1 // SPDX-License-Identifier: GPL-2.0+
2 //
3 // Copyright 2019, Michael Ellerman, IBM Corp.
4 //
5 // Test that out-of-bounds reads/writes behave as expected.
6 
7 #include <setjmp.h>
8 #include <stdbool.h>
9 #include <stdio.h>
10 #include <stdlib.h>
11 #include <string.h>
12 #include <sys/types.h>
13 #include <sys/wait.h>
14 #include <unistd.h>
15 
16 #include "utils.h"
17 
18 // Old distros (Ubuntu 16.04 at least) don't define this
19 #ifndef SEGV_BNDERR
20 #define SEGV_BNDERR	3
21 #endif
22 
23 // 64-bit kernel is always here
24 #define PAGE_OFFSET	(0xcul << 60)
25 
26 static unsigned long kernel_virt_end;
27 
28 static volatile int fault_code;
29 static volatile unsigned long fault_addr;
30 static jmp_buf setjmp_env;
31 
segv_handler(int n,siginfo_t * info,void * ctxt_v)32 static void segv_handler(int n, siginfo_t *info, void *ctxt_v)
33 {
34 	fault_code = info->si_code;
35 	fault_addr = (unsigned long)info->si_addr;
36 	siglongjmp(setjmp_env, 1);
37 }
38 
bad_access(char * p,bool write)39 int bad_access(char *p, bool write)
40 {
41 	char x = 0;
42 
43 	fault_code = 0;
44 	fault_addr = 0;
45 
46 	if (sigsetjmp(setjmp_env, 1) == 0) {
47 		if (write)
48 			*p = 1;
49 		else
50 			x = *p;
51 
52 		printf("Bad - no SEGV! (%c)\n", x);
53 		return 1;
54 	}
55 
56 	// If we see MAPERR that means we took a page fault rather than an SLB
57 	// miss. We only expect to take page faults for addresses within the
58 	// valid kernel range.
59 	FAIL_IF(fault_code == SEGV_MAPERR && \
60 		(fault_addr < PAGE_OFFSET || fault_addr >= kernel_virt_end));
61 
62 	FAIL_IF(fault_code != SEGV_MAPERR && fault_code != SEGV_BNDERR);
63 
64 	return 0;
65 }
66 
test(void)67 static int test(void)
68 {
69 	unsigned long i, j, addr, region_shift, page_shift, page_size;
70 	struct sigaction sig;
71 	bool hash_mmu;
72 
73 	sig = (struct sigaction) {
74 		.sa_sigaction = segv_handler,
75 		.sa_flags = SA_SIGINFO,
76 	};
77 
78 	FAIL_IF(sigaction(SIGSEGV, &sig, NULL) != 0);
79 
80 	FAIL_IF(using_hash_mmu(&hash_mmu));
81 
82 	page_size = sysconf(_SC_PAGESIZE);
83 	if (page_size == (64 * 1024))
84 		page_shift = 16;
85 	else
86 		page_shift = 12;
87 
88 	if (page_size == (64 * 1024) || !hash_mmu) {
89 		region_shift = 52;
90 
91 		// We have 7 512T regions (4 kernel linear, vmalloc, io, vmemmap)
92 		kernel_virt_end = PAGE_OFFSET + (7 * (512ul << 40));
93 	} else if (page_size == (4 * 1024) && hash_mmu) {
94 		region_shift = 46;
95 
96 		// We have 7 64T regions (4 kernel linear, vmalloc, io, vmemmap)
97 		kernel_virt_end = PAGE_OFFSET + (7 * (64ul << 40));
98 	} else
99 		FAIL_IF(true);
100 
101 	printf("Using %s MMU, PAGE_SIZE = %dKB start address 0x%016lx\n",
102 	       hash_mmu ? "hash" : "radix",
103 	       (1 << page_shift) >> 10,
104 	       1ul << region_shift);
105 
106 	// This generates access patterns like:
107 	//   0x0010000000000000
108 	//   0x0010000000010000
109 	//   0x0010000000020000
110 	//   ...
111 	//   0x0014000000000000
112 	//   0x0018000000000000
113 	//   0x0020000000000000
114 	//   0x0020000000010000
115 	//   0x0020000000020000
116 	//   ...
117 	//   0xf400000000000000
118 	//   0xf800000000000000
119 
120 	for (i = 1; i <= ((0xful << 60) >> region_shift); i++) {
121 		for (j = page_shift - 1; j < 60; j++) {
122 			unsigned long base, delta;
123 
124 			base  = i << region_shift;
125 			delta = 1ul << j;
126 
127 			if (delta >= base)
128 				break;
129 
130 			addr = (base | delta) & ~((1 << page_shift) - 1);
131 
132 			FAIL_IF(bad_access((char *)addr, false));
133 			FAIL_IF(bad_access((char *)addr, true));
134 		}
135 	}
136 
137 	return 0;
138 }
139 
main(void)140 int main(void)
141 {
142 	test_harness_set_timeout(300);
143 	return test_harness(test, "bad_accesses");
144 }
145