1*2de3b87aSKai Wang /*- 2*2de3b87aSKai Wang * Copyright (c) 2006,2008 Joseph Koshy 3*2de3b87aSKai Wang * All rights reserved. 4*2de3b87aSKai Wang * 5*2de3b87aSKai Wang * Redistribution and use in source and binary forms, with or without 6*2de3b87aSKai Wang * modification, are permitted provided that the following conditions 7*2de3b87aSKai Wang * are met: 8*2de3b87aSKai Wang * 1. Redistributions of source code must retain the above copyright 9*2de3b87aSKai Wang * notice, this list of conditions and the following disclaimer. 10*2de3b87aSKai Wang * 2. Redistributions in binary form must reproduce the above copyright 11*2de3b87aSKai Wang * notice, this list of conditions and the following disclaimer in the 12*2de3b87aSKai Wang * documentation and/or other materials provided with the distribution. 13*2de3b87aSKai Wang * 14*2de3b87aSKai Wang * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 15*2de3b87aSKai Wang * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 16*2de3b87aSKai Wang * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 17*2de3b87aSKai Wang * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 18*2de3b87aSKai Wang * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 19*2de3b87aSKai Wang * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 20*2de3b87aSKai Wang * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 21*2de3b87aSKai Wang * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 22*2de3b87aSKai Wang * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 23*2de3b87aSKai Wang * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 24*2de3b87aSKai Wang * SUCH DAMAGE. 25*2de3b87aSKai Wang */ 26*2de3b87aSKai Wang 27*2de3b87aSKai Wang #include <sys/param.h> 28*2de3b87aSKai Wang 29*2de3b87aSKai Wang #include <assert.h> 30*2de3b87aSKai Wang #include <gelf.h> 31*2de3b87aSKai Wang 32*2de3b87aSKai Wang #include "_libelf.h" 33*2de3b87aSKai Wang 34*2de3b87aSKai Wang ELFTC_VCSID("$Id: elf_strptr.c 2271 2011-12-03 17:06:35Z jkoshy $"); 35*2de3b87aSKai Wang 36*2de3b87aSKai Wang /* 37*2de3b87aSKai Wang * Convert an ELF section#,offset pair to a string pointer. 38*2de3b87aSKai Wang */ 39*2de3b87aSKai Wang 40*2de3b87aSKai Wang char * 41*2de3b87aSKai Wang elf_strptr(Elf *e, size_t scndx, size_t offset) 42*2de3b87aSKai Wang { 43*2de3b87aSKai Wang Elf_Scn *s; 44*2de3b87aSKai Wang Elf_Data *d; 45*2de3b87aSKai Wang size_t alignment, count; 46*2de3b87aSKai Wang GElf_Shdr shdr; 47*2de3b87aSKai Wang 48*2de3b87aSKai Wang if (e == NULL || e->e_kind != ELF_K_ELF) { 49*2de3b87aSKai Wang LIBELF_SET_ERROR(ARGUMENT, 0); 50*2de3b87aSKai Wang return (NULL); 51*2de3b87aSKai Wang } 52*2de3b87aSKai Wang 53*2de3b87aSKai Wang if ((s = elf_getscn(e, scndx)) == NULL || 54*2de3b87aSKai Wang gelf_getshdr(s, &shdr) == NULL) 55*2de3b87aSKai Wang return (NULL); 56*2de3b87aSKai Wang 57*2de3b87aSKai Wang if (shdr.sh_type != SHT_STRTAB || 58*2de3b87aSKai Wang offset >= shdr.sh_size) { 59*2de3b87aSKai Wang LIBELF_SET_ERROR(ARGUMENT, 0); 60*2de3b87aSKai Wang return (NULL); 61*2de3b87aSKai Wang } 62*2de3b87aSKai Wang 63*2de3b87aSKai Wang d = NULL; 64*2de3b87aSKai Wang if (e->e_flags & ELF_F_LAYOUT) { 65*2de3b87aSKai Wang 66*2de3b87aSKai Wang /* 67*2de3b87aSKai Wang * The application is taking responsibility for the 68*2de3b87aSKai Wang * ELF object's layout, so we can directly translate 69*2de3b87aSKai Wang * an offset to a `char *' address using the `d_off' 70*2de3b87aSKai Wang * members of Elf_Data descriptors. 71*2de3b87aSKai Wang */ 72*2de3b87aSKai Wang while ((d = elf_getdata(s, d)) != NULL) { 73*2de3b87aSKai Wang 74*2de3b87aSKai Wang if (d->d_buf == 0 || d->d_size == 0) 75*2de3b87aSKai Wang continue; 76*2de3b87aSKai Wang 77*2de3b87aSKai Wang if (d->d_type != ELF_T_BYTE) { 78*2de3b87aSKai Wang LIBELF_SET_ERROR(DATA, 0); 79*2de3b87aSKai Wang return (NULL); 80*2de3b87aSKai Wang } 81*2de3b87aSKai Wang 82*2de3b87aSKai Wang if (offset >= d->d_off && 83*2de3b87aSKai Wang offset < d->d_off + d->d_size) 84*2de3b87aSKai Wang return ((char *) d->d_buf + offset - d->d_off); 85*2de3b87aSKai Wang } 86*2de3b87aSKai Wang } else { 87*2de3b87aSKai Wang /* 88*2de3b87aSKai Wang * Otherwise, the `d_off' members are not useable and 89*2de3b87aSKai Wang * we need to compute offsets ourselves, taking into 90*2de3b87aSKai Wang * account 'holes' in coverage of the section introduced 91*2de3b87aSKai Wang * by alignment requirements. 92*2de3b87aSKai Wang */ 93*2de3b87aSKai Wang count = (size_t) 0; /* cumulative count of bytes seen */ 94*2de3b87aSKai Wang while ((d = elf_getdata(s, d)) != NULL && count <= offset) { 95*2de3b87aSKai Wang 96*2de3b87aSKai Wang if (d->d_buf == NULL || d->d_size == 0) 97*2de3b87aSKai Wang continue; 98*2de3b87aSKai Wang 99*2de3b87aSKai Wang if (d->d_type != ELF_T_BYTE) { 100*2de3b87aSKai Wang LIBELF_SET_ERROR(DATA, 0); 101*2de3b87aSKai Wang return (NULL); 102*2de3b87aSKai Wang } 103*2de3b87aSKai Wang 104*2de3b87aSKai Wang if ((alignment = d->d_align) > 1) { 105*2de3b87aSKai Wang if ((alignment & (alignment - 1)) != 0) { 106*2de3b87aSKai Wang LIBELF_SET_ERROR(DATA, 0); 107*2de3b87aSKai Wang return (NULL); 108*2de3b87aSKai Wang } 109*2de3b87aSKai Wang count = roundup2(count, alignment); 110*2de3b87aSKai Wang } 111*2de3b87aSKai Wang 112*2de3b87aSKai Wang if (offset < count) { 113*2de3b87aSKai Wang /* offset starts in the 'hole' */ 114*2de3b87aSKai Wang LIBELF_SET_ERROR(ARGUMENT, 0); 115*2de3b87aSKai Wang return (NULL); 116*2de3b87aSKai Wang } 117*2de3b87aSKai Wang 118*2de3b87aSKai Wang if (offset < count + d->d_size) { 119*2de3b87aSKai Wang if (d->d_buf != NULL) 120*2de3b87aSKai Wang return ((char *) d->d_buf + 121*2de3b87aSKai Wang offset - count); 122*2de3b87aSKai Wang LIBELF_SET_ERROR(DATA, 0); 123*2de3b87aSKai Wang return (NULL); 124*2de3b87aSKai Wang } 125*2de3b87aSKai Wang 126*2de3b87aSKai Wang count += d->d_size; 127*2de3b87aSKai Wang } 128*2de3b87aSKai Wang } 129*2de3b87aSKai Wang 130*2de3b87aSKai Wang LIBELF_SET_ERROR(ARGUMENT, 0); 131*2de3b87aSKai Wang return (NULL); 132*2de3b87aSKai Wang } 133