403 lines
9.3 KiB
C
403 lines
9.3 KiB
C
/*-
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* SPDX-License-Identifier: BSD-2-Clause-FreeBSD
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*
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* Copyright (c) 2019 The FreeBSD Foundation.
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*
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* This software was developed by Bora Ozarslan under sponsorship from
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* the FreeBSD Foundation.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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#include <sys/param.h>
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#include <sys/elf_common.h>
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#include <sys/endian.h>
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#include <sys/stat.h>
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#include <err.h>
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#include <fcntl.h>
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#include <gelf.h>
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#include <getopt.h>
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#include <libelf.h>
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#include <stdbool.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <unistd.h>
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#include "_elftc.h"
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__FBSDID("$FreeBSD$");
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static bool convert_to_feature_val(char *, uint32_t *);
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static bool edit_file_features(Elf *, int, int, char *);
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static bool get_file_features(Elf *, int, int, uint32_t *, uint64_t *);
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static void print_features(void);
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static bool print_file_features(Elf *, int, int, char *);
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static void usage(void);
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struct ControlFeatures {
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const char *alias;
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unsigned long value;
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const char *desc;
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};
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static struct ControlFeatures featurelist[] = {
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{ "aslr", NT_FREEBSD_FCTL_ASLR_DISABLE, "Disable ASLR" },
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{ "protmax", NT_FREEBSD_FCTL_PROTMAX_DISABLE,
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"Disable implicit PROT_MAX" },
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{ "stackgap", NT_FREEBSD_FCTL_STKGAP_DISABLE, "Disable stack gap" },
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{ "wxneeded", NT_FREEBSD_FCTL_WXNEEDED, "Requires W+X mappings" },
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};
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static struct option long_opts[] = {
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{ "help", no_argument, NULL, 'h' },
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{ NULL, 0, NULL, 0 }
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};
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#if BYTE_ORDER == LITTLE_ENDIAN
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#define SUPPORTED_ENDIAN ELFDATA2LSB
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#else
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#define SUPPORTED_ENDIAN ELFDATA2MSB
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#endif
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int
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main(int argc, char **argv)
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{
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GElf_Ehdr ehdr;
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Elf *elf;
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Elf_Kind kind;
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int ch, fd, retval;
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char *features;
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bool editfeatures, lflag;
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lflag = 0;
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editfeatures = false;
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retval = 0;
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features = NULL;
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if (elf_version(EV_CURRENT) == EV_NONE)
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errx(EXIT_FAILURE, "elf_version error");
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while ((ch = getopt_long(argc, argv, "hle:", long_opts, NULL)) != -1) {
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switch (ch) {
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case 'l':
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print_features();
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lflag = true;
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break;
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case 'e':
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features = optarg;
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editfeatures = true;
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break;
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case 'h':
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default:
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usage();
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}
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}
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argc -= optind;
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argv += optind;
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if (argc == 0) {
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if (lflag)
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exit(0);
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else {
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warnx("no file(s) specified");
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usage();
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}
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}
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while (argc) {
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elf = NULL;
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if ((fd = open(argv[0],
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editfeatures ? O_RDWR : O_RDONLY, 0)) < 0) {
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warn("error opening file %s", argv[0]);
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retval = 1;
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goto fail;
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}
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if ((elf = elf_begin(fd, ELF_C_READ, NULL)) == NULL) {
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warnx("elf_begin failed: %s", elf_errmsg(-1));
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retval = 1;
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goto fail;
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}
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if ((kind = elf_kind(elf)) != ELF_K_ELF) {
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if (kind == ELF_K_AR)
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warnx("file '%s' is an archive", argv[0]);
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else
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warnx("file '%s' is not an ELF file", argv[0]);
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retval = 1;
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goto fail;
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}
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if (gelf_getehdr(elf, &ehdr) == NULL) {
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warnx("gelf_getehdr: %s", elf_errmsg(-1));
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retval = 1;
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goto fail;
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}
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/*
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* XXX need to support cross-endian operation, but for now
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* exit on error rather than misbehaving.
