113 lines
2.5 KiB
C
113 lines
2.5 KiB
C
// SPDX-License-Identifier: GPL-2.0-or-later
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#include <errno.h>
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#include <stddef.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 <sys/prctl.h>
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#include "dexcr.h"
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#include "utils.h"
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static void die(const char *msg)
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{
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printf("%s\n", msg);
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exit(1);
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}
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static void help(void)
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{
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printf("Invoke a provided program with a custom DEXCR on-exec reset value\n"
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"\n"
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"usage: chdexcr [CHDEXCR OPTIONS] -- PROGRAM [ARGS...]\n"
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"\n"
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"Each configurable DEXCR aspect is exposed as an option.\n"
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"\n"
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"The normal option sets the aspect in the DEXCR. The --no- variant\n"
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"clears that aspect. For example, --ibrtpd sets the IBRTPD aspect bit,\n"
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"so indirect branch prediction will be disabled in the provided program.\n"
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"Conversely, --no-ibrtpd clears the aspect bit, so indirect branch\n"
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"prediction may occur.\n"
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"\n"
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"CHDEXCR OPTIONS:\n");
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for (int i = 0; i < ARRAY_SIZE(aspects); i++) {
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const struct dexcr_aspect *aspect = &aspects[i];
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if (aspect->prctl == -1)
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continue;
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printf(" --%-6s / --no-%-6s : %s\n", aspect->opt, aspect->opt, aspect->desc);
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}
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}
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static const struct dexcr_aspect *opt_to_aspect(const char *opt)
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{
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for (int i = 0; i < ARRAY_SIZE(aspects); i++)
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if (aspects[i].prctl != -1 && !strcmp(aspects[i].opt, opt))
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return &aspects[i];
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return NULL;
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}
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static int apply_option(const char *option)
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{
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const struct dexcr_aspect *aspect;
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const char *opt = NULL;
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const char *set_prefix = "--";
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const char *clear_prefix = "--no-";
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unsigned long ctrl = 0;
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int err;
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if (!strcmp(option, "-h") || !strcmp(option, "--help")) {
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help();
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exit(0);
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}
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/* Strip out --(no-) prefix and determine ctrl value */
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if (!strncmp(option, clear_prefix, strlen(clear_prefix))) {
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opt = &option[strlen(clear_prefix)];
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ctrl |= PR_PPC_DEXCR_CTRL_CLEAR_ONEXEC;
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} else if (!strncmp(option, set_prefix, strlen(set_prefix))) {
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opt = &option[strlen(set_prefix)];
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ctrl |= PR_PPC_DEXCR_CTRL_SET_ONEXEC;
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}
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if (!opt || !*opt)
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return 1;
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aspect = opt_to_aspect(opt);
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if (!aspect)
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die("unknown aspect");
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err = pr_set_dexcr(aspect->prctl, ctrl);
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if (err)
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die("failed to apply option");
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return 0;
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}
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int main(int argc, char *const argv[])
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{
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int i;
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if (!dexcr_exists())
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die("DEXCR not detected on this hardware");
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for (i = 1; i < argc; i++)
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if (apply_option(argv[i]))
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break;
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if (i < argc && !strcmp(argv[i], "--"))
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i++;
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if (i >= argc)
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die("missing command");
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execvp(argv[i], &argv[i]);
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perror("execve");
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return errno;
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}
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