//===-- asan_poisoning.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 AddressSanitizer, an address sanity checker.
//
// Shadow memory poisoning by ASan RTL and by user application.
//===----------------------------------------------------------------------===//
#include "asan_poisoning.h"
#include "sanitizer_common/sanitizer_libc.h"
namespace __asan {
void PoisonShadow(uptr addr, uptr size, u8 value) {
if (!flags()->poison_heap) return;
CHECK(AddrIsAlignedByGranularity(addr));
CHECK(AddrIsInMem(addr));
CHECK(AddrIsAlignedByGranularity(addr + size));
CHECK(AddrIsInMem(addr + size - SHADOW_GRANULARITY));
CHECK(REAL(memset));
FastPoisonShadow(addr, size, value);
}
void PoisonShadowPartialRightRedzone(uptr addr,
uptr size,
uptr redzone_size,
u8 value) {
if (!flags()->poison_heap) return;
CHECK(AddrIsAlignedByGranularity(addr));
CHECK(AddrIsInMem(addr));
FastPoisonShadowPartialRightRedzone(addr, size, redzone_size, value);
}
struct ShadowSegmentEndpoint {
u8 *chunk;
s8 offset; // in [0, SHADOW_GRANULARITY)
s8 value; // = *chunk;
explicit ShadowSegmentEndpoint(uptr address) {
chunk = (u8*)MemToShadow(address);
offset = address & (SHADOW_GRANULARITY - 1);
value = *chunk;
}
};
} // namespace __asan
// ---------------------- Interface ---------------- {{{1
using namespace __asan; // NOLINT
// Current implementation of __asan_(un)poison_memory_region doesn't check
// that user program (un)poisons the memory it owns. It poisons memory
// conservatively, and unpoisons progressively to make sure asan shadow
// mapping invariant is preserved (see detailed mapping description here:
// http://code.google.com/p/address-sanitizer/wiki/AddressSanitizerAlgorithm).
//
// * if user asks to poison region [left, right), the program poisons
// at least [left, AlignDown(right)).
// * if user asks to unpoison region [left, right), the program unpoisons
// at most [AlignDown(left), right).
void __asan_poison_memory_region(void const volatile *addr, uptr size) {
if (!flags()->allow_user_poisoning || size == 0) return;
uptr beg_addr = (uptr)addr;
uptr end_addr = beg_addr + size;
if (flags()->verbosity >= 1) {
Printf("Trying to poison memory region [%p, %p)\n",
(void*)beg_addr, (void*)end_addr);
}
ShadowSegmentEndpoint beg(beg_addr);
ShadowSegmentEndpoint end(end_addr);
if (beg.chunk == end.chunk) {
CHECK(beg.offset < end.offset);
s8 value = beg.value;
CHECK(value == end.value);
// We can only poison memory if the byte in end.offset is unaddressable.
// No need to re-poison memory if it is poisoned already.
if (value > 0 && value <= end.offset) {
if (beg.offset > 0) {
*beg.chunk = Min(value, beg.offset);
} else {
*beg.chunk = kAsanUserPoisonedMemoryMagic;
}
}
return;
}
CHECK(beg.chunk < end.chunk);
if (beg.offset > 0) {
// Mark bytes from beg.offset as unaddressable.
if (beg.value == 0) {
*beg.chunk = beg.offset;
} else {
*beg.chunk = Min(beg.value, beg.offset);
}
beg.chunk++;
}
REAL(memset)(beg.chunk, kAsanUserPoisonedMemoryMagic, end.chunk - beg.chunk);
// Poison if byte in end.offset is unaddressable.
if (end.value > 0 && end.value <= end.offset) {
*end.chunk = kAsanUserPoisonedMemoryMagic;
}
}
void __asan_unpoison_memory_region(void const volatile *addr, uptr size) {
if (!flags()->allow_user_poisoning || size == 0) return;
uptr beg_addr = (uptr)addr;
uptr end_addr = beg_addr + size;
if (flags()->verbosity >= 1) {
Printf("Trying to unpoison memory region [%p, %p)\n",
(void*)beg_addr, (void*)end_addr);
}
ShadowSegmentEndpoint beg(beg_addr);
ShadowSegmentEndpoint end(end_addr);
if (beg.chunk == end.chunk) {
CHECK(beg.offset < end.offset);
s8 value = beg.value;
CHECK(value == end.value);
// We unpoison memory bytes up to enbytes up to end.offset if it is not
// unpoisoned already.
