* alpha.c, basic_blocks.c, basic_blocks.h, bb_exit_func.c,
[binutils.git] / include / aout / sun4.h
blob623afc13131f1bbd6c689e87238598c3c242c115
1 /* SPARC-specific values for a.out files
3 Copyright 2001 Free Software Foundation, Inc.
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 2 of the License, or
8 (at your option) any later version.
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.
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., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. */
19 /* Some systems, e.g., AIX, may have defined this in header files already
20 included. */
21 #undef TARGET_PAGE_SIZE
22 #define TARGET_PAGE_SIZE 0x2000 /* 8K. aka NBPG in <sys/param.h> */
23 /* Note that some SPARCs have 4K pages, some 8K, some others. */
25 #define SEG_SIZE_SPARC TARGET_PAGE_SIZE
26 #define SEG_SIZE_SUN3 0x20000 /* Resolution of r/w protection hw */
28 #define TEXT_START_ADDR TARGET_PAGE_SIZE /* Location 0 is not accessible */
29 #define N_HEADER_IN_TEXT(x) 1
31 /* Non-default definitions of the accessor macros... */
33 /* Segment size varies on Sun-3 versus Sun-4. */
35 #define N_SEGSIZE(x) (N_MACHTYPE(x) == M_SPARC? SEG_SIZE_SPARC: \
36 N_MACHTYPE(x) == M_68020? SEG_SIZE_SUN3: \
37 /* Guess? */ TARGET_PAGE_SIZE)
39 /* Virtual Address of text segment from the a.out file. For OMAGIC,
40 (almost always "unlinked .o's" these days), should be zero.
41 Sun added a kludge so that shared libraries linked ZMAGIC get
42 an address of zero if a_entry (!!!) is lower than the otherwise
43 expected text address. These kludges have gotta go!
44 For linked files, should reflect reality if we know it. */
46 /* This differs from the version in aout64.h (which we override by defining
47 it here) only for NMAGIC (we return TEXT_START_ADDR+EXEC_BYTES_SIZE;
48 they return 0). */
50 #define N_TXTADDR(x) \
51 (N_MAGIC(x)==OMAGIC? 0 \
52 : (N_MAGIC(x) == ZMAGIC && (x).a_entry < TEXT_START_ADDR)? 0 \
53 : TEXT_START_ADDR+EXEC_BYTES_SIZE)
55 /* When a file is linked against a shared library on SunOS 4, the
56 dynamic bit in the exec header is set, and the first symbol in the
57 symbol table is __DYNAMIC. Its value is the address of the
58 following structure. */
60 struct external_sun4_dynamic
62 /* The version number of the structure. SunOS 4.1.x creates files
63 with version number 3, which is what this structure is based on.
64 According to gdb, version 2 is similar. I believe that version 2
65 used a different type of procedure linkage table, and there may
66 have been other differences. */
67 bfd_byte ld_version[4];
68 /* The virtual address of a 28 byte structure used in debugging.
69 The contents are filled in at run time by ld.so. */
70 bfd_byte ldd[4];
71 /* The virtual address of another structure with information about
72 how to relocate the executable at run time. */
73 bfd_byte ld[4];
76 /* The size of the debugging structure pointed to by the debugger
77 field of __DYNAMIC. */
78 #define EXTERNAL_SUN4_DYNAMIC_DEBUGGER_SIZE (24)
80 /* The structure pointed to by the linker field of __DYNAMIC. As far
81 as I can tell, most of the addresses in this structure are offsets
82 within the file, but some are actually virtual addresses. */
84 struct internal_sun4_dynamic_link
86 /* Linked list of loaded objects. This is filled in at runtime by
87 ld.so and probably by dlopen. */
88 unsigned long ld_loaded;
90 /* The address of the list of names of shared objects which must be
91 included at runtime. Each entry in the list is 16 bytes: the 4
92 byte address of the string naming the object (e.g., for -lc this
93 is "c"); 4 bytes of flags--the high bit is whether to search for
94 the object using the library path; the 2 byte major version
95 number; the 2 byte minor version number; the 4 byte address of
96 the next entry in the list (zero if this is the last entry). The
97 version numbers seem to only be non-zero when doing library
98 searching. */
99 unsigned long ld_need;
101 /* The address of the path to search for the shared objects which
102 must be included. This points to a string in PATH format which
103 is generated from the -L arguments to the linker. According to
104 the man page, ld.so implicitly adds ${LD_LIBRARY_PATH} to the
105 beginning of this string and /lib:/usr/lib:/usr/local/lib to the
106 end. The string is terminated by a null byte. This field is
107 zero if there is no additional path. */
108 unsigned long ld_rules;
110 /* The address of the global offset table. This appears to be a
111 virtual address, not a file offset. The first entry in the
112 global offset table seems to be the virtual address of the
113 sun4_dynamic structure (the same value as the __DYNAMIC symbol).
