xref: /freebsd-13.1/contrib/llvm-project/lldb/source/Plugins/Process/Utility/MemoryTagManagerAArch64MTE.cpp (revision 5f7ddb14)

//===-- MemoryTagManagerAArch64MTE.cpp --------------------------*- C++ -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//

#include "MemoryTagManagerAArch64MTE.h"

using namespace lldb_private;

static const unsigned MTE_START_BIT = 56;
static const unsigned MTE_TAG_MAX = 0xf;
static const unsigned MTE_GRANULE_SIZE = 16;

lldb::addr_t
MemoryTagManagerAArch64MTE::GetLogicalTag(lldb::addr_t addr) const {
  return (addr >> MTE_START_BIT) & MTE_TAG_MAX;
}

lldb::addr_t
MemoryTagManagerAArch64MTE::RemoveNonAddressBits(lldb::addr_t addr) const {
  // Here we're ignoring the whole top byte. If you've got MTE
  // you must also have TBI (top byte ignore).
  // The other 4 bits could contain other extension bits or
  // user metadata.
  return addr & ~((lldb::addr_t)0xFF << MTE_START_BIT);
}

ptrdiff_t MemoryTagManagerAArch64MTE::AddressDiff(lldb::addr_t addr1,
                                                  lldb::addr_t addr2) const {
  return RemoveNonAddressBits(addr1) - RemoveNonAddressBits(addr2);
}

lldb::addr_t MemoryTagManagerAArch64MTE::GetGranuleSize() const {
  return MTE_GRANULE_SIZE;
}

int32_t MemoryTagManagerAArch64MTE::GetAllocationTagType() const {
  return eMTE_allocation;
}

size_t MemoryTagManagerAArch64MTE::GetTagSizeInBytes() const { return 1; }

MemoryTagManagerAArch64MTE::TagRange
MemoryTagManagerAArch64MTE::ExpandToGranule(TagRange range) const {
  // Ignore reading a length of 0
  if (!range.IsValid())
    return range;

  const size_t granule = GetGranuleSize();

  // Align start down to granule start
  lldb::addr_t new_start = range.GetRangeBase();
  lldb::addr_t align_down_amount = new_start % granule;
  new_start -= align_down_amount;

  // Account for the distance we moved the start above
  size_t new_len = range.GetByteSize() + align_down_amount;
  // Then align up to the end of the granule
  size_t align_up_amount = granule - (new_len % granule);
  if (align_up_amount != granule)
    new_len += align_up_amount;

  return TagRange(new_start, new_len);
}

llvm::Expected<MemoryTagManager::TagRange>
MemoryTagManagerAArch64MTE::MakeTaggedRange(
    lldb::addr_t addr, lldb::addr_t end_addr,
    const lldb_private::MemoryRegionInfos &memory_regions) const {
  // First check that the range is not inverted.
  // We must remove tags here otherwise an address with a higher
  // tag value will always be > the other.
  ptrdiff_t len = AddressDiff(end_addr, addr);
  if (len <= 0) {
    return llvm::createStringError(
        llvm::inconvertibleErrorCode(),
        "End address (0x%" PRIx64
        ") must be greater than the start address (0x%" PRIx64 ")",
        end_addr, addr);
  }

  // Region addresses will not have memory tags. So when searching
  // we must use an untagged address.
  MemoryRegionInfo::RangeType tag_range(RemoveNonAddressBits(addr), len);
  tag_range = ExpandToGranule(tag_range);

  // Make a copy so we can use the original for errors and the final return.
  MemoryRegionInfo::RangeType remaining_range(tag_range);

