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1 /* Machine-dependent ELF dynamic relocation inline functions. Alpha version.
2 Copyright (C) 1996, 1997 Free Software Foundation, Inc.
3 This file is part of the GNU C Library.
4 Contributed by Richard Henderson <rth@tamu.edu>.
6 The GNU C Library is free software; you can redistribute it and/or
7 modify it under the terms of the GNU Library General Public License as
8 published by the Free Software Foundation; either version 2 of the
9 License, or (at your option) any later version.
11 The GNU C Library is distributed in the hope that it will be useful,
12 but WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14 Library General Public License for more details.
16 You should have received a copy of the GNU Library General Public
17 License along with the GNU C Library; see the file COPYING.LIB. If not,
18 write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
19 Boston, MA 02111-1307, USA. */
21 /* This was written in the absence of an ABI -- don't expect
22 it to remain unchanged. */
25 #define dl_machine_h 1
27 #define ELF_MACHINE_NAME "alpha"
33 /* Return nonzero iff E_MACHINE is compatible with the running host. */
35 elf_machine_matches_host (Elf64_Word e_machine
)
37 return e_machine
== EM_ALPHA
;
40 /* Return the link-time address of _DYNAMIC. The multiple-got-capable
41 linker no longer allocates the first .got entry for this. But not to
42 worry, no special tricks are needed. */
43 static inline Elf64_Addr
44 elf_machine_dynamic (void)
46 #ifndef NO_AXP_MULTI_GOT_LD
47 return (Elf64_Addr
) &_DYNAMIC
;
49 register Elf64_Addr
*gp
__asm__ ("$29");
54 /* Return the run-time load address of the shared object. */
55 static inline Elf64_Addr
56 elf_machine_load_address (void)
58 /* NOTE: While it is generally unfriendly to put data in the text
59 segment, it is only slightly less so when the "data" is an
60 instruction. While we don't have to worry about GLD just yet, an
61 optimizing linker might decide that our "data" is an unreachable
62 instruction and throw it away -- with the right switches, DEC's
63 linker will do this. What ought to happen is we should add
64 something to GAS to allow us access to the new GPREL_HI32/LO32
65 relocation types stolen from OSF/1 3.0. */
66 /* This code relies on the fact that BRADDR relocations do not
67 appear in dynamic relocation tables. Not that that would be very
68 useful anyway -- br/bsr has a 4MB range and the shared libraries
69 are usually many many terabytes away. */
75 ".weak __load_address_undefined\n\t"
76 "br $0, __load_address_undefined\n"
80 zero_disp
= *(int *)dot
;
81 zero_disp
= (zero_disp
<< 43) >> 41;
83 return dot
+ 4 + zero_disp
;
86 /* Set up the loaded object described by L so its unrelocated PLT
87 entries will jump to the on-demand fixup code in dl-runtime.c. */
90 elf_machine_runtime_setup (struct link_map
*l
, int lazy
, int profile
)
93 extern void _dl_runtime_resolve (void);
95 if (l
->l_info
[DT_JMPREL
] && lazy
)
97 /* The GOT entries for the functions in the PLT have not been
98 filled in yet. Their initial contents are directed to the
99 PLT which arranges for the dynamic linker to be called. */
100 plt
= l
->l_addr
+ l
->l_info
[DT_PLTGOT
]->d_un
.d_ptr
;
102 /* This function will be called to perform the relocation. */
103 *(Elf64_Addr
*)(plt
+ 16) = (Elf64_Addr
) &_dl_runtime_resolve
;
105 /* Identify this shared object */
106 *(Elf64_Addr
*)(plt
+ 24) = (Elf64_Addr
) l
;
108 /* If the first instruction of the plt entry is not
109 "br $28, plt0", we cannot do lazy relocation. */
110 lazy
= (*(unsigned *)(plt
+ 32) == 0xc39ffff7);
116 /* This code is used in dl-runtime.c to call the `fixup' function
117 and then redirect to the address it returns. */
118 #define ELF_MACHINE_RUNTIME_TRAMPOLINE asm ( \
119 "/* Trampoline for _dl_runtime_resolver */
120 .globl _dl_runtime_resolve
121 .ent _dl_runtime_resolve
125 /* Preserve all registers that C normally doesn't. */
147 .mask 0x27ff01ff, -168
152 /* Set up the arguments for _dl_runtime_resolve. */
153 /* $16 = link_map out of plt0 */
154 /* $17 = offset of reloc entry = ($28 - $27 - 20) /12 * 24 */
161 /* Move the destination address into position. */
163 /* Restore program registers. */
185 /* Flush the Icache after having modified the .plt code. */
187 /* Clean up and turn control to the destination */
190 .end _dl_runtime_resolve");
192 /* The PLT uses Elf64_Rela relocs. */
193 #define elf_machine_relplt elf_machine_rela
195 /* Initial entry point code for the dynamic linker.
