1 /* Machine-dependent ELF dynamic relocation inline functions. Alpha version.
2 Copyright (C) 1996-2014 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 Lesser General Public
8 License as published by the Free Software Foundation; either
9 version 2.1 of the 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 Lesser General Public License for more details.
16 You should have received a copy of the GNU Lesser General Public
17 License along with the GNU C Library. If not, see
18 <http://www.gnu.org/licenses/>. */
20 /* This was written in the absence of an ABI -- don't expect
21 it to remain unchanged. */
24 #define dl_machine_h 1
26 #define ELF_MACHINE_NAME "alpha"
31 /* Mask identifying addresses reserved for the user program,
32 where the dynamic linker should not map anything. */
33 #define ELF_MACHINE_USER_ADDRESS_MASK 0x120000000UL
35 /* Translate a processor specific dynamic tag to the index in l_info array. */
36 #define DT_ALPHA(x) (DT_ALPHA_##x - DT_LOPROC + DT_NUM)
38 /* Return nonzero iff ELF header is compatible with the running host. */
40 elf_machine_matches_host (const Elf64_Ehdr
*ehdr
)
42 return ehdr
->e_machine
== EM_ALPHA
;
45 /* Return the link-time address of _DYNAMIC. The multiple-got-capable
46 linker no longer allocates the first .got entry for this. But not to
47 worry, no special tricks are needed. */
48 static inline Elf64_Addr
49 elf_machine_dynamic (void)
51 #ifndef NO_AXP_MULTI_GOT_LD
52 return (Elf64_Addr
) &_DYNAMIC
;
54 register Elf64_Addr
*gp
__asm__ ("$29");
59 /* Return the run-time load address of the shared object. */
61 static inline Elf64_Addr
62 elf_machine_load_address (void)
64 /* This relies on the compiler using gp-relative addresses for static symbols. */
65 static void *dot
= &dot
;
66 return (void *)&dot
- dot
;
69 /* Set up the loaded object described by L so its unrelocated PLT
70 entries will jump to the on-demand fixup code in dl-runtime.c. */
73 elf_machine_runtime_setup (struct link_map
*map
, int lazy
, int profile
)
75 extern char _dl_runtime_resolve_new
[] attribute_hidden
;
76 extern char _dl_runtime_profile_new
[] attribute_hidden
;
77 extern char _dl_runtime_resolve_old
[] attribute_hidden
;
78 extern char _dl_runtime_profile_old
[] attribute_hidden
;
82 struct link_map
*link
;
89 if (map
->l_info
[DT_JMPREL
] == 0 || !lazy
)
92 /* Check to see if we're using the read-only plt form. */
93 secureplt
= map
->l_info
[DT_ALPHA(PLTRO
)] != 0;
95 /* If the binary uses the read-only secure plt format, PG points to
96 the .got.plt section, which is the right place for ld.so to place
97 its hooks. Otherwise, PG is currently pointing at the start of
98 the plt; the hooks go at offset 16. */
99 pg
= (struct pltgot
*) D_PTR (map
, l_info
[DT_PLTGOT
]);
102 /* This function will be called to perform the relocation. They're
103 not declared as functions to convince the compiler to use gp
104 relative relocations for them. */
106 resolve
= _dl_runtime_resolve_new
;
108 resolve
= _dl_runtime_resolve_old
;
110 if (__builtin_expect (profile
, 0))
113 resolve
= _dl_runtime_profile_new
;
115 resolve
= _dl_runtime_profile_old
;
117 if (GLRO(dl_profile
) && _dl_name_match_p (GLRO(dl_profile
), map
))
119 /* This is the object we are looking for. Say that we really
120 want profiling and the timers are started. */
121 GL(dl_profile_map
) = map
;
125 pg
->resolve
= resolve
;
131 /* Initial entry point code for the dynamic linker.
