1/*	$NetBSD: mdreloc.c,v 1.34 2017/08/10 19:03:27 joerg Exp $	*/
2
3#include <sys/cdefs.h>
4#ifndef lint
5__RCSID("$NetBSD: mdreloc.c,v 1.34 2017/08/10 19:03:27 joerg Exp $");
6#endif /* not lint */
7
8#include <sys/types.h>
9
10#include "debug.h"
11#include "rtld.h"
12
13void _rtld_bind_start(void);
14void _rtld_relocate_nonplt_self(Elf_Dyn *, Elf_Addr);
15caddr_t _rtld_bind(const Obj_Entry *, Elf_Word);
16static inline int _rtld_relocate_plt_object(const Obj_Entry *,
17    const Elf_Rela *, Elf_Addr *);
18
19void
20_rtld_setup_pltgot(const Obj_Entry *obj)
21{
22	obj->pltgot[1] = (Elf_Addr) obj;
23	obj->pltgot[2] = (Elf_Addr) &_rtld_bind_start;
24}
25
26void
27_rtld_relocate_nonplt_self(Elf_Dyn *dynp, Elf_Addr relocbase)
28{
29	const Elf_Rela *rela = 0, *relalim;
30	Elf_Addr relasz = 0;
31	Elf_Addr *where;
32
33	for (; dynp->d_tag != DT_NULL; dynp++) {
34		switch (dynp->d_tag) {
35		case DT_RELA:
36			rela = (const Elf_Rela *)(relocbase + dynp->d_un.d_ptr);
37			break;
38		case DT_RELASZ:
39			relasz = dynp->d_un.d_val;
40			break;
41		}
42	}
43	relalim = (const Elf_Rela *)((const uint8_t *)rela + relasz);
44	for (; rela < relalim; rela++) {
45		where = (Elf_Addr *)(relocbase + rela->r_offset);
46		*where = (Elf_Addr)(relocbase + rela->r_addend);
47	}
48}
49
50int
51_rtld_relocate_nonplt_objects(Obj_Entry *obj)
52{
53	const Elf_Rela *rela;
54	const Elf_Sym *def = NULL;
55	const Obj_Entry *defobj = NULL;
56	unsigned long last_symnum = ULONG_MAX;
57
58	for (rela = obj->rela; rela < obj->relalim; rela++) {
59		Elf_Addr        *where;
60		Elf_Addr         tmp;
61		unsigned long    symnum;
62
63		where = (Elf_Addr *)(obj->relocbase + rela->r_offset);
64
65		switch (ELF_R_TYPE(rela->r_info)) {
66		case R_TYPE(32):	/* word32 S + A */
67		case R_TYPE(GLOB_DAT):	/* word32 S + A */
68			symnum = ELF_R_SYM(rela->r_info);
69			if (last_symnum != symnum) {
70				last_symnum = symnum;
71				def = _rtld_find_symdef(symnum, obj, &defobj,
72				    false);
73				if (def == NULL)
74					return -1;
75			}
76			break;
77
78		default:
79			break;
80		}
81
82		switch (ELF_R_TYPE(rela->r_info)) {
83		case R_TYPE(NONE):
84			break;
85
86		case R_TYPE(32):	/* word32 S + A */
87		case R_TYPE(GLOB_DAT):	/* word32 S + A */
88			tmp = (Elf_Addr)(defobj->relocbase + def->st_value +
89			    rela->r_addend);
90
91			if (*where != tmp)
92				*where = tmp;
93			rdbg(("32/GLOB_DAT %s in %s --> %p in %s",
94			    obj->strtab + obj->symtab[symnum].st_name,
95			    obj->path, (void *)*where, defobj->path));
96			break;
97
98		case R_TYPE(RELATIVE):	/* word32 B + A */
99			tmp = (Elf_Addr)(obj->relocbase + rela->r_addend);
100			if (*where != tmp)
101				*where = tmp;
102			rdbg(("RELATIVE in %s --> %p", obj->path,
103			    (void *)*where));
104			break;
105
106		case R_TYPE(COPY):
107			/*
108			 * These are deferred until all other relocations have
109			 * been done.  All we do here is make sure that the
110			 * COPY relocation is not in a shared library.  They
111			 * are allowed only in executable files.
