[compiler-rt][ASan] Add function copying annotations (#91702)

This PR adds a `__sanitizer_copy_contiguous_container_annotations`
function, which copies annotations from one memory area to another. New
area is annotated in the same way as the old region at the beginning
(within limitations of ASan).

Overlapping case: The function supports overlapping containers, however
no assumptions should be made outside of no false positives in new
buffer area. (It doesn't modify old container annotations where it's not
necessary, false negatives may happen in edge granules of the new
container area.) I don't expect this function to be used with
overlapping buffers, but it's designed to work with them and not result
in incorrect ASan errors (false positives).

If buffers have granularity-aligned distance between them (`old_beg %
granularity == new_beg % granularity`), copying algorithm works faster.
If the distance is not granularity-aligned, annotations are copied byte
after byte.

```cpp
void __sanitizer_copy_contiguous_container_annotations(
    const void *old_storage_beg_p, const void *old_storage_end_p,
    const void *new_storage_beg_p, const void *new_storage_end_p) {
```

This function aims to help with short string annotations and similar
container annotations. Right now we change trait types of
`std::basic_string` when compiling with ASan and this function purpose
is reverting that change as soon as possible.


https://github.com/llvm/llvm-project/blob/87f3407856e61a73798af4e41b28bc33b5bf4ce6/libcxx/include/string#L738-L751

The goal is to not change `__trivially_relocatable` when compiling with
ASan. If this function is accepted and upstreamed, the next step is
creating a function like `__memcpy_with_asan` moving memory with ASan.
And then using this function instead of `__builtin__memcpy` while moving
trivially relocatable objects.


https://github.com/llvm/llvm-project/blob/11a6799740f824282650aa9ec249b55dcf1a8aae/libcxx/include/__memory/uninitialized_algorithms.h#L644-L646

---

I'm thinking if there is a good way to address fact that in a container
the new buffer is usually bigger than the previous one. We may add two
more arguments to the functions to address it (the beginning and the end
of the whole buffer.

Another potential change is removing `new_storage_end_p` as it's
redundant, because we require the same size.

Potential future work is creating a function `__asan_unsafe_memmove`,
which will be basically memmove, but with turned off instrumentation
(therefore it will allow copy data from poisoned area).

---------

Co-authored-by: Vitaly Buka <[email protected]>

Author: AdvenamTacet

compiler-rt/include/sanitizer/common_interface_defs.h

@@ -193,6 +193,43 @@ void SANITIZER_CDECL __sanitizer_annotate_double_ended_contiguous_container(
     const void *old_container_beg, const void *old_container_end,
     const void *new_container_beg, const void *new_container_end);
 
+/// Copies memory annotations from a source storage region to a destination
+/// storage region. After the operation, the destination region has the same
+/// memory annotations as the source region, as long as sanitizer limitations
+/// allow it (more bytes may be unpoisoned than in the source region, resulting
+/// in more false negatives, but never false positives). If the source and
+/// destination regions overlap, only the minimal required changes are made to
+/// preserve the correct annotations. Old storage bytes that are not in the new
+/// storage should have the same annotations, as long as sanitizer limitations
+/// allow it.
+///
+/// This function is primarily designed to be used when moving trivially
+/// relocatable objects that may have poisoned memory, making direct copying
+/// problematic under sanitizer. However, this function does not move memory
+/// content itself, only annotations.
+///
+/// A contiguous container is a container that keeps all of its elements in a
+/// contiguous region of memory. The container owns the region of memory
+/// <c>[src_begin, src_end)</c> and <c>[dst_begin, dst_end)</c>. The memory
+/// within these regions may be alternately poisoned and non-poisoned, with
+/// possibly smaller poisoned and unpoisoned regions.
+///
+/// If this function fully poisons a granule, it is marked as "container
+/// overflow".
+///
+/// Argument requirements: The destination container must have the same size as
+/// the source container, which is inferred from the beginning and end of the
+/// source region. Addresses may be granule-unaligned, but this may affect
+/// performance.
+///
+/// \param src_begin Begin of the source container region.
+/// \param src_end End of the source container region.
+/// \param dst_begin Begin of the destination container region.
+/// \param dst_end End of the destination container region.
+void SANITIZER_CDECL __sanitizer_copy_contiguous_container_annotations(
+    const void *src_begin, const void *src_end, const void *dst_begin,
+    const void *dst_end);
+
 /// Returns true if the contiguous container <c>[beg, end)</c> is properly
 /// poisoned.
 ///

