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//===-- 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_common/sanitizer_atomic.h"
#include "sanitizer_common/sanitizer_common.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
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) {
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.ParseString(GetEnv("DFSAN_OPTIONS"));
SetVerbosity(common_flags()->verbosity);
if (Verbosity()) ReportUnrecognizedFlags();
if (common_flags()->help) parser.PrintFlagDescriptions();
}
static void InitializePlatformEarly() {
#ifdef DFSAN_RUNTIME_VMA
__dfsan::vmaSize =
(MostSignificantSetBitIndex(GET_CURRENT_FRAME()) + 1);
if (__dfsan::vmaSize == 39 || __dfsan::vmaSize == 42) {
__dfsan_shadow_ptr_mask = ShadowMask();
} else {
Printf("FATAL: DataFlowSanitizer: unsupported VMA range\n");
Printf("FATAL: Found %d - Supported 39 and 42\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);
}
}
static void dfsan_init(int argc, char **argv, char **envp) {
InitializeFlags();
InitializePlatformEarly();
MmapFixedNoReserve(ShadowAddr(), UnusedAddr() - ShadowAddr());
// 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()))
MmapNoAccess(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