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 SANITIZER_INTERFACE_ATTRIBUTE uptr __dfsan_shadow_ptr_mask;
47 // On Linux/x86_64, memory is laid out as follows:
49 // +--------------------+ 0x800000000000 (top of memory)
50 // | application memory |
51 // +--------------------+ 0x700000008000 (kAppAddr)
55 // +--------------------+ 0x200200000000 (kUnusedAddr)
57 // +--------------------+ 0x200000000000 (kUnionTableAddr)
59 // +--------------------+ 0x000000010000 (kShadowAddr)
60 // | reserved by kernel |
61 // +--------------------+ 0x000000000000
63 // To derive a shadow memory address from an application memory address,
64 // bits 44-46 are cleared to bring the address into the range
65 // [0x000000008000,0x100000000000). Then the address is shifted left by 1 to
66 // account for the double byte representation of shadow labels and move the
67 // address into the shadow memory range. See the function shadow_for below.
69 // On Linux/MIPS64, memory is laid out as follows:
71 // +--------------------+ 0x10000000000 (top of memory)
72 // | application memory |
73 // +--------------------+ 0xF000008000 (kAppAddr)
77 // +--------------------+ 0x2200000000 (kUnusedAddr)
79 // +--------------------+ 0x2000000000 (kUnionTableAddr)
81 // +--------------------+ 0x0000010000 (kShadowAddr)
82 // | reserved by kernel |
83 // +--------------------+ 0x0000000000
85 // On Linux/AArch64 (39-bit VMA), memory is laid out as follow:
87 // +--------------------+ 0x8000000000 (top of memory)
88 // | application memory |
89 // +--------------------+ 0x7000008000 (kAppAddr)
93 // +--------------------+ 0x1200000000 (kUnusedAddr)
95 // +--------------------+ 0x1000000000 (kUnionTableAddr)
97 // +--------------------+ 0x0000010000 (kShadowAddr)
98 // | reserved by kernel |
99 // +--------------------+ 0x0000000000
101 // On Linux/AArch64 (42-bit VMA), memory is laid out as follow:
103 // +--------------------+ 0x40000000000 (top of memory)
104 // | application memory |
105 // +--------------------+ 0x3ff00008000 (kAppAddr)
109 // +--------------------+ 0x1200000000 (kUnusedAddr)
111 // +--------------------+ 0x8000000000 (kUnionTableAddr)
113 // +--------------------+ 0x0000010000 (kShadowAddr)
114 // | reserved by kernel |
115 // +--------------------+ 0x0000000000
117 typedef atomic_dfsan_label dfsan_union_table_t[kNumLabels][kNumLabels];
119 #ifdef DFSAN_RUNTIME_VMA
120 // Runtime detected VMA size.
121 int __dfsan::vmaSize;
124 static uptr UnusedAddr() {
125 return MappingArchImpl<MAPPING_UNION_TABLE_ADDR>()
126 + sizeof(dfsan_union_table_t);
129 static atomic_dfsan_label *union_table(dfsan_label l1, dfsan_label l2) {
130 return &(*(dfsan_union_table_t *) UnionTableAddr())[l1][l2];
133 // Checks we do not run out of labels.
134 static void dfsan_check_label(dfsan_label label) {
135 if (label == kInitializingLabel) {
136 Report("FATAL: DataFlowSanitizer: out of labels\n");
141 // Resolves the union of two unequal labels. Nonequality is a precondition for
142 // this function (the instrumentation pass inlines the equality test).
143 extern "C" SANITIZER_INTERFACE_ATTRIBUTE
144 dfsan_label __dfsan_union(dfsan_label l1, dfsan_label l2) {
155 atomic_dfsan_label *table_ent = union_table(l1, l2);
156 // We need to deal with the case where two threads concurrently request
157 // a union of the same pair of labels. If the table entry is uninitialized,
158 // (i.e. 0) use a compare-exchange to set the entry to kInitializingLabel
159 // (i.e. -1) to mark that we are initializing it.
160 dfsan_label label = 0;
161 if (atomic_compare_exchange_strong(table_ent, &label, kInitializingLabel,
162 memory_order_acquire)) {
163 // Check whether l2 subsumes l1. We don't need to check whether l1
164 // subsumes l2 because we are guaranteed here that l1 < l2, and (at least
165 // in the cases we are interested in) a label may only subsume labels
166 // created earlier (i.e. with a lower numerical value).
167 if (__dfsan_label_info[l2].l1 == l1 ||
168 __dfsan_label_info[l2].l2 == l1) {
172 atomic_fetch_add(&__dfsan_last_label, 1, memory_order_relaxed) + 1;
173 dfsan_check_label(label);
174 __dfsan_label_info[label].l1 = l1;
175 __dfsan_label_info[label].l2 = l2;
177 atomic_store(table_ent, label, memory_order_release);
178 } else if (label == kInitializingLabel) {
179 // Another thread is initializing the entry. Wait until it is finished.