  // While there are parts of the range that don't have a matching tagged memory
  // region
  while (remaining_range.IsValid()) {
    // Search for a region that contains the start of the range
    MemoryRegionInfos::const_iterator region = std::find_if(
        memory_regions.cbegin(), memory_regions.cend(),
        [&remaining_range](const MemoryRegionInfo &region) {
          return region.GetRange().Contains(remaining_range.GetRangeBase());
        });

    if (region == memory_regions.cend() ||
        region->GetMemoryTagged() != MemoryRegionInfo::eYes) {
      // Some part of this range is untagged (or unmapped) so error
      return llvm::createStringError(llvm::inconvertibleErrorCode(),
                                     "Address range 0x%" PRIx64 ":0x%" PRIx64
                                     " is not in a memory tagged region",
                                     tag_range.GetRangeBase(),
                                     tag_range.GetRangeEnd());
    }

    // We've found some part of the range so remove that part and continue
    // searching for the rest. Moving the base "slides" the range so we need to
    // save/restore the original end. If old_end is less than the new base, the
    // range will be set to have 0 size and we'll exit the while.
    lldb::addr_t old_end = remaining_range.GetRangeEnd();
    remaining_range.SetRangeBase(region->GetRange().GetRangeEnd());
    remaining_range.SetRangeEnd(old_end);
  }

  // Every part of the range is contained within a tagged memory region.
  return tag_range;
}

llvm::Expected<std::vector<lldb::addr_t>>
MemoryTagManagerAArch64MTE::UnpackTagsData(const std::vector<uint8_t> &tags,
                                           size_t granules /*=0*/) const {
  // 0 means don't check the number of tags before unpacking
  if (granules) {
    size_t num_tags = tags.size() / GetTagSizeInBytes();
    if (num_tags != granules) {
      return llvm::createStringError(
          llvm::inconvertibleErrorCode(),
          "Packed tag data size does not match expected number of tags. "
          "Expected %zu tag(s) for %zu granule(s), got %zu tag(s).",
          granules, granules, num_tags);
    }
  }

  // (if bytes per tag was not 1, we would reconstruct them here)

  std::vector<lldb::addr_t> unpacked;
  unpacked.reserve(tags.size());
  for (auto it = tags.begin(); it != tags.end(); ++it) {
    // Check all tags are in range
    if (*it > MTE_TAG_MAX) {
      return llvm::createStringError(
          llvm::inconvertibleErrorCode(),
          "Found tag 0x%x which is > max MTE tag value of 0x%x.", *it,
          MTE_TAG_MAX);
    }
    unpacked.push_back(*it);
  }

  return unpacked;
}

llvm::Expected<std::vector<uint8_t>> MemoryTagManagerAArch64MTE::PackTags(
    const std::vector<lldb::addr_t> &tags) const {
  std::vector<uint8_t> packed;
  packed.reserve(tags.size() * GetTagSizeInBytes());

  for (auto tag : tags) {
    if (tag > MTE_TAG_MAX) {
      return llvm::createStringError(llvm::inconvertibleErrorCode(),
                                     "Found tag 0x%" PRIx64
                                     " which is > max MTE tag value of 0x%x.",
                                     tag, MTE_TAG_MAX);
    }
    packed.push_back(static_cast<uint8_t>(tag));
  }

  return packed;
}

llvm::Expected<std::vector<lldb::addr_t>>
MemoryTagManagerAArch64MTE::RepeatTagsForRange(
    const std::vector<lldb::addr_t> &tags, TagRange range) const {
  std::vector<lldb::addr_t> new_tags;

  // If the range is not empty
  if (range.IsValid()) {
    if (tags.empty()) {
      return llvm::createStringError(
          llvm::inconvertibleErrorCode(),
          "Expected some tags to cover given range, got zero.");
    }

    // We assume that this range has already been expanded/aligned to granules
    size_t granules = range.GetByteSize() / GetGranuleSize();
    new_tags.reserve(granules);
    for (size_t to_copy = 0; granules > 0; granules -= to_copy) {
      to_copy = granules > tags.size() ? tags.size() : granules;
      new_tags.insert(new_tags.end(), tags.begin(), tags.begin() + to_copy);
    }
  }

  return new_tags;
}