arch,cpu,sim: Push syscall number determination up to processes.

The logic that determines which syscall to call was built into the
implementation of faults/exceptions or even into the instruction
decoder, but that logic can depend on what OS is being used, and
sometimes even what version, for example 32bit vs. 64bit.

This change pushes that logic up into the Process objects since those
already handle a lot of the aspects of emulating the guest OS. Instead,
the ISA or fault implementations just notify the rest of the system
that a nebulous syscall has happened, and that gets propogated upward
until the process does something with it. That's very analogous to how
a system call would work on a real machine.

When a system call happens, the low level component which detects that
should call tc->syscall(&fault), where tc is the relevant thread (or
execution) context, and fault is a Fault which can ultimately be set
by the system call implementation.

The TC implementor (probably a CPU) will then have a chance to do
whatever it needs to to handle a system call. Currently only O3 does
anything special here. That implementor will end up calling the
Process's syscall() method.

Once in Process::syscall, the process object will use it's contextual
knowledge to determine what system call is being requested. It then
calls Process::doSyscall with the right syscall number, where doSyscall
centralizes the common mechanism for actually retrieving and calling
into the system call implementation.

Jira Issue: https://gem5.atlassian.net/browse/GEM5-187

Change-Id: I937ec1ef0576142c2a182ff33ca508d77ad0e7a1
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/23176
Maintainer: Gabe Black <gabeblack@google.com>
Tested-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: Brandon Potter <Brandon.Potter@amd.com>

46 files changed, 165 insertions, 77 deletions

diff --git a/src/arch/alpha/isa/decoder.isa b/src/arch/alpha/isa/decoder.isa
index 020e43359..abf6fb24a 100644
--- a/src/arch/alpha/isa/decoder.isa
+++ b/src/arch/alpha/isa/decoder.isa
@@ -840,7 +840,7 @@ decode OPCODE default Unknown::unknown() {
                     exitSimLoop("halt instruction encountered");
                 }}, IsNonSpeculative);
                 0x83: callsys({{
-                    xc->syscall(R0, &fault);
+                    xc->syscall(&fault);
                 }}, IsSerializeAfter, IsNonSpeculative, IsSyscall);
                 // Read uniq reg into ABI return value register (r0)
                 0x9e: rduniq({{ R0 = Runiq; }}, IsIprAccess);
diff --git a/src/arch/alpha/linux/process.cc b/src/arch/alpha/linux/process.cc
index 1ac53a5a0..26d5f26cd 100644
--- a/src/arch/alpha/linux/process.cc
+++ b/src/arch/alpha/linux/process.cc
@@ -620,3 +620,10 @@ AlphaLinuxProcess::getDesc(int callnum)
         return NULL;
     return &syscallDescs[callnum];
 }
+
+void
+AlphaLinuxProcess::syscall(ThreadContext *tc, Fault *fault)
+{
+    doSyscall(tc->readIntReg(0), tc, fault);
+}
+
diff --git a/src/arch/alpha/linux/process.hh b/src/arch/alpha/linux/process.hh
index 46c22d288..991ddbd08 100644
--- a/src/arch/alpha/linux/process.hh
+++ b/src/arch/alpha/linux/process.hh
@@ -42,6 +42,8 @@ class AlphaLinuxProcess : public AlphaProcess
     /// Constructor.
     AlphaLinuxProcess(ProcessParams * params, ObjectFile *objFile);
 
+    void syscall(ThreadContext *tc, Fault *fault) override;
+
     virtual SyscallDesc* getDesc(int callnum);
 
