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+//===-- dfsan.cpp ---------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// This file is a part of DataFlowSanitizer.
+//
+// DataFlowSanitizer runtime. This file defines the public interface to
+// DataFlowSanitizer as well as the definition of certain runtime functions
+// called automatically by the compiler (specifically the instrumentation pass
+// in llvm/lib/Transforms/Instrumentation/DataFlowSanitizer.cpp).
+//
+// The public interface is defined in include/sanitizer/dfsan_interface.h whose
+// functions are prefixed dfsan_ while the compiler interface functions are
+// prefixed __dfsan_.
+//===----------------------------------------------------------------------===//
+
+#include "sanitizer_common/sanitizer_atomic.h"
+#include "sanitizer_common/sanitizer_common.h"
+#include "sanitizer_common/sanitizer_file.h"
+#include "sanitizer_common/sanitizer_flags.h"
+#include "sanitizer_common/sanitizer_flag_parser.h"
+#include "sanitizer_common/sanitizer_libc.h"
+
+#include "dfsan/dfsan.h"
+
+using namespace __dfsan;
+
+typedef atomic_uint16_t atomic_dfsan_label;
+static const dfsan_label kInitializingLabel = -1;
+
+static const uptr kNumLabels = 1 << (sizeof(dfsan_label) * 8);
+
+static atomic_dfsan_label __dfsan_last_label;
+static dfsan_label_info __dfsan_label_info[kNumLabels];
+
+Flags __dfsan::flags_data;
+
+SANITIZER_INTERFACE_ATTRIBUTE THREADLOCAL dfsan_label __dfsan_retval_tls;
+SANITIZER_INTERFACE_ATTRIBUTE THREADLOCAL dfsan_label __dfsan_arg_tls[64];
+
+SANITIZER_INTERFACE_ATTRIBUTE uptr __dfsan_shadow_ptr_mask;
+
+// On Linux/x86_64, memory is laid out as follows:
+//
+// +--------------------+ 0x800000000000 (top of memory)
+// | application memory |
+// +--------------------+ 0x700000008000 (kAppAddr)
+// | |
+// | unused |
+// | |
+// +--------------------+ 0x200200000000 (kUnusedAddr)
+// | union table |
+// +--------------------+ 0x200000000000 (kUnionTableAddr)
+// | shadow memory |
+// +--------------------+ 0x000000010000 (kShadowAddr)
+// | reserved by kernel |
+// +--------------------+ 0x000000000000
+//
+// To derive a shadow memory address from an application memory address,
+// bits 44-46 are cleared to bring the address into the range
+// [0x000000008000,0x100000000000). Then the address is shifted left by 1 to
+// account for the double byte representation of shadow labels and move the
+// address into the shadow memory range. See the function shadow_for below.
+
+// On Linux/MIPS64, memory is laid out as follows:
+//
+// +--------------------+ 0x10000000000 (top of memory)
+// | application memory |
+// +--------------------+ 0xF000008000 (kAppAddr)
+// | |
+// | unused |
+// | |
+// +--------------------+ 0x2200000000 (kUnusedAddr)
+// | union table |
+// +--------------------+ 0x2000000000 (kUnionTableAddr)
+// | shadow memory |
+// +--------------------+ 0x0000010000 (kShadowAddr)
+// | reserved by kernel |
+// +--------------------+ 0x0000000000
+
+// On Linux/AArch64 (39-bit VMA), memory is laid out as follow:
+//
+// +--------------------+ 0x8000000000 (top of memory)
+// | application memory |
+// +--------------------+ 0x7000008000 (kAppAddr)
+// | |
+// | unused |
+// | |
+// +--------------------+ 0x1200000000 (kUnusedAddr)
+// | union table |
+// +--------------------+ 0x1000000000 (kUnionTableAddr)
+// | shadow memory |
+// +--------------------+ 0x0000010000 (kShadowAddr)
+// | reserved by kernel |
+// +--------------------+ 0x0000000000
+
+// On Linux/AArch64 (42-bit VMA), memory is laid out as follow:
+//
+// +--------------------+ 0x40000000000 (top of memory)
+// | application memory |
+// +--------------------+ 0x3ff00008000 (kAppAddr)
+// | |
+// | unused |
+// | |
+// +--------------------+ 0x1200000000 (kUnusedAddr)
+// | union table |
+// +--------------------+ 0x8000000000 (kUnionTableAddr)
+// | shadow memory |
+// +--------------------+ 0x0000010000 (kShadowAddr)
+// | reserved by kernel |
+// +--------------------+ 0x0000000000
+
+// On Linux/AArch64 (48-bit VMA), memory is laid out as follow:
+//
+// +--------------------+ 0x1000000000000 (top of memory)
+// | application memory |
+// +--------------------+ 0xffff00008000 (kAppAddr)
+// | unused |
+// +--------------------+ 0xaaaab0000000 (top of PIE address)
+// | application PIE |
+// +--------------------+ 0xaaaaa0000000 (top of PIE address)
+// | |
+// | unused |
+// | |
+// +--------------------+ 0x1200000000 (kUnusedAddr)
+// | union table |
+// +--------------------+ 0x8000000000 (kUnionTableAddr)
+// | shadow memory |
+// +--------------------+ 0x0000010000 (kShadowAddr)
+// | reserved by kernel |
+// +--------------------+ 0x0000000000
+
+typedef atomic_dfsan_label dfsan_union_table_t[kNumLabels][kNumLabels];
+
+#ifdef DFSAN_RUNTIME_VMA
+// Runtime detected VMA size.
