1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  * POWER Data Stream Control Register (DSCR) fork test
4  *
5  * This testcase modifies the DSCR using mtspr, forks and then
6  * verifies that the child process has the correct changed DSCR
7  * value using mfspr.
8  *
9  * When using the privilege state SPR, the instructions such as
10  * mfspr or mtspr are priviledged and the kernel emulates them
11  * for us. Instructions using problem state SPR can be exuecuted
12  * directly without any emulation if the HW supports them. Else
13  * they also get emulated by the kernel.
14  *
15  * Copyright 2012, Anton Blanchard, IBM Corporation.
16  * Copyright 2015, Anshuman Khandual, IBM Corporation.
17  */
18 #include "dscr.h"
19 
20 int dscr_inherit(void)
21 {
22 	unsigned long i, dscr = 0;
23 	pid_t pid;
24 
25 	srand(getpid());
26 	set_dscr(dscr);
27 
28 	for (i = 0; i < COUNT; i++) {
29 		unsigned long cur_dscr, cur_dscr_usr;
30 
31 		dscr++;
32 		if (dscr > DSCR_MAX)
33 			dscr = 0;
34 
35 		if (i % 2 == 0)
36 			set_dscr_usr(dscr);
37 		else
38 			set_dscr(dscr);
39 
40 		pid = fork();
41 		if (pid == -1) {
42 			perror("fork() failed");
43 			exit(1);
44 		} else if (pid) {
45 			int status;
46 
47 			if (waitpid(pid, &status, 0) == -1) {
48 				perror("waitpid() failed");
49 				exit(1);
50 			}
51 
52 			if (!WIFEXITED(status)) {
53 				fprintf(stderr, "Child didn't exit cleanly\n");
54 				exit(1);
55 			}
56 
57 			if (WEXITSTATUS(status) != 0) {
58 				fprintf(stderr, "Child didn't exit cleanly\n");
59 				return 1;
60 			}
61 		} else {
62 			cur_dscr = get_dscr();
63 			if (cur_dscr != dscr) {
64 				fprintf(stderr, "Kernel DSCR should be %ld "
65 					"but is %ld\n", dscr, cur_dscr);
66 				exit(1);
67 			}
68 
69 			cur_dscr_usr = get_dscr_usr();
70 			if (cur_dscr_usr != dscr) {
71 				fprintf(stderr, "User DSCR should be %ld "
72 					"but is %ld\n", dscr, cur_dscr_usr);
73 				exit(1);
74 			}
75 			exit(0);
76 		}
77 	}
78 	return 0;
79 }
80 
81 int main(int argc, char *argv[])
82 {
83 	return test_harness(dscr_inherit, "dscr_inherit_test");
84 }
85