1 //===-- asan_linux.cpp ----------------------------------------------------===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 //
9 // This file is a part of AddressSanitizer, an address sanity checker.
10 //
11 // Linux-specific details.
12 //===----------------------------------------------------------------------===//
13 
14 #include "sanitizer_common/sanitizer_platform.h"
15 #if SANITIZER_FREEBSD || SANITIZER_LINUX || SANITIZER_NETBSD || \
16     SANITIZER_SOLARIS
17 
18 #include "asan_interceptors.h"
19 #include "asan_internal.h"
20 #include "asan_premap_shadow.h"
21 #include "asan_thread.h"
22 #include "sanitizer_common/sanitizer_flags.h"
23 #include "sanitizer_common/sanitizer_freebsd.h"
24 #include "sanitizer_common/sanitizer_libc.h"
25 #include "sanitizer_common/sanitizer_procmaps.h"
26 
27 #include <sys/time.h>
28 #include <sys/resource.h>
29 #include <sys/mman.h>
30 #include <sys/syscall.h>
31 #include <sys/types.h>
32 #include <dlfcn.h>
33 #include <fcntl.h>
34 #include <limits.h>
35 #include <pthread.h>
36 #include <stdio.h>
37 #include <unistd.h>
38 #include <unwind.h>
39 
40 #if SANITIZER_FREEBSD
41 #include <sys/link_elf.h>
42 #endif
43 
44 #if SANITIZER_SOLARIS
45 #include <link.h>
46 #endif
47 
48 #if SANITIZER_ANDROID || SANITIZER_FREEBSD || SANITIZER_SOLARIS
49 #include <ucontext.h>
50 extern "C" void* _DYNAMIC;
51 #elif SANITIZER_NETBSD
52 #include <link_elf.h>
53 #include <ucontext.h>
54 extern Elf_Dyn _DYNAMIC;
55 #else
56 #include <sys/ucontext.h>
57 #include <link.h>
58 #endif
59 
60 // x86-64 FreeBSD 9.2 and older define 'ucontext_t' incorrectly in
61 // 32-bit mode.
62 #if SANITIZER_FREEBSD && (SANITIZER_WORDSIZE == 32) && \
63   __FreeBSD_version <= 902001  // v9.2
64 #define ucontext_t xucontext_t
65 #endif
66 
67 typedef enum {
68   ASAN_RT_VERSION_UNDEFINED = 0,
69   ASAN_RT_VERSION_DYNAMIC,
70   ASAN_RT_VERSION_STATIC,
71 } asan_rt_version_t;
72 
73 // FIXME: perhaps also store abi version here?
74 extern "C" {
75 SANITIZER_INTERFACE_ATTRIBUTE
76 asan_rt_version_t  __asan_rt_version;
77 }
78 
79 namespace __asan {
80 
81 void InitializePlatformInterceptors() {}
82 void InitializePlatformExceptionHandlers() {}
83 bool IsSystemHeapAddress (uptr addr) { return false; }
84 
85 void *AsanDoesNotSupportStaticLinkage() {
86   // This will fail to link with -static.
87   return &_DYNAMIC;  // defined in link.h
88 }
89 
90 #if ASAN_PREMAP_SHADOW
91 uptr FindPremappedShadowStart(uptr shadow_size_bytes) {
92   uptr granularity = GetMmapGranularity();
93   uptr shadow_start = reinterpret_cast<uptr>(&__asan_shadow);
94   uptr premap_shadow_size = PremapShadowSize();
95   uptr shadow_size = RoundUpTo(shadow_size_bytes, granularity);
96   // We may have mapped too much. Release extra memory.
97   UnmapFromTo(shadow_start + shadow_size, shadow_start + premap_shadow_size);
98   return shadow_start;
99 }
100 #endif
101 
102 uptr FindDynamicShadowStart() {
103   uptr shadow_size_bytes = MemToShadowSize(kHighMemEnd);
104 #if ASAN_PREMAP_SHADOW
105   if (!PremapShadowFailed())
106     return FindPremappedShadowStart(shadow_size_bytes);
107 #endif
108 
109   return MapDynamicShadow(shadow_size_bytes, SHADOW_SCALE,
110                           /*min_shadow_base_alignment*/ 0, kHighMemEnd);
111 }
112 
113 void AsanApplyToGlobals(globals_op_fptr op, const void *needle) {
114   UNIMPLEMENTED();
115 }
116 
117 void FlushUnneededASanShadowMemory(uptr p, uptr size) {
118   // Since asan's mapping is compacting, the shadow chunk may be
119   // not page-aligned, so we only flush the page-aligned portion.
120   ReleaseMemoryPagesToOS(MemToShadow(p), MemToShadow(p + size));
121 }
122 
123 #if SANITIZER_ANDROID
124 // FIXME: should we do anything for Android?
