forked from OSchip/llvm-project
68 lines
3.4 KiB
C++
68 lines
3.4 KiB
C++
//===-- sanitizer_coverage_win_sections.cc --------------------------------===//
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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 defines delimiters for Sanitizer Coverage's section. It contains
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// Windows specific tricks to coax the linker into giving us the start and stop
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// addresses of a section, as ELF linkers can do, to get the size of certain
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// arrays. According to https://msdn.microsoft.com/en-us/library/7977wcck.aspx
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// sections with the same name before "$" are sorted alphabetically by the
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// string that comes after "$" and merged into one section. We take advantage
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// of this by putting data we want the size of into the middle (M) of a section,
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// by using the letter "M" after "$". We get the start of this data (ie:
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// __start_section_name) by making the start variable come at the start of the
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// section (using the letter A after "$"). We do the same to get the end of the
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// data by using the letter "Z" after "$" to make the end variable come after
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// the data. Note that because of our technique the address of the start
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// variable is actually the address of data that comes before our middle
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// section. We also need to prevent the linker from adding any padding. Each
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// technique we use for this is explained in the comments below.
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//===----------------------------------------------------------------------===//
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#include "sanitizer_platform.h"
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#if SANITIZER_WINDOWS
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#include <stdint.h>
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extern "C" {
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// Use uint64_t so the linker won't need to add any padding if it tries to word
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// align the start of the 8-bit counters array. The array will always start 8
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// bytes after __start_sancov_cntrs.
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#pragma section(".SCOV$CA", read, write) // NOLINT
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__declspec(allocate(".SCOV$CA")) uint64_t __start___sancov_cntrs = 0;
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// Even though we said not to align __stop__sancov_cntrs (using the "align"
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// declspec), MSVC's linker may try to align the section, .SCOV$CZ, containing
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// it. This can cause a mismatch between the number of PCs and counters since
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// each PCTable element is 8 bytes (unlike counters which are 1 byte) so no
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// padding would be added to align .SCOVP$Z, However, if .SCOV$CZ section is 1
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// byte, the linker won't try to align it on an 8-byte boundary, so use a
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// uint8_t for __stop_sancov_cntrs.
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#pragma section(".SCOV$CZ", read, write) // NOLINT
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__declspec(allocate(".SCOV$CZ")) __declspec(align(1)) uint8_t
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__stop___sancov_cntrs = 0;
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#pragma section(".SCOV$GA", read, write) // NOLINT
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__declspec(allocate(".SCOV$GA")) uint64_t __start___sancov_guards = 0;
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#pragma section(".SCOV$GZ", read, write) // NOLINT
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__declspec(allocate(".SCOV$GZ")) __declspec(align(1)) uint8_t
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__stop___sancov_guards = 0;
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// The guard array and counter array should both be merged into the .data
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// section to reduce the number of PE sections. However, because PCTable is
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// constant it should be merged with the .rdata section.
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#pragma comment(linker, "/MERGE:.SCOV=.data")
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#pragma section(".SCOVP$A", read) // NOLINT
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__declspec(allocate(".SCOVP$A")) uint64_t __start___sancov_pcs = 0;
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#pragma section(".SCOVP$Z", read) // NOLINT
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__declspec(allocate(".SCOVP$Z")) __declspec(align(1)) uint8_t
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__stop___sancov_pcs = 0;
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#pragma comment(linker, "/MERGE:.SCOVP=.rdata")
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}
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#endif // SANITIZER_WINDOWS
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