112			 */
113			if (obj->isdynamic) {
114				_rtld_error(
115			"%s: Unexpected R_COPY relocation in shared library",
116				    obj->path);
117				return -1;
118			}
119			rdbg(("COPY (avoid in main)"));
120			break;
121
122		default:
123			rdbg(("sym = %lu, type = %lu, offset = %p, "
124			    "addend = %p, contents = %p",
125			    (u_long)ELF_R_SYM(rela->r_info),
126			    (u_long)ELF_R_TYPE(rela->r_info),
127			    (void *)rela->r_offset, (void *)rela->r_addend,
128			    (void *)*where));
129			_rtld_error("%s: Unsupported relocation type %ld "
130			    "in non-PLT relocations",
131			    obj->path, (u_long) ELF_R_TYPE(rela->r_info));
132			return -1;
133		}
134	}
135	return 0;
136}
137
138int
139_rtld_relocate_plt_lazy(Obj_Entry *obj)
140{
141	const Elf_Rela *rela;
142
143	if (!obj->relocbase)
144		return 0;
145
146	for (rela = obj->pltrela; rela < obj->pltrelalim; rela++) {
147		Elf_Addr *where = (Elf_Addr *)(obj->relocbase + rela->r_offset);
148
149		assert(ELF_R_TYPE(rela->r_info) == R_TYPE(JMP_SLOT));
150
151		/* Just relocate the GOT slots pointing into the PLT */
152		*where += (Elf_Addr)obj->relocbase;
153		rdbg(("lazy fixup pltgot %p in %s --> %p", where, obj->path,
154		    (void *)*where));
155	}
156
157	return 0;
158}
159
160static inline int
161_rtld_relocate_plt_object(const Obj_Entry *obj, const Elf_Rela *rela, Elf_Addr *tp)
162{
163	Elf_Addr *where = (Elf_Addr *)(obj->relocbase + rela->r_offset);
164	Elf_Addr new_value;
165	const Elf_Sym  *def;
166	const Obj_Entry *defobj;
167	unsigned long info = rela->r_info;
168
169	assert(ELF_R_TYPE(info) == R_TYPE(JMP_SLOT));
170
171	def = _rtld_find_plt_symdef(ELF_R_SYM(info), obj, &defobj, tp != NULL);
172	if (__predict_false(def == NULL))
173		return -1;
174	if (__predict_false(def == &_rtld_sym_zero))
175		return 0;
176
177	if (ELF_ST_TYPE(def->st_info) == STT_GNU_IFUNC) {
178		if (tp == NULL)
179			return 0;
180		new_value = _rtld_resolve_ifunc(defobj, def);
181	} else {
182		new_value = (Elf_Addr)(defobj->relocbase + def->st_value +
183		    rela->r_addend);
184	}
185	rdbg(("bind now/fixup pltgot %p in %s --> old=%p new=%p", where,
186	    defobj->strtab + def->st_name, (void *)*where, (void *)new_value));
187	if (*where != new_value)
188		*where = new_value;
189
190	if (tp)
191		*tp = new_value - rela->r_addend;
192
193	return 0;
194}
195
196caddr_t
197_rtld_bind(const Obj_Entry *obj, Elf_Word reloff)
198{
199	const Elf_Rela *rela = (const Elf_Rela *)((const uint8_t *)obj->pltrela + reloff);
200	Elf_Addr result;
201	int err;
202
203	result = 0;	/* XXX gcc */
204
205	_rtld_shared_enter();
206	err = _rtld_relocate_plt_object(obj, rela, &result);
207	if (err)
208		_rtld_die();
209	_rtld_shared_exit();
210
211	return (caddr_t)result;
212}
213
214int
215_rtld_relocate_plt_objects(const Obj_Entry *obj)
216{
217	const Elf_Rela *rela;
218
219	for (rela = obj->pltrela; rela < obj->pltrelalim; rela++)
220		if (_rtld_relocate_plt_object(obj, rela, NULL) < 0)
221			return -1;
222
223	return 0;
224}
225