X86: Fix argument register indexing.

Code was assuming that all argument registers followed in order from ArgumentReg0. There is now an ArgumentReg array which is indexed to find the right index. There is a constant, NumArgumentRegs, which can be used to protect against using an invalid ArgumentReg.

--HG--
extra : convert_revision : f448a3ca4d6adc3fc3323562870f70eec05a8a1f

2 files changed, 14 insertions, 8 deletions

diff --git a/src/arch/x86/isa_traits.hh b/src/arch/x86/isa_traits.hh
index 4c02ee35e..63bcfead9 100644
--- a/src/arch/x86/isa_traits.hh
+++ b/src/arch/x86/isa_traits.hh
@@ -99,12 +99,17 @@ namespace X86ISA
     const int ReturnAddressReg = 0;
     const int ReturnValueReg = INTREG_RAX;
     const int FramePointerReg = INTREG_RBP;
-    const int ArgumentReg0 = INTREG_RDI;
-    const int ArgumentReg1 = INTREG_RSI;
-    const int ArgumentReg2 = INTREG_RDX;
-    const int ArgumentReg3 = INTREG_RCX;
-    const int ArgumentReg4 = INTREG_R8W;
-    const int ArgumentReg5 = INTREG_R9W;
+    const int ArgumentReg[] = {
+        INTREG_RDI,
+        INTREG_RSI,
+        INTREG_RDX,
+        //This argument register is r10 for syscalls and rcx for C.
+        INTREG_R10W,
+        //INTREG_RCX,
+        INTREG_R8W,
+        INTREG_R9W
+    };
+    const int NumArgumentRegs = sizeof(ArgumentReg) / sizeof(const int);
 
     // Some OS syscalls use a second register (rdx) to return a second
     // value
diff --git a/src/arch/x86/process.cc b/src/arch/x86/process.cc
index 7deb54945..09962fdb6 100644
--- a/src/arch/x86/process.cc
+++ b/src/arch/x86/process.cc
@@ -338,8 +338,9 @@ X86LiveProcess::argsInit(int intSize, int pageSize)
     initVirtMem->writeBlob(argc_base, (uint8_t*)&guestArgc, intSize);
 
     //Set up the thread context to start running the process
-    threadContexts[0]->setIntReg(ArgumentReg0, argc);
-    threadContexts[0]->setIntReg(ArgumentReg1, argv_array_base);
+    assert(NumArgumentRegs >= 2);
+    threadContexts[0]->setIntReg(ArgumentReg[0], argc);
+    threadContexts[0]->setIntReg(ArgumentReg[1], argv_array_base);
     threadContexts[0]->setIntReg(StackPointerReg, stack_min);
 
     Addr prog_entry = objFile->entryPoint();