compiler-rt/lib/asan/asan_errors.cpp

@@ -348,6 +348,20 @@ void ErrorBadParamsToAnnotateDoubleEndedContiguousContainer::Print() {
   ReportErrorSummary(scariness.GetDescription(), stack);
 }
 
+void ErrorBadParamsToCopyContiguousContainerAnnotations::Print() {
+  Report(
+      "ERROR: AddressSanitizer: bad parameters to "
+      "__sanitizer_copy_contiguous_container_annotations:\n"
+      "      src_storage_beg : %p\n"
+      "      src_storage_end : %p\n"
+      "      dst_storage_beg : %p\n"
+      "      new_storage_end : %p\n",
+      (void *)old_storage_beg, (void *)old_storage_end, (void *)new_storage_beg,
+      (void *)new_storage_end);
+  stack->Print();
+  ReportErrorSummary(scariness.GetDescription(), stack);
+}
+
 void ErrorODRViolation::Print() {
   Decorator d;
   Printf("%s", d.Error());

compiler-rt/lib/asan/asan_errors.h

@@ -353,6 +353,24 @@ struct ErrorBadParamsToAnnotateDoubleEndedContiguousContainer : ErrorBase {
   void Print();
 };
 
+struct ErrorBadParamsToCopyContiguousContainerAnnotations : ErrorBase {
+  const BufferedStackTrace *stack;
+  uptr old_storage_beg, old_storage_end, new_storage_beg, new_storage_end;
+
+  ErrorBadParamsToCopyContiguousContainerAnnotations() = default;  // (*)
+  ErrorBadParamsToCopyContiguousContainerAnnotations(
+      u32 tid, BufferedStackTrace *stack_, uptr old_storage_beg_,
+      uptr old_storage_end_, uptr new_storage_beg_, uptr new_storage_end_)
+      : ErrorBase(tid, 10,
+                  "bad-__sanitizer_annotate_double_ended_contiguous_container"),
+        stack(stack_),
+        old_storage_beg(old_storage_beg_),
+        old_storage_end(old_storage_end_),
+        new_storage_beg(new_storage_beg_),
+        new_storage_end(new_storage_end_) {}
+  void Print();
+};
+
 struct ErrorODRViolation : ErrorBase {
   __asan_global global1, global2;
   u32 stack_id1, stack_id2;
@@ -421,6 +439,7 @@ struct ErrorGeneric : ErrorBase {
   macro(StringFunctionSizeOverflow)                        \
   macro(BadParamsToAnnotateContiguousContainer)            \
   macro(BadParamsToAnnotateDoubleEndedContiguousContainer) \
+  macro(BadParamsToCopyContiguousContainerAnnotations)     \
   macro(ODRViolation)                                      \
   macro(InvalidPointerPair)                                \
   macro(Generic)

compiler-rt/lib/asan/asan_poisoning.cpp

@@ -16,6 +16,7 @@
 #include "asan_report.h"
 #include "asan_stack.h"
 #include "sanitizer_common/sanitizer_atomic.h"
+#include "sanitizer_common/sanitizer_common.h"
 #include "sanitizer_common/sanitizer_flags.h"
 #include "sanitizer_common/sanitizer_interface_internal.h"
 #include "sanitizer_common/sanitizer_libc.h"
@@ -576,6 +577,185 @@ void __sanitizer_annotate_double_ended_contiguous_container(
   }
 }
 
