113 lines · c
1// SPDX-License-Identifier: GPL-2.0-or-later2 3#include <errno.h>4#include <stddef.h>5#include <stdio.h>6#include <stdlib.h>7#include <string.h>8#include <sys/prctl.h>9 10#include "dexcr.h"11#include "utils.h"12 13static void die(const char *msg)14{15 printf("%s\n", msg);16 exit(1);17}18 19static void help(void)20{21 printf("Invoke a provided program with a custom DEXCR on-exec reset value\n"22 "\n"23 "usage: chdexcr [CHDEXCR OPTIONS] -- PROGRAM [ARGS...]\n"24 "\n"25 "Each configurable DEXCR aspect is exposed as an option.\n"26 "\n"27 "The normal option sets the aspect in the DEXCR. The --no- variant\n"28 "clears that aspect. For example, --ibrtpd sets the IBRTPD aspect bit,\n"29 "so indirect branch prediction will be disabled in the provided program.\n"30 "Conversely, --no-ibrtpd clears the aspect bit, so indirect branch\n"31 "prediction may occur.\n"32 "\n"33 "CHDEXCR OPTIONS:\n");34 35 for (int i = 0; i < ARRAY_SIZE(aspects); i++) {36 const struct dexcr_aspect *aspect = &aspects[i];37 38 if (aspect->prctl == -1)39 continue;40 41 printf(" --%-6s / --no-%-6s : %s\n", aspect->opt, aspect->opt, aspect->desc);42 }43}44 45static const struct dexcr_aspect *opt_to_aspect(const char *opt)46{47 for (int i = 0; i < ARRAY_SIZE(aspects); i++)48 if (aspects[i].prctl != -1 && !strcmp(aspects[i].opt, opt))49 return &aspects[i];50 51 return NULL;52}53 54static int apply_option(const char *option)55{56 const struct dexcr_aspect *aspect;57 const char *opt = NULL;58 const char *set_prefix = "--";59 const char *clear_prefix = "--no-";60 unsigned long ctrl = 0;61 int err;62 63 if (!strcmp(option, "-h") || !strcmp(option, "--help")) {64 help();65 exit(0);66 }67 68 /* Strip out --(no-) prefix and determine ctrl value */69 if (!strncmp(option, clear_prefix, strlen(clear_prefix))) {70 opt = &option[strlen(clear_prefix)];71 ctrl |= PR_PPC_DEXCR_CTRL_CLEAR_ONEXEC;72 } else if (!strncmp(option, set_prefix, strlen(set_prefix))) {73 opt = &option[strlen(set_prefix)];74 ctrl |= PR_PPC_DEXCR_CTRL_SET_ONEXEC;75 }76 77 if (!opt || !*opt)78 return 1;79 80 aspect = opt_to_aspect(opt);81 if (!aspect)82 die("unknown aspect");83 84 err = pr_set_dexcr(aspect->prctl, ctrl);85 if (err)86 die("failed to apply option");87 88 return 0;89}90 91int main(int argc, char *const argv[])92{93 int i;94 95 if (!dexcr_exists())96 die("DEXCR not detected on this hardware");97 98 for (i = 1; i < argc; i++)99 if (apply_option(argv[i]))100 break;101 102 if (i < argc && !strcmp(argv[i], "--"))103 i++;104 105 if (i >= argc)106 die("missing command");107 108 execvp(argv[i], &argv[i]);109 perror("execve");110 111 return errno;112}113