phys_bytes *tot_bytes,        /* place to return total size */
  19   vir_bytes *pc,                /* program entry point (initial PC) */
  20   int *hdrlenp
  21 )
  22 {
  23 /* Read the header and extract the text, data, bss and total sizes from it. */
  24   struct exec *hdr;             /* a.out header is read in here */
  25
  26   /* Read the header and check the magic number.  The standard MINIX header
  27    * is defined in <a.out.h>.  It consists of 8 chars followed by 6 longs.
  28    * Then come 4 more longs that are not used here.
  29    *    Byte 0: magic number 0x01
  30    *    Byte 1: magic number 0x03
  31    *    Byte 2: normal = 0x10 (not checked, 0 is OK), separate I/D = 0x20
  32    *    Byte 3: CPU type, Intel 16 bit = 0x04, Intel 32 bit = 0x10,
  33    *            Motorola = 0x0B, Sun SPARC = 0x17
  34    *    Byte 4: Header length = 0x20
  35    *    Bytes 5-7 are not used.
  36    *
  37    *    Now come the 6 longs
  38    *    Bytes  8-11: size of text segments in bytes
  39    *    Bytes 12-15: size of initialized data segment in bytes
  40    *    Bytes 16-19: size of bss in bytes
  41    *    Bytes 20-23: program entry point
  42    *    Bytes 24-27: total memory allocated to program (text, data + stack)
  43    *    Bytes 28-31: size of symbol table in bytes
  44    * The longs are represented in a machine dependent order,
  45    * little-endian on the 8088, big-endian on the 68000.
  46    * The header is followed directly by the text and data segments, and the
  47    * symbol table (if any). The sizes are given in the header. Only the
  48    * text and data segments are copied into memory by exec. The header is
  49    * used here only. The symbol table is for the benefit of a debugger and
  50    * is ignored here.
  51    */
  52
  53   assert(exec_hdr != NULL);
  54
  55   hdr = (struct exec *)exec_hdr;
  56   if (exec_len < A_MINHDR) return(ENOEXEC);
  57
  58   /* Check magic number, cpu type, and flags. */
  59   if (BADMAG(*hdr)) return(ENOEXEC);
  60 #if defined(__i386__)
  61   if (hdr->a_cpu != A_I80386) return(ENOEXEC);
  62 #endif
  63   if ((hdr->a_flags & ~(A_NSYM | A_EXEC | A_SEP)) != 0) return(ENOEXEC);
  64
  65   *sep_id = !!(hdr->a_flags & A_SEP);       /* separate I & D or not */
  66
  67   /* Get text and data sizes. */
  68   *text_bytes = (vir_bytes) hdr->a_text;        /* text size in bytes */
  69   *data_bytes = (vir_bytes) hdr->a_data;        /* data size in bytes */
  70   *bss_bytes  = (vir_bytes) hdr->a_bss; /* bss size in bytes */
  71   *tot_bytes  = hdr->a_total;           /* total bytes to allocate for prog */
  72   if (*tot_bytes == 0) return(ENOEXEC);
  73
  74   if (!*sep_id) {
  75         /* If I & D space is not separated, it is all considered data. Text=0*/
  76         *data_bytes += *text_bytes;
  77         *text_bytes = 0;
  78   }
  79   *pc = hdr->a_entry;   /* initial address to start execution */
  80   *hdrlenp = hdr->a_hdrlen & BYTE;              /* header length */
  81
  82   return(OK);
  83 }