      /// Array of syscall descriptors, indexed by call number.
diff --git a/src/arch/arm/fastmodel/iris/thread_context.hh b/src/arch/arm/fastmodel/iris/thread_context.hh
index c0f40d76c..d0e920e60 100644
--- a/src/arch/arm/fastmodel/iris/thread_context.hh
+++ b/src/arch/arm/fastmodel/iris/thread_context.hh
@@ -419,7 +419,7 @@ class ThreadContext : public ::ThreadContext
     }
 
     void
-    syscall(int64_t callnum, Fault *fault) override
+    syscall(Fault *fault) override
     {
         panic("%s not implemented.", __FUNCTION__);
     }
diff --git a/src/arch/arm/faults.cc b/src/arch/arm/faults.cc
index 85e9fa7e9..5a7b8e8ea 100644
--- a/src/arch/arm/faults.cc
+++ b/src/arch/arm/faults.cc
@@ -845,15 +845,8 @@ SupervisorCall::invoke(ThreadContext *tc, const StaticInstPtr &inst)
 
     // As of now, there isn't a 32 bit thumb version of this instruction.
     assert(!machInst.bigThumb);
-    uint32_t callNum;
-    CPSR cpsr = tc->readMiscReg(MISCREG_CPSR);
-    OperatingMode mode = (OperatingMode)(uint8_t)cpsr.mode;
-    if (opModeIs64(mode))
-        callNum = tc->readIntReg(INTREG_X8);
-    else
-        callNum = tc->readIntReg(INTREG_R7);
     Fault fault;
-    tc->syscall(callNum, &fault);
+    tc->syscall(&fault);
 
     // Advance the PC since that won't happen automatically.
     PCState pc = tc->pcState();
diff --git a/src/arch/arm/freebsd/process.cc b/src/arch/arm/freebsd/process.cc
index 901b2411b..a603777a1 100644
--- a/src/arch/arm/freebsd/process.cc
+++ b/src/arch/arm/freebsd/process.cc
@@ -1317,3 +1317,15 @@ ArmFreebsdProcess64::initState()
     ArmProcess64::initState();
     // The 64 bit equivalent of the comm page would be set up here.
 }
+
+void
+ArmFreebsdProcess32::syscall(ThreadContext *tc, Fault *fault)
+{
+    doSyscall(tc->readIntReg(INTREG_R7), tc, fault);
+}
+
+void
+ArmFreebsdProcess64::syscall(ThreadContext *tc, Fault *fault)
+{
+    doSyscall(tc->readIntReg(INTREG_X8), tc, fault);
+}
diff --git a/src/arch/arm/freebsd/process.hh b/src/arch/arm/freebsd/process.hh
index 28504d7d8..5f4a89600 100644
--- a/src/arch/arm/freebsd/process.hh
+++ b/src/arch/arm/freebsd/process.hh
@@ -63,6 +63,8 @@ class ArmFreebsdProcess32 : public ArmProcess32, public ArmFreebsdProcessBits
 
     void initState();
 
+    void syscall(ThreadContext *tc, Fault *fault) override;
+
     /// Explicitly import the otherwise hidden getSyscallArg
     using ArmProcess::getSyscallArg;
 
@@ -80,6 +82,7 @@ class ArmFreebsdProcess64 : public ArmProcess64, public ArmFreebsdProcessBits
                         ObjectFile::Arch _arch);
 
     void initState();
+    void syscall(ThreadContext *tc, Fault *fault) override;
     SyscallDesc* getDesc(int callnum);
 };
 
diff --git a/src/arch/arm/linux/process.cc b/src/arch/arm/linux/process.cc
index d3d0e85be..bc41932b8 100644
--- a/src/arch/arm/linux/process.cc
+++ b/src/arch/arm/linux/process.cc
@@ -1777,3 +1777,15 @@ ArmLinuxProcess64::initState()
     ArmProcess64::initState();
     // The 64 bit equivalent of the comm page would be set up here.
 }
+
+void
+ArmLinuxProcess32::syscall(ThreadContext *tc, Fault *fault)
+{
+    doSyscall(tc->readIntReg(INTREG_R7), tc, fault);
+}
+
+void
+ArmLinuxProcess64::syscall(ThreadContext *tc, Fault *fault)
+{
+    doSyscall(tc->readIntReg(INTREG_X8), tc, fault);
+}
diff --git a/src/arch/arm/linux/process.hh b/src/arch/arm/linux/process.hh
index d4b7ca7d3..8e2709fcd 100644
--- a/src/arch/arm/linux/process.hh
+++ b/src/arch/arm/linux/process.hh
@@ -73,6 +73,8 @@ class ArmLinuxProcess32 : public ArmProcess32, public ArmLinuxProcessBits
 
     void initState();
 