+// Marks the specified number of bytes in a granule as accessible or
+// poisones the whole granule with kAsanContiguousContainerOOBMagic value.
+static void SetContainerGranule(uptr ptr, u8 n) {
+  constexpr uptr granularity = ASAN_SHADOW_GRANULARITY;
+  u8 s = (n == granularity) ? 0 : (n ? n : kAsanContiguousContainerOOBMagic);
+  *(u8 *)MemToShadow(ptr) = s;
+}
+
+// Performs a byte-by-byte copy of ASan annotations (shadow memory values).
+// Result may be different due to ASan limitations, but result cannot lead
+// to false positives (more memory than requested may get unpoisoned).
+static void SlowCopyContainerAnnotations(uptr src_beg, uptr src_end,
+                                         uptr dst_beg, uptr dst_end) {
+  constexpr uptr granularity = ASAN_SHADOW_GRANULARITY;
+  uptr dst_end_down = RoundDownTo(dst_end, granularity);
+  uptr src_ptr = src_beg;
+  uptr dst_ptr = dst_beg;
+
+  while (dst_ptr < dst_end) {
+    uptr granule_beg = RoundDownTo(dst_ptr, granularity);
+    uptr granule_end = granule_beg + granularity;
+    uptr unpoisoned_bytes = 0;
+
+    uptr end = Min(granule_end, dst_end);
+    for (; dst_ptr != end; ++dst_ptr, ++src_ptr)
+      if (!AddressIsPoisoned(src_ptr))
+        unpoisoned_bytes = dst_ptr - granule_beg + 1;
+
+    if (dst_ptr == dst_end && dst_end != dst_end_down &&
+        !AddressIsPoisoned(dst_end))
+      continue;
+
+    if (unpoisoned_bytes != 0 || granule_beg >= dst_beg)
+      SetContainerGranule(granule_beg, unpoisoned_bytes);
+    else if (!AddressIsPoisoned(dst_beg))
+      SetContainerGranule(granule_beg, dst_beg - granule_beg);
+  }
+}
+
+// Performs a byte-by-byte copy of ASan annotations (shadow memory values),
+// going through bytes in reversed order, but not reversing annotations.
+// Result may be different due to ASan limitations, but result cannot lead
+// to false positives (more memory than requested may get unpoisoned).
+static void SlowReversedCopyContainerAnnotations(uptr src_beg, uptr src_end,
+                                                 uptr dst_beg, uptr dst_end) {
+  constexpr uptr granularity = ASAN_SHADOW_GRANULARITY;
+  uptr dst_end_down = RoundDownTo(dst_end, granularity);
+  uptr src_ptr = src_end;
+  uptr dst_ptr = dst_end;
+
+  while (dst_ptr > dst_beg) {
+    uptr granule_beg = RoundDownTo(dst_ptr - 1, granularity);
+    uptr unpoisoned_bytes = 0;
+
+    uptr end = Max(granule_beg, dst_beg);
+    for (; dst_ptr != end; --dst_ptr, --src_ptr)
+      if (unpoisoned_bytes == 0 && !AddressIsPoisoned(src_ptr - 1))
+        unpoisoned_bytes = dst_ptr - granule_beg;
+
+    if (dst_ptr >= dst_end_down && !AddressIsPoisoned(dst_end))
+      continue;
+
+    if (granule_beg == dst_ptr || unpoisoned_bytes != 0)
+      SetContainerGranule(granule_beg, unpoisoned_bytes);
+    else if (!AddressIsPoisoned(dst_beg))
+      SetContainerGranule(granule_beg, dst_beg - granule_beg);
+  }
+}
+
+// A helper function for __sanitizer_copy_contiguous_container_annotations,
+// has assumption about begin and end of the container.
+// Should not be used stand alone.
+static void CopyContainerFirstGranuleAnnotation(uptr src_beg, uptr dst_beg) {
+  constexpr uptr granularity = ASAN_SHADOW_GRANULARITY;
+  // First granule
+  uptr src_beg_down = RoundDownTo(src_beg, granularity);
+  uptr dst_beg_down = RoundDownTo(dst_beg, granularity);
+  if (dst_beg_down == dst_beg)
+    return;
+  if (!AddressIsPoisoned(src_beg))
+    *(u8 *)MemToShadow(dst_beg_down) = *(u8 *)MemToShadow(src_beg_down);
+  else if (!AddressIsPoisoned(dst_beg))
+    SetContainerGranule(dst_beg_down, dst_beg - dst_beg_down);
+}
+
+// A helper function for __sanitizer_copy_contiguous_container_annotations,
+// has assumption about begin and end of the container.
+// Should not be used stand alone.
+static void CopyContainerLastGranuleAnnotation(uptr src_end, uptr dst_end) {
+  constexpr uptr granularity = ASAN_SHADOW_GRANULARITY;
+  // Last granule
+  uptr src_end_down = RoundDownTo(src_end, granularity);
