[libFuzzer] Port to Windows
Summary:
Port libFuzzer to windows-msvc.
This patch allows libFuzzer targets to be built and run on Windows, using -fsanitize=fuzzer and/or fsanitize=fuzzer-no-link. It allows these forms of coverage instrumentation to work on Windows as well.
It does not fix all issues, such as those with -fsanitize-coverage=stack-depth, which is not usable on Windows as of this patch.
It also does not fix any libFuzzer integration tests. Nearly all of them fail to compile, fixing them will come in a later patch, so libFuzzer tests are disabled on Windows until them.
Patch By: metzman
Reviewers: morehouse, rnk
Reviewed By: morehouse, rnk
Subscribers: #sanitizers, delcypher, morehouse, kcc, eraman
Differential Revision: https://reviews.llvm.org/D51022
llvm-svn: 341082
GitOrigin-RevId: 7e042bb1d18a06fc4b67143b5615acb15b4b8c57
diff --git a/lib/sanitizer_common/sanitizer_coverage_win_sections.cc b/lib/sanitizer_common/sanitizer_coverage_win_sections.cc
index 4b0bbf1..108f76e 100644
--- a/lib/sanitizer_common/sanitizer_coverage_win_sections.cc
+++ b/lib/sanitizer_common/sanitizer_coverage_win_sections.cc
@@ -7,16 +7,57 @@
//
//===----------------------------------------------------------------------===//
//
-// This file defines delimiters for Sanitizer Coverage's section.
+// This file defines delimiters for Sanitizer Coverage's section. It contains
+// Windows specific tricks to coax the linker into giving us the start and stop
+// addresses of a section, as ELF linkers can do, to get the size of certain
+// arrays. According to https://msdn.microsoft.com/en-us/library/7977wcck.aspx
+// sections with the same name before "$" are sorted alphabetically by the
+// string that comes after "$" and merged into one section. We take advantage
+// of this by putting data we want the size of into the middle (M) of a section,
+// by using the letter "M" after "$". We get the start of this data (ie:
+// __start_section_name) by making the start variable come at the start of the
+// section (using the letter A after "$"). We do the same to get the end of the
+// data by using the letter "Z" after "$" to make the end variable come after
+// the data. Note that because of our technique the address of the start
+// variable is actually the address of data that comes before our middle
+// section. We also need to prevent the linker from adding any padding. Each
+// technique we use for this is explained in the comments below.
//===----------------------------------------------------------------------===//
#include "sanitizer_platform.h"
#if SANITIZER_WINDOWS
#include <stdint.h>
-#pragma section(".SCOV$A", read, write) // NOLINT
-#pragma section(".SCOV$Z", read, write) // NOLINT
extern "C" {
-__declspec(allocate(".SCOV$A")) uint32_t __start___sancov_guards = 0;
-__declspec(allocate(".SCOV$Z")) uint32_t __stop___sancov_guards = 0;
+// The Guard array and counter array should both be merged into the .data
+// section to reduce the number of PE sections However, because PCTable is
+// constant it should be merged with the .rdata section.
+#pragma section(".SCOV$GA", read, write) // NOLINT
+// Use align(1) to avoid adding any padding that will mess up clients trying to
+// determine the start and end of the array.
+__declspec(allocate(".SCOV$GA")) __declspec(align(1)) uint64_t
+ __start___sancov_guards = 0;
+#pragma section(".SCOV$GZ", read, write) // NOLINT
+__declspec(allocate(".SCOV$GZ")) __declspec(align(1)) uint64_t
+ __stop___sancov_guards = 0;
+
+#pragma section(".SCOV$CA", read, write) // NOLINT
+__declspec(allocate(".SCOV$CA")) __declspec(align(1)) uint64_t
+ __start___sancov_cntrs = 0;
+#pragma section(".SCOV$CZ", read, write) // NOLINT
+__declspec(allocate(".SCOV$CZ")) __declspec(align(1)) uint64_t
+ __stop___sancov_cntrs = 0;
+
+#pragma comment(linker, "/MERGE:.SCOV=.data")
+
+// Use uint64_t so there won't be any issues if the linker tries to word align
+// the pc array.
+#pragma section(".SCOVP$A", read) // NOLINT
+__declspec(allocate(".SCOVP$A")) __declspec(align(1)) uint64_t
+ __start___sancov_pcs = 0;
+#pragma section(".SCOVP$Z", read) // NOLINT
+__declspec(allocate(".SCOVP$Z")) __declspec(align(1)) uint64_t
+ __stop___sancov_pcs = 0;
+
+#pragma comment(linker, "/MERGE:.SCOVP=.rdata")
}
-#endif // SANITIZER_WINDOWS
+#endif // SANITIZER_WINDOWS
