1 //===-- dfsan.cc ----------------------------------------------------------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file is a part of DataFlowSanitizer.
12 // DataFlowSanitizer runtime. This file defines the public interface to
13 // DataFlowSanitizer as well as the definition of certain runtime functions
14 // called automatically by the compiler (specifically the instrumentation pass
15 // in llvm/lib/Transforms/Instrumentation/DataFlowSanitizer.cpp).
17 // The public interface is defined in include/sanitizer/dfsan_interface.h whose
18 // functions are prefixed dfsan_ while the compiler interface functions are
20 //===----------------------------------------------------------------------===//
22 #include "sanitizer_common/sanitizer_atomic.h"
23 #include "sanitizer_common/sanitizer_common.h"
24 #include "sanitizer_common/sanitizer_flags.h"
25 #include "sanitizer_common/sanitizer_flag_parser.h"
26 #include "sanitizer_common/sanitizer_libc.h"
28 #include "dfsan/dfsan.h"
30 using namespace __dfsan;
32 typedef atomic_uint16_t atomic_dfsan_label;
33 static const dfsan_label kInitializingLabel = -1;
35 static const uptr kNumLabels = 1 << (sizeof(dfsan_label) * 8);
37 static atomic_dfsan_label __dfsan_last_label;
38 static dfsan_label_info __dfsan_label_info[kNumLabels];
40 Flags __dfsan::flags_data;
42 SANITIZER_INTERFACE_ATTRIBUTE THREADLOCAL dfsan_label __dfsan_retval_tls;
43 SANITIZER_INTERFACE_ATTRIBUTE THREADLOCAL dfsan_label __dfsan_arg_tls[64];
45 // On Linux/x86_64, memory is laid out as follows:
47 // +--------------------+ 0x800000000000 (top of memory)
48 // | application memory |
49 // +--------------------+ 0x700000008000 (kAppAddr)
53 // +--------------------+ 0x200200000000 (kUnusedAddr)
55 // +--------------------+ 0x200000000000 (kUnionTableAddr)
57 // +--------------------+ 0x000000010000 (kShadowAddr)
58 // | reserved by kernel |
59 // +--------------------+ 0x000000000000
61 // To derive a shadow memory address from an application memory address,
62 // bits 44-46 are cleared to bring the address into the range
63 // [0x000000008000,0x100000000000). Then the address is shifted left by 1 to
64 // account for the double byte representation of shadow labels and move the
65 // address into the shadow memory range. See the function shadow_for below.
67 // On Linux/MIPS64, memory is laid out as follows:
69 // +--------------------+ 0x10000000000 (top of memory)
70 // | application memory |
71 // +--------------------+ 0xF000008000 (kAppAddr)
75 // +--------------------+ 0x2200000000 (kUnusedAddr)
77 // +--------------------+ 0x2000000000 (kUnionTableAddr)
79 // +--------------------+ 0x0000010000 (kShadowAddr)
80 // | reserved by kernel |
81 // +--------------------+ 0x0000000000
83 typedef atomic_dfsan_label dfsan_union_table_t[kNumLabels][kNumLabels];
85 #if defined(__x86_64__)
86 static const uptr kShadowAddr = 0x10000;
87 static const uptr kUnionTableAddr = 0x200000000000;
88 static const uptr kUnusedAddr = kUnionTableAddr + sizeof(dfsan_union_table_t);
89 static const uptr kAppAddr = 0x700000008000;
90 #elif defined(__mips64)
91 static const uptr kShadowAddr = 0x10000;
92 static const uptr kUnionTableAddr = 0x2000000000;
93 static const uptr kUnusedAddr = kUnionTableAddr + sizeof(dfsan_union_table_t);
94 static const uptr kAppAddr = 0xF000008000;
96 # error "DFSan not supported for this platform!"
99 static atomic_dfsan_label *union_table(dfsan_label l1, dfsan_label l2) {
100 return &(*(dfsan_union_table_t *) kUnionTableAddr)[l1][l2];
103 // Checks we do not run out of labels.
104 static void dfsan_check_label(dfsan_label label) {
105 if (label == kInitializingLabel) {
106 Report("FATAL: DataFlowSanitizer: out of labels\n");
111 // Resolves the union of two unequal labels. Nonequality is a precondition for
112 // this function (the instrumentation pass inlines the equality test).
113 extern "C" SANITIZER_INTERFACE_ATTRIBUTE
114 dfsan_label __dfsan_union(dfsan_label l1, dfsan_label l2) {
125 atomic_dfsan_label *table_ent = union_table(l1, l2);
126 // We need to deal with the case where two threads concurrently request
127 // a union of the same pair of labels. If the table entry is uninitialized,
128 // (i.e. 0) use a compare-exchange to set the entry to kInitializingLabel
129 // (i.e. -1) to mark that we are initializing it.