+int __dfsan::vmaSize;
+#endif
+
+static uptr UnusedAddr() {
+ return MappingArchImpl<MAPPING_UNION_TABLE_ADDR>()
+ + sizeof(dfsan_union_table_t);
+}
+
+static atomic_dfsan_label *union_table(dfsan_label l1, dfsan_label l2) {
+ return &(*(dfsan_union_table_t *) UnionTableAddr())[l1][l2];
+}
+
+// Checks we do not run out of labels.
+static void dfsan_check_label(dfsan_label label) {
+ if (label == kInitializingLabel) {
+ Report("FATAL: DataFlowSanitizer: out of labels\n");
+ Die();
+ }
+}
+
+// Resolves the union of two unequal labels. Nonequality is a precondition for
+// this function (the instrumentation pass inlines the equality test).
+extern "C" SANITIZER_INTERFACE_ATTRIBUTE
+dfsan_label __dfsan_union(dfsan_label l1, dfsan_label l2) {
+ if (flags().fast16labels)
+ return l1 | l2;
+ DCHECK_NE(l1, l2);
+
+ if (l1 == 0)
+ return l2;
+ if (l2 == 0)
+ return l1;
+
+ if (l1 > l2)
+ Swap(l1, l2);
+
+ atomic_dfsan_label *table_ent = union_table(l1, l2);
+ // We need to deal with the case where two threads concurrently request
+ // a union of the same pair of labels. If the table entry is uninitialized,
+ // (i.e. 0) use a compare-exchange to set the entry to kInitializingLabel
+ // (i.e. -1) to mark that we are initializing it.
+ dfsan_label label = 0;
+ if (atomic_compare_exchange_strong(table_ent, &label, kInitializingLabel,
+ memory_order_acquire)) {
+ // Check whether l2 subsumes l1. We don't need to check whether l1
+ // subsumes l2 because we are guaranteed here that l1 < l2, and (at least
+ // in the cases we are interested in) a label may only subsume labels
+ // created earlier (i.e. with a lower numerical value).
+ if (__dfsan_label_info[l2].l1 == l1 ||
+ __dfsan_label_info[l2].l2 == l1) {
+ label = l2;
+ } else {
+ label =
+ atomic_fetch_add(&__dfsan_last_label, 1, memory_order_relaxed) + 1;
+ dfsan_check_label(label);
+ __dfsan_label_info[label].l1 = l1;
+ __dfsan_label_info[label].l2 = l2;
+ }
+ atomic_store(table_ent, label, memory_order_release);
+ } else if (label == kInitializingLabel) {
+ // Another thread is initializing the entry. Wait until it is finished.
+ do {
+ internal_sched_yield();
+ label = atomic_load(table_ent, memory_order_acquire);
+ } while (label == kInitializingLabel);
+ }
+ return label;
+}
+
+extern "C" SANITIZER_INTERFACE_ATTRIBUTE
+dfsan_label __dfsan_union_load(const dfsan_label *ls, uptr n) {
+ dfsan_label label = ls[0];
+ for (uptr i = 1; i != n; ++i) {
+ dfsan_label next_label = ls[i];
+ if (label != next_label)
+ label = __dfsan_union(label, next_label);
+ }
+ return label;
+}
+
+extern "C" SANITIZER_INTERFACE_ATTRIBUTE
+void __dfsan_unimplemented(char *fname) {
+ if (flags().warn_unimplemented)
+ Report("WARNING: DataFlowSanitizer: call to uninstrumented function %s\n",
+ fname);
+}
+
+// Use '-mllvm -dfsan-debug-nonzero-labels' and break on this function
+// to try to figure out where labels are being introduced in a nominally
+// label-free program.
+extern "C" SANITIZER_INTERFACE_ATTRIBUTE void __dfsan_nonzero_label() {
+ if (flags().warn_nonzero_labels)
+ Report("WARNING: DataFlowSanitizer: saw nonzero label\n");
+}
+
+// Indirect call to an uninstrumented vararg function. We don't have a way of
+// handling these at the moment.
