xref: /freebsd/libexec/rtld-elf/i386/reloc.c (revision 4bc52338) 
1 /*-
2  * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
3  *
4  * Copyright 1996, 1997, 1998, 1999 John D. Polstra.
5  * All rights reserved.
6  *
7  * Redistribution and use in source and binary forms, with or without
8  * modification, are permitted provided that the following conditions
9  * are met:
10  * 1. Redistributions of source code must retain the above copyright
11  *    notice, this list of conditions and the following disclaimer.
12  * 2. Redistributions in binary form must reproduce the above copyright
13  *    notice, this list of conditions and the following disclaimer in the
14  *    documentation and/or other materials provided with the distribution.
15  *
16  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
17  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
18  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
19  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
20  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
21  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
22  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
23  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
24  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
25  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
26  *
27  * $FreeBSD$
28  */
29 
30 /*
31  * Dynamic linker for ELF.
32  *
33  * John Polstra <jdp@polstra.com>.
34  */
35 
36 #include <sys/param.h>
37 #include <sys/mman.h>
38 #include <machine/segments.h>
39 #include <machine/sysarch.h>
40 
41 #include <dlfcn.h>
42 #include <err.h>
43 #include <errno.h>
44 #include <fcntl.h>
45 #include <stdarg.h>
46 #include <stdio.h>
47 #include <stdlib.h>
48 #include <string.h>
49 #include <unistd.h>
50 
51 #include "debug.h"
52 #include "rtld.h"
53 #include "rtld_tls.h"
54 
55 /*
56  * Process the special R_386_COPY relocations in the main program.  These
57  * copy data from a shared object into a region in the main program's BSS
58  * segment.
59  *
60  * Returns 0 on success, -1 on failure.
61  */
62 int
63 do_copy_relocations(Obj_Entry *dstobj)
64 {
65     const Elf_Rel *rellim;
66     const Elf_Rel *rel;
67 
68     assert(dstobj->mainprog);	/* COPY relocations are invalid elsewhere */
69 
70     rellim = (const Elf_Rel *)((const char *)dstobj->rel + dstobj->relsize);
71     for (rel = dstobj->rel;  rel < rellim;  rel++) {
72 	if (ELF_R_TYPE(rel->r_info) == R_386_COPY) {
73 	    void *dstaddr;
74 	    const Elf_Sym *dstsym;
75 	    const char *name;
76 	    size_t size;
77 	    const void *srcaddr;
78 	    const Elf_Sym *srcsym;
79 	    const Obj_Entry *srcobj, *defobj;
80 	    SymLook req;
81 	    int res;
82 
83 	    dstaddr = (void *)(dstobj->relocbase + rel->r_offset);
84 	    dstsym = dstobj->symtab + ELF_R_SYM(rel->r_info);
85 	    name = dstobj->strtab + dstsym->st_name;
86 	    size = dstsym->st_size;
87 	    symlook_init(&req, name);
88 	    req.ventry = fetch_ventry(dstobj, ELF_R_SYM(rel->r_info));
89 	    req.flags = SYMLOOK_EARLY;
90 
91 	    for (srcobj = globallist_next(dstobj);  srcobj != NULL;
92 	      srcobj = globallist_next(srcobj)) {
93 		res = symlook_obj(&req, srcobj);
94 		if (res == 0) {
95 		    srcsym = req.sym_out;
96 		    defobj = req.defobj_out;
97 		    break;
98 		}
99 	    }
100 
101 	    if (srcobj == NULL) {
102 		_rtld_error("Undefined symbol \"%s\" referenced from COPY"
103 		  " relocation in %s", name, dstobj->path);
104 		return -1;
105 	    }
106 
107 	    srcaddr = (const void *)(defobj->relocbase + srcsym->st_value);
108 	    memcpy(dstaddr, srcaddr, size);
109 	}
110     }
111 
112     return 0;
113 }
114 
115 /* Initialize the special GOT entries. */
116 void
117 init_pltgot(Obj_Entry *obj)
118 {
119     if (obj->pltgot != NULL) {
120 	obj->pltgot[1] = (Elf_Addr) obj;
121 	obj->pltgot[2] = (Elf_Addr) &_rtld_bind_start;
122     }
123 }
124 
125 /* Process the non-PLT relocations. */
126 int
127 reloc_non_plt(Obj_Entry *obj, Obj_Entry *obj_rtld, int flags,
128     RtldLockState *lockstate)
129 {
130 	const Elf_Rel *rellim;
131 	const Elf_Rel *rel;
132 	SymCache *cache;
133 	const Elf_Sym *def;
134 	const Obj_Entry *defobj;
135 	Elf_Addr *where, symval, add;
136 	int r;
137 
138 	r = -1;
139 	/*
140 	 * The dynamic loader may be called from a thread, we have
141 	 * limited amounts of stack available so we cannot use alloca().
