forked from OSchip/llvm-project
128 lines
3.9 KiB
C++
128 lines
3.9 KiB
C++
//===-- dfsan_origin.h ----------------------------------*- C++ -*-===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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//
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// This file is a part of DataFlowSanitizer.
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//
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// Origin id utils.
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//===----------------------------------------------------------------------===//
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#ifndef DFSAN_ORIGIN_H
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#define DFSAN_ORIGIN_H
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#include "dfsan_chained_origin_depot.h"
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#include "dfsan_flags.h"
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#include "sanitizer_common/sanitizer_stackdepot.h"
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namespace __dfsan {
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// Origin handling.
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//
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// Origin is a 32-bit identifier that is attached to any taint value in the
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// program and describes how this memory came to be tainted.
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//
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// Chained origin id is like:
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// zzzz xxxx xxxx xxxx
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//
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// Chained origin id describes an event of storing a taint value to
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// memory. The xxx part is a value of ChainedOriginDepot, which is a mapping of
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// (stack_id, prev_id) -> id, where
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// * stack_id describes the event.
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// StackDepot keeps a mapping between those and corresponding stack traces.
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// * prev_id is another origin id that describes the earlier part of the
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// taint value history. 0 prev_id indicates the start of a chain.
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// Following a chain of prev_id provides the full recorded history of a taint
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// value.
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//
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// This, effectively, defines a forest where nodes are points in value history
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// marked with origin ids, and edges are events that are marked with stack_id.
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//
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// The "zzzz" bits of chained origin id are used to store the length of the
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// origin chain.
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class Origin {
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public:
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static bool isValidId(u32 id) { return id != 0; }
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u32 raw_id() const { return raw_id_; }
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bool isChainedOrigin() const { return Origin::isValidId(raw_id_); }
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u32 getChainedId() const {
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CHECK(Origin::isValidId(raw_id_));
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return raw_id_ & kChainedIdMask;
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}
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// Returns the next origin in the chain and the current stack trace.
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//
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// It scans a partition of StackDepot linearly, and is used only by origin
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// tracking report.
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Origin getNextChainedOrigin(StackTrace *stack) const {
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CHECK(Origin::isValidId(raw_id_));
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u32 prev_id;
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u32 stack_id = GetChainedOriginDepot()->Get(getChainedId(), &prev_id);
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if (stack)
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*stack = StackDepotGet(stack_id);
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return Origin(prev_id);
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}
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static Origin CreateChainedOrigin(Origin prev, StackTrace *stack) {
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int depth = prev.isChainedOrigin() ? prev.depth() : -1;
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// depth is the length of the chain minus 1.
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// origin_history_size of 0 means unlimited depth.
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if (flags().origin_history_size > 0) {
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++depth;
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if (depth >= flags().origin_history_size || depth > kMaxDepth)
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return prev;
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}
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StackDepotHandle h = StackDepotPut_WithHandle(*stack);
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if (!h.valid())
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return prev;
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if (flags().origin_history_per_stack_limit > 0) {
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int use_count = h.use_count();
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if (use_count > flags().origin_history_per_stack_limit)
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return prev;
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}
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u32 chained_id;
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bool inserted =
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GetChainedOriginDepot()->Put(h.id(), prev.raw_id(), &chained_id);
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CHECK((chained_id & kChainedIdMask) == chained_id);
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if (inserted && flags().origin_history_per_stack_limit > 0)
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h.inc_use_count_unsafe();
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return Origin((depth << kDepthShift) | chained_id);
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}
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static Origin FromRawId(u32 id) { return Origin(id); }
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private:
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static const int kDepthBits = 4;
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static const int kDepthShift = 32 - kDepthBits;
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static const u32 kChainedIdMask = ((u32)-1) >> kDepthBits;
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u32 raw_id_;
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explicit Origin(u32 raw_id) : raw_id_(raw_id) {}
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int depth() const {
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CHECK(isChainedOrigin());
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return (raw_id_ >> kDepthShift) & ((1 << kDepthBits) - 1);
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}
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public:
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static const int kMaxDepth = (1 << kDepthBits) - 1;
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};
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} // namespace __dfsan
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#endif // DFSAN_ORIGIN_H
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