181 internal_sched_yield();
182 label = atomic_load(table_ent, memory_order_acquire);
183 } while (label == kInitializingLabel);
188 extern "C" SANITIZER_INTERFACE_ATTRIBUTE
189 dfsan_label __dfsan_union_load(const dfsan_label *ls, uptr n) {
190 dfsan_label label = ls[0];
191 for (uptr i = 1; i != n; ++i) {
192 dfsan_label next_label = ls[i];
193 if (label != next_label)
194 label = __dfsan_union(label, next_label);
199 extern "C" SANITIZER_INTERFACE_ATTRIBUTE
200 void __dfsan_unimplemented(char *fname) {
201 if (flags().warn_unimplemented)
202 Report("WARNING: DataFlowSanitizer: call to uninstrumented function %s\n",
206 // Use '-mllvm -dfsan-debug-nonzero-labels' and break on this function
207 // to try to figure out where labels are being introduced in a nominally
208 // label-free program.
209 extern "C" SANITIZER_INTERFACE_ATTRIBUTE void __dfsan_nonzero_label() {
210 if (flags().warn_nonzero_labels)
211 Report("WARNING: DataFlowSanitizer: saw nonzero label\n");
214 // Indirect call to an uninstrumented vararg function. We don't have a way of
215 // handling these at the moment.
216 extern "C" SANITIZER_INTERFACE_ATTRIBUTE void
217 __dfsan_vararg_wrapper(const char *fname) {
218 Report("FATAL: DataFlowSanitizer: unsupported indirect call to vararg "
219 "function %s\n", fname);
223 // Like __dfsan_union, but for use from the client or custom functions. Hence
224 // the equality comparison is done here before calling __dfsan_union.
225 SANITIZER_INTERFACE_ATTRIBUTE dfsan_label
226 dfsan_union(dfsan_label l1, dfsan_label l2) {
229 return __dfsan_union(l1, l2);
232 extern "C" SANITIZER_INTERFACE_ATTRIBUTE
233 dfsan_label dfsan_create_label(const char *desc, void *userdata) {
235 atomic_fetch_add(&__dfsan_last_label, 1, memory_order_relaxed) + 1;
236 dfsan_check_label(label);
237 __dfsan_label_info[label].l1 = __dfsan_label_info[label].l2 = 0;
238 __dfsan_label_info[label].desc = desc;
239 __dfsan_label_info[label].userdata = userdata;
243 extern "C" SANITIZER_INTERFACE_ATTRIBUTE
244 void __dfsan_set_label(dfsan_label label, void *addr, uptr size) {
245 for (dfsan_label *labelp = shadow_for(addr); size != 0; --size, ++labelp) {
246 // Don't write the label if it is already the value we need it to be.
247 // In a program where most addresses are not labeled, it is common that
248 // a page of shadow memory is entirely zeroed. The Linux copy-on-write
249 // implementation will share all of the zeroed pages, making a copy of a
250 // page when any value is written. The un-sharing will happen even if
251 // the value written does not change the value in memory. Avoiding the
252 // write when both |label| and |*labelp| are zero dramatically reduces
253 // the amount of real memory used by large programs.
254 if (label == *labelp)
261 SANITIZER_INTERFACE_ATTRIBUTE
262 void dfsan_set_label(dfsan_label label, void *addr, uptr size) {
263 __dfsan_set_label(label, addr, size);
266 SANITIZER_INTERFACE_ATTRIBUTE
267 void dfsan_add_label(dfsan_label label, void *addr, uptr size) {
268 for (dfsan_label *labelp = shadow_for(addr); size != 0; --size, ++labelp)
269 if (*labelp != label)
270 *labelp = __dfsan_union(*labelp, label);
273 // Unlike the other dfsan interface functions the behavior of this function
274 // depends on the label of one of its arguments. Hence it is implemented as a
276 extern "C" SANITIZER_INTERFACE_ATTRIBUTE dfsan_label
277 __dfsw_dfsan_get_label(long data, dfsan_label data_label,
278 dfsan_label *ret_label) {
283 SANITIZER_INTERFACE_ATTRIBUTE dfsan_label
284 dfsan_read_label(const void *addr, uptr size) {
287 return __dfsan_union_load(shadow_for(addr), size);
290 extern "C" SANITIZER_INTERFACE_ATTRIBUTE
291 const struct dfsan_label_info *dfsan_get_label_info(dfsan_label label) {
292 return &__dfsan_label_info[label];
295 extern "C" SANITIZER_INTERFACE_ATTRIBUTE int
296 dfsan_has_label(dfsan_label label, dfsan_label elem) {