132 The C function `_dl_start' is the real entry point;
133 its return value is the user program's entry point. */
135 #define RTLD_START asm ("\
141 .frame $31,0,$31,0 \n\
143 0: ldgp $gp, 0($gp) \n\
145 /* Pass pointer to argument block to _dl_start. */ \n\
147 bsr $26, _dl_start !samegp \n\
150 .globl _dl_start_user \n\
151 .ent _dl_start_user \n\
153 .frame $31,0,$31,0 \n\
155 /* Save the user entry point address in s0. */ \n\
157 /* See if we were run as a command with the executable \n\
158 file name as an extra leading argument. */ \n\
159 ldah $1, _dl_skip_args($gp) !gprelhigh \n\
160 ldl $1, _dl_skip_args($1) !gprellow \n\
161 bne $1, $fixup_stack \n\
162 $fixup_stack_ret: \n\
163 /* The special initializer gets called with the stack \n\
164 just as the application's entry point will see it; \n\
165 it can switch stacks if it moves these contents \n\
167 " RTLD_START_SPECIAL_INIT " \n\
168 /* Call _dl_init(_dl_loaded, argc, argv, envp) to run \n\
170 ldah $16, _rtld_local($gp) !gprelhigh \n\
171 ldq $16, _rtld_local($16) !gprellow \n\
174 s8addq $17, 8, $19 \n\
175 addq $19, $18, $19 \n\
176 bsr $26, _dl_init_internal !samegp \n\
177 /* Pass our finalizer function to the user in $0. */ \n\
178 ldah $0, _dl_fini($gp) !gprelhigh \n\
179 lda $0, _dl_fini($0) !gprellow \n\
180 /* Jump to the user's entry point. */ \n\
184 /* Adjust the stack pointer to skip _dl_skip_args words.\n\
185 This involves copying everything down, since the \n\
186 stack pointer must always be 16-byte aligned. */ \n\
187 ldah $7, _dl_argv_internal($gp) !gprelhigh \n\
189 ldq $5, _dl_argv_internal($7) !gprellow \n\
192 s8addq $6, $5, $5 \n\
194 s8addq $1, $sp, $3 \n\
196 stq $5, _dl_argv_internal($7) !gprellow \n\
197 /* Copy down argv. */ \n\
203 /* Copy down envp. */ \n\
209 /* Copy down auxiliary table. */ \n\
217 br $fixup_stack_ret \n\
218 .end _dl_start_user \n\
222 #ifndef RTLD_START_SPECIAL_INIT
223 #define RTLD_START_SPECIAL_INIT /* nothing */
226 /* ELF_RTYPE_CLASS_PLT iff TYPE describes relocation of a PLT entry
227 or TLS variables, so undefined references should not be allowed
230 ELF_RTYPE_CLASS_NOCOPY iff TYPE should not be allowed to resolve
231 to one of the main executable's symbols, as for a COPY reloc.
232 This is unused on Alpha. */
234 # define elf_machine_type_class(type) \
235 (((type) == R_ALPHA_JMP_SLOT \
236 || (type) == R_ALPHA_DTPMOD64 \
237 || (type) == R_ALPHA_DTPREL64 \
238 || (type) == R_ALPHA_TPREL64) * ELF_RTYPE_CLASS_PLT)
240 /* A reloc type used for ld.so cmdline arg lookups to reject PLT entries. */
241 #define ELF_MACHINE_JMP_SLOT R_ALPHA_JMP_SLOT
243 /* The alpha never uses Elf64_Rel relocations. */
244 #define ELF_MACHINE_NO_REL 1
246 /* We define an initialization functions. This is called very early in
247 * _dl_sysdep_start. */
248 #define DL_PLATFORM_INIT dl_platform_init ()
250 static inline void __attribute__ ((unused
))
251 dl_platform_init (void)
253 if (GLRO(dl_platform
) != NULL
&& *GLRO(dl_platform
) == '\0')
254 /* Avoid an empty string which would disturb us. */
255 GLRO(dl_platform
) = NULL
;
258 /* Fix up the instructions of a PLT entry to invoke the function
259 rather than the dynamic linker. */
260 static inline Elf64_Addr
261 elf_machine_fixup_plt (struct link_map
*map
, lookup_t t
,
262 const Elf64_Rela
*reloc
,
263 Elf64_Addr
*got_addr
, Elf64_Addr value
)
265 const Elf64_Rela
*rela_plt
;
269 /* Store the value we are going to load. */
272 /* If this binary uses the read-only secure plt format, we're done. */
273 if (map
->l_info
[DT_ALPHA(PLTRO
)])
276 /* Otherwise we have to modify the plt entry in place to do the branch. */