130 dfsan_label label = 0;
131 if (atomic_compare_exchange_strong(table_ent, &label, kInitializingLabel,
132 memory_order_acquire)) {
133 // Check whether l2 subsumes l1. We don't need to check whether l1
134 // subsumes l2 because we are guaranteed here that l1 < l2, and (at least
135 // in the cases we are interested in) a label may only subsume labels
136 // created earlier (i.e. with a lower numerical value).
137 if (__dfsan_label_info[l2].l1 == l1 ||
138 __dfsan_label_info[l2].l2 == l1) {
142 atomic_fetch_add(&__dfsan_last_label, 1, memory_order_relaxed) + 1;
143 dfsan_check_label(label);
144 __dfsan_label_info[label].l1 = l1;
145 __dfsan_label_info[label].l2 = l2;
147 atomic_store(table_ent, label, memory_order_release);
148 } else if (label == kInitializingLabel) {
149 // Another thread is initializing the entry. Wait until it is finished.
151 internal_sched_yield();
152 label = atomic_load(table_ent, memory_order_acquire);
153 } while (label == kInitializingLabel);
158 extern "C" SANITIZER_INTERFACE_ATTRIBUTE
159 dfsan_label __dfsan_union_load(const dfsan_label *ls, uptr n) {
160 dfsan_label label = ls[0];
161 for (uptr i = 1; i != n; ++i) {
162 dfsan_label next_label = ls[i];
163 if (label != next_label)
164 label = __dfsan_union(label, next_label);
169 extern "C" SANITIZER_INTERFACE_ATTRIBUTE
170 void __dfsan_unimplemented(char *fname) {
171 if (flags().warn_unimplemented)
172 Report("WARNING: DataFlowSanitizer: call to uninstrumented function %s\n",
176 // Use '-mllvm -dfsan-debug-nonzero-labels' and break on this function
177 // to try to figure out where labels are being introduced in a nominally
178 // label-free program.
179 extern "C" SANITIZER_INTERFACE_ATTRIBUTE void __dfsan_nonzero_label() {
180 if (flags().warn_nonzero_labels)
181 Report("WARNING: DataFlowSanitizer: saw nonzero label\n");
184 // Indirect call to an uninstrumented vararg function. We don't have a way of
185 // handling these at the moment.
186 extern "C" SANITIZER_INTERFACE_ATTRIBUTE void
187 __dfsan_vararg_wrapper(const char *fname) {
188 Report("FATAL: DataFlowSanitizer: unsupported indirect call to vararg "
189 "function %s\n", fname);
193 // Like __dfsan_union, but for use from the client or custom functions. Hence
194 // the equality comparison is done here before calling __dfsan_union.
195 SANITIZER_INTERFACE_ATTRIBUTE dfsan_label
196 dfsan_union(dfsan_label l1, dfsan_label l2) {
199 return __dfsan_union(l1, l2);
202 extern "C" SANITIZER_INTERFACE_ATTRIBUTE
203 dfsan_label dfsan_create_label(const char *desc, void *userdata) {
205 atomic_fetch_add(&__dfsan_last_label, 1, memory_order_relaxed) + 1;
206 dfsan_check_label(label);
207 __dfsan_label_info[label].l1 = __dfsan_label_info[label].l2 = 0;
208 __dfsan_label_info[label].desc = desc;
209 __dfsan_label_info[label].userdata = userdata;
213 extern "C" SANITIZER_INTERFACE_ATTRIBUTE
214 void __dfsan_set_label(dfsan_label label, void *addr, uptr size) {
215 for (dfsan_label *labelp = shadow_for(addr); size != 0; --size, ++labelp) {
216 // Don't write the label if it is already the value we need it to be.
217 // In a program where most addresses are not labeled, it is common that
218 // a page of shadow memory is entirely zeroed. The Linux copy-on-write
219 // implementation will share all of the zeroed pages, making a copy of a
220 // page when any value is written. The un-sharing will happen even if
221 // the value written does not change the value in memory. Avoiding the
222 // write when both |label| and |*labelp| are zero dramatically reduces
223 // the amount of real memory used by large programs.
