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76 lines
2.5 KiB
C
76 lines
2.5 KiB
C
/*
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american fuzzy lop++ - high-performance binary-only instrumentation
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-------------------------------------------------------------------
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Originally written by Andrew Griffiths <agriffiths@google.com> and
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Michal Zalewski
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TCG instrumentation and block chaining support by Andrea Biondo
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<andrea.biondo965@gmail.com>
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QEMU 3.1.1 port, TCG thread-safety, CompareCoverage and NeverZero
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counters by Andrea Fioraldi <andreafioraldi@gmail.com>
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Copyright 2015, 2016, 2017 Google Inc. All rights reserved.
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Copyright 2019-2020 AFLplusplus Project. All rights reserved.
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at:
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http://www.apache.org/licenses/LICENSE-2.0
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This code is a shim patched into the separately-distributed source
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code of QEMU 3.1.0. It leverages the built-in QEMU tracing functionality
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to implement AFL-style instrumentation and to take care of the remaining
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parts of the AFL fork server logic.
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The resulting QEMU binary is essentially a standalone instrumentation
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tool; for an example of how to leverage it for other purposes, you can
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have a look at afl-showmap.c.
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*/
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#include "afl-qemu-common.h"
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#include "tcg-op.h"
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void HELPER(afl_maybe_log)(target_ulong cur_loc) {
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register uintptr_t afl_idx = cur_loc ^ afl_prev_loc;
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INC_AFL_AREA(afl_idx);
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afl_prev_loc = cur_loc >> 1;
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}
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/* Generates TCG code for AFL's tracing instrumentation. */
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static void afl_gen_trace(target_ulong cur_loc) {
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/* Optimize for cur_loc > afl_end_code, which is the most likely case on
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Linux systems. */
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if (cur_loc > afl_end_code ||
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cur_loc < afl_start_code /*|| !afl_area_ptr*/) // not needed because of
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// static dummy buffer
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return;
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/* Looks like QEMU always maps to fixed locations, so ASLR is not a
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concern. Phew. But instruction addresses may be aligned. Let's mangle
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the value to get something quasi-uniform. */
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cur_loc = (cur_loc >> 4) ^ (cur_loc << 8);
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cur_loc &= MAP_SIZE - 1;
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/* Implement probabilistic instrumentation by looking at scrambled block
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address. This keeps the instrumented locations stable across runs. */
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if (cur_loc >= afl_inst_rms) return;
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TCGv cur_loc_v = tcg_const_tl(cur_loc);
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gen_helper_afl_maybe_log(cur_loc_v);
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tcg_temp_free(cur_loc_v);
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}
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