1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  * POWER Data Stream Control Register (DSCR) fork exec test
4  *
5  * This testcase modifies the DSCR using mtspr, forks & execs and
6  * verifies that the child is using the changed DSCR using mfspr.
7  *
8  * When using the privilege state SPR, the instructions such as
9  * mfspr or mtspr are privileged and the kernel emulates them
10  * for us. Instructions using problem state SPR can be executed
11  * directly without any emulation if the HW supports them. Else
12  * they also get emulated by the kernel.
13  *
14  * Copyright 2012, Anton Blanchard, IBM Corporation.
15  * Copyright 2015, Anshuman Khandual, IBM Corporation.
16  */
17 #include "dscr.h"
18 
19 static char *prog;
20 
21 static void do_exec(unsigned long parent_dscr)
22 {
23 	unsigned long cur_dscr, cur_dscr_usr;
24 
25 	cur_dscr = get_dscr();
26 	cur_dscr_usr = get_dscr_usr();
27 
28 	if (cur_dscr != parent_dscr) {
29 		fprintf(stderr, "Parent DSCR %ld was not inherited "
30 				"over exec (kernel value)\n", parent_dscr);
31 		exit(1);
32 	}
33 
34 	if (cur_dscr_usr != parent_dscr) {
35 		fprintf(stderr, "Parent DSCR %ld was not inherited "
36 				"over exec (user value)\n", parent_dscr);
37 		exit(1);
38 	}
39 	exit(0);
40 }
41 
42 int dscr_inherit_exec(void)
43 {
44 	unsigned long i, dscr = 0;
45 	pid_t pid;
46 
47 	SKIP_IF(!have_hwcap2(PPC_FEATURE2_DSCR));
48 
49 	for (i = 0; i < COUNT; i++) {
50 		dscr++;
51 		if (dscr > DSCR_MAX)
52 			dscr = 0;
53 
54 		if (dscr == get_default_dscr())
55 			continue;
56 
57 		if (i % 2 == 0)
58 			set_dscr_usr(dscr);
59 		else
60 			set_dscr(dscr);
61 
62 		pid = fork();
63 		if (pid == -1) {
64 			perror("fork() failed");
65 			exit(1);
66 		} else if (pid) {
67 			int status;
68 
69 			if (waitpid(pid, &status, 0) == -1) {
70 				perror("waitpid() failed");
71 				exit(1);
72 			}
73 
74 			if (!WIFEXITED(status)) {
75 				fprintf(stderr, "Child didn't exit cleanly\n");
76 				exit(1);
77 			}
78 
79 			if (WEXITSTATUS(status) != 0) {
80 				fprintf(stderr, "Child didn't exit cleanly\n");
81 				return 1;
82 			}
83 		} else {
84 			char dscr_str[16];
85 
86 			sprintf(dscr_str, "%ld", dscr);
87 			execlp(prog, prog, "exec", dscr_str, NULL);
88 			exit(1);
89 		}
90 	}
91 	return 0;
92 }
93 
94 int main(int argc, char *argv[])
95 {
96 	if (argc == 3 && !strcmp(argv[1], "exec")) {
97 		unsigned long parent_dscr;
98 
99 		parent_dscr = atoi(argv[2]);
100 		do_exec(parent_dscr);
101 	} else if (argc != 1) {
102 		fprintf(stderr, "Usage: %s\n", argv[0]);
103 		exit(1);
104 	}
105 
106 	prog = argv[0];
107 	return test_harness(dscr_inherit_exec, "dscr_inherit_exec_test");
108 }
109