142 	 */
143 	if (obj != obj_rtld) {
144 		cache = calloc(obj->dynsymcount, sizeof(SymCache));
145 		/* No need to check for NULL here */
146 	} else
147 		cache = NULL;
148 
149 	/* Appease some compilers. */
150 	symval = 0;
151 	def = NULL;
152 
153 	rellim = (const Elf_Rel *)((const char *)obj->rel + obj->relsize);
154 	for (rel = obj->rel;  rel < rellim;  rel++) {
155 		switch (ELF_R_TYPE(rel->r_info)) {
156 		case R_386_32:
157 		case R_386_PC32:
158 		case R_386_GLOB_DAT:
159 		case R_386_TLS_TPOFF:
160 		case R_386_TLS_TPOFF32:
161 		case R_386_TLS_DTPMOD32:
162 		case R_386_TLS_DTPOFF32:
163 			def = find_symdef(ELF_R_SYM(rel->r_info), obj, &defobj,
164 			    flags, cache, lockstate);
165 			if (def == NULL)
166 				goto done;
167 			if (ELF_ST_TYPE(def->st_info) == STT_GNU_IFUNC) {
168 				switch (ELF_R_TYPE(rel->r_info)) {
169 				case R_386_32:
170 				case R_386_PC32:
171 				case R_386_GLOB_DAT:
172 					if ((flags & SYMLOOK_IFUNC) == 0) {
173 						obj->non_plt_gnu_ifunc = true;
174 						continue;
175 					}
176 					symval = (Elf_Addr)rtld_resolve_ifunc(
177 					    defobj, def);
178 					break;
179 				case R_386_TLS_TPOFF:
180 				case R_386_TLS_TPOFF32:
181 				case R_386_TLS_DTPMOD32:
182 				case R_386_TLS_DTPOFF32:
183 					_rtld_error("%s: IFUNC for TLS reloc",
184 					    obj->path);
185 					goto done;
186 				}
187 			} else {
188 				if ((flags & SYMLOOK_IFUNC) != 0)
189 					continue;
190 				symval = (Elf_Addr)defobj->relocbase +
191 				    def->st_value;
192 			}
193 			break;
194 		default:
195 			if ((flags & SYMLOOK_IFUNC) != 0)
196 				continue;
197 			break;
198 		}
199 		where = (Elf_Addr *)(obj->relocbase + rel->r_offset);
200 
201 		switch (ELF_R_TYPE(rel->r_info)) {
202 		case R_386_NONE:
203 			break;
204 		case R_386_32:
205 			*where += symval;
206 			break;
207 		case R_386_PC32:
208 		    /*
209 		     * I don't think the dynamic linker should ever
210 		     * see this type of relocation.  But the
211 		     * binutils-2.6 tools sometimes generate it.
