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[/] [openrisc/] [trunk/] [gnu-old/] [binutils-2.18.50/] [include/] [aout/] [sun4.h] - Blame information for rev 156

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1 38 julius
/* SPARC-specific values for a.out files
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   Copyright 2001 Free Software Foundation, Inc.
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   This program is free software; you can redistribute it and/or modify
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   it under the terms of the GNU General Public License as published by
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   the Free Software Foundation; either version 2 of the License, or
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   (at your option) any later version.
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   This program is distributed in the hope that it will be useful,
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   but WITHOUT ANY WARRANTY; without even the implied warranty of
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   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
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   GNU General Public License for more details.
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   You should have received a copy of the GNU General Public License
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   along with this program; if not, write to the Free Software
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   Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston, MA 02110-1301, USA.  */
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/* Some systems, e.g., AIX, may have defined this in header files already
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   included.  */
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#undef  TARGET_PAGE_SIZE
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#define TARGET_PAGE_SIZE        0x2000          /* 8K.  aka NBPG in <sys/param.h> */
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/* Note that some SPARCs have 4K pages, some 8K, some others.  */
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#define SEG_SIZE_SPARC  TARGET_PAGE_SIZE
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#define SEG_SIZE_SUN3   0x20000         /* Resolution of r/w protection hw */
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#define TEXT_START_ADDR TARGET_PAGE_SIZE        /* Location 0 is not accessible */
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#define N_HEADER_IN_TEXT(x) 1
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/* Non-default definitions of the accessor macros... */
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/* Segment size varies on Sun-3 versus Sun-4.  */
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#define N_SEGSIZE(x)    (N_MACHTYPE(x) == M_SPARC?      SEG_SIZE_SPARC: \
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                         N_MACHTYPE(x) == M_68020?      SEG_SIZE_SUN3:  \
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                        /* Guess? */                    TARGET_PAGE_SIZE)
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/* Virtual Address of text segment from the a.out file.  For OMAGIC,
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   (almost always "unlinked .o's" these days), should be zero.
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   Sun added a kludge so that shared libraries linked ZMAGIC get
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   an address of zero if a_entry (!!!) is lower than the otherwise
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   expected text address.  These kludges have gotta go!
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   For linked files, should reflect reality if we know it.  */
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/* This differs from the version in aout64.h (which we override by defining
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   it here) only for NMAGIC (we return TEXT_START_ADDR+EXEC_BYTES_SIZE;
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   they return 0).  */
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#define N_TXTADDR(x) \
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    (N_MAGIC(x)==OMAGIC? 0 \
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     : (N_MAGIC(x) == ZMAGIC && (x).a_entry < TEXT_START_ADDR)? 0 \
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     : TEXT_START_ADDR+EXEC_BYTES_SIZE)
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/* When a file is linked against a shared library on SunOS 4, the
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   dynamic bit in the exec header is set, and the first symbol in the
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   symbol table is __DYNAMIC.  Its value is the address of the
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   following structure.  */
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struct external_sun4_dynamic
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{
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  /* The version number of the structure.  SunOS 4.1.x creates files
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     with version number 3, which is what this structure is based on.
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     According to gdb, version 2 is similar.  I believe that version 2
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     used a different type of procedure linkage table, and there may
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     have been other differences.  */
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  bfd_byte ld_version[4];
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  /* The virtual address of a 28 byte structure used in debugging.
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     The contents are filled in at run time by ld.so.  */
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  bfd_byte ldd[4];
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  /* The virtual address of another structure with information about
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     how to relocate the executable at run time.  */
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  bfd_byte ld[4];
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};
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/* The size of the debugging structure pointed to by the debugger
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   field of __DYNAMIC.  */
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#define EXTERNAL_SUN4_DYNAMIC_DEBUGGER_SIZE (24)
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/* The structure pointed to by the linker field of __DYNAMIC.  As far
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   as I can tell, most of the addresses in this structure are offsets
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   within the file, but some are actually virtual addresses.  */
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struct internal_sun4_dynamic_link
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{
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  /* Linked list of loaded objects.  This is filled in at runtime by
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     ld.so and probably by dlopen.  */
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  unsigned long ld_loaded;
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  /* The address of the list of names of shared objects which must be
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     included at runtime.  Each entry in the list is 16 bytes: the 4
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     byte address of the string naming the object (e.g., for -lc this
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     is "c"); 4 bytes of flags--the high bit is whether to search for
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     the object using the library path; the 2 byte major version
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     number; the 2 byte minor version number; the 4 byte address of
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     the next entry in the list (zero if this is the last entry).  The
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     version numbers seem to only be non-zero when doing library
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     searching.  */
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  unsigned long ld_need;
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  /* The address of the path to search for the shared objects which
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     must be included.  This points to a string in PATH format which
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     is generated from the -L arguments to the linker.  According to
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     the man page, ld.so implicitly adds ${LD_LIBRARY_PATH} to the
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     beginning of this string and /lib:/usr/lib:/usr/local/lib to the
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     end.  The string is terminated by a null byte.  This field is
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     zero if there is no additional path.  */
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  unsigned long ld_rules;
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  /* The address of the global offset table.  This appears to be a
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     virtual address, not a file offset.  The first entry in the
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     global offset table seems to be the virtual address of the
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     sun4_dynamic structure (the same value as the __DYNAMIC symbol).