299 const dfsan_label_info *info = dfsan_get_label_info(label);
301 return dfsan_has_label(info->l1, elem) || dfsan_has_label(info->l2, elem);
307 extern "C" SANITIZER_INTERFACE_ATTRIBUTE dfsan_label
308 dfsan_has_label_with_desc(dfsan_label label, const char *desc) {
309 const dfsan_label_info *info = dfsan_get_label_info(label);
311 return dfsan_has_label_with_desc(info->l1, desc) ||
312 dfsan_has_label_with_desc(info->l2, desc);
314 return internal_strcmp(desc, info->desc) == 0;
318 extern "C" SANITIZER_INTERFACE_ATTRIBUTE uptr
319 dfsan_get_label_count(void) {
320 dfsan_label max_label_allocated =
321 atomic_load(&__dfsan_last_label, memory_order_relaxed);
323 return static_cast<uptr>(max_label_allocated);
326 extern "C" SANITIZER_INTERFACE_ATTRIBUTE void
327 dfsan_dump_labels(int fd) {
328 dfsan_label last_label =
329 atomic_load(&__dfsan_last_label, memory_order_relaxed);
331 for (uptr l = 1; l <= last_label; ++l) {
333 internal_snprintf(buf, sizeof(buf), "%u %u %u ", l,
334 __dfsan_label_info[l].l1, __dfsan_label_info[l].l2);
335 WriteToFile(fd, buf, internal_strlen(buf));
336 if (__dfsan_label_info[l].l1 == 0 && __dfsan_label_info[l].desc) {
337 WriteToFile(fd, __dfsan_label_info[l].desc,
338 internal_strlen(__dfsan_label_info[l].desc));
340 WriteToFile(fd, "\n", 1);
344 void Flags::SetDefaults() {
345 #define DFSAN_FLAG(Type, Name, DefaultValue, Description) Name = DefaultValue;
346 #include "dfsan_flags.inc"
350 static void RegisterDfsanFlags(FlagParser *parser, Flags *f) {
351 #define DFSAN_FLAG(Type, Name, DefaultValue, Description) \
352 RegisterFlag(parser, #Name, Description, &f->Name);
353 #include "dfsan_flags.inc"
357 static void InitializeFlags() {
358 SetCommonFlagsDefaults();
359 flags().SetDefaults();
362 RegisterCommonFlags(&parser);
363 RegisterDfsanFlags(&parser, &flags());
364 parser.ParseString(GetEnv("DFSAN_OPTIONS"));
365 SetVerbosity(common_flags()->verbosity);
366 if (Verbosity()) ReportUnrecognizedFlags();
367 if (common_flags()->help) parser.PrintFlagDescriptions();
370 static void InitializePlatformEarly() {
371 #ifdef DFSAN_RUNTIME_VMA
373 (MostSignificantSetBitIndex(GET_CURRENT_FRAME()) + 1);
374 if (__dfsan::vmaSize == 39 || __dfsan::vmaSize == 42) {
375 __dfsan_shadow_ptr_mask = ShadowMask();
377 Printf("FATAL: DataFlowSanitizer: unsupported VMA range\n");
378 Printf("FATAL: Found %d - Supported 39 and 42\n", __dfsan::vmaSize);
384 static void dfsan_fini() {
385 if (internal_strcmp(flags().dump_labels_at_exit, "") != 0) {
386 fd_t fd = OpenFile(flags().dump_labels_at_exit, WrOnly);
387 if (fd == kInvalidFd) {
388 Report("WARNING: DataFlowSanitizer: unable to open output file %s\n",
389 flags().dump_labels_at_exit);
393 Report("INFO: DataFlowSanitizer: dumping labels to %s\n",
394 flags().dump_labels_at_exit);
395 dfsan_dump_labels(fd);
400 static void dfsan_init(int argc, char **argv, char **envp) {
403 InitializePlatformEarly();
405 MmapFixedNoReserve(ShadowAddr(), UnusedAddr() - ShadowAddr());
407 // Protect the region of memory we don't use, to preserve the one-to-one
408 // mapping from application to shadow memory. But if ASLR is disabled, Linux
409 // will load our executable in the middle of our unused region. This mostly
410 // works so long as the program doesn't use too much memory. We support this
411 // case by disabling memory protection when ASLR is disabled.
412 uptr init_addr = (uptr)&dfsan_init;
413 if (!(init_addr >= UnusedAddr() && init_addr < AppAddr()))
414 MmapNoAccess(UnusedAddr(), AppAddr() - UnusedAddr());
416 InitializeInterceptors();
418 // Register the fini callback to run when the program terminates successfully
419 // or it is killed by the runtime.
421 AddDieCallback(dfsan_fini);
423 __dfsan_label_info[kInitializingLabel].desc = "<init label>";
426 #if SANITIZER_CAN_USE_PREINIT_ARRAY
427 __attribute__((section(".preinit_array"), used))
428 static void (*dfsan_init_ptr)(int, char **, char **) = dfsan_init;