1 /*
2  * Copyright (C) 2010 The Android Open Source Project
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License");
5  * you may not use this file except in compliance with the License.
6  * You may obtain a copy of the License at
7  *
8  *      http://www.apache.org/licenses/LICENSE-2.0
9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  */
16 #include <cpu-features.h>
17 #include <setjmp.h>
18 #include <stdio.h>
19 #include <signal.h>
20 
21 #ifndef __arm__
22 #error "Only compile this file for an ARM target"
23 #endif
24 
25 static int volatile g_signal_raised;
26 static sigjmp_buf g_jumper;
27 
my_signal_handler(int signum)28 static void my_signal_handler(int signum) {
29     g_signal_raised = 1;
30     siglongjmp(g_jumper, 1);
31 }
32 
do_idiv(int32_t a,int32_t b)33 static int32_t do_idiv(int32_t a, int32_t b) {
34   __asm__ __volatile__(
35       "sdiv %0, %0, %1\n\t"
36       : "=&r"(a)
37       : "r"(b)
38       : "cc");
39   return a;
40 }
41 
42 // Check that the ARM idiv instruction is supported.
43 // Returns 1 on success, 0 otherwise.
check_idiv(void)44 static int check_idiv(void) {
45     // Setup SIGILL signal handler.
46     struct sigaction old_handler, new_handler;
47     memset(&new_handler, 0, sizeof(new_handler));
48     new_handler.sa_handler = my_signal_handler;
49     sigaction(SIGILL, &new_handler, &old_handler);
50 
51     // Do the division.
52     g_signal_raised = 0;
53     if (sigsetjmp(g_jumper, 0) == 0)
54         do_idiv(12345, 17);
55 
56     // Restore SIGILL handler.
57     sigaction(SIGILL, &old_handler, NULL);
58 
59     return g_signal_raised == 0;
60 }
61 
main(void)62 int main(void)
63 {
64     uint32_t cpu_id = android_getCpuIdArm();
65     printf("cpu-features reports the following CPUID: 0x%08x\n",
66            cpu_id);
67 
68     uint64_t features = android_getCpuFeatures();
69 #ifdef __thumb2__
70     const uint64_t idiv_flag = ANDROID_CPU_ARM_FEATURE_IDIV_THUMB2;
71     const char* variant = "thumb";
72 #else
73     const uint64_t idiv_flag = ANDROID_CPU_ARM_FEATURE_IDIV_ARM;
74     const char* variant = "arm";
75 #endif
76 
77     printf("status of %s idiv instruction:\n", variant);
78     int idiv_reported = (features & idiv_flag) != 0;
79     printf("  reported      : %s\n",
80            idiv_reported ? "supported" : "unsupported");
81 
82     int idiv_checked = check_idiv();
83     printf("  runtime check : %s\n",
84            idiv_checked ? "supported" : "unsupported");
85 
86     return (idiv_reported != idiv_checked);
87 }
88