[sanitizer_common] Fuchsia support for interceptors

Summary:
Actually Fuchsia non-support for interceptors.  Fuchsia doesn't use
interceptors in the common sense at all.  Almost all system library
functions don't need interception at all, because the system
libraries are just themselves compiled with sanitizers enabled and
have specific hook interfaces where needed to inform the sanitizer
runtime about thread lifetimes and the like.  For the few functions
that do get intercepted, they don't use a generic mechanism like
dlsym with RTLD_NEXT to find the underlying system library function.
Instead, they use specific extra symbol names published by the
system library (e.g. __unsanitized_memcpy).

Submitted on behalf of Roland McGrath.

Reviewers: vitalybuka, alekseyshl, kcc, filcab

Reviewed By: filcab

Subscribers: kubamracek, phosek, filcab, llvm-commits

Tags: #sanitizers

Differential Revision: https://reviews.llvm.org/D36028

git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@309745 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 30 insertions, 7 deletions

diff --git a/lib/interception/interception.h b/lib/interception/interception.h
index d79fa67ba..2d280731e 100644
--- a/lib/interception/interception.h
+++ b/lib/interception/interception.h
@@ -15,8 +15,8 @@
 #ifndef INTERCEPTION_H
 #define INTERCEPTION_H
 
-#if !defined(__linux__) && !defined(__FreeBSD__) && \
-  !defined(__APPLE__) && !defined(_WIN32)
+#if !defined(__linux__) && !defined(__FreeBSD__) && !defined(__APPLE__) && \
+    !defined(_WIN32) && !defined(__Fuchsia__)
 # error "Interception doesn't work on this operating system."
 #endif
 
@@ -139,7 +139,7 @@ const interpose_substitution substitution_##func_name[] \
 # define DECLARE_WRAPPER(ret_type, func, ...) \
      extern "C" ret_type func(__VA_ARGS__) \
      __attribute__((alias("__interceptor_" #func), visibility("default")));
-#else
+#elif !defined(__Fuchsia__)
 # define WRAP(x) __interceptor_ ## x
 # define WRAPPER_NAME(x) "__interceptor_" #x
 # define INTERCEPTOR_ATTRIBUTE __attribute__((visibility("default")))
@@ -148,7 +148,15 @@ const interpose_substitution substitution_##func_name[] \
     __attribute__((weak, alias("__interceptor_" #func), visibility("default")));
 #endif
 
-#if !defined(__APPLE__)
+#if defined(__Fuchsia__)
+// There is no general interception at all on Fuchsia.
+// Sanitizer runtimes just define functions directly to preempt them,
+// and have bespoke ways to access the underlying libc functions.
+# include <magenta/sanitizer.h>
+# define INTERCEPTOR_ATTRIBUTE __attribute__((visibility("default")))
+# define REAL(x) __unsanitized_##x
+# define DECLARE_REAL(ret_type, func, ...)
+#elif !defined(__APPLE__)
 # define PTR_TO_REAL(x) real_##x
 # define REAL(x) __interception::PTR_TO_REAL(x)
 # define FUNC_TYPE(x) x##_f
@@ -166,15 +174,19 @@ const interpose_substitution substitution_##func_name[] \
 # define ASSIGN_REAL(x, y)
 #endif  // __APPLE__
 
+#if !defined(__Fuchsia__)
 #define DECLARE_REAL_AND_INTERCEPTOR(ret_type, func, ...) \
   DECLARE_REAL(ret_type, func, __VA_ARGS__) \
   extern "C" ret_type WRAP(func)(__VA_ARGS__);
+#else
+#define DECLARE_REAL_AND_INTERCEPTOR(ret_type, func, ...)
+#endif
 
 // Generally, you don't need to use DEFINE_REAL by itself, as INTERCEPTOR
 // macros does its job. In exceptional cases you may need to call REAL(foo)
 // without defining INTERCEPTOR(..., foo, ...). For example, if you override
 // foo with an interceptor for other function.
-#if !defined(__APPLE__)
+#if !defined(__APPLE__) && !defined(__Fuchsia__)
 # define DEFINE_REAL(ret_type, func, ...) \
     typedef ret_type (*FUNC_TYPE(func))(__VA_ARGS__); \
     namespace __interception { \
@@ -184,7 +196,18 @@ const interpose_substitution substitution_##func_name[] \
 # define DEFINE_REAL(ret_type, func, ...)
 #endif
 
-#if !defined(__APPLE__)
+#if defined(__Fuchsia__)
+
+// We need to define the __interceptor_func name just to get
+// sanitizer_common/scripts/gen_dynamic_list.py to export func.
+// But we don't need to export __interceptor_func to get that.
+#define INTERCEPTOR(ret_type, func, ...)                                \
+  extern "C"[[ gnu::alias(#func), gnu::visibility("hidden") ]] ret_type \
+      __interceptor_##func(__VA_ARGS__);                                \
+  extern "C" INTERCEPTOR_ATTRIBUTE ret_type func(__VA_ARGS__)
+
+#elif !defined(__APPLE__)
+
 #define INTERCEPTOR(ret_type, func, ...) \
   DEFINE_REAL(ret_type, func, __VA_ARGS__) \
   DECLARE_WRAPPER(ret_type, func, __VA_ARGS__) \
@@ -251,7 +274,7 @@ typedef unsigned long uptr;  // NOLINT
 # define INTERCEPT_FUNCTION(func) INTERCEPT_FUNCTION_MAC(func)
 # define INTERCEPT_FUNCTION_VER(func, symver) \
     INTERCEPT_FUNCTION_VER_MAC(func, symver)
-#else  // defined(_WIN32)
+#elif defined(_WIN32)
 # include "interception_win.h"
 # define INTERCEPT_FUNCTION(func) INTERCEPT_FUNCTION_WIN(func)
 # define INTERCEPT_FUNCTION_VER(func, symver) \