381 lines
13 KiB
C++
381 lines
13 KiB
C++
//===-- dfsan.cc ----------------------------------------------------------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This file is a part of DataFlowSanitizer.
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//
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// DataFlowSanitizer runtime. This file defines the public interface to
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// DataFlowSanitizer as well as the definition of certain runtime functions
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// called automatically by the compiler (specifically the instrumentation pass
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// in llvm/lib/Transforms/Instrumentation/DataFlowSanitizer.cpp).
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//
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// The public interface is defined in include/sanitizer/dfsan_interface.h whose
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// functions are prefixed dfsan_ while the compiler interface functions are
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// prefixed __dfsan_.
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//===----------------------------------------------------------------------===//
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#include "sanitizer_common/sanitizer_atomic.h"
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#include "sanitizer_common/sanitizer_common.h"
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#include "sanitizer_common/sanitizer_flags.h"
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#include "sanitizer_common/sanitizer_flag_parser.h"
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#include "sanitizer_common/sanitizer_libc.h"
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#include "dfsan/dfsan.h"
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using namespace __dfsan;
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typedef atomic_uint16_t atomic_dfsan_label;
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static const dfsan_label kInitializingLabel = -1;
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static const uptr kNumLabels = 1 << (sizeof(dfsan_label) * 8);
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static atomic_dfsan_label __dfsan_last_label;
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static dfsan_label_info __dfsan_label_info[kNumLabels];
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Flags __dfsan::flags_data;
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SANITIZER_INTERFACE_ATTRIBUTE THREADLOCAL dfsan_label __dfsan_retval_tls;
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SANITIZER_INTERFACE_ATTRIBUTE THREADLOCAL dfsan_label __dfsan_arg_tls[64];
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// On Linux/x86_64, memory is laid out as follows:
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//
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// +--------------------+ 0x800000000000 (top of memory)
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// | application memory |
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// +--------------------+ 0x700000008000 (kAppAddr)
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// | |
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// | unused |
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// | |
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// +--------------------+ 0x200200000000 (kUnusedAddr)
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// | union table |
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// +--------------------+ 0x200000000000 (kUnionTableAddr)
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// | shadow memory |
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// +--------------------+ 0x000000010000 (kShadowAddr)
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// | reserved by kernel |
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// +--------------------+ 0x000000000000
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//
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// To derive a shadow memory address from an application memory address,
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// bits 44-46 are cleared to bring the address into the range
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// [0x000000008000,0x100000000000). Then the address is shifted left by 1 to
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// account for the double byte representation of shadow labels and move the
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// address into the shadow memory range. See the function shadow_for below.
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// On Linux/MIPS64, memory is laid out as follows:
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//
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// +--------------------+ 0x10000000000 (top of memory)
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// | application memory |
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// +--------------------+ 0xF000008000 (kAppAddr)
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// | |
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// | unused |
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// | |
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// +--------------------+ 0x2200000000 (kUnusedAddr)
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// | union table |
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// +--------------------+ 0x2000000000 (kUnionTableAddr)
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// | shadow memory |
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// +--------------------+ 0x0000010000 (kShadowAddr)
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// | reserved by kernel |
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// +--------------------+ 0x0000000000
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typedef atomic_dfsan_label dfsan_union_table_t[kNumLabels][kNumLabels];
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#if defined(__x86_64__)
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static const uptr kShadowAddr = 0x10000;
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static const uptr kUnionTableAddr = 0x200000000000;
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static const uptr kUnusedAddr = kUnionTableAddr + sizeof(dfsan_union_table_t);
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static const uptr kAppAddr = 0x700000008000;
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#elif defined(__mips64)
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static const uptr kShadowAddr = 0x10000;
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static const uptr kUnionTableAddr = 0x2000000000;
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static const uptr kUnusedAddr = kUnionTableAddr + sizeof(dfsan_union_table_t);
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static const uptr kAppAddr = 0xF000008000;
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#else
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# error "DFSan not supported for this platform!"