278 /* Recover the PLT entry address by calculating reloc's index into the
279 .rela.plt, and finding that entry in the .plt. */
280 rela_plt
= (const Elf64_Rela
*) D_PTR (map
, l_info
[DT_JMPREL
]);
281 plte
= (Elf64_Word
*) (D_PTR (map
, l_info
[DT_PLTGOT
]) + 32);
282 plte
+= 3 * (reloc
- rela_plt
);
284 /* Find the displacement from the plt entry to the function. */
285 edisp
= (long int) (value
- (Elf64_Addr
)&plte
[3]) / 4;
287 if (edisp
>= -0x100000 && edisp
< 0x100000)
289 /* If we are in range, use br to perfect branch prediction and
290 elide the dependency on the address load. This case happens,
291 e.g., when a shared library call is resolved to the same library. */
294 hi
= value
- (Elf64_Addr
)&plte
[0];
296 hi
= (hi
- lo
) >> 16;
298 /* Emit "lda $27,lo($27)" */
299 plte
[1] = 0x237b0000 | (lo
& 0xffff);
301 /* Emit "br $31,function" */
302 plte
[2] = 0xc3e00000 | (edisp
& 0x1fffff);
304 /* Think about thread-safety -- the previous instructions must be
305 committed to memory before the first is overwritten. */
306 __asm__
__volatile__("wmb" : : : "memory");
308 /* Emit "ldah $27,hi($27)" */
309 plte
[0] = 0x277b0000 | (hi
& 0xffff);
313 /* Don't bother with the hint since we already know the hint is
314 wrong. Eliding it prevents the wrong page from getting pulled
318 hi
= (Elf64_Addr
)got_addr
- (Elf64_Addr
)&plte
[0];
320 hi
= (hi
- lo
) >> 16;
322 /* Emit "ldq $27,lo($27)" */
323 plte
[1] = 0xa77b0000 | (lo
& 0xffff);
325 /* Emit "jmp $31,($27)" */
326 plte
[2] = 0x6bfb0000;
328 /* Think about thread-safety -- the previous instructions must be
329 committed to memory before the first is overwritten. */
330 __asm__
__volatile__("wmb" : : : "memory");
332 /* Emit "ldah $27,hi($27)" */
333 plte
[0] = 0x277b0000 | (hi
& 0xffff);
336 /* At this point, if we've been doing runtime resolution, Icache is dirty.
337 This will be taken care of in _dl_runtime_resolve. If instead we are
338 doing this as part of non-lazy startup relocation, that bit of code
339 hasn't made it into Icache yet, so there's nothing to clean up. */
344 /* Return the final value of a plt relocation. */
345 static inline Elf64_Addr
346 elf_machine_plt_value (struct link_map
*map
, const Elf64_Rela
*reloc
,
349 return value
+ reloc
->r_addend
;
352 /* Names of the architecture-specific auditing callback functions. */
353 #define ARCH_LA_PLTENTER alpha_gnu_pltenter
354 #define ARCH_LA_PLTEXIT alpha_gnu_pltexit
356 #endif /* !dl_machine_h */
360 /* Perform the relocation specified by RELOC and SYM (which is fully resolved).
361 MAP is the object containing the reloc. */
363 __attribute__ ((always_inline
))
364 elf_machine_rela (struct link_map
*map
,
365 const Elf64_Rela
*reloc
,
366 const Elf64_Sym
*sym
,
367 const struct r_found_version
*version
,
368 void *const reloc_addr_arg
,
371 Elf64_Addr
*const reloc_addr
= reloc_addr_arg
;
372 unsigned long int const r_type
= ELF64_R_TYPE (reloc
->r_info
);
374 #if !defined RTLD_BOOTSTRAP && !defined HAVE_Z_COMBRELOC && !defined SHARED
375 /* This is defined in rtld.c, but nowhere in the static libc.a; make the
376 reference weak so static programs can still link. This declaration
377 cannot be done when compiling rtld.c (i.e. #ifdef RTLD_BOOTSTRAP)
378 because rtld.c contains the common defn for _dl_rtld_map, which is
379 incompatible with a weak decl in the same file. */
380 weak_extern (_dl_rtld_map
);
383 /* We cannot use a switch here because we cannot locate the switch
384 jump table until we've self-relocated. */
386 #if !defined RTLD_BOOTSTRAP || !defined HAVE_Z_COMBRELOC
387 if (__builtin_expect (r_type
== R_ALPHA_RELATIVE
, 0))
389 # if !defined RTLD_BOOTSTRAP && !defined HAVE_Z_COMBRELOC
