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      1 //===-- asan_poisoning.h ----------------------------------------*- C++ -*-===//
      2 //
      3 //                     The LLVM Compiler Infrastructure
      4 //
      5 // This file is distributed under the University of Illinois Open Source
      6 // License. See LICENSE.TXT for details.
      7 //
      8 //===----------------------------------------------------------------------===//
      9 //
     10 // This file is a part of AddressSanitizer, an address sanity checker.
     11 //
     12 // Shadow memory poisoning by ASan RTL and by user application.
     13 //===----------------------------------------------------------------------===//
     14 
     15 #include "asan_interceptors.h"
     16 #include "asan_internal.h"
     17 #include "asan_mapping.h"
     18 #include "sanitizer_common/sanitizer_flags.h"
     19 
     20 namespace __asan {
     21 
     22 // Enable/disable memory poisoning.
     23 void SetCanPoisonMemory(bool value);
     24 bool CanPoisonMemory();
     25 
     26 // Poisons the shadow memory for "size" bytes starting from "addr".
     27 void PoisonShadow(uptr addr, uptr size, u8 value);
     28 
     29 // Poisons the shadow memory for "redzone_size" bytes starting from
     30 // "addr + size".
     31 void PoisonShadowPartialRightRedzone(uptr addr,
     32                                      uptr size,
     33                                      uptr redzone_size,
     34                                      u8 value);
     35 
     36 // Fast versions of PoisonShadow and PoisonShadowPartialRightRedzone that
     37 // assume that memory addresses are properly aligned. Use in
     38 // performance-critical code with care.
     39 ALWAYS_INLINE void FastPoisonShadow(uptr aligned_beg, uptr aligned_size,
     40                                     u8 value) {
     41   DCHECK(!value || CanPoisonMemory());
     42   uptr shadow_beg = MEM_TO_SHADOW(aligned_beg);
     43   uptr shadow_end = MEM_TO_SHADOW(
     44       aligned_beg + aligned_size - SHADOW_GRANULARITY) + 1;
     45   // FIXME: Page states are different on Windows, so using the same interface
     46   // for mapping shadow and zeroing out pages doesn't "just work", so we should
     47   // probably provide higher-level interface for these operations.
     48   // For now, just memset on Windows.
     49   if (value || SANITIZER_WINDOWS == 1 ||
     50       // TODO(mcgrathr): Fuchsia doesn't allow the shadow mapping to be
     51       // changed at all.  It doesn't currently have an efficient means
     52       // to zero a bunch of pages, but maybe we should add one.
     53       SANITIZER_FUCHSIA == 1 ||
     54       // RTEMS doesn't have have pages, let alone a fast way to zero
     55       // them, so default to memset.
     56       SANITIZER_RTEMS == 1 ||
     57       shadow_end - shadow_beg < common_flags()->clear_shadow_mmap_threshold) {
     58     REAL(memset)((void*)shadow_beg, value, shadow_end - shadow_beg);
     59   } else {
     60     uptr page_size = GetPageSizeCached();
     61     uptr page_beg = RoundUpTo(shadow_beg, page_size);
     62     uptr page_end = RoundDownTo(shadow_end, page_size);
     63 
     64     if (page_beg >= page_end) {
     65       REAL(memset)((void *)shadow_beg, 0, shadow_end - shadow_beg);
     66     } else {
     67       if (page_beg != shadow_beg) {
     68         REAL(memset)((void *)shadow_beg, 0, page_beg - shadow_beg);
     69       }
     70       if (page_end != shadow_end) {
     71         REAL(memset)((void *)page_end, 0, shadow_end - page_end);
     72       }
     73       ReserveShadowMemoryRange(page_beg, page_end - 1, nullptr);
     74     }
     75   }
     76 }
     77 
     78 ALWAYS_INLINE void FastPoisonShadowPartialRightRedzone(
     79     uptr aligned_addr, uptr size, uptr redzone_size, u8 value) {
     80   DCHECK(CanPoisonMemory());
     81   bool poison_partial = flags()->poison_partial;
     82   u8 *shadow = (u8*)MEM_TO_SHADOW(aligned_addr);
     83   for (uptr i = 0; i < redzone_size; i += SHADOW_GRANULARITY, shadow++) {
     84     if (i + SHADOW_GRANULARITY <= size) {
     85       *shadow = 0;  // fully addressable
     86     } else if (i >= size) {
     87       *shadow = (SHADOW_GRANULARITY == 128) ? 0xff : value;  // unaddressable
     88     } else {
     89       // first size-i bytes are addressable
     90       *shadow = poison_partial ? static_cast<u8>(size - i) : 0;
     91     }
     92   }
     93 }
     94 
     95 // Calls __sanitizer::ReleaseMemoryPagesToOS() on
     96 // [MemToShadow(p), MemToShadow(p+size)].
     97 void FlushUnneededASanShadowMemory(uptr p, uptr size);
     98 
     99 }  // namespace __asan
    100