source: trunk/libs/newlib/src/include/aout/sun4.h @ 503

Last change on this file since 503 was 444, checked in by satin@…, 6 years ago

add newlib,libalmos-mkh, restructure shared_syscalls.h and mini-libc

File size: 9.8 KB
Line 
1/* SPARC-specific values for a.out files
2
3   Copyright 2001, 2009, 2010 Free Software Foundation, Inc.
4
5   This program is free software; you can redistribute it and/or modify
6   it under the terms of the GNU General Public License as published by
7   the Free Software Foundation; either version 3 of the License, or
8   (at your option) any later version.
9   
10   This program is distributed in the hope that it will be useful,
11   but WITHOUT ANY WARRANTY; without even the implied warranty of
12   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
13   GNU General Public License for more details.
14   
15   You should have received a copy of the GNU General Public License
16   along with this program; if not, write to the Free Software
17   Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston,
18   MA 02110-1301, USA.  */
19
20/* Some systems, e.g., AIX, may have defined this in header files already
21   included.  */
22#undef  TARGET_PAGE_SIZE
23#define TARGET_PAGE_SIZE        0x2000          /* 8K.  aka NBPG in <sys/param.h> */
24/* Note that some SPARCs have 4K pages, some 8K, some others.  */
25
26#define SEG_SIZE_SPARC  TARGET_PAGE_SIZE
27#define SEG_SIZE_SUN3   0x20000         /* Resolution of r/w protection hw */
28
29#define TEXT_START_ADDR TARGET_PAGE_SIZE        /* Location 0 is not accessible */
30#define N_HEADER_IN_TEXT(x) 1
31
32/* Non-default definitions of the accessor macros... */
33
34/* Segment size varies on Sun-3 versus Sun-4.  */
35
36#define N_SEGSIZE(x)    (N_MACHTYPE(x) == M_SPARC?      SEG_SIZE_SPARC: \
37                         N_MACHTYPE(x) == M_68020?      SEG_SIZE_SUN3:  \
38                        /* Guess? */                    TARGET_PAGE_SIZE)
39
40/* Virtual Address of text segment from the a.out file.  For OMAGIC,
41   (almost always "unlinked .o's" these days), should be zero.
42   Sun added a kludge so that shared libraries linked ZMAGIC get
43   an address of zero if a_entry (!!!) is lower than the otherwise
44   expected text address.  These kludges have gotta go!
45   For linked files, should reflect reality if we know it.  */
46
47#define N_SHARED_LIB(x) ((x).a_entry < TEXT_START_ADDR \
48                         && (x).a_text >= EXEC_BYTES_SIZE)
49
50/* This differs from the version in aout64.h (which we override by defining
51   it here) only for NMAGIC (we return TEXT_START_ADDR+EXEC_BYTES_SIZE;
52   they return 0).  */
53
54#define N_TXTADDR(x) \
55    (N_MAGIC(x)==OMAGIC? 0 \
56     : (N_MAGIC(x) == ZMAGIC && (x).a_entry < TEXT_START_ADDR)? 0 \
57     : TEXT_START_ADDR+EXEC_BYTES_SIZE)
58
59/* When a file is linked against a shared library on SunOS 4, the
60   dynamic bit in the exec header is set, and the first symbol in the
61   symbol table is __DYNAMIC.  Its value is the address of the
62   following structure.  */
63
64struct external_sun4_dynamic
65{
66  /* The version number of the structure.  SunOS 4.1.x creates files
67     with version number 3, which is what this structure is based on.
68     According to gdb, version 2 is similar.  I believe that version 2
69     used a different type of procedure linkage table, and there may
70     have been other differences.  */
71  bfd_byte ld_version[4];
72  /* The virtual address of a 28 byte structure used in debugging.
73     The contents are filled in at run time by ld.so.  */
74  bfd_byte ldd[4];
75  /* The virtual address of another structure with information about
76     how to relocate the executable at run time.  */
77  bfd_byte ld[4];
78};
79
80/* The size of the debugging structure pointed to by the debugger
81   field of __DYNAMIC.  */
82#define EXTERNAL_SUN4_DYNAMIC_DEBUGGER_SIZE (24)
83
84/* The structure pointed to by the linker field of __DYNAMIC.  As far
85   as I can tell, most of the addresses in this structure are offsets
86   within the file, but some are actually virtual addresses.  */
87
88struct internal_sun4_dynamic_link
89{
90  /* Linked list of loaded objects.  This is filled in at runtime by
91     ld.so and probably by dlopen.  */
92  unsigned long ld_loaded;
93
94  /* The address of the list of names of shared objects which must be
95     included at runtime.  Each entry in the list is 16 bytes: the 4
96     byte address of the string naming the object (e.g., for -lc this
97     is "c"); 4 bytes of flags--the high bit is whether to search for
98     the object using the library path; the 2 byte major version
99     number; the 2 byte minor version number; the 4 byte address of
100     the next entry in the list (zero if this is the last entry).  The
101     version numbers seem to only be non-zero when doing library
102     searching.  */
103  unsigned long ld_need;
104
105  /* The address of the path to search for the shared objects which
106     must be included.  This points to a string in PATH format which
107     is generated from the -L arguments to the linker.  According to
108     the man page, ld.so implicitly adds ${LD_LIBRARY_PATH} to the
109     beginning of this string and /lib:/usr/lib:/usr/local/lib to the
110     end.  The string is terminated by a null byte.  This field is
111     zero if there is no additional path.  */
112  unsigned long ld_rules;
113
114  /* The address of the global offset table.  This appears to be a
115     virtual address, not a file offset.  The first entry in the