+    void syscall(ThreadContext *tc, Fault *fault) override;
+
     /// Explicitly import the otherwise hidden getSyscallArg
     using ArmProcess::getSyscallArg;
 
@@ -90,6 +92,7 @@ class ArmLinuxProcess64 : public ArmProcess64, public ArmLinuxProcessBits
                       ObjectFile::Arch _arch);
 
     void initState();
+    void syscall(ThreadContext *tc, Fault *fault) override;
     SyscallDesc* getDesc(int callnum);
 };
 
diff --git a/src/arch/mips/isa/decoder.isa b/src/arch/mips/isa/decoder.isa
index 3406ed5d2..856a34083 100644
--- a/src/arch/mips/isa/decoder.isa
+++ b/src/arch/mips/isa/decoder.isa
@@ -163,7 +163,7 @@ decode OPCODE_HI default Unknown::unknown() {
                     0x2: movz({{ Rd = (Rt == 0) ? Rs : Rd; }});
                     0x3: movn({{ Rd = (Rt != 0) ? Rs : Rd; }});
                     0x4: decode FullSystemInt {
-                        0: syscall_se({{ xc->syscall(R2, &fault); }},
+                        0: syscall_se({{ xc->syscall(&fault); }},
                                 IsSerializeAfter, IsNonSpeculative);
                       default: syscall({{ fault = std::make_shared<SystemCallFault>(); }});
                     }
diff --git a/src/arch/mips/isa/operands.isa b/src/arch/mips/isa/operands.isa
index 2d44bb30e..f81df73fd 100644
--- a/src/arch/mips/isa/operands.isa
+++ b/src/arch/mips/isa/operands.isa
@@ -51,9 +51,8 @@ def operands {{
     #Immediate Value operand
     'IntImm': ('IntReg', 'uw', 'INTIMM', 'IsInteger', 3),
 
-    #Operands used for Link or Syscall Insts
+    #Operands used for Link Insts
     'R31': ('IntReg', 'uw','31','IsInteger', 4),
-    'R2':  ('IntReg', 'uw','2', 'IsInteger', 5),
 
     #Special Integer Reg operands
     'LO0':  ('IntReg', 'uw','INTREG_LO', 'IsInteger', 6),
diff --git a/src/arch/mips/linux/process.cc b/src/arch/mips/linux/process.cc
index adfbfd3f6..2dc1bcdaf 100644
--- a/src/arch/mips/linux/process.cc
+++ b/src/arch/mips/linux/process.cc
@@ -509,7 +509,8 @@ MipsLinuxProcess::getDesc(int callnum)
     return &syscallDescs[m5_sys_idx];
 }
 
-
-
-
-
+void
+MipsLinuxProcess::syscall(ThreadContext *tc, Fault *fault)
+{
+    doSyscall(tc->readIntReg(2), tc, fault);
+}
diff --git a/src/arch/mips/linux/process.hh b/src/arch/mips/linux/process.hh
index cbf0d78ea..7fcb6f014 100644
--- a/src/arch/mips/linux/process.hh
+++ b/src/arch/mips/linux/process.hh
@@ -51,6 +51,8 @@ class MipsLinuxProcess : public MipsProcess
     /// ID of the thread group leader for the process
     uint64_t __tgid;
 
+    void syscall(ThreadContext *tc, Fault *fault) override;
+
     /// Array of syscall descriptors, indexed by call number.
     static SyscallDesc syscallDescs[];
     const int Num_Syscall_Descs;
diff --git a/src/arch/power/isa/decoder.isa b/src/arch/power/isa/decoder.isa
index 060d6a34d..3f10fe48b 100644
--- a/src/arch/power/isa/decoder.isa
+++ b/src/arch/power/isa/decoder.isa
@@ -517,7 +517,7 @@ decode OPCODE default Unknown::unknown() {
         55: stfdu({{ Mem_df = Fs; }});
     }
 
