be8a2f7565
Summary: This patch introduces stack frame compression to GWP-ASan. Each stack frame is variable-length integer encoded as the difference between frame[i] and frame[i - 1]. Furthermore, we use zig-zag encoding on the difference to ensure that negative differences are also encoded into a relatively small number of bytes. Examples of what the compression looks like can be seen in `gwp_asan/tests/compression.cpp`. This compression can reduce the memory consumption cost of stack traces by ~50%. Reviewers: vlad.tsyrklevich Reviewed By: vlad.tsyrklevich Subscribers: mgorny, #sanitizers, llvm-commits, eugenis, morehouse Tags: #sanitizers, #llvm Differential Revision: https://reviews.llvm.org/D66189 llvm-svn: 369048
39 lines
1.5 KiB
C++
39 lines
1.5 KiB
C++
//===-- stack_trace_compressor.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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#ifndef GWP_ASAN_STACK_TRACE_COMPRESSOR_
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#define GWP_ASAN_STACK_TRACE_COMPRESSOR_
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#include <stddef.h>
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#include <stdint.h>
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// These functions implement stack frame compression and decompression. We store
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// the zig-zag encoded pointer difference between frame[i] and frame[i - 1] as
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// a variable-length integer. This can reduce the memory overhead of stack
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// traces by 50%.
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namespace gwp_asan {
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namespace compression {
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// For the stack trace in `Unpacked` with length `UnpackedSize`, pack it into
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// the buffer `Packed` maximum length `PackedMaxSize`. The return value is the
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// number of bytes that were written to the output buffer.
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size_t pack(const uintptr_t *Unpacked, size_t UnpackedSize, uint8_t *Packed,
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size_t PackedMaxSize);
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// From the packed stack trace in `Packed` of length `PackedSize`, write the
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// unpacked stack trace of maximum length `UnpackedMaxSize` into `Unpacked`.
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// Returns the number of full entries unpacked, or zero on error.
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size_t unpack(const uint8_t *Packed, size_t PackedSize, uintptr_t *Unpacked,
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size_t UnpackedMaxSize);
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} // namespace compression
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} // namespace gwp_asan
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#endif // GWP_ASAN_STACK_TRACE_COMPRESSOR_
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