196 The C function `_dl_start' is the real entry point;
197 its return value is the user program's entry point. */
199 #define RTLD_START asm ("\
206 /* Pass pointer to argument block to _dl_start. */
208 bsr $26, _dl_start..ng
211 .globl _dl_start_user
214 /* Save the user entry point address in s0. */
216 /* See if we were run as a command with the executable file
217 name as an extra leading argument. If so, adjust the stack
218 pointer to skip _dl_skip_args words. */
219 ldl $1, _dl_skip_args
225 /* Load _dl_default_scope[2] into s1 to pass to _dl_init_next. */
226 0: ldq $10, _dl_default_scope+16
227 /* Call _dl_init_next to return the address of an initializer
230 jsr $26, _dl_init_next
237 2: /* Clear the startup flag. */
239 stl $31, _dl_starting_up
241 /* Pass our finalizer function to the user in $0. */
243 /* Jump to the user's entry point. */
249 /* Nonzero iff TYPE describes relocation of a PLT entry, so
250 PLT entries should not be allowed to define the value. */
251 #define elf_machine_lookup_noplt_p(type) ((type) == R_ALPHA_JMP_SLOT)
253 /* Nonzero iff TYPE should not be allowed to resolve to one of
254 the main executable's symbols, as for a COPY reloc, which we don't use. */
255 #define elf_machine_lookup_noexec_p(type) (0)
257 /* A reloc type used for ld.so cmdline arg lookups to reject PLT entries. */
258 #define ELF_MACHINE_RELOC_NOPLT R_ALPHA_JMP_SLOT
260 /* The alpha never uses Elf64_Rel relocations. */
261 #define ELF_MACHINE_NO_REL 1
263 #endif /* !dl_machine_h */
267 /* Fix up the instructions of a PLT entry to invoke the function
268 rather than the dynamic linker. */
270 elf_alpha_fix_plt(struct link_map
*l
,
271 const Elf64_Rela
*reloc
,
275 const Elf64_Rela
*rela_plt
;
279 /* Recover the PLT entry address by calculating reloc's index into the
280 .rela.plt, and finding that entry in the .plt. */
282 rela_plt
= (void *)(l
->l_addr
+ l
->l_info
[DT_JMPREL
]->d_un
.d_ptr
);
284 plte
= (void *)(l
->l_addr
+ l
->l_info
[DT_PLTGOT
]->d_un
.d_ptr
+ 32);
285 plte
+= 3 * (reloc
- rela_plt
);
287 /* Find the displacement from the plt entry to the function. */
289 edisp
= (long)(value
- (Elf64_Addr
)&plte
[3]) / 4;
291 if (edisp
>= -0x100000 && edisp
< 0x100000)
293 /* If we are in range, use br to perfect branch prediction and
294 elide the dependency on the address load. This case happens,
295 e.g., when a shared library call is resolved to the same library. */
298 hi
= value
- (Elf64_Addr
)&plte
[0];
300 hi
= (hi
- lo
) >> 16;
302 /* Emit "lda $27,L($27)" */
303 plte
[1] = 0x237b0000 | (lo
& 0xffff);
305 /* Emit "br $31,function" */
306 plte
[2] = 0xc3e00000 | (edisp
& 0x1fffff);
308 /* Think about thread-safety -- the previous instructions must be
309 committed to memory before the first is overwritten. */
310 __asm__
__volatile__("wmb" : : : "memory");
312 /* Emit "ldah $27,H($27)" */
313 plte
[0] = 0x277b0000 | (hi
& 0xffff);
317 /* Don't bother with the hint since we already know the hint is
318 wrong. Eliding it prevents the wrong page from getting pulled
322 hi
= got_addr
- (Elf64_Addr
)&plte
[0];
324 hi
= (hi
- lo
) >> 16;
326 /* Emit "ldq $27,L($27)" */
327 plte
[1] = 0xa77b0000 | (lo
& 0xffff);
329 /* Emit "jmp $31,($27)" */
330 plte
[2] = 0x6bfb0000;
332 /* Think about thread-safety -- the previous instructions must be
333 committed to memory before the first is overwritten. */
334 __asm__
__volatile__("wmb" : : : "memory");
336 /* Emit "ldah $27,H($27)" */
337 plte
[0] = 0x277b0000 | (hi
& 0xffff);
340 /* At this point, if we've been doing runtime resolution, Icache is dirty.
