1 /* $NetBSD: msan.h,v 1.8 2022/09/13 09:39:49 riastradh Exp $ */
2
3 /*
4 * Copyright (c) 2019-2020 Maxime Villard, m00nbsd.net
5 * All rights reserved.
6 *
7 * This code is part of the KMSAN subsystem of the NetBSD kernel.
8 *
9 * Redistribution and use in source and binary forms, with or without
10 * modification, are permitted provided that the following conditions
11 * are met:
12 * 1. Redistributions of source code must retain the above copyright
13 * notice, this list of conditions and the following disclaimer.
14 * 2. Redistributions in binary form must reproduce the above copyright
15 * notice, this list of conditions and the following disclaimer in the
16 * documentation and/or other materials provided with the distribution.
17 *
18 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
19 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
20 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
21 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
22 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
23 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
24 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
25 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
26 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
27 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
28 * SUCH DAMAGE.
29 */
30
31 #ifndef _AMD64_MSAN_H_
32 #define _AMD64_MSAN_H_
33
34 #include <sys/ksyms.h>
35
36 #include <uvm/uvm.h>
37
38 #include <machine/pmap.h>
39 #include <machine/pmap_private.h>
40 #include <machine/pte.h>
41 #include <machine/vmparam.h>
42
43 #include <x86/bootspace.h>
44
45 #ifdef __HAVE_PCPU_AREA
46 #error "PCPU area not allowed with KMSAN"
47 #endif
48 #ifdef __HAVE_DIRECT_MAP
49 #error "DMAP not allowed with KMSAN"
50 #endif
51
52 /*
53 * One big shadow, divided in two sub-shadows (SHAD and ORIG), themselves
54 * divided in two regions (MAIN and KERN).
55 */
56
57 #define __MD_SHADOW_SIZE 0x20000000000ULL /* 4 * NBPD_L4 */
58 #define __MD_SHADOW_START (VA_SIGN_NEG((L4_SLOT_KMSAN * NBPD_L4)))
59 #define __MD_SHADOW_END (__MD_SHADOW_START + __MD_SHADOW_SIZE)
60
61 #define __MD_SHAD_MAIN_START (__MD_SHADOW_START)
62 #define __MD_SHAD_KERN_START (__MD_SHADOW_START + 0x8000000000ULL)
63
64 #define __MD_ORIG_MAIN_START (__MD_SHAD_KERN_START + 0x8000000000ULL)
65 #define __MD_ORIG_KERN_START (__MD_ORIG_MAIN_START + 0x8000000000ULL)
66
67 #define __MD_PTR_BASE 0xFFFFFFFF80000000ULL
68 #define __MD_ORIG_TYPE __BITS(31,28)
69
70 static inline int8_t *
kmsan_md_addr_to_shad(const void * addr)71 kmsan_md_addr_to_shad(const void *addr)
72 {
73 vaddr_t va = (vaddr_t)addr;
74
75 if (va >= vm_min_kernel_address && va < vm_max_kernel_address) {
76 return (int8_t *)(__MD_SHAD_MAIN_START + (va - vm_min_kernel_address));
77 } else if (va >= KERNBASE) {
78 return (int8_t *)(__MD_SHAD_KERN_START + (va - KERNBASE));
79 } else {
80 panic("%s: impossible, va=%p", __func__, (void *)va);
81 }
82 }
83
84 static inline int8_t *
kmsan_md_addr_to_orig(const void * addr)85 kmsan_md_addr_to_orig(const void *addr)
86 {
87 vaddr_t va = (vaddr_t)addr;
88
89 if (va >= vm_min_kernel_address && va < vm_max_kernel_address) {
90 return (int8_t *)(__MD_ORIG_MAIN_START + (va - vm_min_kernel_address));
91 } else if (va >= KERNBASE) {
92 return (int8_t *)(__MD_ORIG_KERN_START + (va - KERNBASE));
93 } else {
94 panic("%s: impossible, va=%p", __func__, (void *)va);
95 }
96 }
97
98 static inline bool
kmsan_md_unsupported(vaddr_t addr)99 kmsan_md_unsupported(vaddr_t addr)
100 {
101 return (addr >= (vaddr_t)PTE_BASE &&
102 addr < ((vaddr_t)PTE_BASE + NBPD_L4));
103 }
104
105 static inline paddr_t
__md_palloc(void)106 __md_palloc(void)
107 {
108 /* The page is zeroed. */
109 return pmap_get_physpage();
110 }
111
112 static inline paddr_t
__md_palloc_large(void)113 __md_palloc_large(void)
114 {
115 struct pglist pglist;
116 int ret;
117
118 if (!uvm.page_init_done)
119 return 0;
120
121 kmsan_init_arg(sizeof(psize_t) + 4 * sizeof(paddr_t) +
122 sizeof(struct pglist *) + 2 * sizeof(int));