125 void AsanCheckDynamicRTPrereqs() {}
126 void AsanCheckIncompatibleRT() {}
127 #else
128 static int FindFirstDSOCallback(struct dl_phdr_info *info, size_t size,
129                                 void *data) {
130   VReport(2, "info->dlpi_name = %s\tinfo->dlpi_addr = %p\n",
131           info->dlpi_name, info->dlpi_addr);
132 
133   // Continue until the first dynamic library is found
134   if (!info->dlpi_name || info->dlpi_name[0] == 0)
135     return 0;
136 
137   // Ignore vDSO
138   if (internal_strncmp(info->dlpi_name, "linux-", sizeof("linux-") - 1) == 0)
139     return 0;
140 
141 #if SANITIZER_FREEBSD || SANITIZER_NETBSD
142   // Ignore first entry (the main program)
143   char **p = (char **)data;
144   if (!(*p)) {
145     *p = (char *)-1;
146     return 0;
147   }
148 #endif
149 
150 #if SANITIZER_SOLARIS
151   // Ignore executable on Solaris
152   if (info->dlpi_addr == 0)
153     return 0;
154 #endif
155 
156   *(const char **)data = info->dlpi_name;
157   return 1;
158 }
159 
160 static bool IsDynamicRTName(const char *libname) {
161   return internal_strstr(libname, "libclang_rt.asan") ||
162     internal_strstr(libname, "libasan.so");
163 }
164 
165 static void ReportIncompatibleRT() {
166   Report("Your application is linked against incompatible ASan runtimes.\n");
167   Die();
168 }
169 
170 void AsanCheckDynamicRTPrereqs() {
171   if (!ASAN_DYNAMIC || !flags()->verify_asan_link_order)
172     return;
173 
174   // Ensure that dynamic RT is the first DSO in the list
175   const char *first_dso_name = nullptr;
176   dl_iterate_phdr(FindFirstDSOCallback, &first_dso_name);
177   if (first_dso_name && !IsDynamicRTName(first_dso_name)) {
178     Report("ASan runtime does not come first in initial library list; "
179            "you should either link runtime to your application or "
180            "manually preload it with LD_PRELOAD.\n");
181     Die();
182   }
183 }
184 
185 void AsanCheckIncompatibleRT() {
186   if (ASAN_DYNAMIC) {
187     if (__asan_rt_version == ASAN_RT_VERSION_UNDEFINED) {
188       __asan_rt_version = ASAN_RT_VERSION_DYNAMIC;
189     } else if (__asan_rt_version != ASAN_RT_VERSION_DYNAMIC) {
190       ReportIncompatibleRT();
191     }
192   } else {
193     if (__asan_rt_version == ASAN_RT_VERSION_UNDEFINED) {
194       // Ensure that dynamic runtime is not present. We should detect it
195       // as early as possible, otherwise ASan interceptors could bind to
196       // the functions in dynamic ASan runtime instead of the functions in
197       // system libraries, causing crashes later in ASan initialization.
198       MemoryMappingLayout proc_maps(/*cache_enabled*/true);
199       char filename[PATH_MAX];
200       MemoryMappedSegment segment(filename, sizeof(filename));
201       while (proc_maps.Next(&segment)) {
202         if (IsDynamicRTName(segment.filename)) {
203           Report("Your application is linked against "
204                  "incompatible ASan runtimes.\n");
205           Die();
206         }
207       }
208       __asan_rt_version = ASAN_RT_VERSION_STATIC;
209     } else if (__asan_rt_version != ASAN_RT_VERSION_STATIC) {
210       ReportIncompatibleRT();
211     }
212   }
213 }
214 #endif // SANITIZER_ANDROID
215 
216 #if !SANITIZER_ANDROID
217 void ReadContextStack(void *context, uptr *stack, uptr *ssize) {
218   ucontext_t *ucp = (ucontext_t*)context;
219   *stack = (uptr)ucp->uc_stack.ss_sp;
220   *ssize = ucp->uc_stack.ss_size;
221 }
222 #else
223 void ReadContextStack(void *context, uptr *stack, uptr *ssize) {
224   UNIMPLEMENTED();
225 }
226 #endif
227 
228 void *AsanDlSymNext(const char *sym) {
229   return dlsym(RTLD_NEXT, sym);
230 }
231 
232 bool HandleDlopenInit() {
233   // Not supported on this platform.
234   static_assert(!SANITIZER_SUPPORTS_INIT_FOR_DLOPEN,
235                 "Expected SANITIZER_SUPPORTS_INIT_FOR_DLOPEN to be false");
236   return false;
237 }
238 
239 } // namespace __asan
240 
241 #endif  // SANITIZER_FREEBSD || SANITIZER_LINUX || SANITIZER_NETBSD ||
242         // SANITIZER_SOLARIS
243