Add support for x86_64 emulation options

A test case is added that compiles and links a
minimal program with a custom _start() function that performs a syscall
to exit with code 5. The test requires --image-base for correct execution.

Fixes #105
Signed-off-by: Bhoumik Patidar <[email protected]>

Author: bhoumik03

include/eld/Driver/x86_64LinkDriver.h

@@ -40,6 +40,8 @@ class x86_64LinkDriver : public GnuLdDriver {
 
   virtual ~x86_64LinkDriver() {}
 
+  static bool isValidEmulation(llvm::StringRef Emulation );
+
   // Main entry point.
   int link(llvm::ArrayRef<const char *> Args,
            llvm::ArrayRef<llvm::StringRef> ELDFlagsArgs) override;

lib/LinkerWrapper/Driver.cpp

@@ -11,6 +11,7 @@
 #include "eld/Driver/GnuLdDriver.h"
 #include "eld/Driver/HexagonLinkDriver.h"
 #include "eld/Driver/RISCVLinkDriver.h"
+#include "eld/Driver/x86_64LinkDriver.h"
 #include "eld/PluginAPI/DiagnosticEntry.h"
 #include "eld/Support/Memory.h"
 #include "eld/Support/TargetRegistry.h"
@@ -182,6 +183,10 @@ Driver::getFlavorAndTripleFromLinkCommand(llvm::ArrayRef<const char *> Args) {
       else if (EmulationTriple.getArch() == llvm::Triple::aarch64)
         F = Flavor::AArch64;
     }
+#endif
+#if defined(ELD_ENABLE_TARGET_X86_64)
+    if (x86_64LinkDriver::isValidEmulation(Emulation))
+      F = Flavor::x86_64;
 #endif
     if (F == Flavor::Invalid)
       return std::make_unique<eld::DiagnosticEntry>(

lib/LinkerWrapper/x86_64LinkDriver.cpp

@@ -161,3 +161,8 @@ template <class T>
 bool x86_64LinkDriver::processLLVMOptions(llvm::opt::InputArgList &Args) {
   return GnuLdDriver::processLLVMOptions<T>(Args);
 }
+
+
+bool x86_64LinkDriver::isValidEmulation(llvm::StringRef Emulation){
+  return Emulation == "elf_x86_64" || Emulation == "elf_amd64";
+}

test/lit.cfg

@@ -277,11 +277,11 @@ if config.test_target == 'Hexagon':
 
 if config.test_target == 'X86':
     config.march = ''
-    clang = 'clang'
+    clang = 'clang -target x86_64-linux-gnu'
     clangxx = 'clang++'
     llvmmc = 'llvm-mc'
     readelf = 'llvm-readelf'
-    link = 'x86_64-link'
+    link = 'ld.eld -m elf_x86_64'
     ar = 'llvm-ar'
     nm = 'llvm-nm'
     objdump = 'llvm-objdump'

test/x86_64/linux/EmulationSupport/EmulationOption.test

@@ -0,0 +1,16 @@
+#---x86_64_Emulation.test----------------- Executable --------------------#
+
+BEGIN_COMMENT
+# Test x86_64 emulation support in eld
+# This test verifies that eld correctly handles the -m elf_x86_64 emulation flag.
+# It compiles a minimal C program with a custom _start() that performs a syscall
+# to exit with code 5. The program is linked using eld with --image-base.
+#END_COMMENT
+
+#START_TEST
+RUN: %clang %clangopts -c %p/Inputs/1.c -o %t.1.o
+RUN: %link %linkopts -o %t.1.out %t.1.o --image-base=0x400000
+RUN: %t.1.out; echo $? > %t.code
+RUN: %filecheck --input-file=%t.code %s --check-prefix=EXITCODE
+EXITCODE: 5
+#END_TEST

test/x86_64/linux/EmulationSupport/Inputs/1.c

@@ -0,0 +1,11 @@
+void _start() {
+  long u = 5;
+  asm (
+    "movq $60, %%rax\n"
+    "movq %0, %%rdi\n"
+    "syscall\n"
+    :
+    : "r" (u)
+    : "%rax", "%rdi"
+  );
+}