1 /* Report a module to libdwfl based on ELF program headers.
2 Copyright (C) 2005, 2007 Red Hat, Inc.
3 This file is part of Red Hat elfutils.
4
5 Red Hat elfutils is free software; you can redistribute it and/or modify
6 it under the terms of the GNU General Public License as published by the
7 Free Software Foundation; version 2 of the License.
8
9 Red Hat elfutils is distributed in the hope that it will be useful, but
10 WITHOUT ANY WARRANTY; without even the implied warranty of
11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
12 General Public License for more details.
13
14 You should have received a copy of the GNU General Public License along
15 with Red Hat elfutils; if not, write to the Free Software Foundation,
16 Inc., 51 Franklin Street, Fifth Floor, Boston MA 02110-1301 USA.
17
18 In addition, as a special exception, Red Hat, Inc. gives You the
19 additional right to link the code of Red Hat elfutils with code licensed
20 under any Open Source Initiative certified open source license
21 (http://www.opensource.org/licenses/index.php) which requires the
22 distribution of source code with any binary distribution and to
23 distribute linked combinations of the two. Non-GPL Code permitted under
24 this exception must only link to the code of Red Hat elfutils through
25 those well defined interfaces identified in the file named EXCEPTION
26 found in the source code files (the "Approved Interfaces"). The files
27 of Non-GPL Code may instantiate templates or use macros or inline
28 functions from the Approved Interfaces without causing the resulting
29 work to be covered by the GNU General Public License. Only Red Hat,
30 Inc. may make changes or additions to the list of Approved Interfaces.
31 Red Hat's grant of this exception is conditioned upon your not adding
32 any new exceptions. If you wish to add a new Approved Interface or
33 exception, please contact Red Hat. You must obey the GNU General Public
34 License in all respects for all of the Red Hat elfutils code and other
35 code used in conjunction with Red Hat elfutils except the Non-GPL Code
36 covered by this exception. If you modify this file, you may extend this
37 exception to your version of the file, but you are not obligated to do
38 so. If you do not wish to provide this exception without modification,
39 you must delete this exception statement from your version and license
40 this file solely under the GPL without exception.
41
42 Red Hat elfutils is an included package of the Open Invention Network.
43 An included package of the Open Invention Network is a package for which
44 Open Invention Network licensees cross-license their patents. No patent
45 license is granted, either expressly or impliedly, by designation as an
46 included package. Should you wish to participate in the Open Invention
47 Network licensing program, please visit www.openinventionnetwork.com
48 <http://www.openinventionnetwork.com>. */
49
50 #include "libdwflP.h"
51 #include <fcntl.h>
52 #include <unistd.h>
53
54
55 /* We start every ET_REL module at a moderately aligned boundary.
56 This keeps the low addresses easy to read compared to a layout
57 starting at 0 (as when using -e). It also makes it unlikely
58 that a middle section will have a larger alignment and require
59 rejiggering (see below). */
60 #define REL_MIN_ALIGN ((GElf_Xword) 0x100)
61
62 Dwfl_Module *
63 internal_function
__libdwfl_report_elf(Dwfl * dwfl,const char * name,const char * file_name,int fd,Elf * elf,GElf_Addr base)64 __libdwfl_report_elf (Dwfl *dwfl, const char *name, const char *file_name,
65 int fd, Elf *elf, GElf_Addr base)
66 {
67 GElf_Ehdr ehdr_mem, *ehdr = gelf_getehdr (elf, &ehdr_mem);
68 if (ehdr == NULL)
69 {
70 elf_error:
71 __libdwfl_seterrno (DWFL_E_LIBELF);
72 return NULL;
73 }
74
75 GElf_Addr start = 0, end = 0, bias = 0;
76 switch (ehdr->e_type)
77 {
78 case ET_REL:
79 /* For a relocatable object, we do an arbitrary section layout.
80 By updating the section header in place, we leave the layout
81 information to be found by relocation. */
82
83 start = end = base = (base + REL_MIN_ALIGN - 1) & -REL_MIN_ALIGN;
84
85 bool first = true;
86 Elf_Scn *scn = NULL;
87 while ((scn = elf_nextscn (elf, scn)) != NULL)
88 {
89 GElf_Shdr shdr_mem;
90 GElf_Shdr *shdr = gelf_getshdr (scn, &shdr_mem);
91 if (unlikely (shdr == NULL))
92 goto elf_error;
93
94 if (shdr->sh_flags & SHF_ALLOC)
95 {
96 const GElf_Xword align = shdr->sh_addralign ?: 1;
97 const GElf_Addr next = (end + align - 1) & -align;
98 if (shdr->sh_addr == 0
99 /* Once we've started doing layout we have to do it all,
100 unless we just layed out the first section at 0 when
101 it already was at 0. */
102 || (bias == 0 && end > start && end != next))
103 {
104 shdr->sh_addr = next;
105 if (end == base)
106 /* This is the first section assigned a location.
