1 /*-
2 * Copyright (c) 2014 Ian Lepore <ian@freebsd.org>
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 * notice, this list of conditions and the following disclaimer in the
12 * documentation and/or other materials provided with the distribution.
13 *
14 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
15 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
16 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
17 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
18 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
19 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
20 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
21 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
22 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
23 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
24 * SUCH DAMAGE.
25 */
26
27 #include <sys/types.h>
28 #include <machine/elf.h>
29 #include <link.h>
30 #include <stddef.h>
31
32 /*
33 * ARM EABI unwind helper.
34 *
35 * This finds the exidx section address and size associated with a given code
36 * address. There are separate implementations for static and dynamic code.
37 *
38 * GCC expects this function to exist as __gnu_Unwind_Find_exidx(), clang and
39 * BSD tools expect it to be dl_unwind_find_exidx(). Both have the same API, so
40 * we set up an alias for GCC.
41 */
42 __strong_reference(dl_unwind_find_exidx, __gnu_Unwind_Find_exidx);
43
44 /*
45 * Each entry in the exidx section is a pair of 32-bit words. We don't
46 * interpret the contents of the entries here; this typedef is just a local
47 * convenience for using sizeof() and doing pointer math.
48 */
49 typedef struct exidx_entry {
50 uint32_t data[2];
51 } exidx_entry;
52
53 #ifdef __PIC__
54
55 /*
56 * Unwind helper for dynamically linked code.
57 *
58 * This finds the shared object that contains the given address, and returns the
59 * address of the exidx section in that shared object along with the number of
60 * entries in that section, or NULL if it wasn't found.
61 */
62 void *
dl_unwind_find_exidx(const void * pc,int * pcount)63 dl_unwind_find_exidx(const void *pc, int *pcount)
64 {
65 const Elf_Phdr *hdr;
66 struct dl_phdr_info info;
67 int i;
68
69 if (_rtld_addr_phdr(pc, &info)) {
70 hdr = info.dlpi_phdr;
71 for (i = 0; i < info.dlpi_phnum; i++, hdr++) {
72 if (hdr->p_type == PT_ARM_EXIDX) {
73 *pcount = hdr->p_memsz / sizeof(exidx_entry);
74 return ((void *)(info.dlpi_addr + hdr->p_vaddr));
75 }
76 }
77 }
78 return (NULL);
79 }
80
81 #else /* !__PIC__ */
82
83 /*
84 * Unwind helper for statically linked code.
85 *
86 * In a statically linked program, the linker populates a pair of symbols with
87 * the addresses of the start and end of the exidx table, so returning the
88 * address and count of elements is pretty straighforward.
89 */
90 void *
dl_unwind_find_exidx(const void * pc,int * pcount)91 dl_unwind_find_exidx(const void *pc, int *pcount)
92 {
93 extern struct exidx_entry __exidx_start;
94 extern struct exidx_entry __exidx_end;
95
96 *pcount = (int)(&__exidx_end - &__exidx_start);
97 return (&__exidx_start);
98 }
99
100 #endif /* __PIC__ */
101
102