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_libc.h"
27 #include "dfsan/dfsan.h"
29 using namespace __dfsan;
31 typedef atomic_uint16_t atomic_dfsan_label;
32 static const dfsan_label kInitializingLabel = -1;
34 static const uptr kNumLabels = 1 << (sizeof(dfsan_label) * 8);
36 static atomic_dfsan_label __dfsan_last_label;
37 static dfsan_label_info __dfsan_label_info[kNumLabels];
39 Flags __dfsan::flags_data;
41 SANITIZER_INTERFACE_ATTRIBUTE THREADLOCAL dfsan_label __dfsan_retval_tls;
42 SANITIZER_INTERFACE_ATTRIBUTE THREADLOCAL dfsan_label __dfsan_arg_tls[64];
44 // On Linux/x86_64, memory is laid out as follows:
46 // +--------------------+ 0x800000000000 (top of memory)
47 // | application memory |
48 // +--------------------+ 0x700000008000 (kAppAddr)
52 // +--------------------+ 0x200200000000 (kUnusedAddr)
54 // +--------------------+ 0x200000000000 (kUnionTableAddr)
56 // +--------------------+ 0x000000010000 (kShadowAddr)
57 // | reserved by kernel |
58 // +--------------------+ 0x000000000000
60 // To derive a shadow memory address from an application memory address,
61 // bits 44-46 are cleared to bring the address into the range
62 // [0x000000008000,0x100000000000). Then the address is shifted left by 1 to
63 // account for the double byte representation of shadow labels and move the
64 // address into the shadow memory range. See the function shadow_for below.
66 // On Linux/MIPS64, memory is laid out as follows:
68 // +--------------------+ 0x10000000000 (top of memory)
69 // | application memory |
70 // +--------------------+ 0xF000008000 (kAppAddr)
74 // +--------------------+ 0x2200000000 (kUnusedAddr)
76 // +--------------------+ 0x2000000000 (kUnionTableAddr)
78 // +--------------------+ 0x0000010000 (kShadowAddr)
79 // | reserved by kernel |
80 // +--------------------+ 0x0000000000
82 typedef atomic_dfsan_label dfsan_union_table_t[kNumLabels][kNumLabels];
84 #if defined(__x86_64__)
85 static const uptr kShadowAddr = 0x10000;
86 static const uptr kUnionTableAddr = 0x200000000000;
87 static const uptr kUnusedAddr = kUnionTableAddr + sizeof(dfsan_union_table_t);
88 static const uptr kAppAddr = 0x700000008000;
89 #elif defined(__mips64)
90 static const uptr kShadowAddr = 0x10000;
91 static const uptr kUnionTableAddr = 0x2000000000;
92 static const uptr kUnusedAddr = kUnionTableAddr + sizeof(dfsan_union_table_t);
93 static const uptr kAppAddr = 0xF000008000;
95 # error "DFSan not supported for this platform!"
98 static atomic_dfsan_label *union_table(dfsan_label l1, dfsan_label l2) {
99 return &(*(dfsan_union_table_t *) kUnionTableAddr)[l1][l2];
102 // Checks we do not run out of labels.
103 static void dfsan_check_label(dfsan_label label) {
104 if (label == kInitializingLabel) {
105 Report("FATAL: DataFlowSanitizer: out of labels\n");
110 // Resolves the union of two unequal labels. Nonequality is a precondition for
111 // this function (the instrumentation pass inlines the equality test).
112 extern "C" SANITIZER_INTERFACE_ATTRIBUTE
113 dfsan_label __dfsan_union(dfsan_label l1, dfsan_label l2) {
124 atomic_dfsan_label *table_ent = union_table(l1, l2);
125 // We need to deal with the case where two threads concurrently request
126 // a union of the same pair of labels. If the table entry is uninitialized,
127 // (i.e. 0) use a compare-exchange to set the entry to kInitializingLabel
128 // (i.e. -1) to mark that we are initializing it.
129 dfsan_label label = 0;
130 if (atomic_compare_exchange_strong(table_ent, &label, kInitializingLabel,
131 memory_order_acquire)) {
132 // Check whether l2 subsumes l1. We don't need to check whether l1
133 // subsumes l2 because we are guaranteed here that l1 < l2, and (at least
134 // in the cases we are interested in) a label may only subsume labels
135 // created earlier (i.e. with a lower numerical value).
