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 } 62