llvm/compiler-rt/lib/msan/msan_origin.h

//===-- msan_origin.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
//
//===----------------------------------------------------------------------===//
//
// Origin id utils.
//===----------------------------------------------------------------------===//
#ifndef MSAN_ORIGIN_H
#define MSAN_ORIGIN_H

#include "sanitizer_common/sanitizer_stackdepot.h"
#include "msan_chained_origin_depot.h"

namespace __msan {

// Origin handling.
//
// Origin is a 32-bit identifier that is attached to any uninitialized value in
// the program and describes, more or less exactly, how this memory came to be
// uninitialized.
//
// There are 3 kinds of origin ids:
// 1xxx xxxx xxxx xxxx   heap origin id
// 0000 xxxx xxxx xxxx   stack origin id
// 0zzz xxxx xxxx xxxx   chained origin id
//
// Heap origin id describes a heap memory allocation and contains (in the xxx
// part) a value of StackDepot.
//
// Stack origin id describes a stack memory allocation and contains (in the xxx
// part) an index into StackOriginDescr and StackOriginPC. We don't store a
// stack trace for such origins for performance reasons.
//
// Chained origin id describes an event of storing an uninitialized value to
// memory. The xxx part is a value of ChainedOriginDepot, which is a mapping of
// (stack_id, prev_id) -> id, where
//  * stack_id describes the event.
//    StackDepot keeps a mapping between those and corresponding stack traces.
//  * prev_id is another origin id that describes the earlier part of the
//    uninitialized value history.
// Following a chain of prev_id provides the full recorded history of an
// uninitialized value.
//
// This, effectively, defines a tree (or 2 trees, see below) where nodes are
// points in value history marked with origin ids, and edges are events that are
// marked with stack_id.
//
// The "zzz" bits of chained origin id are used to store the length (or depth)
// of the origin chain.

class Origin { … };

}  // namespace __msan

#endif  // MSAN_ORIGIN_H