+  uptr dst_end_down = RoundDownTo(dst_end, granularity);
+  if (dst_end_down == dst_end || !AddressIsPoisoned(dst_end))
+    return;
+  if (AddressIsPoisoned(src_end))
+    *(u8 *)MemToShadow(dst_end_down) = *(u8 *)MemToShadow(src_end_down);
+  else
+    SetContainerGranule(dst_end_down, src_end - src_end_down);
+}
+
+// This function copies ASan memory annotations (poisoned/unpoisoned states)
+// from one buffer to another.
+// It's main purpose is to help with relocating trivially relocatable objects,
+// which memory may be poisoned, without calling copy constructor.
+// However, it does not move memory content itself, only annotations.
+// If the buffers aren't aligned (the distance between buffers isn't
+// granule-aligned)
+//     // src_beg % granularity != dst_beg % granularity
+// the function handles this by going byte by byte, slowing down performance.
+// The old buffer annotations are not removed. If necessary,
+// user can unpoison old buffer with __asan_unpoison_memory_region.
+void __sanitizer_copy_contiguous_container_annotations(const void *src_beg_p,
+                                                       const void *src_end_p,
+                                                       const void *dst_beg_p,
+                                                       const void *dst_end_p) {
+  if (!flags()->detect_container_overflow)
+    return;
+
+  VPrintf(3, "contiguous_container_src: %p %p\n", src_beg_p, src_end_p);
+  VPrintf(3, "contiguous_container_dst: %p %p\n", dst_beg_p, dst_end_p);
+
+  uptr src_beg = reinterpret_cast<uptr>(src_beg_p);
+  uptr src_end = reinterpret_cast<uptr>(src_end_p);
+  uptr dst_beg = reinterpret_cast<uptr>(dst_beg_p);
+  uptr dst_end = reinterpret_cast<uptr>(dst_end_p);
+
+  constexpr uptr granularity = ASAN_SHADOW_GRANULARITY;
+
+  if (src_beg > src_end || (dst_end - dst_beg) != (src_end - src_beg)) {
+    GET_STACK_TRACE_FATAL_HERE;
+    ReportBadParamsToCopyContiguousContainerAnnotations(
+        src_beg, src_end, dst_beg, dst_end, &stack);
+  }
+
+  if (src_beg == src_end || src_beg == dst_beg)
+    return;
+  // Due to support for overlapping buffers, we may have to copy elements
+  // in reversed order, when destination buffer starts in the middle of
+  // the source buffer (or shares first granule with it).
+  //
+  // When buffers are not granule-aligned (or distance between them,
+  // to be specific), annotatios have to be copied byte by byte.
+  //
+  // The only remaining edge cases involve edge granules,
+  // when the container starts or ends within a granule.
+  uptr src_beg_up = RoundUpTo(src_beg, granularity);
+  uptr src_end_up = RoundUpTo(src_end, granularity);
+  bool copy_in_reversed_order = src_beg < dst_beg && dst_beg <= src_end_up;
+  if (src_beg % granularity != dst_beg % granularity ||
+      RoundDownTo(dst_end - 1, granularity) <= dst_beg) {
+    if (copy_in_reversed_order)
+      SlowReversedCopyContainerAnnotations(src_beg, src_end, dst_beg, dst_end);
+    else
+      SlowCopyContainerAnnotations(src_beg, src_end, dst_beg, dst_end);
+    return;
+  }
+
+  // As buffers are granule-aligned, we can just copy annotations of granules
+  // from the middle.
+  uptr dst_beg_up = RoundUpTo(dst_beg, granularity);
+  uptr dst_end_down = RoundDownTo(dst_end, granularity);
+  if (copy_in_reversed_order)
+    CopyContainerLastGranuleAnnotation(src_end, dst_end);
+  else
+    CopyContainerFirstGranuleAnnotation(src_beg, dst_beg);
+
+  if (dst_beg_up < dst_end_down) {
+    internal_memmove((u8 *)MemToShadow(dst_beg_up),
+                     (u8 *)MemToShadow(src_beg_up),
+                     (dst_end_down - dst_beg_up) / granularity);
+  }
+
+  if (copy_in_reversed_order)
+    CopyContainerFirstGranuleAnnotation(src_beg, dst_beg);
+  else
+    CopyContainerLastGranuleAnnotation(src_end, dst_end);
+}
+
 static const void *FindBadAddress(uptr begin, uptr end, bool poisoned) {
   CHECK_LE(begin, end);
   constexpr uptr kMaxRangeToCheck = 32;

