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/*-
* Copyright (c) 2006 Joseph Koshy
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
#include <sys/param.h>
#include <assert.h>
#include "gelf.h"
#include "_libelf.h"
/*
* Convert an ELF section#,offset pair to a string pointer.
*/
char *
elf_strptr(Elf *e, size_t scndx, size_t offset)
{
Elf_Scn *s;
Elf_Data *d;
size_t alignment, count;
GElf_Shdr shdr;
if (e == NULL || e->e_kind != ELF_K_ELF) {
LIBELF_SET_ERROR(ARGUMENT, 0);
return (NULL);
}
if ((s = elf_getscn(e, scndx)) == NULL ||
gelf_getshdr(s, &shdr) == NULL)
return (NULL);
if (shdr.sh_type != SHT_STRTAB ||
offset >= shdr.sh_size) {
LIBELF_SET_ERROR(ARGUMENT, 0);
return (NULL);
}
d = NULL;
if (e->e_flags & ELF_F_LAYOUT) {
/*
* The application is taking responsibility for the
* ELF object's layout, so we can directly translate
* an offset to a `char *' address using the `d_off'
* members of Elf_Data descriptors.
*/
while ((d = elf_getdata(s, d)) != NULL) {
if (d->d_buf == 0 || d->d_size == 0)
continue;
if (d->d_type != ELF_T_BYTE) {
LIBELF_SET_ERROR(DATA, 0);
return (NULL);
}
if (offset >= d->d_off &&
offset < d->d_off + d->d_size)
return ((char *) d->d_buf + offset - d->d_off);
}
} else {
/*
* Otherwise, the `d_off' members are not useable and
* we need to compute offsets ourselves, taking into
* account 'holes' in coverage of the section introduced
* by alignment requirements.
*/
count = (size_t) 0; /* cumulative count of bytes seen */
while ((d = elf_getdata(s, d)) != NULL && count <= offset) {
if (d->d_buf == NULL || d->d_size == 0)
continue;
if (d->d_type != ELF_T_BYTE) {
LIBELF_SET_ERROR(DATA, 0);
return (NULL);
}
if ((alignment = d->d_align) > 1) {
if ((alignment & (alignment - 1)) != 0) {
LIBELF_SET_ERROR(DATA, 0);
return (NULL);
}
count = roundup(count, alignment);
}
if (offset < count) {
/* offset starts in the 'hole' */
LIBELF_SET_ERROR(ARGUMENT, 0);
return (NULL);
}
if (offset < count + d->d_size) {
if (d->d_buf != NULL)
return ((char *) d->d_buf +
offset - count);
LIBELF_SET_ERROR(DATA, 0);
return (NULL);
}
count += d->d_size;
}
}
LIBELF_SET_ERROR(ARGUMENT, 0);
return (NULL);
}
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