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     The global offset table is used for PIC code to hold the
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     addresses of variables.  A dynamically linked file which does not
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     itself contain PIC code has a four byte global offset table.  */
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  unsigned long ld_got;
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  /* The address of the procedure linkage table.  This appears to be a
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     virtual address, not a file offset.
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     On a SPARC, the table is composed of 12 byte entries, each of
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     which consists of three instructions.  The first entry is
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         sethi %hi(0),%g1
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         jmp %g1
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         nop
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     These instructions are changed by ld.so into a jump directly into
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     ld.so itself.  Each subsequent entry is
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         save %sp, -96, %sp
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         call <address of first entry in procedure linkage table>
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         <reloc_number | 0x01000000>
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     The reloc_number is the number of the reloc to use to resolve
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     this entry.  The reloc will be a JMP_SLOT reloc against some
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     symbol that is not defined in this object file but should be
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     defined in a shared object (if it is not, ld.so will report a
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     runtime error and exit).  The constant 0x010000000 turns the
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     reloc number into a sethi of %g0, which does nothing since %g0 is
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     hardwired to zero.
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     When one of these entries is executed, it winds up calling into
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     ld.so.  ld.so looks at the reloc number, available via the return
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     address, to determine which entry this is.  It then looks at the
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     reloc and patches up the entry in the table into a sethi and jmp
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     to the real address followed by a nop.  This means that the reloc
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     lookup only has to happen once, and it also means that the
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     relocation only needs to be done if the function is actually
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     called.  The relocation is expensive because ld.so must look up
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     the symbol by name.
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     The size of the procedure linkage table is given by the ld_plt_sz
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     field.  */
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  unsigned long ld_plt;
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  /* The address of the relocs.  These are in the same format as
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     ordinary relocs.  Symbol index numbers refer to the symbols
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     pointed to by ld_stab.  I think the only way to determine the
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     number of relocs is to assume that all the bytes from ld_rel to
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     ld_hash contain reloc entries.  */
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  unsigned long ld_rel;
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  /* The address of a hash table of symbols.  The hash table has
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     roughly the same number of entries as there are dynamic symbols;
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     I think the only way to get the exact size is to assume that
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     every byte from ld_hash to ld_stab is devoted to the hash table.
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     Each entry in the hash table is eight bytes.  The first four
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     bytes are a symbol index into the dynamic symbols.  The second
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     four bytes are the index of the next hash table entry in the
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     bucket.  The ld_buckets field gives the number of buckets, say B.
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     The first B entries in the hash table each start a bucket which
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     is chained through the second four bytes of each entry.  A value
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     of zero ends the chain.
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     The hash function is simply
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         h = 0;
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         while (*string != '\0')
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           h = (h << 1) + *string++;
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         h &= 0x7fffffff;
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     To look up a symbol, compute the hash value of the name.  Take
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     the modulos of hash value and the number of buckets.  Start at
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     that entry in the hash table.  See if the symbol (from the first
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     four bytes of the hash table entry) has the name you are looking
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     for.  If not, use the chain field (the second four bytes of the
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     hash table entry) to move on to the next entry in this bucket.
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     If the chain field is zero you have reached the end of the
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     bucket, and the symbol is not in the hash table.  */
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  unsigned long ld_hash;
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  /* The address of the symbol table.  This is a list of
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     external_nlist structures.  The string indices are relative to
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     the ld_symbols field.  I think the only way to determine the
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     number of symbols is to assume that all the bytes between ld_stab
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     and ld_symbols are external_nlist structures.  */
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  unsigned long ld_stab;
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  /* I don't know what this is for.  It seems to always be zero.  */
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  unsigned long ld_stab_hash;
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  /* The number of buckets in the hash table.  */
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  unsigned long ld_buckets;
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  /* The address of the symbol string table.  The first string in this
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     string table need not be the empty string.  */
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  unsigned long ld_symbols;
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  /* The size in bytes of the symbol string table.  */
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  unsigned long ld_symb_size;
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  /* The size in bytes of the text segment.  */
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  unsigned long ld_text;
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  /* The size in bytes of the procedure linkage table.  */
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  unsigned long ld_plt_sz;
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};
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/* The external form of the structure.  */
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struct external_sun4_dynamic_link
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{
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  bfd_byte ld_loaded[4];
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  bfd_byte ld_need[4];
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  bfd_byte ld_rules[4];
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  bfd_byte ld_got[4];
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  bfd_byte ld_plt[4];
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  bfd_byte ld_rel[4];
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  bfd_byte ld_hash[4];
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  bfd_byte ld_stab[4];
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  bfd_byte ld_stab_hash[4];
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  bfd_byte ld_buckets[4];
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  bfd_byte ld_symbols[4];
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  bfd_byte ld_symb_size[4];
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  bfd_byte ld_text[4];
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  bfd_byte ld_plt_sz[4];
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};

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