tests/tcg/arm/commpage.c

   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
  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 }