[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

git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@277536 91177308-0d34-0410-b5e6-96231b3b80d8

4 files changed, 29 insertions, 16 deletions

diff --git a/lib/scudo/scudo_allocator.cpp b/lib/scudo/scudo_allocator.cpp
index 3ad499aed..ceb7bbdd4 100644
--- a/lib/scudo/scudo_allocator.cpp
+++ b/lib/scudo/scudo_allocator.cpp
@@ -76,7 +76,7 @@ struct UnpackedHeader {
   u64 Offset        : 20; // Offset from the beginning of the backend
                           // allocation to the beginning chunk itself, in
                           // multiples of MinAlignment. See comment about its
-                          // maximum value and test in Initialize.
+                          // maximum value and test in init().
   u64 Unused_1_     : 28;
   u16 Salt          : 16;
 };
diff --git a/lib/scudo/scudo_flags.cpp b/lib/scudo/scudo_flags.cpp
index 430dcd299..f0d208863 100644
--- a/lib/scudo/scudo_flags.cpp
+++ b/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;
 }
 
 }
diff --git a/lib/scudo/scudo_termination.cpp b/lib/scudo/scudo_termination.cpp
index 32421d3d8..a53338315 100644
--- a/lib/scudo/scudo_termination.cpp
+++ b/lib/scudo/scudo_termination.cpp
@@ -13,15 +13,17 @@
 ///
 //===----------------------------------------------------------------------===//
 
+#include "scudo_utils.h"
+
 #include "sanitizer_common/sanitizer_common.h"
 
 namespace __sanitizer {
 
-bool AddDieCallback(DieCallbackType callback) { return true; }
+bool AddDieCallback(DieCallbackType Callback) { return true; }
 
-bool RemoveDieCallback(DieCallbackType callback) { return true; }
+bool RemoveDieCallback(DieCallbackType Callback) { return true; }
 
-void SetUserDieCallback(DieCallbackType callback) {}
+void SetUserDieCallback(DieCallbackType Callback) {}
 
 void NORETURN Die() {
   if (common_flags()->abort_on_error)
@@ -31,11 +33,10 @@ void NORETURN Die() {
 
 void SetCheckFailedCallback(CheckFailedCallbackType callback) {}
 
-void NORETURN CheckFailed(const char *file, int line, const char *cond,
-                          u64 v1, u64 v2) {
-  Report("Sanitizer CHECK failed: %s:%d %s (%lld, %lld)\n", file, line, cond,
-                                                            v1, v2);
-  Die();
+void NORETURN CheckFailed(const char *File, int Line, const char *Condition,
+                          u64 Value1, u64 Value2) {
+  __scudo::dieWithMessage("Scudo CHECK failed: %s:%d %s (%lld, %lld)\n",
+                          File, Line, Condition, Value1, Value2);
 }
 
 } // namespace __sanitizer
diff --git a/lib/scudo/scudo_utils.cpp b/lib/scudo/scudo_utils.cpp
index 6b96e84ee..f45569e03 100644
--- a/lib/scudo/scudo_utils.cpp
+++ b/lib/scudo/scudo_utils.cpp
@@ -33,7 +33,7 @@ extern int VSNPrintf(char *buff, int buff_length, const char *format,
 namespace __scudo {
 
 FORMAT(1, 2)
-void dieWithMessage(const char *Format, ...) {
+void NORETURN dieWithMessage(const char *Format, ...) {
   // Our messages are tiny, 128 characters is more than enough.
   char Message[128];
   va_list Args;