| //===-- dfsan.cc ----------------------------------------------------------===// |
| // |
| // The LLVM Compiler Infrastructure |
| // |
| // This file is distributed under the University of Illinois Open Source |
| // License. See LICENSE.TXT for details. |
| // |
| //===----------------------------------------------------------------------===// |
| // |
| // 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/dfsan_interface.h" |
| #include "sanitizer_common/sanitizer_atomic.h" |
| #include "sanitizer_common/sanitizer_common.h" |
| #include "sanitizer_common/sanitizer_libc.h" |
| |
| 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]; |
| |
| SANITIZER_INTERFACE_ATTRIBUTE THREADLOCAL dfsan_label __dfsan_retval_tls; |
| SANITIZER_INTERFACE_ATTRIBUTE THREADLOCAL dfsan_label __dfsan_arg_tls[64]; |
| |
| // 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. |
| |
| typedef atomic_dfsan_label dfsan_union_table_t[kNumLabels][kNumLabels]; |
| |
| static const uptr kShadowAddr = 0x10000; |
| static const uptr kUnionTableAddr = 0x200000000000; |
| static const uptr kUnusedAddr = kUnionTableAddr + sizeof(dfsan_union_table_t); |
| static const uptr kAppAddr = 0x700000008000; |
| |
| static atomic_dfsan_label *union_table(dfsan_label l1, dfsan_label l2) { |
| return &(*(dfsan_union_table_t *) kUnionTableAddr)[l1][l2]; |
| } |
| |
| static dfsan_label *shadow_for(void *ptr) { |
| return (dfsan_label *) ((((uintptr_t) ptr) & ~0x700000000000) << 1); |
| } |
| |
| // 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) { |
| 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; |
| CHECK_NE(label, kInitializingLabel); |
| __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(dfsan_label *ls, size_t n) { |
| dfsan_label label = ls[0]; |
| for (size_t 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_memcpy(void *dest, const void *src, size_t n) { |
| dfsan_label *sdest = shadow_for(dest), *ssrc = shadow_for((void *)src); |
| internal_memcpy((void *)sdest, (void *)ssrc, n * sizeof(dfsan_label)); |
| return internal_memcpy(dest, src, n); |
| } |
| |
| 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; |
| CHECK_NE(label, kInitializingLabel); |
| __dfsan_label_info[label].l1 = __dfsan_label_info[label].l2 = 0; |
| __dfsan_label_info[label].desc = desc; |
| __dfsan_label_info[label].userdata = userdata; |
| __dfsan_retval_tls = 0; // Ensures return value is unlabelled in the caller. |
| return label; |
| } |
| |
| SANITIZER_INTERFACE_ATTRIBUTE |
| void dfsan_set_label(dfsan_label label, void *addr, size_t size) { |
| for (dfsan_label *labelp = shadow_for(addr); size != 0; --size, ++labelp) |
| *labelp = label; |
| } |
| |
| SANITIZER_INTERFACE_ATTRIBUTE |
| void dfsan_add_label(dfsan_label label, void *addr, size_t size) { |
| for (dfsan_label *labelp = shadow_for(addr); size != 0; --size, ++labelp) |
| if (*labelp != label) |
| *labelp = __dfsan_union(*labelp, label); |
| } |
| |
| SANITIZER_INTERFACE_ATTRIBUTE dfsan_label dfsan_get_label(long data) { |
| // The label for 'data' is implicitly passed by the instrumentation pass in |
| // the first element of __dfsan_arg_tls. So we can just return it. |
| __dfsan_retval_tls = 0; // Ensures return value is unlabelled in the caller. |
| return __dfsan_arg_tls[0]; |
| } |
| |
| SANITIZER_INTERFACE_ATTRIBUTE |
| const struct dfsan_label_info *dfsan_get_label_info(dfsan_label label) { |
| __dfsan_retval_tls = 0; // Ensures return value is unlabelled in the caller. |
| return &__dfsan_label_info[label]; |
| } |
| |
| int dfsan_has_label(dfsan_label label, dfsan_label elem) { |
| __dfsan_retval_tls = 0; // Ensures return value is unlabelled in the caller. |
| 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; |
| } |
| } |
| |
| dfsan_label dfsan_has_label_with_desc(dfsan_label label, const char *desc) { |
| __dfsan_retval_tls = 0; // Ensures return value is unlabelled in the caller. |
| 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; |
| } |
| } |
| |
| #ifdef DFSAN_NOLIBC |
| extern "C" void dfsan_init() { |
| #else |
| static void dfsan_init(int argc, char **argv, char **envp) { |
| #endif |
| MmapFixedNoReserve(kShadowAddr, kUnusedAddr - kShadowAddr); |
| |
| // 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 >= kUnusedAddr && init_addr < kAppAddr)) |
| Mprotect(kUnusedAddr, kAppAddr - kUnusedAddr); |
| } |
| |
| #ifndef DFSAN_NOLIBC |
| __attribute__((section(".preinit_array"), used)) |
| static void (*dfsan_init_ptr)(int, char **, char **) = dfsan_init; |
| #endif |