107 Use its aligned address as the module's base. */
108 start = base = shdr->sh_addr;
109 else if (unlikely (base & (align - 1)))
110 {
111 /* If BASE has less than the maximum alignment of
112 any section, we eat more than the optimal amount
113 of padding and so make the module's apparent
114 size come out larger than it would when placed
115 at zero. So reset the layout with a better base. */
116
117 start = end = base = (base + align - 1) & -align;
118 Elf_Scn *prev_scn = NULL;
119 do
120 {
121 prev_scn = elf_nextscn (elf, prev_scn);
122 GElf_Shdr prev_shdr_mem;
123 GElf_Shdr *prev_shdr = gelf_getshdr (prev_scn,
124 &prev_shdr_mem);
125 if (unlikely (prev_shdr == NULL))
126 goto elf_error;
127 if (prev_shdr->sh_flags & SHF_ALLOC)
128 {
129 const GElf_Xword prev_align
130 = prev_shdr->sh_addralign ?: 1;
131
132 prev_shdr->sh_addr
133 = (end + prev_align - 1) & -prev_align;
134 end = prev_shdr->sh_addr + prev_shdr->sh_size;
135
136 if (unlikely (! gelf_update_shdr (prev_scn,
137 prev_shdr)))
138 goto elf_error;
139 }
140 }
141 while (prev_scn != scn);
142 continue;
143 }
144
145 end = shdr->sh_addr + shdr->sh_size;
146 if (likely (shdr->sh_addr != 0)
147 && unlikely (! gelf_update_shdr (scn, shdr)))
148 goto elf_error;
149 }
150 else
151 {
152 /* The address is already assigned. Just track it. */
153 if (first || end < shdr->sh_addr + shdr->sh_size)
154 end = shdr->sh_addr + shdr->sh_size;
155 if (first || bias > shdr->sh_addr)
156 /* This is the lowest address in the module. */
157 bias = shdr->sh_addr;
158
159 if ((shdr->sh_addr - bias + base) & (align - 1))
160 /* This section winds up misaligned using BASE.
161 Adjust BASE upwards to make it congruent to
162 the lowest section address in the file modulo ALIGN. */
163 base = (((base + align - 1) & -align)
164 + (bias & (align - 1)));
165 }
166
167 first = false;
168 }
169 }
170
171 if (bias != 0)
172 {
173 /* The section headers had nonzero sh_addr values. The layout
174 was already done. We've just collected the total span.
175 Now just compute the bias from the requested base. */
176 start = base;
177 end = end - bias + start;
178 bias = start - bias;
179 }
180 break;
181
182 /* Everything else has to have program headers. */
183
184 case ET_EXEC:
185 case ET_CORE:
186 /* An assigned base address is meaningless for these. */
187 base = 0;
188
189 case ET_DYN:
190 default:
191 for (uint_fast16_t i = 0; i < ehdr->e_phnum; ++i)
192 {
193 GElf_Phdr phdr_mem, *ph = gelf_getphdr (elf, i, &phdr_mem);
194 if (unlikely (ph == NULL))
195 goto elf_error;
196 if (ph->p_type == PT_LOAD)
197 {
198 if ((base & (ph->p_align - 1)) != 0)
199 base = (base + ph->p_align - 1) & -ph->p_align;
200 start = base + (ph->p_vaddr & -ph->p_align);
201 break;
202 }
203 }
204 bias = base;
205
206 for (uint_fast16_t i = ehdr->e_phnum; i-- > 0;)
207 {
208 GElf_Phdr phdr_mem, *ph = gelf_getphdr (elf, i, &phdr_mem);
209 if (unlikely (ph == NULL))
210 goto elf_error;
211 if (ph->p_type == PT_LOAD)
212 {
213 end = base + (ph->p_vaddr + ph->p_memsz);
214 break;
215 }
216 }
217
218 if (end == 0)
219 {
220 __libdwfl_seterrno (DWFL_E_NO_PHDR);
221 return NULL;
222 }
223 break;
224 }
225
226 Dwfl_Module *m = INTUSE(dwfl_report_module) (dwfl, name, start, end);
227 if (m != NULL)
228 {
229 if (m->main.name == NULL)
230 {
231 m->main.name = strdup (file_name);
232 m->main.fd = fd;
233 }
234 else if ((fd >= 0 && m->main.fd != fd)
235 || strcmp (m->main.name, file_name))
236 {
237 elf_end (elf);
238 overlap:
239 m->gc = true;
240 __libdwfl_seterrno (DWFL_E_OVERLAP);
241 m = NULL;
242 }
243
244 /* Preinstall the open ELF handle for the module. */
245 if (m->main.elf == NULL)
246 {
247 m->main.elf = elf;
248 m->main.bias = bias;
249 m->e_type = ehdr->e_type;
250 }
251 else
252 {
253 elf_end (elf);
254 if (m->main.bias != base)
255 goto overlap;
256 }
257 }
258 return m;
259 }
260
261 Dwfl_Module *
dwfl_report_elf(Dwfl * dwfl,const char * name,const char * file_name,int fd,GElf_Addr base)262 dwfl_report_elf (Dwfl *dwfl, const char *name,
263 const char *file_name, int fd, GElf_Addr base)
264 {
265 bool closefd = false;
266 if (fd < 0)
267 {
268 closefd = true;
269 fd = open64 (file_name, O_RDONLY);
270 if (fd < 0)
271 {
272 __libdwfl_seterrno (DWFL_E_ERRNO);
273 return NULL;
274 }
275 }
276
277 Elf *elf = elf_begin (fd, ELF_C_READ_MMAP_PRIVATE, NULL);
278 Dwfl_Module *mod = __libdwfl_report_elf (dwfl, name, file_name,
279 fd, elf, base);
280 if (mod == NULL)
281 {
282 elf_end (elf);
283 if (closefd)
284 close (fd);
285 }
286
287 return mod;
288 }
289 INTDEF (dwfl_report_elf)
290