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#endif
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static atomic_dfsan_label *union_table(dfsan_label l1, dfsan_label l2) {
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return &(*(dfsan_union_table_t *) kUnionTableAddr)[l1][l2];
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}
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// Checks we do not run out of labels.
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static void dfsan_check_label(dfsan_label label) {
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if (label == kInitializingLabel) {
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Report("FATAL: DataFlowSanitizer: out of labels\n");
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Die();
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}
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}
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// Resolves the union of two unequal labels. Nonequality is a precondition for
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// this function (the instrumentation pass inlines the equality test).
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extern "C" SANITIZER_INTERFACE_ATTRIBUTE
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dfsan_label __dfsan_union(dfsan_label l1, dfsan_label l2) {
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DCHECK_NE(l1, l2);
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if (l1 == 0)
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return l2;
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if (l2 == 0)
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return l1;
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if (l1 > l2)
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Swap(l1, l2);
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atomic_dfsan_label *table_ent = union_table(l1, l2);
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// We need to deal with the case where two threads concurrently request
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// a union of the same pair of labels. If the table entry is uninitialized,
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// (i.e. 0) use a compare-exchange to set the entry to kInitializingLabel
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// (i.e. -1) to mark that we are initializing it.
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dfsan_label label = 0;
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if (atomic_compare_exchange_strong(table_ent, &label, kInitializingLabel,
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memory_order_acquire)) {
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// Check whether l2 subsumes l1. We don't need to check whether l1
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// subsumes l2 because we are guaranteed here that l1 < l2, and (at least
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// in the cases we are interested in) a label may only subsume labels
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// created earlier (i.e. with a lower numerical value).
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if (__dfsan_label_info[l2].l1 == l1 ||
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__dfsan_label_info[l2].l2 == l1) {
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label = l2;
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} else {
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label =
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atomic_fetch_add(&__dfsan_last_label, 1, memory_order_relaxed) + 1;
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dfsan_check_label(label);
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__dfsan_label_info[label].l1 = l1;
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__dfsan_label_info[label].l2 = l2;
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}
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atomic_store(table_ent, label, memory_order_release);
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} else if (label == kInitializingLabel) {
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// Another thread is initializing the entry. Wait until it is finished.
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do {
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internal_sched_yield();
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label = atomic_load(table_ent, memory_order_acquire);
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} while (label == kInitializingLabel);
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}
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return label;
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}
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extern "C" SANITIZER_INTERFACE_ATTRIBUTE
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dfsan_label __dfsan_union_load(const dfsan_label *ls, uptr n) {
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dfsan_label label = ls[0];
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for (uptr i = 1; i != n; ++i) {
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dfsan_label next_label = ls[i];
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if (label != next_label)
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label = __dfsan_union(label, next_label);
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}
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return label;
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}
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extern "C" SANITIZER_INTERFACE_ATTRIBUTE
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void __dfsan_unimplemented(char *fname) {
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if (flags().warn_unimplemented)
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Report("WARNING: DataFlowSanitizer: call to uninstrumented function %s\n",
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fname);
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}
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// Use '-mllvm -dfsan-debug-nonzero-labels' and break on this function
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// to try to figure out where labels are being introduced in a nominally
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// label-free program.
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extern "C" SANITIZER_INTERFACE_ATTRIBUTE void __dfsan_nonzero_label() {
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if (flags().warn_nonzero_labels)
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Report("WARNING: DataFlowSanitizer: saw nonzero label\n");
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}
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// Indirect call to an uninstrumented vararg function. We don't have a way of
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// handling these at the moment.
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extern "C" SANITIZER_INTERFACE_ATTRIBUTE void
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__dfsan_vararg_wrapper(const char *fname) {
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Report("FATAL: DataFlowSanitizer: unsupported indirect call to vararg "
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"function %s\n", fname);
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Die();
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}
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// Like __dfsan_union, but for use from the client or custom functions. Hence
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// the equality comparison is done here before calling __dfsan_union.