212 		     */
213 		    *where += symval - (Elf_Addr)where;
214 		    break;
215 		case R_386_COPY:
216 			/*
217 			 * These are deferred until all other
218 			 * relocations have been done.  All we do here
219 			 * is make sure that the COPY relocation is
220 			 * not in a shared library.  They are allowed
221 			 * only in executable files.
222 			 */
223 			if (!obj->mainprog) {
224 				_rtld_error("%s: Unexpected R_386_COPY "
225 				    "relocation in shared library", obj->path);
226 				goto done;
227 			}
228 			break;
229 		case R_386_GLOB_DAT:
230 			*where = symval;
231 			break;
232 		case R_386_RELATIVE:
233 			*where += (Elf_Addr)obj->relocbase;
234 			break;
235 		case R_386_TLS_TPOFF:
236 		case R_386_TLS_TPOFF32:
237 			/*
238 			 * We lazily allocate offsets for static TLS
239 			 * as we see the first relocation that
240 			 * references the TLS block. This allows us to
241 			 * support (small amounts of) static TLS in
242 			 * dynamically loaded modules. If we run out
243 			 * of space, we generate an error.
244 			 */
245 			if (!defobj->tls_done) {
246 				if (!allocate_tls_offset(
247 				    __DECONST(Obj_Entry *, defobj))) {
248 					_rtld_error("%s: No space available "
249 					    "for static Thread Local Storage",
250 					    obj->path);
251 					goto done;
252 				}
253 			}
254 			add = (Elf_Addr)(def->st_value - defobj->tlsoffset);
255 			if (ELF_R_TYPE(rel->r_info) == R_386_TLS_TPOFF)
256 				*where += add;
257 			else
258 				*where -= add;
259 			break;
260 		case R_386_TLS_DTPMOD32:
261 			*where += (Elf_Addr)defobj->tlsindex;
262 			break;
263 		case R_386_TLS_DTPOFF32:
264 			*where += (Elf_Addr) def->st_value;
265 			break;
266 		default:
267 			_rtld_error("%s: Unsupported relocation type %d"
268 			    " in non-PLT relocations\n", obj->path,
269 			    ELF_R_TYPE(rel->r_info));
270 			goto done;
271 		}
272 	}
273 	r = 0;
274 done:
275 	free(cache);
276 	return (r);
277 }
278 
279 /* Process the PLT relocations. */
280 int
281 reloc_plt(Obj_Entry *obj, int flags __unused, RtldLockState *lockstate __unused)
282 {
283     const Elf_Rel *rellim;
284     const Elf_Rel *rel;
285 
286     rellim = (const Elf_Rel *)((const char *)obj->pltrel + obj->pltrelsize);
287     for (rel = obj->pltrel;  rel < rellim;  rel++) {
288 	Elf_Addr *where/*, val*/;
289 
290 	switch (ELF_R_TYPE(rel->r_info)) {
291 	case R_386_JMP_SLOT:
292 	  /* Relocate the GOT slot pointing into the PLT. */
293 	  where = (Elf_Addr *)(obj->relocbase + rel->r_offset);
294 	  *where += (Elf_Addr)obj->relocbase;
295 	  break;
296 
297 	case R_386_IRELATIVE:
298 	  obj->irelative = true;
299 	  break;
300 
301 	default:
302 	  _rtld_error("Unknown relocation type %x in PLT",
303 	    ELF_R_TYPE(rel->r_info));
304 	  return (-1);
305 	}
306     }
307     return 0;
308 }
309 
310 /* Relocate the jump slots in an object. */
311 int