compiler-rt/lib/asan/asan_report.cpp

@@ -367,6 +367,16 @@ void ReportBadParamsToAnnotateDoubleEndedContiguousContainer(
   in_report.ReportError(error);
 }
 
+void ReportBadParamsToCopyContiguousContainerAnnotations(
+    uptr old_storage_beg, uptr old_storage_end, uptr new_storage_beg,
+    uptr new_storage_end, BufferedStackTrace *stack) {
+  ScopedInErrorReport in_report;
+  ErrorBadParamsToCopyContiguousContainerAnnotations error(
+      GetCurrentTidOrInvalid(), stack, old_storage_beg, old_storage_end,
+      new_storage_beg, new_storage_end);
+  in_report.ReportError(error);
+}
+
 void ReportODRViolation(const __asan_global *g1, u32 stack_id1,
                         const __asan_global *g2, u32 stack_id2) {
   ScopedInErrorReport in_report;

compiler-rt/lib/asan/asan_report.h

@@ -88,6 +88,9 @@ void ReportBadParamsToAnnotateDoubleEndedContiguousContainer(
     uptr storage_beg, uptr storage_end, uptr old_container_beg,
     uptr old_container_end, uptr new_container_beg, uptr new_container_end,
     BufferedStackTrace *stack);
+void ReportBadParamsToCopyContiguousContainerAnnotations(
+    uptr old_storage_beg, uptr old_storage_end, uptr new_storage_beg,
+    uptr new_storage_end, BufferedStackTrace *stack);
 
 void ReportODRViolation(const __asan_global *g1, u32 stack_id1,
                         const __asan_global *g2, u32 stack_id2);

compiler-rt/lib/sanitizer_common/sanitizer_common_interface.inc

@@ -10,6 +10,7 @@
 INTERFACE_FUNCTION(__sanitizer_acquire_crash_state)
 INTERFACE_FUNCTION(__sanitizer_annotate_contiguous_container)
 INTERFACE_FUNCTION(__sanitizer_annotate_double_ended_contiguous_container)
+INTERFACE_FUNCTION(__sanitizer_copy_contiguous_container_annotations)
 INTERFACE_FUNCTION(__sanitizer_contiguous_container_find_bad_address)
 INTERFACE_FUNCTION(
     __sanitizer_double_ended_contiguous_container_find_bad_address)

compiler-rt/lib/sanitizer_common/sanitizer_interface_internal.h

@@ -76,6 +76,11 @@ void __sanitizer_annotate_double_ended_contiguous_container(
     const void *old_container_beg, const void *old_container_end,
     const void *new_container_beg, const void *new_container_end);
 SANITIZER_INTERFACE_ATTRIBUTE
+void __sanitizer_copy_contiguous_container_annotations(const void *src_begin,
+                                                       const void *src_end,
+                                                       const void *dst_begin,
+                                                       const void *dst_end);
+SANITIZER_INTERFACE_ATTRIBUTE
 int __sanitizer_verify_contiguous_container(const void *beg, const void *mid,
                                             const void *end);
 SANITIZER_INTERFACE_ATTRIBUTE