hwasan_thread_list.h | Explore in Territory

//===-- hwasan_thread_list.h ------------------------------------*- 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
//
//===----------------------------------------------------------------------===//
//
// This file is a part of HWAddressSanitizer.
//
//===----------------------------------------------------------------------===//

// HwasanThreadList is a registry for live threads, as well as an allocator for
// HwasanThread objects and their stack history ring buffers. There are
// constraints on memory layout of the shadow region and CompactRingBuffer that
// are part of the ABI contract between compiler-rt and llvm.
//
// * Start of the shadow memory region is aligned to 2**kShadowBaseAlignment.
// * All stack ring buffers are located within (2**kShadowBaseAlignment)
// sized region below and adjacent to the shadow region.
// * Each ring buffer has a size of (2**N)*4096 where N is in [0, 7), and is
// aligned to twice its size. The value of N can be different for each buffer.
//
// These constrains guarantee that, given an address A of any element of the
// ring buffer,
//     A_next = (A + sizeof(uptr)) & ~((1 << (N + 13)) - 1)
//   is the address of the next element of that ring buffer (with wrap-around).
// And, with K = kShadowBaseAlignment,
//     S = (A | ((1 << K) - 1)) + 1
//   (align up to kShadowBaseAlignment) is the start of the shadow region.
//
// These calculations are used in compiler instrumentation to update the ring
// buffer and obtain the base address of shadow using only two inputs: address
// of the current element of the ring buffer, and N (i.e. size of the ring
// buffer). Since the value of N is very limited, we pack both inputs into a
// single thread-local word as
//   (1 << (N + 56)) | A
// See the implementation of class CompactRingBuffer, which is what is stored in
// said thread-local word.
//
// Note the unusual way of aligning up the address of the shadow:
//   (A | ((1 << K) - 1)) + 1
// It is only correct if A is not already equal to the shadow base address, but
// it saves 2 instructions on AArch64.

#include "hwasan.h"
#include "hwasan_allocator.h"
#include "hwasan_flags.h"
#include "hwasan_thread.h"
#include "sanitizer_common/sanitizer_thread_arg_retval.h"

namespace __hwasan {

static uptr RingBufferSize() { … }

struct ThreadStats { … };

class SANITIZER_MUTEX HwasanThreadList { … };

void InitThreadList(uptr storage, uptr size);
HwasanThreadList &hwasanThreadList();
ThreadArgRetval &hwasanThreadArgRetval();

} // namespace __hwasan
llvm/compiler-rt/lib/hwasan/hwasan_thread_list.h
