Add a framework for intercepting system calls
llvm-svn: 6190
diff --git a/llvm/lib/ExecutionEngine/JIT/Intercept.cpp b/llvm/lib/ExecutionEngine/JIT/Intercept.cpp
new file mode 100644
index 0000000..4314fb6
--- /dev/null
+++ b/llvm/lib/ExecutionEngine/JIT/Intercept.cpp
@@ -0,0 +1,52 @@
+//===-- Intercept.cpp - System function interception routines -------------===//
+//
+// If a function call occurs to an external function, the JIT is designed to use
+// dlsym on the current process to find a function to call. This is useful for
+// calling system calls and library functions that are not available in LLVM.
+// Some system calls, however, need to be handled specially. For this reason,
+// we intercept some of them here and use our own stubs to handle them.
+//
+//===----------------------------------------------------------------------===//
+
+#include "VM.h"
+#include <dlfcn.h> // dlsym access
+
+//===----------------------------------------------------------------------===//
+// Function stubs that are invoked instead of raw system calls
+//===----------------------------------------------------------------------===//
+
+// NoopFn - Used if we have nothing else to call...
+static void NoopFn() {}
+
+// jit_exit - Used to intercept the "exit" system call.
+static void jit_exit(int Status) {
+ exit(Status); // Do nothing for now.
+}
+
+// jit_atexit - Used to intercept the "at_exit" system call.
+static int jit_atexit(void (*Fn)(void)) {
+ atexit(Fn); // Do nothing for now.
+}
+
+//===----------------------------------------------------------------------===//
+//
+/// getPointerToNamedFunction - This method returns the address of the specified
+/// function by using the dlsym function call. As such it is only useful for
+/// resolving library symbols, not code generated symbols.
+///
+void *VM::getPointerToNamedFunction(const std::string &Name) {
+ // Check to see if this is one of the functions we want to intercept...
+ if (Name == "exit") return jit_exit;
+ if (Name == "at_exit") return jit_atexit;
+
+ // If it's an external function, look it up in the process image...
+ void *Ptr = dlsym(0, Name.c_str());
+ if (Ptr == 0) {
+ std::cerr << "WARNING: Cannot resolve fn '" << Name
+ << "' using a dummy noop function instead!\n";
+ Ptr = (void*)NoopFn;
+ }
+
+ return Ptr;
+}
+
diff --git a/llvm/lib/ExecutionEngine/JIT/VM.cpp b/llvm/lib/ExecutionEngine/JIT/VM.cpp
index 6fd366e..c6748fa 100644
--- a/llvm/lib/ExecutionEngine/JIT/VM.cpp
+++ b/llvm/lib/ExecutionEngine/JIT/VM.cpp
@@ -1,4 +1,4 @@
-//===-- jello.cpp - LLVM Just in Time Compiler ----------------------------===//
+//===-- VM.cpp - LLVM Just in Time Compiler -------------------------------===//
//
// This tool implements a just-in-time compiler for LLVM, allowing direct
// execution of LLVM bytecode in an efficient manner.
@@ -9,8 +9,6 @@
#include "llvm/Target/TargetMachine.h"
#include "llvm/CodeGen/MachineCodeEmitter.h"
#include "llvm/Function.h"
-#include <dlfcn.h> // dlsym access
-
VM::~VM() {
delete MCE;
@@ -50,27 +48,10 @@
}
const std::string &VM::getFunctionReferencedName(void *RefAddr) {
+ assert(FunctionRefs[RefAddr] && "Function address unknown!");
return FunctionRefs[RefAddr]->getName();
}
-static void NoopFn() {}
-
-/// getPointerToNamedFunction - This method returns the address of the specified
-/// function by using the dlsym function call. As such it is only useful for
-/// resolving library symbols, not code generated symbols.
-///
-void *VM::getPointerToNamedFunction(const std::string &Name) {
- // If it's an external function, look it up in the process image...
- void *Ptr = dlsym(0, Name.c_str());
- if (Ptr == 0) {
- std::cerr << "WARNING: Cannot resolve fn '" << Name
- << "' using a dummy noop function instead!\n";
- Ptr = (void*)NoopFn;
- }
-
- return Ptr;
-}
-
/// getPointerToFunction - This method is used to get the address of the
/// specified function, compiling it if neccesary.
///