390 /* Already done in dynamic linker. */
391 if (map
!= &GL(dl_rtld_map
))
394 /* XXX Make some timings. Maybe it's preferable to test for
395 unaligned access and only do it the complex way if necessary. */
396 Elf64_Addr reloc_addr_val
;
398 /* Load value without causing unaligned trap. */
399 memcpy (&reloc_addr_val
, reloc_addr_arg
, 8);
400 reloc_addr_val
+= map
->l_addr
;
402 /* Store value without causing unaligned trap. */
403 memcpy (reloc_addr_arg
, &reloc_addr_val
, 8);
408 if (__builtin_expect (r_type
== R_ALPHA_NONE
, 0))
412 struct link_map
*sym_map
= RESOLVE_MAP (&sym
, version
, r_type
);
413 Elf64_Addr sym_value
;
414 Elf64_Addr sym_raw_value
;
416 sym_raw_value
= sym_value
= reloc
->r_addend
;
419 sym_raw_value
+= sym
->st_value
;
420 sym_value
= sym_raw_value
+ sym_map
->l_addr
;
423 if (r_type
== R_ALPHA_GLOB_DAT
)
424 *reloc_addr
= sym_value
;
425 #ifdef RESOLVE_CONFLICT_FIND_MAP
426 /* In .gnu.conflict section, R_ALPHA_JMP_SLOT relocations have
427 R_ALPHA_JMP_SLOT in lower 8 bits and the remaining 24 bits
428 are .rela.plt index. */
429 else if ((r_type
& 0xff) == R_ALPHA_JMP_SLOT
)
431 /* elf_machine_fixup_plt needs the map reloc_addr points into,
432 while in _dl_resolve_conflicts map is _dl_loaded. */
433 RESOLVE_CONFLICT_FIND_MAP (map
, reloc_addr
);
434 reloc
= ((const Elf64_Rela
*) D_PTR (map
, l_info
[DT_JMPREL
]))
436 elf_machine_fixup_plt (map
, 0, reloc
, reloc_addr
, sym_value
);
439 else if (r_type
== R_ALPHA_JMP_SLOT
)
440 elf_machine_fixup_plt (map
, 0, reloc
, reloc_addr
, sym_value
);
442 #ifndef RTLD_BOOTSTRAP
443 else if (r_type
== R_ALPHA_REFQUAD
)
445 /* Store value without causing unaligned trap. */
446 memcpy (reloc_addr_arg
, &sym_value
, 8);
449 else if (r_type
== R_ALPHA_DTPMOD64
)
451 # ifdef RTLD_BOOTSTRAP
452 /* During startup the dynamic linker is always index 1. */
455 /* Get the information from the link map returned by the
458 *reloc_addr
= sym_map
->l_tls_modid
;
461 else if (r_type
== R_ALPHA_DTPREL64
)
463 # ifndef RTLD_BOOTSTRAP
464 /* During relocation all TLS symbols are defined and used.
465 Therefore the offset is already correct. */
466 *reloc_addr
= sym_raw_value
;
469 else if (r_type
== R_ALPHA_TPREL64
)
471 # ifdef RTLD_BOOTSTRAP
472 *reloc_addr
= sym_raw_value
+ map
->l_tls_offset
;
476 CHECK_STATIC_TLS (map
, sym_map
);
477 *reloc_addr
= sym_raw_value
+ sym_map
->l_tls_offset
;
482 _dl_reloc_bad_type (map
, r_type
, 0);
486 /* Let do-rel.h know that on Alpha if l_addr is 0, all RELATIVE relocs
488 #define ELF_MACHINE_REL_RELATIVE 1
491 __attribute__ ((always_inline
))
492 elf_machine_rela_relative (Elf64_Addr l_addr
, const Elf64_Rela
*reloc
,
493 void *const reloc_addr_arg
)
495 /* XXX Make some timings. Maybe it's preferable to test for
496 unaligned access and only do it the complex way if necessary. */
497 Elf64_Addr reloc_addr_val
;
499 /* Load value without causing unaligned trap. */
500 memcpy (&reloc_addr_val
, reloc_addr_arg
, 8);
501 reloc_addr_val
+= l_addr
;
503 /* Store value without causing unaligned trap. */
504 memcpy (reloc_addr_arg
, &reloc_addr_val
, 8);
508 __attribute__ ((always_inline
))
509 elf_machine_lazy_rel (struct link_map
*map
,
510 Elf64_Addr l_addr
, const Elf64_Rela
*reloc
,
513 Elf64_Addr
* const reloc_addr
= (void *)(l_addr
+ reloc
->r_offset
);
514 unsigned long int const r_type
= ELF64_R_TYPE (reloc
->r_info
);
516 if (r_type
== R_ALPHA_JMP_SLOT
)
518 /* Perform a RELATIVE reloc on the .got entry that transfers
520 *reloc_addr
+= l_addr
;
522 else if (r_type
== R_ALPHA_NONE
)
525 _dl_reloc_bad_type (map
, r_type
, 1);
528 #endif /* RESOLVE_MAP */