//===-- 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_interceptors.h"
#include "asan_internal.h"
#include "asan_mapping.h"
#include "sanitizer/asan_interface.h"
namespace __asan {
void PoisonShadow(uptr addr, uptr size, u8 value) {
CHECK(AddrIsAlignedByGranularity(addr));
CHECK(AddrIsAlignedByGranularity(addr + size));
uptr shadow_beg = MemToShadow(addr);
uptr shadow_end = MemToShadow(addr + size);
CHECK(REAL(memset) != 0);
REAL(memset)((void*)shadow_beg, value, shadow_end - shadow_beg);
}
void PoisonShadowPartialRightRedzone(uptr addr,
uptr size,
uptr redzone_size,
u8 value) {
CHECK(AddrIsAlignedByGranularity(addr));
u8 *shadow = (u8*)MemToShadow(addr);
for (uptr i = 0; i < redzone_size;
i += SHADOW_GRANULARITY, shadow++) {
if (i + SHADOW_GRANULARITY <= size) {
*shadow = 0; // fully addressable
} else if (i >= size) {
*shadow = (SHADOW_GRANULARITY == 128) ? 0xff : value; // unaddressable
} else {
*shadow = size - i; // first size-i bytes are addressable
}
}
}
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);
}