1 // SPDX-License-Identifier: GPL-2.0-or-later
2
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
13 static void die(const char *msg)
14 {
15 printf("%s\n", msg);
16 exit(1);
17 }
18
19 static 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
45 static 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
54 static 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
91 int 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
Linux® is a registered trademark of Linus Torvalds in the United States and other countries.
TOMOYO® is a registered trademark of NTT DATA CORPORATION.