312 reloc_jmpslots(Obj_Entry *obj, int flags, RtldLockState *lockstate)
313 {
314     const Elf_Rel *rellim;
315     const Elf_Rel *rel;
316 
317     if (obj->jmpslots_done)
318 	return 0;
319     rellim = (const Elf_Rel *)((const char *)obj->pltrel + obj->pltrelsize);
320     for (rel = obj->pltrel;  rel < rellim;  rel++) {
321 	Elf_Addr *where, target;
322 	const Elf_Sym *def;
323 	const Obj_Entry *defobj;
324 
325 	switch (ELF_R_TYPE(rel->r_info)) {
326 	case R_386_JMP_SLOT:
327 	  where = (Elf_Addr *)(obj->relocbase + rel->r_offset);
328 	  def = find_symdef(ELF_R_SYM(rel->r_info), obj, &defobj,
329 		SYMLOOK_IN_PLT | flags, NULL, lockstate);
330 	  if (def == NULL)
331 	      return (-1);
332 	  if (ELF_ST_TYPE(def->st_info) == STT_GNU_IFUNC) {
333 	      obj->gnu_ifunc = true;
334 	      continue;
335 	  }
336 	  target = (Elf_Addr)(defobj->relocbase + def->st_value);
337 	  reloc_jmpslot(where, target, defobj, obj, rel);
338 	  break;
339 
340 	case R_386_IRELATIVE:
341 	  break;
342 
343 	default:
344 	  _rtld_error("Unknown relocation type %x in PLT",
345 	    ELF_R_TYPE(rel->r_info));
346 	  return (-1);
347 	}
348     }
349 
350     obj->jmpslots_done = true;
351     return 0;
352 }
353 
354 /* Fixup the jump slot at "where" to transfer control to "target". */
355 Elf_Addr
356 reloc_jmpslot(Elf_Addr *where, Elf_Addr target,
357     const Obj_Entry *obj __unused, const Obj_Entry *refobj __unused,
358     const Elf_Rel *rel __unused)
359 {
360 #ifdef dbg
361 	dbg("reloc_jmpslot: *%p = %p", where, (void *)target);
362 #endif
363 	if (!ld_bind_not)
364 		*where = target;
365 	return (target);
366 }
367 
368 int
369 reloc_iresolve(Obj_Entry *obj, RtldLockState *lockstate)
370 {
371     const Elf_Rel *rellim;
372     const Elf_Rel *rel;
373     Elf_Addr *where, target;
374 
375     if (!obj->irelative)
376 	return (0);
377     rellim = (const Elf_Rel *)((const char *)obj->pltrel + obj->pltrelsize);
378     for (rel = obj->pltrel;  rel < rellim;  rel++) {
379 	switch (ELF_R_TYPE(rel->r_info)) {
380 	case R_386_IRELATIVE:
381 	  where = (Elf_Addr *)(obj->relocbase + rel->r_offset);
382 	  lock_release(rtld_bind_lock, lockstate);
383 	  target = call_ifunc_resolver(obj->relocbase + *where);
384 	  wlock_acquire(rtld_bind_lock, lockstate);
385 	  *where = target;
386 	  break;
387 	}
388     }
389     obj->irelative = false;
390     return (0);
391 }
392 
393 int
394 reloc_gnu_ifunc(Obj_Entry *obj, int flags, RtldLockState *lockstate)
395 {
396     const Elf_Rel *rellim;
397     const Elf_Rel *rel;
398 
399     if (!obj->gnu_ifunc)
400 	return (0);
401     rellim = (const Elf_Rel *)((const char *)obj->pltrel + obj->pltrelsize);
402     for (rel = obj->pltrel;  rel < rellim;  rel++) {
403 	Elf_Addr *where, target;
404 	const Elf_Sym *def;
405 	const Obj_Entry *defobj;
406 
407 	switch (ELF_R_TYPE(rel->r_info)) {
408 	case R_386_JMP_SLOT:
409 	  where = (Elf_Addr *)(obj->relocbase + rel->r_offset);