123 ret = uvm_pglistalloc(NBPD_L2, 0, ~0UL, NBPD_L2, 0,
124 &pglist, 1, 0);
125 if (ret != 0)
126 return 0;
127
128 /* The page may not be zeroed. */
129 return VM_PAGE_TO_PHYS(TAILQ_FIRST(&pglist));
130 }
131
132 static void
kmsan_md_shadow_map_page(vaddr_t va)133 kmsan_md_shadow_map_page(vaddr_t va)
134 {
135 const pt_entry_t pteflags = PTE_W | pmap_pg_nx | PTE_P;
136 paddr_t pa;
137
138 KASSERT(va >= __MD_SHADOW_START && va < __MD_SHADOW_END);
139
140 if (!pmap_valid_entry(L4_BASE[pl4_i(va)])) {
141 pa = __md_palloc();
142 L4_BASE[pl4_i(va)] = pa | pteflags;
143 }
144 if (!pmap_valid_entry(L3_BASE[pl3_i(va)])) {
145 pa = __md_palloc();
146 L3_BASE[pl3_i(va)] = pa | pteflags;
147 }
148 if (!pmap_valid_entry(L2_BASE[pl2_i(va)])) {
149 if ((pa = __md_palloc_large()) != 0) {
150 L2_BASE[pl2_i(va)] = pa | pteflags | PTE_PS |
151 pmap_pg_g;
152 __insn_barrier();
153 __builtin_memset((void *)va, 0, NBPD_L2);
154 return;
155 }
156 pa = __md_palloc();
157 L2_BASE[pl2_i(va)] = pa | pteflags;
158 } else if (L2_BASE[pl2_i(va)] & PTE_PS) {
159 return;
160 }
161 if (!pmap_valid_entry(L1_BASE[pl1_i(va)])) {
162 pa = __md_palloc();
163 L1_BASE[pl1_i(va)] = pa | pteflags | pmap_pg_g;
164 }
165 }
166
167 static void
kmsan_md_init(void)168 kmsan_md_init(void)
169 {
170 extern struct bootspace bootspace;
171 size_t i;
172
173 CTASSERT((__MD_SHADOW_SIZE / NBPD_L4) == NL4_SLOT_KMSAN);
174
175 /* Kernel. */
176 for (i = 0; i < BTSPACE_NSEGS; i++) {
177 if (bootspace.segs[i].type == BTSEG_NONE) {
178 continue;
179 }
180 kmsan_shadow_map((void *)bootspace.segs[i].va,
181 bootspace.segs[i].sz);
182 }
183
184 /* Boot region. */
185 kmsan_shadow_map((void *)bootspace.boot.va, bootspace.boot.sz);
186
187 /* Module map. */
188 kmsan_shadow_map((void *)bootspace.smodule,
189 (size_t)(bootspace.emodule - bootspace.smodule));
190
191 /* The bootstrap spare va. */
192 kmsan_shadow_map((void *)bootspace.spareva, PAGE_SIZE);
193 }
194
195 static inline msan_orig_t
kmsan_md_orig_encode(int type,uintptr_t ptr)196 kmsan_md_orig_encode(int type, uintptr_t ptr)
197 {
198 msan_orig_t ret;
199
200 ret = (ptr & 0xFFFFFFFF) & ~__MD_ORIG_TYPE;
201 ret |= __SHIFTIN(type, __MD_ORIG_TYPE);
202
203 return ret;
204 }
205
206 static inline void
kmsan_md_orig_decode(msan_orig_t orig,int * type,uintptr_t * ptr)207 kmsan_md_orig_decode(msan_orig_t orig, int *type, uintptr_t *ptr)
208 {
209 *type = __SHIFTOUT(orig, __MD_ORIG_TYPE);
210 *ptr = (uintptr_t)(orig & ~__MD_ORIG_TYPE) | __MD_PTR_BASE;
211 }
212
213 static inline bool
kmsan_md_is_pc(uintptr_t ptr)214 kmsan_md_is_pc(uintptr_t ptr)
215 {
216 extern uint8_t __rodata_start;
217
218 return (ptr < (uintptr_t)&__rodata_start);
219 }
220
221 static inline bool
__md_unwind_end(const char * name)222 __md_unwind_end(const char *name)
223 {
224 if (!strcmp(name, "syscall") ||
225 !strcmp(name, "alltraps") ||
226 !strcmp(name, "handle_syscall") ||
227 !strncmp(name, "Xtrap", 5) ||
228 !strncmp(name, "Xintr", 5) ||
229 !strncmp(name, "Xhandle", 7) ||
230 !strncmp(name, "Xresume", 7) ||
231 !strncmp(name, "Xstray", 6) ||
232 !strncmp(name, "Xhold", 5) ||
233 !strncmp(name, "Xrecurse", 8) ||
234 !strcmp(name, "Xdoreti") ||
235 !strncmp(name, "Xsoft", 5)) {
236 return true;
237 }
238
239 return false;
240 }
241
242 static void
kmsan_md_unwind(void)243 kmsan_md_unwind(void)
244 {
245 uint64_t *rbp, rip;
246 const char *mod;
247 const char *sym;
248 size_t nsym;
249 int error;
250
251 rbp = (uint64_t *)__builtin_frame_address(0);
252 nsym = 0;
253
254 while (1) {
255 /* 8(%rbp) contains the saved %rip. */
256 rip = *(rbp + 1);
257
258 if (rip < KERNBASE) {
259 break;
260 }
261 error = ksyms_getname(&mod, &sym, (vaddr_t)rip, KSYMS_PROC);
262 if (error) {
263 break;
264 }
265 kmsan_printf("#%zu %p in %s <%s>\n", nsym, (void *)rip, sym, mod);
266 if (__md_unwind_end(sym)) {
267 break;
268 }
269
270 rbp = (uint64_t *)*(rbp);
271 if (rbp == 0) {
272 break;
273 }
274 nsym++;
275
276 if (nsym >= 15) {
277 break;
278 }
279 }
280 }
281
282 #endif /* _AMD64_MSAN_H_ */
283