-    17: IntOp::sc({{ xc->syscall(R0, &fault); }},
+    17: IntOp::sc({{ xc->syscall(&fault); }},
                   [ IsSyscall, IsNonSpeculative, IsSerializeAfter ]);
 
     format FloatArithOp {
diff --git a/src/arch/power/isa/operands.isa b/src/arch/power/isa/operands.isa
index a72a0714d..117c8ad02 100644
--- a/src/arch/power/isa/operands.isa
+++ b/src/arch/power/isa/operands.isa
@@ -75,7 +75,4 @@ def operands {{
     'Rsv': ('IntReg', 'uw', 'INTREG_RSV', 'IsInteger', 9),
     'RsvLen': ('IntReg', 'uw', 'INTREG_RSV_LEN', 'IsInteger', 9),
     'RsvAddr': ('IntReg', 'uw', 'INTREG_RSV_ADDR', 'IsInteger', 9),
-
-    # Hack for non-full-system syscall emulation
-    'R0':  ('IntReg', 'uw', '0', None, 1),
 }};
diff --git a/src/arch/power/linux/process.cc b/src/arch/power/linux/process.cc
index ac032275e..a63d9a30c 100644
--- a/src/arch/power/linux/process.cc
+++ b/src/arch/power/linux/process.cc
@@ -468,6 +468,12 @@ PowerLinuxProcess::initState()
     PowerProcess::initState();
 }
 
+void
+PowerLinuxProcess::syscall(ThreadContext *tc, Fault *fault)
+{
+    doSyscall(tc->readIntReg(0), tc, fault);
+}
+
 RegVal
 PowerLinuxProcess::getSyscallArg(ThreadContext *tc, int &i)
 {
diff --git a/src/arch/power/linux/process.hh b/src/arch/power/linux/process.hh
index 5a2ad92a4..ef96dae5f 100644
--- a/src/arch/power/linux/process.hh
+++ b/src/arch/power/linux/process.hh
@@ -45,6 +45,8 @@ class PowerLinuxProcess : public PowerProcess
 
     void initState();
 
+    void syscall(ThreadContext *tc, Fault *fault) override;
+
     RegVal getSyscallArg(ThreadContext *tc, int &i);
     /// Explicitly import the otherwise hidden getSyscallArg
     using Process::getSyscallArg;
diff --git a/src/arch/riscv/faults.cc b/src/arch/riscv/faults.cc
index 6b79eb838..83adcba69 100644
--- a/src/arch/riscv/faults.cc
+++ b/src/arch/riscv/faults.cc
@@ -191,7 +191,7 @@ void
 SyscallFault::invokeSE(ThreadContext *tc, const StaticInstPtr &inst)
 {
     Fault *fault = NoFault;
-    tc->syscall(tc->readIntReg(SyscallNumReg), fault);
+    tc->syscall(fault);
 }
 
 } // namespace RiscvISA
diff --git a/src/arch/riscv/linux/process.cc b/src/arch/riscv/linux/process.cc
index d6a41e240..49e32de92 100644
--- a/src/arch/riscv/linux/process.cc
+++ b/src/arch/riscv/linux/process.cc
@@ -795,6 +795,12 @@ RiscvLinuxProcess64::getDesc(int callnum)
         &syscallDescs.at(callnum) : nullptr;
 }
 
+void
+RiscvLinuxProcess64::syscall(ThreadContext *tc, Fault *fault)
+{
+    doSyscall(tc->readIntReg(SyscallNumReg), tc, fault);
+}
+
 RiscvLinuxProcess32::RiscvLinuxProcess32(ProcessParams * params,
     ObjectFile *objFile) : RiscvProcess32(params, objFile)
 {}
@@ -805,3 +811,9 @@ RiscvLinuxProcess32::getDesc(int callnum)
     return syscallDescs.find(callnum) != syscallDescs.end() ?
         &syscallDescs.at(callnum) : nullptr;
 }
+
+void
+RiscvLinuxProcess32::syscall(ThreadContext *tc, Fault *fault)
+{
+    doSyscall(tc->readIntReg(SyscallNumReg), tc, fault);
+}
diff --git a/src/arch/riscv/linux/process.hh b/src/arch/riscv/linux/process.hh
index 1256ac667..65daca35e 100644
--- a/src/arch/riscv/linux/process.hh
+++ b/src/arch/riscv/linux/process.hh
@@ -55,6 +55,8 @@ class RiscvLinuxProcess64 : public RiscvProcess64
     /// ID of the thread group leader for the process
     uint64_t __tgid;
 