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SANITIZER_INTERFACE_ATTRIBUTE dfsan_label
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dfsan_union(dfsan_label l1, dfsan_label l2) {
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if (l1 == l2)
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return l1;
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return __dfsan_union(l1, l2);
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}
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extern "C" SANITIZER_INTERFACE_ATTRIBUTE
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dfsan_label dfsan_create_label(const char *desc, void *userdata) {
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dfsan_label label =
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atomic_fetch_add(&__dfsan_last_label, 1, memory_order_relaxed) + 1;
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dfsan_check_label(label);
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__dfsan_label_info[label].l1 = __dfsan_label_info[label].l2 = 0;
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__dfsan_label_info[label].desc = desc;
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__dfsan_label_info[label].userdata = userdata;
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return label;
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}
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extern "C" SANITIZER_INTERFACE_ATTRIBUTE
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void __dfsan_set_label(dfsan_label label, void *addr, uptr size) {
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for (dfsan_label *labelp = shadow_for(addr); size != 0; --size, ++labelp) {
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// Don't write the label if it is already the value we need it to be.
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// In a program where most addresses are not labeled, it is common that
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// a page of shadow memory is entirely zeroed. The Linux copy-on-write
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// implementation will share all of the zeroed pages, making a copy of a
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// page when any value is written. The un-sharing will happen even if
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// the value written does not change the value in memory. Avoiding the
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// write when both |label| and |*labelp| are zero dramatically reduces
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// the amount of real memory used by large programs.
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if (label == *labelp)
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continue;
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*labelp = label;
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}
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}
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SANITIZER_INTERFACE_ATTRIBUTE
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void dfsan_set_label(dfsan_label label, void *addr, uptr size) {
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__dfsan_set_label(label, addr, size);
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}
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SANITIZER_INTERFACE_ATTRIBUTE
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void dfsan_add_label(dfsan_label label, void *addr, uptr size) {
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for (dfsan_label *labelp = shadow_for(addr); size != 0; --size, ++labelp)
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if (*labelp != label)
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*labelp = __dfsan_union(*labelp, label);
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}
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// Unlike the other dfsan interface functions the behavior of this function
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// depends on the label of one of its arguments. Hence it is implemented as a
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// custom function.
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extern "C" SANITIZER_INTERFACE_ATTRIBUTE dfsan_label
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__dfsw_dfsan_get_label(long data, dfsan_label data_label,
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dfsan_label *ret_label) {
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*ret_label = 0;
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return data_label;
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}
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SANITIZER_INTERFACE_ATTRIBUTE dfsan_label
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dfsan_read_label(const void *addr, uptr size) {
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if (size == 0)
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return 0;
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return __dfsan_union_load(shadow_for(addr), size);
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}
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extern "C" SANITIZER_INTERFACE_ATTRIBUTE
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const struct dfsan_label_info *dfsan_get_label_info(dfsan_label label) {
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return &__dfsan_label_info[label];
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}
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extern "C" SANITIZER_INTERFACE_ATTRIBUTE int
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dfsan_has_label(dfsan_label label, dfsan_label elem) {
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if (label == elem)
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return true;
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const dfsan_label_info *info = dfsan_get_label_info(label);
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if (info->l1 != 0) {
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return dfsan_has_label(info->l1, elem) || dfsan_has_label(info->l2, elem);
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} else {
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return false;
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}
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}
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extern "C" SANITIZER_INTERFACE_ATTRIBUTE dfsan_label
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dfsan_has_label_with_desc(dfsan_label label, const char *desc) {
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const dfsan_label_info *info = dfsan_get_label_info(label);
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if (info->l1 != 0) {
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return dfsan_has_label_with_desc(info->l1, desc) ||
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dfsan_has_label_with_desc(info->l2, desc);
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} else {
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return internal_strcmp(desc, info->desc) == 0;
