377b82a088
The differential fuzzer for atof found a bug in glibc's handling of hexadecimal rounding. Since we can't easily update glibc and we want to avoid false positives when running the fuzzer, I've added an exception to skip all hexadecimal subnormal cases. Reviewed By: sivachandra Differential Revision: https://reviews.llvm.org/D149359
70 lines
2.0 KiB
C++
70 lines
2.0 KiB
C++
//===-- atof_fuzz.cpp -----------------------------------------------------===//
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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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/// Fuzzing test for llvm-libc atof implementation.
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///
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//===----------------------------------------------------------------------===//
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#include "src/stdlib/atof.h"
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#include <stddef.h>
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#include <stdint.h>
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#include <stdlib.h>
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#include "fuzzing/stdlib/StringParserOutputDiff.h"
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// TODO: Remove this once glibc fixes hex subnormal rounding. See
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// https://sourceware.org/bugzilla/show_bug.cgi?id=30220
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#ifdef LLVM_LIBC_ATOF_DIF_FUZZ_SKIP_GLIBC_HEX_SUBNORMAL_ERR
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#include <ctype.h>
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constexpr double MIN_NORMAL = 0x1p-1022;
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bool has_hex_prefix(const uint8_t *str) {
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size_t index = 0;
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// Skip over leading whitespace
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while (isspace(str[index])) {
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++index;
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}
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// Skip over sign
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if (str[index] == '-' || str[index] == '+') {
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++index;
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}
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return str[index] == '0' && (tolower(str[index + 1])) == 'x';
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}
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bool should_be_skipped(const uint8_t *str) {
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double init_result = ::atof(reinterpret_cast<const char *>(str));
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if (init_result < 0) {
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init_result = -init_result;
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}
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if (init_result < MIN_NORMAL && init_result != 0) {
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return has_hex_prefix(str);
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}
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return false;
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}
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#else
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bool should_be_skipped(const uint8_t *) { return false; }
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#endif // LLVM_LIBC_ATOF_DIF_FUZZ_SKIP_GLIBC_HEX_SUBNORMAL_ERR
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extern "C" int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size) {
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uint8_t *container = new uint8_t[size + 1];
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if (!container)
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__builtin_trap();
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size_t i;
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for (i = 0; i < size; ++i)
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container[i] = data[i];
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container[size] = '\0'; // Add null terminator to container.
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if (!should_be_skipped(container)) {
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StringParserOutputDiff<double>(&__llvm_libc::atof, &::atof, container,
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size);
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}
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delete[] container;
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return 0;
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}
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