+    void syscall(ThreadContext *tc, Fault *fault) override;
+
     /// Array of syscall descriptors, indexed by call number.
     static std::map<int, SyscallDesc> syscallDescs;
 };
@@ -73,6 +75,8 @@ class RiscvLinuxProcess32 : public RiscvProcess32
     /// ID of the thread group leader for the process
     uint64_t __tgid;
 
+    void syscall(ThreadContext *tc, Fault *fault) override;
+
     /// Array of syscall descriptors, indexed by call number.
     static std::map<int, SyscallDesc> syscallDescs;
 };
diff --git a/src/arch/sparc/linux/process.cc b/src/arch/sparc/linux/process.cc
index 5fb3b0348..530cf8512 100644
--- a/src/arch/sparc/linux/process.cc
+++ b/src/arch/sparc/linux/process.cc
@@ -100,12 +100,18 @@ Sparc32LinuxProcess::Sparc32LinuxProcess(ProcessParams * params,
     : Sparc32Process(params, objFile)
 {}
 
-void Sparc32LinuxProcess::handleTrap(int trapNum, ThreadContext *tc,
-                                     Fault *fault)
+void
+Sparc32LinuxProcess::syscall(ThreadContext *tc, Fault *fault)
+{
+    doSyscall(tc->readIntReg(1), tc, fault);
+}
+
+void
+Sparc32LinuxProcess::handleTrap(int trapNum, ThreadContext *tc, Fault *fault)
 {
     switch (trapNum) {
       case 0x10: //Linux 32 bit syscall trap
-        tc->syscall(tc->readIntReg(1), fault);
+        tc->syscall(fault);
         break;
       default:
         SparcProcess::handleTrap(trapNum, tc, fault);
@@ -117,13 +123,19 @@ Sparc64LinuxProcess::Sparc64LinuxProcess(ProcessParams * params,
     : Sparc64Process(params, objFile)
 {}
 
-void Sparc64LinuxProcess::handleTrap(int trapNum, ThreadContext *tc,
-                                     Fault *fault)
+void
+Sparc64LinuxProcess::syscall(ThreadContext *tc, Fault *fault)
+{
+    doSyscall(tc->readIntReg(1), tc, fault);
+}
+
+void
+Sparc64LinuxProcess::handleTrap(int trapNum, ThreadContext *tc, Fault *fault)
 {
     switch (trapNum) {
       // case 0x10: // Linux 32 bit syscall trap
       case 0x6d: // Linux 64 bit syscall trap
-        tc->syscall(tc->readIntReg(1), fault);
+        tc->syscall(fault);
         break;
       default:
         SparcProcess::handleTrap(trapNum, tc, fault);
diff --git a/src/arch/sparc/linux/process.hh b/src/arch/sparc/linux/process.hh
index f5260cdf1..5c673db26 100644
--- a/src/arch/sparc/linux/process.hh
+++ b/src/arch/sparc/linux/process.hh
@@ -70,6 +70,8 @@ class Sparc32LinuxProcess : public SparcLinuxProcess, public Sparc32Process
         return SparcLinuxProcess::getDesc32(callnum);
     }
 
+    void syscall(ThreadContext *tc, Fault *fault) override;
+
     void handleTrap(int trapNum, ThreadContext *tc, Fault *fault);
 };
 
@@ -86,6 +88,8 @@ class Sparc64LinuxProcess : public SparcLinuxProcess, public Sparc64Process
         return SparcLinuxProcess::getDesc(callnum);
     }
 
