1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3  * Userspace test harness for load_unaligned_zeropad. Creates two
4  * pages and uses mprotect to prevent access to the second page and
5  * a SEGV handler that walks the exception tables and runs the fixup
6  * routine.
7  *
8  * The results are compared against a normal load that is that is
9  * performed while access to the second page is enabled via mprotect.
10  *
11  * Copyright (C) 2014 Anton Blanchard <anton@au.ibm.com>, IBM
12  */
13 
14 #include <stdlib.h>
15 #include <string.h>
16 #include <stdio.h>
17 #include <stdbool.h>
18 #include <signal.h>
19 #include <unistd.h>
20 #include <sys/mman.h>
21 
22 #define FIXUP_SECTION ".ex_fixup"
23 
24 static inline unsigned long __fls(unsigned long x);
25 
26 #include "word-at-a-time.h"
27 
28 #include "utils.h"
29 
30 static inline unsigned long __fls(unsigned long x)
31 {
32 	int lz;
33 
34 	asm (PPC_CNTLZL "%0,%1" : "=r" (lz) : "r" (x));
35 	return sizeof(unsigned long) - 1 - lz;
36 }
37 
38 static int page_size;
39 static char *mem_region;
40 
41 static int protect_region(void)
42 {
43 	if (mprotect(mem_region + page_size, page_size, PROT_NONE)) {
44 		perror("mprotect");
45 		return 1;
46 	}
47 
48 	return 0;
49 }
50 
51 static int unprotect_region(void)
52 {
53 	if (mprotect(mem_region + page_size, page_size, PROT_READ|PROT_WRITE)) {
54 		perror("mprotect");
55 		return 1;
56 	}
57 
58 	return 0;
59 }
60 
61 extern char __start___ex_table[];
62 extern char __stop___ex_table[];
63 
64 struct extbl_entry {
65 	int insn;
66 	int fixup;
67 };
68 
69 static void segv_handler(int signr, siginfo_t *info, void *ptr)
70 {
71 	ucontext_t *uc = (ucontext_t *)ptr;
72 	unsigned long addr = (unsigned long)info->si_addr;
73 	unsigned long *ip = &UCONTEXT_NIA(uc);
74 	struct extbl_entry *entry = (struct extbl_entry *)__start___ex_table;
75 
76 	while (entry < (struct extbl_entry *)__stop___ex_table) {
77 		unsigned long insn, fixup;
78 
79 		insn  = (unsigned long)&entry->insn + entry->insn;
80 		fixup = (unsigned long)&entry->fixup + entry->fixup;
81 
82 		if (insn == *ip) {
83 			*ip = fixup;
84 			return;
85 		}
86 	}
87 
88 	printf("No exception table match for NIA %lx ADDR %lx\n", *ip, addr);
89 	abort();
90 }
91 
92 static void setup_segv_handler(void)
93 {
94 	struct sigaction action;
95 
96 	memset(&action, 0, sizeof(action));
97 	action.sa_sigaction = segv_handler;
98 	action.sa_flags = SA_SIGINFO;
99 	sigaction(SIGSEGV, &action, NULL);
100 }
101 
102 static int do_one_test(char *p, int page_offset)
103 {
104 	unsigned long should;
105 	unsigned long got;
106 
107 	FAIL_IF(unprotect_region());
108 	should = *(unsigned long *)p;
109 	FAIL_IF(protect_region());
110 
111 	got = load_unaligned_zeropad(p);
112 
113 	if (should != got) {
114 		printf("offset %u load_unaligned_zeropad returned 0x%lx, should be 0x%lx\n", page_offset, got, should);
115 		return 1;
116 	}
117 
118 	return 0;
119 }
120 
121 static int test_body(void)
122 {
123 	unsigned long i;
124 
125 	page_size = getpagesize();
126 	mem_region = mmap(NULL, page_size * 2, PROT_READ|PROT_WRITE,
127 		MAP_PRIVATE|MAP_ANONYMOUS, -1, 0);
128 
129 	FAIL_IF(mem_region == MAP_FAILED);
130 
131 	for (i = 0; i < page_size; i++)
132 		mem_region[i] = i;
133 
134 	memset(mem_region+page_size, 0, page_size);
135 
136 	setup_segv_handler();
137 
138 	for (i = 0; i < page_size; i++)
139 		FAIL_IF(do_one_test(mem_region+i, i));
140 
141 	return 0;
142 }
143 
144 int main(void)
145 {
146 	return test_harness(test_body, "load_unaligned_zeropad");
147 }
148