116     global offset table seems to be the virtual address of the
117     sun4_dynamic structure (the same value as the __DYNAMIC symbol).
118     The global offset table is used for PIC code to hold the
119     addresses of variables.  A dynamically linked file which does not
120     itself contain PIC code has a four byte global offset table.  */
121  unsigned long ld_got;
122
123  /* The address of the procedure linkage table.  This appears to be a
124     virtual address, not a file offset.
125
126     On a SPARC, the table is composed of 12 byte entries, each of
127     which consists of three instructions.  The first entry is
128         sethi %hi(0),%g1
129         jmp %g1
130         nop
131     These instructions are changed by ld.so into a jump directly into
132     ld.so itself.  Each subsequent entry is
133         save %sp, -96, %sp
134         call <address of first entry in procedure linkage table>
135         <reloc_number | 0x01000000>
136     The reloc_number is the number of the reloc to use to resolve
137     this entry.  The reloc will be a JMP_SLOT reloc against some
138     symbol that is not defined in this object file but should be
139     defined in a shared object (if it is not, ld.so will report a
140     runtime error and exit).  The constant 0x010000000 turns the
141     reloc number into a sethi of %g0, which does nothing since %g0 is
142     hardwired to zero.
143
144     When one of these entries is executed, it winds up calling into
145     ld.so.  ld.so looks at the reloc number, available via the return
146     address, to determine which entry this is.  It then looks at the
147     reloc and patches up the entry in the table into a sethi and jmp
148     to the real address followed by a nop.  This means that the reloc
149     lookup only has to happen once, and it also means that the
150     relocation only needs to be done if the function is actually
151     called.  The relocation is expensive because ld.so must look up
152     the symbol by name.
153
154     The size of the procedure linkage table is given by the ld_plt_sz
155     field.  */
156  unsigned long ld_plt;
157
158  /* The address of the relocs.  These are in the same format as
159     ordinary relocs.  Symbol index numbers refer to the symbols
160     pointed to by ld_stab.  I think the only way to determine the
161     number of relocs is to assume that all the bytes from ld_rel to
162     ld_hash contain reloc entries.  */
163  unsigned long ld_rel;
164
165  /* The address of a hash table of symbols.  The hash table has
166     roughly the same number of entries as there are dynamic symbols;
167     I think the only way to get the exact size is to assume that
168     every byte from ld_hash to ld_stab is devoted to the hash table.
169
170     Each entry in the hash table is eight bytes.  The first four
171     bytes are a symbol index into the dynamic symbols.  The second
172     four bytes are the index of the next hash table entry in the
173     bucket.  The ld_buckets field gives the number of buckets, say B.
174     The first B entries in the hash table each start a bucket which
175     is chained through the second four bytes of each entry.  A value
176     of zero ends the chain.
177
178     The hash function is simply
179         h = 0;
180         while (*string != '\0')
181           h = (h << 1) + *string++;
182         h &= 0x7fffffff;
183
184     To look up a symbol, compute the hash value of the name.  Take
185     the modulos of hash value and the number of buckets.  Start at
186     that entry in the hash table.  See if the symbol (from the first
187     four bytes of the hash table entry) has the name you are looking
188     for.  If not, use the chain field (the second four bytes of the
189     hash table entry) to move on to the next entry in this bucket.
190     If the chain field is zero you have reached the end of the
191     bucket, and the symbol is not in the hash table.  */ 
192  unsigned long ld_hash;
193
194  /* The address of the symbol table.  This is a list of
195     external_nlist structures.  The string indices are relative to
196     the ld_symbols field.  I think the only way to determine the
197     number of symbols is to assume that all the bytes between ld_stab
198     and ld_symbols are external_nlist structures.  */
199  unsigned long ld_stab;
200
201  /* I don't know what this is for.  It seems to always be zero.  */
202  unsigned long ld_stab_hash;
203
204  /* The number of buckets in the hash table.  */
205  unsigned long ld_buckets;
206
207  /* The address of the symbol string table.  The first string in this
208     string table need not be the empty string.  */
209  unsigned long ld_symbols;
210
211  /* The size in bytes of the symbol string table.  */
212  unsigned long ld_symb_size;
213
214  /* The size in bytes of the text segment.  */
215  unsigned long ld_text;
216
217  /* The size in bytes of the procedure linkage table.  */
218  unsigned long ld_plt_sz;
219};
220
221/* The external form of the structure.  */
222
223struct external_sun4_dynamic_link
224{
225  bfd_byte ld_loaded[4];
226  bfd_byte ld_need[4];
227  bfd_byte ld_rules[4];
228  bfd_byte ld_got[4];
229  bfd_byte ld_plt[4];
230  bfd_byte ld_rel[4];
231  bfd_byte ld_hash[4];
232  bfd_byte ld_stab[4];
233  bfd_byte ld_stab_hash[4];
234  bfd_byte ld_buckets[4];
235  bfd_byte ld_symbols[4];
236  bfd_byte ld_symb_size[4];
237  bfd_byte ld_text[4];
238  bfd_byte ld_plt_sz[4];
239};
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