136 if (__dfsan_label_info[l2].l1 == l1 ||
137 __dfsan_label_info[l2].l2 == l1) {
141 atomic_fetch_add(&__dfsan_last_label, 1, memory_order_relaxed) + 1;
142 dfsan_check_label(label);
143 __dfsan_label_info[label].l1 = l1;
144 __dfsan_label_info[label].l2 = l2;
146 atomic_store(table_ent, label, memory_order_release);
147 } else if (label == kInitializingLabel) {
148 // Another thread is initializing the entry. Wait until it is finished.
150 internal_sched_yield();
151 label = atomic_load(table_ent, memory_order_acquire);
152 } while (label == kInitializingLabel);
157 extern "C" SANITIZER_INTERFACE_ATTRIBUTE
158 dfsan_label __dfsan_union_load(const dfsan_label *ls, uptr n) {
159 dfsan_label label = ls[0];
160 for (uptr i = 1; i != n; ++i) {
161 dfsan_label next_label = ls[i];
162 if (label != next_label)
163 label = __dfsan_union(label, next_label);
168 extern "C" SANITIZER_INTERFACE_ATTRIBUTE
169 void __dfsan_unimplemented(char *fname) {
170 if (flags().warn_unimplemented)
171 Report("WARNING: DataFlowSanitizer: call to uninstrumented function %s\n",
175 // Use '-mllvm -dfsan-debug-nonzero-labels' and break on this function
176 // to try to figure out where labels are being introduced in a nominally
177 // label-free program.
178 extern "C" SANITIZER_INTERFACE_ATTRIBUTE void __dfsan_nonzero_label() {
179 if (flags().warn_nonzero_labels)
180 Report("WARNING: DataFlowSanitizer: saw nonzero label\n");
183 // Indirect call to an uninstrumented vararg function. We don't have a way of
184 // handling these at the moment.
185 extern "C" SANITIZER_INTERFACE_ATTRIBUTE void
186 __dfsan_vararg_wrapper(const char *fname) {
187 Report("FATAL: DataFlowSanitizer: unsupported indirect call to vararg "
188 "function %s\n", fname);
192 // Like __dfsan_union, but for use from the client or custom functions. Hence
193 // the equality comparison is done here before calling __dfsan_union.
194 SANITIZER_INTERFACE_ATTRIBUTE dfsan_label
195 dfsan_union(dfsan_label l1, dfsan_label l2) {
198 return __dfsan_union(l1, l2);
201 extern "C" SANITIZER_INTERFACE_ATTRIBUTE
202 dfsan_label dfsan_create_label(const char *desc, void *userdata) {
204 atomic_fetch_add(&__dfsan_last_label, 1, memory_order_relaxed) + 1;
205 dfsan_check_label(label);
206 __dfsan_label_info[label].l1 = __dfsan_label_info[label].l2 = 0;
207 __dfsan_label_info[label].desc = desc;
208 __dfsan_label_info[label].userdata = userdata;
212 extern "C" SANITIZER_INTERFACE_ATTRIBUTE
213 void __dfsan_set_label(dfsan_label label, void *addr, uptr size) {
214 for (dfsan_label *labelp = shadow_for(addr); size != 0; --size, ++labelp) {
215 // Don't write the label if it is already the value we need it to be.
216 // In a program where most addresses are not labeled, it is common that
217 // a page of shadow memory is entirely zeroed. The Linux copy-on-write
218 // implementation will share all of the zeroed pages, making a copy of a
219 // page when any value is written. The un-sharing will happen even if
220 // the value written does not change the value in memory. Avoiding the
221 // write when both |label| and |*labelp| are zero dramatically reduces
222 // the amount of real memory used by large programs.