114 The global offset table is used for PIC code to hold the
115 addresses of variables. A dynamically linked file which does not
116 itself contain PIC code has a four byte global offset table. */
117 unsigned long ld_got;
119 /* The address of the procedure linkage table. This appears to be a
120 virtual address, not a file offset.
122 On a SPARC, the table is composed of 12 byte entries, each of
123 which consists of three instructions. The first entry is
124 sethi %hi(0),%g1
125 jmp %g1
127 These instructions are changed by ld.so into a jump directly into
128 ld.so itself. Each subsequent entry is
129 save %sp, -96, %sp
130 call <address of first entry in procedure linkage table>
131 <reloc_number | 0x01000000>
132 The reloc_number is the number of the reloc to use to resolve
133 this entry. The reloc will be a JMP_SLOT reloc against some
134 symbol that is not defined in this object file but should be
135 defined in a shared object (if it is not, ld.so will report a
136 runtime error and exit). The constant 0x010000000 turns the
137 reloc number into a sethi of %g0, which does nothing since %g0 is
138 hardwired to zero.
140 When one of these entries is executed, it winds up calling into
141 ld.so. ld.so looks at the reloc number, available via the return
142 address, to determine which entry this is. It then looks at the
143 reloc and patches up the entry in the table into a sethi and jmp
144 to the real address followed by a nop. This means that the reloc
145 lookup only has to happen once, and it also means that the
146 relocation only needs to be done if the function is actually
147 called. The relocation is expensive because ld.so must look up
148 the symbol by name.
150 The size of the procedure linkage table is given by the ld_plt_sz
151 field. */
152 unsigned long ld_plt;
154 /* The address of the relocs. These are in the same format as
155 ordinary relocs. Symbol index numbers refer to the symbols
156 pointed to by ld_stab. I think the only way to determine the
157 number of relocs is to assume that all the bytes from ld_rel to
158 ld_hash contain reloc entries. */
159 unsigned long ld_rel;
161 /* The address of a hash table of symbols. The hash table has
162 roughly the same number of entries as there are dynamic symbols;
163 I think the only way to get the exact size is to assume that
164 every byte from ld_hash to ld_stab is devoted to the hash table.
166 Each entry in the hash table is eight bytes. The first four
167 bytes are a symbol index into the dynamic symbols. The second
168 four bytes are the index of the next hash table entry in the
169 bucket. The ld_buckets field gives the number of buckets, say B.
170 The first B entries in the hash table each start a bucket which
171 is chained through the second four bytes of each entry. A value
172 of zero ends the chain.
174 The hash function is simply
175 h = 0;
176 while (*string != '\0')
177 h = (h << 1) + *string++;
178 h &= 0x7fffffff;
180 To look up a symbol, compute the hash value of the name. Take
181 the modulos of hash value and the number of buckets. Start at
182 that entry in the hash table. See if the symbol (from the first
183 four bytes of the hash table entry) has the name you are looking
184 for. If not, use the chain field (the second four bytes of the
185 hash table entry) to move on to the next entry in this bucket.
186 If the chain field is zero you have reached the end of the
187 bucket, and the symbol is not in the hash table. */
188 unsigned long ld_hash;
190 /* The address of the symbol table. This is a list of
191 external_nlist structures. The string indices are relative to
192 the ld_symbols field. I think the only way to determine the
193 number of symbols is to assume that all the bytes between ld_stab
194 and ld_symbols are external_nlist structures. */
195 unsigned long ld_stab;
197 /* I don't know what this is for. It seems to always be zero. */
198 unsigned long ld_stab_hash;
200 /* The number of buckets in the hash table. */
201 unsigned long ld_buckets;
203 /* The address of the symbol string table. The first string in this
204 string table need not be the empty string. */
205 unsigned long ld_symbols;
207 /* The size in bytes of the symbol string table. */
208 unsigned long ld_symb_size;
210 /* The size in bytes of the text segment. */
211 unsigned long ld_text;
213 /* The size in bytes of the procedure linkage table. */
214 unsigned long ld_plt_sz;
217 /* The external form of the structure. */
219 struct external_sun4_dynamic_link
221 bfd_byte ld_loaded[4];
222 bfd_byte ld_need[4];
223 bfd_byte ld_rules[4];
224 bfd_byte ld_got[4];
225 bfd_byte ld_plt[4];
226 bfd_byte ld_rel[4];
227 bfd_byte ld_hash[4];
228 bfd_byte ld_stab[4];
229 bfd_byte ld_stab_hash[4];
230 bfd_byte ld_buckets[4];
231 bfd_byte ld_symbols[4];
232 bfd_byte ld_symb_size[4];
233 bfd_byte ld_text[4];
234 bfd_byte ld_plt_sz[4];