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*/
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if (ehdr.e_ident[EI_DATA] != SUPPORTED_ENDIAN) {
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warnx("file endianness must match host");
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retval = 1;
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goto fail;
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}
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if (!editfeatures) {
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if (!print_file_features(elf, ehdr.e_phnum, fd,
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argv[0])) {
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retval = 1;
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goto fail;
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}
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} else if (!edit_file_features(elf, ehdr.e_phnum, fd,
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features)) {
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retval = 1;
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goto fail;
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}
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fail:
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if (elf != NULL)
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elf_end(elf);
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if (fd >= 0)
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close(fd);
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argc--;
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argv++;
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}
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return (retval);
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}
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#define USAGE_MESSAGE \
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"\
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Usage: %s [options] file...\n\
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Set or display the control features for an ELF object.\n\n\
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Supported options are:\n\
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-l List known control features.\n\
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-e [+-=]feature,list Edit features from a comma separated list.\n\
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-h | --help Print a usage message and exit.\n"
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static void
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usage(void)
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{
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fprintf(stderr, USAGE_MESSAGE, ELFTC_GETPROGNAME());
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exit(1);
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}
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static bool
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convert_to_feature_val(char *feature_str, uint32_t *feature_val)
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{
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char *feature;
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int i, len;
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uint32_t input;
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char operation;
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input = 0;
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operation = *feature_str;
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feature_str++;
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len = nitems(featurelist);
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while ((feature = strsep(&feature_str, ",")) != NULL) {
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for (i = 0; i < len; ++i) {
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if (strcmp(featurelist[i].alias, feature) == 0) {
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input |= featurelist[i].value;
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break;
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}
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}
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if (i == len) {
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warnx("%s is not a valid feature", feature);
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return (false);
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}
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}
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if (operation == '+') {
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*feature_val |= input;
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} else if (operation == '=') {
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*feature_val = input;
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} else if (operation == '-') {
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*feature_val &= ~input;
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} else {
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warnx("'%c' not an operator - use '+', '-', '='",
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feature_str[0]);
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return (false);
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}
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return (true);
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}
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static bool
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edit_file_features(Elf *elf, int phcount, int fd, char *val)
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{
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uint32_t features;
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uint64_t off;
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if (!get_file_features(elf, phcount, fd, &features, &off)) {
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warnx("NT_FREEBSD_FEATURE_CTL note not found");
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return (false);
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}
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if (!convert_to_feature_val(val, &features))
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return (false);
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if (lseek(fd, off, SEEK_SET) == -1 ||
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write(fd, &features, sizeof(features)) <
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(ssize_t)sizeof(features)) {
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warnx("error writing feature value");
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return (false);
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}
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return (true);
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}
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static void
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print_features(void)
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{
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size_t i;
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printf("Known features are:\n");
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for (i = 0; i < nitems(featurelist); ++i)
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printf("%-16s%s\n", featurelist[i].alias,
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featurelist[i].desc);
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}
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static bool
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print_file_features(Elf *elf, int phcount, int fd, char *filename)
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{
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uint32_t features;
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unsigned long i;
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if (!get_file_features(elf, phcount, fd, &features, NULL)) {
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return (false);
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}
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printf("File '%s' features:\n", filename);
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for (i = 0; i < nitems(featurelist); ++i) {
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printf("%-16s'%s' is ", featurelist[i].alias,
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featurelist[i].desc);
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if ((featurelist[i].value & features) == 0)
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printf("un");
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printf("set.\n");
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}
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return (true);
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}
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static bool
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get_file_features(Elf *elf, int phcount, int fd, uint32_t *features,
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uint64_t *off)
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{
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GElf_Phdr phdr;
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Elf_Note note;
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unsigned long read_total;
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int namesz, descsz, i;
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char *name;
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/*
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* Go through each program header to find one that is of type PT_NOTE
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* and has a note for feature control.
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*/
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for (i = 0; i < phcount; ++i) {
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if (gelf_getphdr(elf, i, &phdr) == NULL) {
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warnx("gelf_getphdr failed: %s", elf_errmsg(-1));
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return (false);
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}
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if (phdr.p_type != PT_NOTE)
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continue;
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if (lseek(fd, phdr.p_offset, SEEK_SET) < 0) {
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warn("lseek() failed:");
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return (false);
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}
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read_total = 0;
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while (read_total < phdr.p_filesz) {
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if (read(fd, ¬e, sizeof(note)) <
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(ssize_t)sizeof(note)) {
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warnx("elf note header too short");
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return (false);
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}
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read_total += sizeof(note);
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/*
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* XXX: Name and descriptor are 4 byte aligned, however,
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* the size given doesn't include the padding.
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*/
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namesz = roundup2(note.n_namesz, 4);
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name = malloc(namesz);
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if (name == NULL) {
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warn("malloc() failed.");
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return (false);
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}
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descsz = roundup2(note.n_descsz, 4);
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if (read(fd, name, namesz) < namesz) {
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warnx("elf note name too short");
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free(name);
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return (false);
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}
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read_total += namesz;
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if (note.n_namesz != 8 ||
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strncmp("FreeBSD", name, 7) != 0 ||
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note.n_type != NT_FREEBSD_FEATURE_CTL) {
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/* Not the right note. Skip the description */
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if (lseek(fd, descsz, SEEK_CUR) < 0) {
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warn("lseek() failed.");
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free(name);
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return (false);
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}
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read_total += descsz;
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free(name);
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continue;
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}
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if (note.n_descsz < sizeof(uint32_t)) {
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warnx("Feature descriptor can't "
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"be less than 4 bytes");
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free(name);
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return (false);
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}
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/*
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* XXX: For now we look at only 4 bytes of the
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* descriptor. This should respect descsz.
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*/
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if (note.n_descsz > sizeof(uint32_t))
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warnx("Feature note is bigger than expected");
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if (read(fd, features, sizeof(uint32_t)) <
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(ssize_t)sizeof(uint32_t)) {
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warnx("feature note data too short");
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free(name);
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return (false);
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}
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if (off != NULL)
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*off = phdr.p_offset + read_total;
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free(name);
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return (true);
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}
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}
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warnx("NT_FREEBSD_FEATURE_CTL note not found");
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return (false);
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}
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