if (value != 0) {
*beg.chunk = Max(value, end.offset);
}
return;
}
CHECK(beg.chunk < end.chunk);
if (beg.offset > 0) {
*beg.chunk = 0;
beg.chunk++;
}
REAL(memset)(beg.chunk, 0, end.chunk - beg.chunk);
if (end.offset > 0 && end.value != 0) {
*end.chunk = Max(end.value, end.offset);
}
}
bool __asan_address_is_poisoned(void const volatile *addr) {
return __asan::AddressIsPoisoned((uptr)addr);
}
uptr __asan_region_is_poisoned(uptr beg, uptr size) {
if (!size) return 0;
uptr end = beg + size;
if (!AddrIsInMem(beg)) return beg;
if (!AddrIsInMem(end)) return end;
uptr aligned_b = RoundUpTo(beg, SHADOW_GRANULARITY);
uptr aligned_e = RoundDownTo(end, SHADOW_GRANULARITY);
uptr shadow_beg = MemToShadow(aligned_b);
uptr shadow_end = MemToShadow(aligned_e);
// First check the first and the last application bytes,
// then check the SHADOW_GRANULARITY-aligned region by calling
// mem_is_zero on the corresponding shadow.
if (!__asan::AddressIsPoisoned(beg) &&
!__asan::AddressIsPoisoned(end - 1) &&
(shadow_end <= shadow_beg ||
__sanitizer::mem_is_zero((const char *)shadow_beg,
shadow_end - shadow_beg)))
return 0;
// The fast check failed, so we have a poisoned byte somewhere.
// Find it slowly.
for (; beg < end; beg++)
if (__asan::AddressIsPoisoned(beg))
return beg;
UNREACHABLE("mem_is_zero returned false, but poisoned byte was not found");
return 0;
}
#define CHECK_SMALL_REGION(p, size, isWrite) \
do { \
uptr __p = reinterpret_cast<uptr>(p); \
uptr __size = size; \
if (UNLIKELY(__asan::AddressIsPoisoned(__p) || \
__asan::AddressIsPoisoned(__p + __size - 1))) { \
GET_CURRENT_PC_BP_SP; \
uptr __bad = __asan_region_is_poisoned(__p, __size); \
__asan_report_error(pc, bp, sp, __bad, isWrite, __size);\
} \
} while (false); \
extern "C" SANITIZER_INTERFACE_ATTRIBUTE
u16 __sanitizer_unaligned_load16(const uu16 *p) {
CHECK_SMALL_REGION(p, sizeof(*p), false);
return *p;
}
extern "C" SANITIZER_INTERFACE_ATTRIBUTE
u32 __sanitizer_unaligned_load32(const uu32 *p) {
CHECK_SMALL_REGION(p, sizeof(*p), false);
return *p;
}
extern "C" SANITIZER_INTERFACE_ATTRIBUTE
u64 __sanitizer_unaligned_load64(const uu64 *p) {
CHECK_SMALL_REGION(p, sizeof(*p), false);
return *p;
}
extern "C" SANITIZER_INTERFACE_ATTRIBUTE
void __sanitizer_unaligned_store16(uu16 *p, u16 x) {
CHECK_SMALL_REGION(p, sizeof(*p), true);
*p = x;
}
extern "C" SANITIZER_INTERFACE_ATTRIBUTE
void __sanitizer_unaligned_store32(uu32 *p, u32 x) {
CHECK_SMALL_REGION(p, sizeof(*p), true);
*p = x;
}
extern "C" SANITIZER_INTERFACE_ATTRIBUTE
void __sanitizer_unaligned_store64(uu64 *p, u64 x) {
CHECK_SMALL_REGION(p, sizeof(*p), true);
*p = x;
}
// This is a simplified version of __asan_(un)poison_memory_region, which
// assumes that left border of region to be poisoned is properly aligned.
static void PoisonAlignedStackMemory(uptr addr, uptr size, bool do_poison) {
if (size == 0) return;
uptr aligned_size = size & ~(SHADOW_GRANULARITY - 1);
PoisonShadow(addr, aligned_size,
do_poison ? kAsanStackUseAfterScopeMagic : 0);
if (size == aligned_size)
return;
s8 end_offset = (s8)(size - aligned_size);
s8* shadow_end = (s8*)MemToShadow(addr + aligned_size);
s8 end_value = *shadow_end;
if (do_poison) {
// If possible, mark all the bytes mapping to last shadow byte as
// unaddressable.
if (end_value > 0 && end_value <= end_offset)
*shadow_end = (s8)kAsanStackUseAfterScopeMagic;
} else {
// If necessary, mark few first bytes mapping to last shadow byte
// as addressable
if (end_value != 0)
*shadow_end = Max(end_value, end_offset);
}
}
void __asan_poison_stack_memory(uptr addr, uptr size) {
if (flags()->verbosity > 0)
Report("poisoning: %p %zx\n", (void*)addr, size);
PoisonAlignedStackMemory(addr, size, true);
}
void __asan_unpoison_stack_memory(uptr addr, uptr size) {
if (flags()->verbosity > 0)
Report("unpoisoning: %p %zx\n", (void*)addr, size);
PoisonAlignedStackMemory(addr, size, false);
}