+extern "C" SANITIZER_INTERFACE_ATTRIBUTE void
+__dfsan_vararg_wrapper(const char *fname) {
+ Report("FATAL: DataFlowSanitizer: unsupported indirect call to vararg "
+ "function %s\n", fname);
+ Die();
+}
+
+// Like __dfsan_union, but for use from the client or custom functions. Hence
+// the equality comparison is done here before calling __dfsan_union.
+SANITIZER_INTERFACE_ATTRIBUTE dfsan_label
+dfsan_union(dfsan_label l1, dfsan_label l2) {
+ if (l1 == l2)
+ return l1;
+ return __dfsan_union(l1, l2);
+}
+
+extern "C" SANITIZER_INTERFACE_ATTRIBUTE
+dfsan_label dfsan_create_label(const char *desc, void *userdata) {
+ dfsan_label label =
+ atomic_fetch_add(&__dfsan_last_label, 1, memory_order_relaxed) + 1;
+ dfsan_check_label(label);
+ __dfsan_label_info[label].l1 = __dfsan_label_info[label].l2 = 0;
+ __dfsan_label_info[label].desc = desc;
+ __dfsan_label_info[label].userdata = userdata;
+ return label;
+}
+
+extern "C" SANITIZER_INTERFACE_ATTRIBUTE
+void __dfsan_set_label(dfsan_label label, void *addr, uptr size) {
+ for (dfsan_label *labelp = shadow_for(addr); size != 0; --size, ++labelp) {
+ // Don't write the label if it is already the value we need it to be.
+ // In a program where most addresses are not labeled, it is common that
+ // a page of shadow memory is entirely zeroed. The Linux copy-on-write
+ // implementation will share all of the zeroed pages, making a copy of a
+ // page when any value is written. The un-sharing will happen even if
+ // the value written does not change the value in memory. Avoiding the
+ // write when both |label| and |*labelp| are zero dramatically reduces
+ // the amount of real memory used by large programs.
+ if (label == *labelp)
+ continue;
+
+ *labelp = label;
+ }
+}
+
+SANITIZER_INTERFACE_ATTRIBUTE
+void dfsan_set_label(dfsan_label label, void *addr, uptr size) {
+ __dfsan_set_label(label, addr, size);
+}
+
+SANITIZER_INTERFACE_ATTRIBUTE
+void dfsan_add_label(dfsan_label label, void *addr, uptr size) {
+ for (dfsan_label *labelp = shadow_for(addr); size != 0; --size, ++labelp)
+ if (*labelp != label)
+ *labelp = __dfsan_union(*labelp, label);
+}
+
+// Unlike the other dfsan interface functions the behavior of this function
+// depends on the label of one of its arguments. Hence it is implemented as a
+// custom function.
+extern "C" SANITIZER_INTERFACE_ATTRIBUTE dfsan_label
+__dfsw_dfsan_get_label(long data, dfsan_label data_label,
+ dfsan_label *ret_label) {
+ *ret_label = 0;
+ return data_label;
+}
+
+SANITIZER_INTERFACE_ATTRIBUTE dfsan_label
+dfsan_read_label(const void *addr, uptr size) {
+ if (size == 0)
+ return 0;
+ return __dfsan_union_load(shadow_for(addr), size);
+}
+
+extern "C" SANITIZER_INTERFACE_ATTRIBUTE
+const struct dfsan_label_info *dfsan_get_label_info(dfsan_label label) {
+ return &__dfsan_label_info[label];
+}
+
+extern "C" SANITIZER_INTERFACE_ATTRIBUTE int
+dfsan_has_label(dfsan_label label, dfsan_label elem) {
+ if (label == elem)
+ return true;
+ const dfsan_label_info *info = dfsan_get_label_info(label);
+ if (info->l1 != 0) {
+ return dfsan_has_label(info->l1, elem) || dfsan_has_label(info->l2, elem);
+ } else {
+ return false;
+ }
+}
+
+extern "C" SANITIZER_INTERFACE_ATTRIBUTE dfsan_label
+dfsan_has_label_with_desc(dfsan_label label, const char *desc) {
+ const dfsan_label_info *info = dfsan_get_label_info(label);
+ if (info->l1 != 0) {
+ return dfsan_has_label_with_desc(info->l1, desc) ||
+ dfsan_has_label_with_desc(info->l2, desc);
+ } else {
+ return internal_strcmp(desc, info->desc) == 0;
+ }
+}
+
+extern "C" SANITIZER_INTERFACE_ATTRIBUTE uptr
+dfsan_get_label_count(void) {
+ dfsan_label max_label_allocated =
+ atomic_load(&__dfsan_last_label, memory_order_relaxed);