223 if (label == *labelp)
230 SANITIZER_INTERFACE_ATTRIBUTE
231 void dfsan_set_label(dfsan_label label, void *addr, uptr size) {
232 __dfsan_set_label(label, addr, size);
235 SANITIZER_INTERFACE_ATTRIBUTE
236 void dfsan_add_label(dfsan_label label, void *addr, uptr size) {
237 for (dfsan_label *labelp = shadow_for(addr); size != 0; --size, ++labelp)
238 if (*labelp != label)
239 *labelp = __dfsan_union(*labelp, label);
242 // Unlike the other dfsan interface functions the behavior of this function
243 // depends on the label of one of its arguments. Hence it is implemented as a
245 extern "C" SANITIZER_INTERFACE_ATTRIBUTE dfsan_label
246 __dfsw_dfsan_get_label(long data, dfsan_label data_label,
247 dfsan_label *ret_label) {
252 SANITIZER_INTERFACE_ATTRIBUTE dfsan_label
253 dfsan_read_label(const void *addr, uptr size) {
256 return __dfsan_union_load(shadow_for(addr), size);
259 SANITIZER_INTERFACE_ATTRIBUTE
260 const struct dfsan_label_info *dfsan_get_label_info(dfsan_label label) {
261 return &__dfsan_label_info[label];
264 extern "C" SANITIZER_INTERFACE_ATTRIBUTE int
265 dfsan_has_label(dfsan_label label, dfsan_label elem) {
268 const dfsan_label_info *info = dfsan_get_label_info(label);
270 return dfsan_has_label(info->l1, elem) || dfsan_has_label(info->l2, elem);
276 extern "C" SANITIZER_INTERFACE_ATTRIBUTE dfsan_label
277 dfsan_has_label_with_desc(dfsan_label label, const char *desc) {
278 const dfsan_label_info *info = dfsan_get_label_info(label);
280 return dfsan_has_label_with_desc(info->l1, desc) ||
281 dfsan_has_label_with_desc(info->l2, desc);
283 return internal_strcmp(desc, info->desc) == 0;
287 extern "C" SANITIZER_INTERFACE_ATTRIBUTE uptr
288 dfsan_get_label_count(void) {
289 dfsan_label max_label_allocated =
290 atomic_load(&__dfsan_last_label, memory_order_relaxed);
292 return static_cast<uptr>(max_label_allocated);
295 extern "C" SANITIZER_INTERFACE_ATTRIBUTE void
296 dfsan_dump_labels(int fd) {
297 dfsan_label last_label =
298 atomic_load(&__dfsan_last_label, memory_order_relaxed);
300 for (uptr l = 1; l <= last_label; ++l) {
302 internal_snprintf(buf, sizeof(buf), "%u %u %u ", l,
303 __dfsan_label_info[l].l1, __dfsan_label_info[l].l2);
304 internal_write(fd, buf, internal_strlen(buf));
305 if (__dfsan_label_info[l].l1 == 0 && __dfsan_label_info[l].desc) {
306 internal_write(fd, __dfsan_label_info[l].desc,
307 internal_strlen(__dfsan_label_info[l].desc));
309 internal_write(fd, "\n", 1);
313 static void InitializeFlags(Flags &f, const char *env) {
314 f.warn_unimplemented = true;
315 f.warn_nonzero_labels = false;
316 f.strict_data_dependencies = true;
317 f.dump_labels_at_exit = "";
319 ParseFlag(env, &f.warn_unimplemented, "warn_unimplemented", "");
320 ParseFlag(env, &f.warn_nonzero_labels, "warn_nonzero_labels", "");
321 ParseFlag(env, &f.strict_data_dependencies, "strict_data_dependencies", "");
322 ParseFlag(env, &f.dump_labels_at_exit, "dump_labels_at_exit", "");
325 static void dfsan_fini() {
326 if (internal_strcmp(flags().dump_labels_at_exit, "") != 0) {
327 fd_t fd = OpenFile(flags().dump_labels_at_exit, true /* write */);
328 if (fd == kInvalidFd) {
329 Report("WARNING: DataFlowSanitizer: unable to open output file %s\n",
330 flags().dump_labels_at_exit);
334 Report("INFO: DataFlowSanitizer: dumping labels to %s\n",
335 flags().dump_labels_at_exit);
336 dfsan_dump_labels(fd);
342 extern "C" void dfsan_init() {
344 static void dfsan_init(int argc, char **argv, char **envp) {
346 MmapFixedNoReserve(kShadowAddr, kUnusedAddr - kShadowAddr);
348 // Protect the region of memory we don't use, to preserve the one-to-one
349 // mapping from application to shadow memory. But if ASLR is disabled, Linux
350 // will load our executable in the middle of our unused region. This mostly
351 // works so long as the program doesn't use too much memory. We support this
352 // case by disabling memory protection when ASLR is disabled.
353 uptr init_addr = (uptr)&dfsan_init;
354 if (!(init_addr >= kUnusedAddr && init_addr < kAppAddr))
355 Mprotect(kUnusedAddr, kAppAddr - kUnusedAddr);
357 InitializeFlags(flags(), GetEnv("DFSAN_OPTIONS"));
359 InitializeInterceptors();
361 // Register the fini callback to run when the program terminates successfully
362 // or it is killed by the runtime.
364 SetDieCallback(dfsan_fini);
366 __dfsan_label_info[kInitializingLabel].desc = "<init label>";
369 #if !defined(DFSAN_NOLIBC) && SANITIZER_CAN_USE_PREINIT_ARRAY
370 __attribute__((section(".preinit_array"), used))
371 static void (*dfsan_init_ptr)(int, char **, char **) = dfsan_init;