410 	  def = find_symdef(ELF_R_SYM(rel->r_info), obj, &defobj,
411 		SYMLOOK_IN_PLT | flags, NULL, lockstate);
412 	  if (def == NULL)
413 	      return (-1);
414 	  if (ELF_ST_TYPE(def->st_info) != STT_GNU_IFUNC)
415 	      continue;
416 	  lock_release(rtld_bind_lock, lockstate);
417 	  target = (Elf_Addr)rtld_resolve_ifunc(defobj, def);
418 	  wlock_acquire(rtld_bind_lock, lockstate);
419 	  reloc_jmpslot(where, target, defobj, obj, rel);
420 	  break;
421 	}
422     }
423 
424     obj->gnu_ifunc = false;
425     return (0);
426 }
427 
428 uint32_t cpu_feature, cpu_feature2, cpu_stdext_feature, cpu_stdext_feature2;
429 
430 static void
431 rtld_cpuid_count(int idx, int cnt, u_int *p)
432 {
433 
434 	__asm __volatile(
435 	    "	pushl	%%ebx\n"
436 	    "	cpuid\n"
437 	    "	movl	%%ebx,%1\n"
438 	    "	popl	%%ebx\n"
439 	    : "=a" (p[0]), "=r" (p[1]), "=c" (p[2]), "=d" (p[3])
440 	    :  "0" (idx), "2" (cnt));
441 }
442 
443 void
444 ifunc_init(Elf_Auxinfo aux_info[__min_size(AT_COUNT)] __unused)
445 {
446 	u_int p[4], cpu_high;
447 	int cpuid_supported;
448 
449 	__asm __volatile(
450 	    "	pushfl\n"
451 	    "	popl	%%eax\n"
452 	    "	movl    %%eax,%%ecx\n"
453 	    "	xorl    $0x200000,%%eax\n"
454 	    "	pushl	%%eax\n"
455 	    "	popfl\n"
456 	    "	pushfl\n"
457 	    "	popl    %%eax\n"
458 	    "	xorl    %%eax,%%ecx\n"
459 	    "	je	1f\n"
460 	    "	movl	$1,%0\n"
461 	    "	jmp	2f\n"
462 	    "1:	movl	$0,%0\n"
463 	    "2:\n"
464 	    : "=r" (cpuid_supported) : : "eax", "ecx");
465 	if (!cpuid_supported)
466 		return;
467 
468 	rtld_cpuid_count(1, 0, p);
469 	cpu_feature = p[3];
470 	cpu_feature2 = p[2];
471 	rtld_cpuid_count(0, 0, p);
472 	cpu_high = p[0];
473 	if (cpu_high >= 7) {
474 		rtld_cpuid_count(7, 0, p);
475 		cpu_stdext_feature = p[1];
476 		cpu_stdext_feature2 = p[2];
477 	}
478 }
479 
480 void
481 pre_init(void)
482 {
483 
484 }
485 
486 void
487 allocate_initial_tls(Obj_Entry *objs)
488 {
489     void* tls;
490 
491     /*
492      * Fix the size of the static TLS block by using the maximum
493      * offset allocated so far and adding a bit for dynamic modules to
494      * use.
495      */
496     tls_static_space = tls_last_offset + RTLD_STATIC_TLS_EXTRA;
497     tls = allocate_tls(objs, NULL, 3*sizeof(Elf_Addr), sizeof(Elf_Addr));
498     i386_set_gsbase(tls);
499 }
500 
501 /* GNU ABI */
502 __attribute__((__regparm__(1)))
503 void *___tls_get_addr(tls_index *ti)
504 {
505     Elf_Addr** segbase;
506 
507     __asm __volatile("movl %%gs:0, %0" : "=r" (segbase));
508 
509     return tls_get_addr_common(&segbase[1], ti->ti_module, ti->ti_offset);
510 }
511 
512 /* Sun ABI */
513 void *__tls_get_addr(tls_index *ti)
514 {
515     Elf_Addr** segbase;
516 
517     __asm __volatile("movl %%gs:0, %0" : "=r" (segbase));
518 
519     return tls_get_addr_common(&segbase[1], ti->ti_module, ti->ti_offset);
520 }
521