224 if (label == *labelp)
231 SANITIZER_INTERFACE_ATTRIBUTE
232 void dfsan_set_label(dfsan_label label, void *addr, uptr size) {
233 __dfsan_set_label(label, addr, size);
236 SANITIZER_INTERFACE_ATTRIBUTE
237 void dfsan_add_label(dfsan_label label, void *addr, uptr size) {
238 for (dfsan_label *labelp = shadow_for(addr); size != 0; --size, ++labelp)
239 if (*labelp != label)
240 *labelp = __dfsan_union(*labelp, label);
243 // Unlike the other dfsan interface functions the behavior of this function
244 // depends on the label of one of its arguments. Hence it is implemented as a
246 extern "C" SANITIZER_INTERFACE_ATTRIBUTE dfsan_label
247 __dfsw_dfsan_get_label(long data, dfsan_label data_label,
248 dfsan_label *ret_label) {
253 SANITIZER_INTERFACE_ATTRIBUTE dfsan_label
254 dfsan_read_label(const void *addr, uptr size) {
257 return __dfsan_union_load(shadow_for(addr), size);
260 extern "C" SANITIZER_INTERFACE_ATTRIBUTE
261 const struct dfsan_label_info *dfsan_get_label_info(dfsan_label label) {
262 return &__dfsan_label_info[label];
265 extern "C" SANITIZER_INTERFACE_ATTRIBUTE int
266 dfsan_has_label(dfsan_label label, dfsan_label elem) {
269 const dfsan_label_info *info = dfsan_get_label_info(label);
271 return dfsan_has_label(info->l1, elem) || dfsan_has_label(info->l2, elem);
277 extern "C" SANITIZER_INTERFACE_ATTRIBUTE dfsan_label
278 dfsan_has_label_with_desc(dfsan_label label, const char *desc) {
279 const dfsan_label_info *info = dfsan_get_label_info(label);
281 return dfsan_has_label_with_desc(info->l1, desc) ||
282 dfsan_has_label_with_desc(info->l2, desc);
284 return internal_strcmp(desc, info->desc) == 0;
288 extern "C" SANITIZER_INTERFACE_ATTRIBUTE uptr
289 dfsan_get_label_count(void) {
290 dfsan_label max_label_allocated =
291 atomic_load(&__dfsan_last_label, memory_order_relaxed);
293 return static_cast<uptr>(max_label_allocated);
296 extern "C" SANITIZER_INTERFACE_ATTRIBUTE void
297 dfsan_dump_labels(int fd) {
298 dfsan_label last_label =
299 atomic_load(&__dfsan_last_label, memory_order_relaxed);
301 for (uptr l = 1; l <= last_label; ++l) {
303 internal_snprintf(buf, sizeof(buf), "%u %u %u ", l,
304 __dfsan_label_info[l].l1, __dfsan_label_info[l].l2);
305 internal_write(fd, buf, internal_strlen(buf));
306 if (__dfsan_label_info[l].l1 == 0 && __dfsan_label_info[l].desc) {
307 internal_write(fd, __dfsan_label_info[l].desc,
308 internal_strlen(__dfsan_label_info[l].desc));
310 internal_write(fd, "\n", 1);
314 void Flags::SetDefaults() {
315 #define DFSAN_FLAG(Type, Name, DefaultValue, Description) Name = DefaultValue;
316 #include "dfsan_flags.inc"
320 static void RegisterDfsanFlags(FlagParser *parser, Flags *f) {
321 #define DFSAN_FLAG(Type, Name, DefaultValue, Description) \
322 RegisterFlag(parser, #Name, Description, &f->Name);
323 #include "dfsan_flags.inc"
327 static void InitializeFlags() {
329 RegisterDfsanFlags(&parser, &flags());
330 flags().SetDefaults();
331 parser.ParseString(GetEnv("DFSAN_OPTIONS"));
334 static void dfsan_fini() {
335 if (internal_strcmp(flags().dump_labels_at_exit, "") != 0) {
336 fd_t fd = OpenFile(flags().dump_labels_at_exit, true /* write */);
337 if (fd == kInvalidFd) {
338 Report("WARNING: DataFlowSanitizer: unable to open output file %s\n",
339 flags().dump_labels_at_exit);
343 Report("INFO: DataFlowSanitizer: dumping labels to %s\n",
344 flags().dump_labels_at_exit);
345 dfsan_dump_labels(fd);
351 extern "C" void dfsan_init() {
353 static void dfsan_init(int argc, char **argv, char **envp) {
355 MmapFixedNoReserve(kShadowAddr, kUnusedAddr - kShadowAddr);
357 // Protect the region of memory we don't use, to preserve the one-to-one
358 // mapping from application to shadow memory. But if ASLR is disabled, Linux
359 // will load our executable in the middle of our unused region. This mostly
360 // works so long as the program doesn't use too much memory. We support this
361 // case by disabling memory protection when ASLR is disabled.
362 uptr init_addr = (uptr)&dfsan_init;
363 if (!(init_addr >= kUnusedAddr && init_addr < kAppAddr))
364 Mprotect(kUnusedAddr, kAppAddr - kUnusedAddr);
367 InitializeInterceptors();
369 // Register the fini callback to run when the program terminates successfully
370 // or it is killed by the runtime.
372 SetDieCallback(dfsan_fini);
374 __dfsan_label_info[kInitializingLabel].desc = "<init label>";
377 #if !defined(DFSAN_NOLIBC) && SANITIZER_CAN_USE_PREINIT_ARRAY
378 __attribute__((section(".preinit_array"), used))
379 static void (*dfsan_init_ptr)(int, char **, char **) = dfsan_init;