[sanitizer] Implement a __asan_default_options() equivalent for Scudo

Summary:
Currently, the Scudo Hardened Allocator only gets its flags via the SCUDO_OPTIONS environment variable.
With this patch, we offer the opportunity for programs to define their own options via __scudo_default_options() which behaves like __asan_default_options() (weak symbol).
A relevant test has been added as well, and the documentation updated accordingly.
I also used this patch as an opportunity to rename a few variables to comply with the LLVM naming scheme, and replaced a use of Report with dieWithMessage for consistency (and to avoid a callback).

Reviewers: llvm-commits, kcc

Differential Revision: https://reviews.llvm.org/D23018

llvm-svn: 277536

1 files changed, 18 insertions, 6 deletions

diff --git a/compiler-rt/lib/scudo/scudo_flags.cpp b/compiler-rt/lib/scudo/scudo_flags.cpp
index 430dcd2995d..f0d208863bc 100644
--- a/compiler-rt/lib/scudo/scudo_flags.cpp
+++ b/compiler-rt/lib/scudo/scudo_flags.cpp
@@ -17,9 +17,12 @@
 #include "sanitizer_common/sanitizer_flags.h"
 #include "sanitizer_common/sanitizer_flag_parser.h"
 
+extern "C" SANITIZER_INTERFACE_ATTRIBUTE SANITIZER_WEAK_ATTRIBUTE
+const char* __scudo_default_options();
+
 namespace __scudo {
 
-Flags scudo_flags_dont_use_directly;  // use via flags().
+Flags ScudoFlags;  // Use via getFlags().
 
 void Flags::setDefaults() {
 #define SCUDO_FLAG(Type, Name, DefaultValue, Description) Name = DefaultValue;
@@ -34,6 +37,10 @@ static void RegisterScudoFlags(FlagParser *parser, Flags *f) {
 #undef SCUDO_FLAG
 }
 
+static const char *callGetScudoDefaultOptions() {
+  return (&__scudo_default_options) ? __scudo_default_options() : "";
+}
+
 void initFlags() {
   SetCommonFlagsDefaults();
   {
@@ -45,11 +52,16 @@ void initFlags() {
   Flags *f = getFlags();
   f->setDefaults();
 
-  FlagParser scudo_parser;
-  RegisterScudoFlags(&scudo_parser, f);
-  RegisterCommonFlags(&scudo_parser);
+  FlagParser ScudoParser;
+  RegisterScudoFlags(&ScudoParser, f);
+  RegisterCommonFlags(&ScudoParser);
+
+  // Override from user-specified string.
+  const char *ScudoDefaultOptions = callGetScudoDefaultOptions();
+  ScudoParser.ParseString(ScudoDefaultOptions);
 
-  scudo_parser.ParseString(GetEnv("SCUDO_OPTIONS"));
+  // Override from environment.
+  ScudoParser.ParseString(GetEnv("SCUDO_OPTIONS"));
 
   InitializeCommonFlags();
 
@@ -75,7 +87,7 @@ void initFlags() {
 }
 
 Flags *getFlags() {
-  return &scudo_flags_dont_use_directly;
+  return &ScudoFlags;
 }
 
 }