libsanitizer/asan/asan_poisoning.cc - chromiumos/third_party/gcc - Git at Google

 //===-- asan_poisoning.cc -------------------------------------------------===//
 //
 // 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"
 #include "sanitizer_common/sanitizer_flags.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 (common_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 (common_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 (common_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 (common_flags()->verbosity > 0)
     Report("unpoisoning: %p %zx\n", (void*)addr, size);
   PoisonAlignedStackMemory(addr, size, false);
 }

 void __sanitizer_annotate_contiguous_container(const void *beg_p,
                                                const void *end_p,
                                                const void *old_mid_p,
                                                const void *new_mid_p) {
   if (common_flags()->verbosity >= 2)
     Printf("contiguous_container: %p %p %p %p\n", beg_p, end_p, old_mid_p,
            new_mid_p);
   uptr beg = reinterpret_cast<uptr>(beg_p);
   uptr end= reinterpret_cast<uptr>(end_p);
   uptr old_mid = reinterpret_cast<uptr>(old_mid_p);
   uptr new_mid = reinterpret_cast<uptr>(new_mid_p);
   uptr granularity = SHADOW_GRANULARITY;
   CHECK(beg <= old_mid && beg <= new_mid && old_mid <= end && new_mid <= end &&
         IsAligned(beg, granularity));
   CHECK_LE(end - beg,
            FIRST_32_SECOND_64(1UL << 30, 1UL << 34)); // Sanity check.

   uptr a = RoundDownTo(Min(old_mid, new_mid), granularity);
   uptr c = RoundUpTo(Max(old_mid, new_mid), granularity);
   uptr d1 = RoundDownTo(old_mid, granularity);
   uptr d2 = RoundUpTo(old_mid, granularity);
   // Currently we should be in this state:
   // [a, d1) is good, [d2, c) is bad, [d1, d2) is partially good.
   // Make a quick sanity check that we are indeed in this state.
   if (d1 != d2)
     CHECK_EQ(*(u8*)MemToShadow(d1), old_mid - d1);
   if (a + granularity <= d1)
     CHECK_EQ(*(u8*)MemToShadow(a), 0);
   if (d2 + granularity <= c && c <= end)
     CHECK_EQ(*(u8 *)MemToShadow(c - granularity),
              kAsanContiguousContainerOOBMagic);

   uptr b1 = RoundDownTo(new_mid, granularity);
   uptr b2 = RoundUpTo(new_mid, granularity);
   // New state:
   // [a, b1) is good, [b2, c) is bad, [b1, b2) is partially good.
   PoisonShadow(a, b1 - a, 0);
   PoisonShadow(b2, c - b2, kAsanContiguousContainerOOBMagic);
   if (b1 != b2) {
     CHECK_EQ(b2 - b1, granularity);
     *(u8*)MemToShadow(b1) = static_cast<u8>(new_mid - b1);
   }
 }
	//===-- asan_poisoning.cc -------------------------------------------------===//
	//
	// 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"
	#include "sanitizer_common/sanitizer_flags.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 (common_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 (common_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 (common_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 (common_flags()->verbosity > 0)
	Report("unpoisoning: %p %zx\n", (void*)addr, size);
	PoisonAlignedStackMemory(addr, size, false);
	}

	void __sanitizer_annotate_contiguous_container(const void *beg_p,
	const void *end_p,
	const void *old_mid_p,
	const void *new_mid_p) {
	if (common_flags()->verbosity >= 2)
	Printf("contiguous_container: %p %p %p %p\n", beg_p, end_p, old_mid_p,
	new_mid_p);
	uptr beg = reinterpret_cast<uptr>(beg_p);
	uptr end= reinterpret_cast<uptr>(end_p);
	uptr old_mid = reinterpret_cast<uptr>(old_mid_p);
	uptr new_mid = reinterpret_cast<uptr>(new_mid_p);
	uptr granularity = SHADOW_GRANULARITY;
	CHECK(beg <= old_mid && beg <= new_mid && old_mid <= end && new_mid <= end &&
	IsAligned(beg, granularity));
	CHECK_LE(end - beg,
	FIRST_32_SECOND_64(1UL << 30, 1UL << 34)); // Sanity check.

	uptr a = RoundDownTo(Min(old_mid, new_mid), granularity);
	uptr c = RoundUpTo(Max(old_mid, new_mid), granularity);
	uptr d1 = RoundDownTo(old_mid, granularity);
	uptr d2 = RoundUpTo(old_mid, granularity);
	// Currently we should be in this state:
	// [a, d1) is good, [d2, c) is bad, [d1, d2) is partially good.
	// Make a quick sanity check that we are indeed in this state.
	if (d1 != d2)
	CHECK_EQ((u8)MemToShadow(d1), old_mid - d1);
	if (a + granularity <= d1)
	CHECK_EQ((u8)MemToShadow(a), 0);
	if (d2 + granularity <= c && c <= end)
	CHECK_EQ((u8 )MemToShadow(c - granularity),
	kAsanContiguousContainerOOBMagic);

	uptr b1 = RoundDownTo(new_mid, granularity);
	uptr b2 = RoundUpTo(new_mid, granularity);
	// New state:
	// [a, b1) is good, [b2, c) is bad, [b1, b2) is partially good.
	PoisonShadow(a, b1 - a, 0);
	PoisonShadow(b2, c - b2, kAsanContiguousContainerOOBMagic);
	if (b1 != b2) {
	CHECK_EQ(b2 - b1, granularity);
	(u8)MemToShadow(b1) = static_cast<u8>(new_mid - b1);
	}
	}