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 * 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 * 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