1 /*
2 * Verify the COMMPAGE emulation
3 *
4 * The ARM commpage is a set of user space helper functions provided
5 * by the kernel in an effort to ease portability of user space code
6 * between different CPUs with potentially different capabilities. It
7 * is a 32 bit invention and similar to the vdso segment in many ways.
8 *
9 * The ABI is documented in the Linux kernel:
10 * Documentation/arm/kernel_userspace_helpers.rst
11 *
12 * Copyright (c) 2020 Linaro Ltd
13 *
14 * SPDX-License-Identifier: GPL-2.0-or-later
15 */
16
17 #include <stdlib.h>
18 #include <stdio.h>
19 #include <stdint.h>
20
21 #define ARM_COMMPAGE (0xffff0f00u)
22 #define ARM_KUSER_VERSION (*(int32_t *)(ARM_COMMPAGE + 0xfc))
23 typedef void * (get_tls_fn)(void);
24 #define ARM_KUSER_GET_TLS (*(get_tls_fn *)(ARM_COMMPAGE + 0xe0))
25 typedef int (cmpxchg_fn)(int oldval, int newval, volatile int *ptr);
26 #define ARM_KUSER_CMPXCHG (*(cmpxchg_fn *)(ARM_COMMPAGE + 0xc0))
27 typedef void (dmb_fn)(void);
28 #define ARM_KUSER_DMB (*(dmb_fn *)(ARM_COMMPAGE + 0xa0))
29 typedef int (cmpxchg64_fn)(const int64_t *oldval,
30 const int64_t *newval,
31 volatile int64_t *ptr);
32 #define ARM_KUSER_CMPXCHG64 (*(cmpxchg64_fn *)(ARM_COMMPAGE + 0x60))
33
34 #define fail_unless(x) \
35 do { \
36 if (!(x)) { \
37 fprintf(stderr, "FAILED at %s:%d\n", __FILE__, __LINE__); \
38 exit(EXIT_FAILURE); \
39 } \
40 } while (0)
41
42
main(int argc,char * argv[argc])43 int main(int argc, char *argv[argc])
44 {
45 void *kuser_tls;
46 int val = 1;
47 const int64_t oldval = 1, newval = 2;
48 int64_t val64 = 1;
49
50 fail_unless(ARM_KUSER_VERSION == 0x5);
51 kuser_tls = ARM_KUSER_GET_TLS();
52 printf("TLS = %p\n", kuser_tls);
53 fail_unless(kuser_tls != 0);
54 fail_unless(ARM_KUSER_CMPXCHG(1, 2, &val) == 0);
55 printf("val = %d\n", val);
56 /* this is a crash test, not checking an actual barrier occurs */
57 ARM_KUSER_DMB();
58 fail_unless(ARM_KUSER_CMPXCHG64(&oldval, &newval, &val64) == 0);
59 printf("val64 = %lld\n", val64);
60 return 0;
61 }
62