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}
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}
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extern "C" SANITIZER_INTERFACE_ATTRIBUTE uptr
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dfsan_get_label_count(void) {
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dfsan_label max_label_allocated =
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atomic_load(&__dfsan_last_label, memory_order_relaxed);
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return static_cast<uptr>(max_label_allocated);
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}
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extern "C" SANITIZER_INTERFACE_ATTRIBUTE void
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dfsan_dump_labels(int fd) {
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dfsan_label last_label =
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atomic_load(&__dfsan_last_label, memory_order_relaxed);
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for (uptr l = 1; l <= last_label; ++l) {
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char buf[64];
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internal_snprintf(buf, sizeof(buf), "%u %u %u ", l,
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__dfsan_label_info[l].l1, __dfsan_label_info[l].l2);
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internal_write(fd, buf, internal_strlen(buf));
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if (__dfsan_label_info[l].l1 == 0 && __dfsan_label_info[l].desc) {
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internal_write(fd, __dfsan_label_info[l].desc,
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internal_strlen(__dfsan_label_info[l].desc));
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}
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internal_write(fd, "\n", 1);
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}
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}
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void Flags::SetDefaults() {
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#define DFSAN_FLAG(Type, Name, DefaultValue, Description) Name = DefaultValue;
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#include "dfsan_flags.inc"
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#undef DFSAN_FLAG
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}
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static void RegisterDfsanFlags(FlagParser *parser, Flags *f) {
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#define DFSAN_FLAG(Type, Name, DefaultValue, Description) \
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RegisterFlag(parser, #Name, Description, &f->Name);
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#include "dfsan_flags.inc"
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#undef DFSAN_FLAG
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}
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static void InitializeFlags() {
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FlagParser parser;
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RegisterDfsanFlags(&parser, &flags());
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flags().SetDefaults();
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parser.ParseString(GetEnv("DFSAN_OPTIONS"));
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}
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static void dfsan_fini() {
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if (internal_strcmp(flags().dump_labels_at_exit, "") != 0) {
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fd_t fd = OpenFile(flags().dump_labels_at_exit, true /* write */);
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if (fd == kInvalidFd) {
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Report("WARNING: DataFlowSanitizer: unable to open output file %s\n",
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flags().dump_labels_at_exit);
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return;
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}
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Report("INFO: DataFlowSanitizer: dumping labels to %s\n",
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flags().dump_labels_at_exit);
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dfsan_dump_labels(fd);
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internal_close(fd);
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}
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}
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#ifdef DFSAN_NOLIBC
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extern "C" void dfsan_init() {
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#else
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static void dfsan_init(int argc, char **argv, char **envp) {
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#endif
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MmapFixedNoReserve(kShadowAddr, kUnusedAddr - kShadowAddr);
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// Protect the region of memory we don't use, to preserve the one-to-one
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// mapping from application to shadow memory. But if ASLR is disabled, Linux
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// will load our executable in the middle of our unused region. This mostly
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// works so long as the program doesn't use too much memory. We support this
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// case by disabling memory protection when ASLR is disabled.
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uptr init_addr = (uptr)&dfsan_init;
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if (!(init_addr >= kUnusedAddr && init_addr < kAppAddr))
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Mprotect(kUnusedAddr, kAppAddr - kUnusedAddr);
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InitializeFlags();
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InitializeInterceptors();
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// Register the fini callback to run when the program terminates successfully
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// or it is killed by the runtime.
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Atexit(dfsan_fini);
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SetDieCallback(dfsan_fini);
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__dfsan_label_info[kInitializingLabel].desc = "<init label>";
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}
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#if !defined(DFSAN_NOLIBC) && SANITIZER_CAN_USE_PREINIT_ARRAY
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__attribute__((section(".preinit_array"), used))
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static void (*dfsan_init_ptr)(int, char **, char **) = dfsan_init;
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#endif
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