341 This will be taken care of in _dl_runtime_resolve. If instead we are
342 doing this as part of non-lazy startup relocation, that bit of code
343 hasn't made it into Icache yet, so there's nothing to clean up. */
346 /* Perform the relocation specified by RELOC and SYM (which is fully resolved).
347 MAP is the object containing the reloc. */
349 elf_machine_rela (struct link_map
*map
,
350 const Elf64_Rela
*reloc
,
351 const Elf64_Sym
*sym
,
352 const struct r_found_version
*version
,
353 Elf64_Addr
*const reloc_addr
)
355 unsigned long const r_type
= ELF64_R_TYPE (reloc
->r_info
);
357 #ifndef RTLD_BOOTSTRAP
358 /* This is defined in rtld.c, but nowhere in the static libc.a; make the
359 reference weak so static programs can still link. This declaration
360 cannot be done when compiling rtld.c (i.e. #ifdef RTLD_BOOTSTRAP)
361 because rtld.c contains the common defn for _dl_rtld_map, which is
362 incompatible with a weak decl in the same file. */
363 weak_extern (_dl_rtld_map
);
366 /* We cannot use a switch here because we cannot locate the switch
367 jump table until we've self-relocated. */
369 if (r_type
== R_ALPHA_RELATIVE
)
371 #ifndef RTLD_BOOTSTRAP
372 /* Already done in dynamic linker. */
373 if (map
!= &_dl_rtld_map
)
375 *reloc_addr
+= map
->l_addr
;
377 else if (r_type
== R_ALPHA_NONE
)
381 Elf64_Addr loadbase
, sym_value
;
383 loadbase
= RESOLVE (&sym
, version
, r_type
);
384 sym_value
= sym
? loadbase
+ sym
->st_value
: 0;
386 if (r_type
== R_ALPHA_GLOB_DAT
)
387 *reloc_addr
= sym_value
;
388 else if (r_type
== R_ALPHA_JMP_SLOT
)
390 *reloc_addr
= sym_value
;
391 elf_alpha_fix_plt (map
, reloc
, (Elf64_Addr
) reloc_addr
, sym_value
);
393 else if (r_type
== R_ALPHA_REFQUAD
)
395 sym_value
+= *reloc_addr
;
396 #ifndef RTLD_BOOTSTRAP
397 if (map
== &_dl_rtld_map
)
399 /* Undo the relocation done here during bootstrapping.
400 Now we will relocate anew, possibly using a binding
401 found in the user program or a loaded library rather
402 than the dynamic linker's built-in definitions used
403 while loading those libraries. */
404 const Elf64_Sym
*const dlsymtab
405 = (void *)(map
->l_addr
+ map
->l_info
[DT_SYMTAB
]->d_un
.d_ptr
);
406 sym_value
-= map
->l_addr
;
407 sym_value
-= dlsymtab
[ELF64_R_SYM(reloc
->r_info
)].st_value
;
411 sym_value
+= reloc
->r_addend
;
412 *reloc_addr
= sym_value
;
415 assert (! "unexpected dynamic reloc type");
420 elf_machine_lazy_rel (struct link_map
*map
, const Elf64_Rela
*reloc
)
422 Elf64_Addr
* const reloc_addr
= (void *)(map
->l_addr
+ reloc
->r_offset
);
423 unsigned long const r_type
= ELF64_R_TYPE (reloc
->r_info
);
425 if (r_type
== R_ALPHA_JMP_SLOT
)
427 /* Perform a RELATIVE reloc on the .got entry that transfers
429 *reloc_addr
+= map
->l_addr
;
431 else if (r_type
== R_ALPHA_NONE
)
434 assert (! "unexpected PLT reloc type");
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