+
+ return static_cast<uptr>(max_label_allocated);
+}
+
+extern "C" SANITIZER_INTERFACE_ATTRIBUTE void
+dfsan_dump_labels(int fd) {
+ dfsan_label last_label =
+ atomic_load(&__dfsan_last_label, memory_order_relaxed);
+
+ for (uptr l = 1; l <= last_label; ++l) {
+ char buf[64];
+ internal_snprintf(buf, sizeof(buf), "%u %u %u ", l,
+ __dfsan_label_info[l].l1, __dfsan_label_info[l].l2);
+ WriteToFile(fd, buf, internal_strlen(buf));
+ if (__dfsan_label_info[l].l1 == 0 && __dfsan_label_info[l].desc) {
+ WriteToFile(fd, __dfsan_label_info[l].desc,
+ internal_strlen(__dfsan_label_info[l].desc));
+ }
+ WriteToFile(fd, "\n", 1);
+ }
+}
+
+void Flags::SetDefaults() {
+#define DFSAN_FLAG(Type, Name, DefaultValue, Description) Name = DefaultValue;
+#include "dfsan_flags.inc"
+#undef DFSAN_FLAG
+}
+
+static void RegisterDfsanFlags(FlagParser *parser, Flags *f) {
+#define DFSAN_FLAG(Type, Name, DefaultValue, Description) \
+ RegisterFlag(parser, #Name, Description, &f->Name);
+#include "dfsan_flags.inc"
+#undef DFSAN_FLAG
+}
+
+static void InitializeFlags() {
+ SetCommonFlagsDefaults();
+ flags().SetDefaults();
+
+ FlagParser parser;
+ RegisterCommonFlags(&parser);
+ RegisterDfsanFlags(&parser, &flags());
+ parser.ParseStringFromEnv("DFSAN_OPTIONS");
+ InitializeCommonFlags();
+ if (Verbosity()) ReportUnrecognizedFlags();
+ if (common_flags()->help) parser.PrintFlagDescriptions();
+}
+
+static void InitializePlatformEarly() {
+ AvoidCVE_2016_2143();
+#ifdef DFSAN_RUNTIME_VMA
+ __dfsan::vmaSize =
+ (MostSignificantSetBitIndex(GET_CURRENT_FRAME()) + 1);
+ if (__dfsan::vmaSize == 39 || __dfsan::vmaSize == 42 ||
+ __dfsan::vmaSize == 48) {
+ __dfsan_shadow_ptr_mask = ShadowMask();
+ } else {
+ Printf("FATAL: DataFlowSanitizer: unsupported VMA range\n");
+ Printf("FATAL: Found %d - Supported 39, 42, and 48\n", __dfsan::vmaSize);
+ Die();
+ }
+#endif
+}
+
+static void dfsan_fini() {
+ if (internal_strcmp(flags().dump_labels_at_exit, "") != 0) {
+ fd_t fd = OpenFile(flags().dump_labels_at_exit, WrOnly);
+ if (fd == kInvalidFd) {
+ Report("WARNING: DataFlowSanitizer: unable to open output file %s\n",
+ flags().dump_labels_at_exit);
+ return;
+ }
+
+ Report("INFO: DataFlowSanitizer: dumping labels to %s\n",
+ flags().dump_labels_at_exit);
+ dfsan_dump_labels(fd);
+ CloseFile(fd);
+ }
+}
+
+extern "C" void dfsan_flush() {
+ UnmapOrDie((void*)ShadowAddr(), UnusedAddr() - ShadowAddr());
+ if (!MmapFixedNoReserve(ShadowAddr(), UnusedAddr() - ShadowAddr()))
+ Die();
+}
+
+static void dfsan_init(int argc, char **argv, char **envp) {
+ InitializeFlags();
+
+ ::InitializePlatformEarly();
+
+ if (!MmapFixedNoReserve(ShadowAddr(), UnusedAddr() - ShadowAddr()))
+ Die();
+
+ // Protect the region of memory we don't use, to preserve the one-to-one
+ // mapping from application to shadow memory. But if ASLR is disabled, Linux
+ // will load our executable in the middle of our unused region. This mostly
+ // works so long as the program doesn't use too much memory. We support this
+ // case by disabling memory protection when ASLR is disabled.
+ uptr init_addr = (uptr)&dfsan_init;
+ if (!(init_addr >= UnusedAddr() && init_addr < AppAddr()))
+ MmapFixedNoAccess(UnusedAddr(), AppAddr() - UnusedAddr());
+
+ InitializeInterceptors();
+
+ // Register the fini callback to run when the program terminates successfully
+ // or it is killed by the runtime.
+ Atexit(dfsan_fini);
+ AddDieCallback(dfsan_fini);
+
+ __dfsan_label_info[kInitializingLabel].desc = "<init label>";
+}
+
+#if SANITIZER_CAN_USE_PREINIT_ARRAY
+__attribute__((section(".preinit_array"), used))
+static void (*dfsan_init_ptr)(int, char **, char **) = dfsan_init;
+#endif