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