+    void syscall(ThreadContext *tc, Fault *fault) override;
+
     void handleTrap(int trapNum, ThreadContext *tc, Fault *fault);
 };
 
diff --git a/src/arch/sparc/solaris/process.cc b/src/arch/sparc/solaris/process.cc
index 18f2316a2..d51b9519c 100644
--- a/src/arch/sparc/solaris/process.cc
+++ b/src/arch/sparc/solaris/process.cc
@@ -368,3 +368,9 @@ SparcSolarisProcess::getDesc(int callnum)
         return NULL;
     return &syscallDescs[callnum];
 }
+
+void
+SparcSolarisProcess::syscall(ThreadContext *tc, Fault *fault)
+{
+    doSyscall(tc->readIntReg(1), tc, fault);
+}
diff --git a/src/arch/sparc/solaris/process.hh b/src/arch/sparc/solaris/process.hh
index 660802cef..39e3aef17 100644
--- a/src/arch/sparc/solaris/process.hh
+++ b/src/arch/sparc/solaris/process.hh
@@ -49,6 +49,8 @@ class SparcSolarisProcess : public Sparc64Process
     /// The target system's hostname.
     static const char *hostname;
 
+    void syscall(ThreadContext *tc, Fault *fault) override;
+
      /// Array of syscall descriptors, indexed by call number.
     static SyscallDesc syscallDescs[];
 
diff --git a/src/arch/x86/isa/decoder/one_byte_opcodes.isa b/src/arch/x86/isa/decoder/one_byte_opcodes.isa
index 95bc7a5c1..1fbf32748 100644
--- a/src/arch/x86/isa/decoder/one_byte_opcodes.isa
+++ b/src/arch/x86/isa/decoder/one_byte_opcodes.isa
@@ -400,7 +400,7 @@
                         // will sign extend it, and there's no easy way to
                         // specify only checking the first byte.
                         0xffffffffffffff80:
-                            SyscallInst::int80('xc->syscall(Rax, &fault)',
+                            SyscallInst::int80('xc->syscall(&fault)',
                                                IsSyscall, IsNonSpeculative,
                                                IsSerializeAfter);
                     }
diff --git a/src/arch/x86/isa/decoder/two_byte_opcodes.isa b/src/arch/x86/isa/decoder/two_byte_opcodes.isa
index 51154d5b8..43a62d76c 100644
--- a/src/arch/x86/isa/decoder/two_byte_opcodes.isa
+++ b/src/arch/x86/isa/decoder/two_byte_opcodes.isa
@@ -235,7 +235,7 @@
                 }
             }
             0x05: decode FullSystemInt {
-                0: SyscallInst::syscall('xc->syscall(Rax, &fault)',
+                0: SyscallInst::syscall('xc->syscall(&fault)',
                                         IsSyscall, IsNonSpeculative,
                                         IsSerializeAfter);
                 default: decode MODE_MODE {
@@ -429,7 +429,7 @@
             0x2: Inst::RDMSR();
             0x3: rdpmc();
             0x4: decode FullSystemInt {
-                0: SyscallInst::sysenter('xc->syscall(Rax, &fault)',
+                0: SyscallInst::sysenter('xc->syscall(&fault)',
                                          IsSyscall, IsNonSpeculative,
                                          IsSerializeAfter);
                 default: sysenter();
diff --git a/src/arch/x86/linux/process.cc b/src/arch/x86/linux/process.cc
index 6befafde4..d58d965af 100644
--- a/src/arch/x86/linux/process.cc
+++ b/src/arch/x86/linux/process.cc
@@ -584,8 +584,15 @@ X86_64LinuxProcess::X86_64LinuxProcess(ProcessParams * params,
                     sizeof(syscallDescs64) / sizeof(SyscallDesc))
 {}
 
-void X86_64LinuxProcess::clone(ThreadContext *old_tc, ThreadContext *new_tc,
-                               Process *process, RegVal flags)
+void
+X86_64LinuxProcess::syscall(ThreadContext *tc, Fault *fault)
+{
+    doSyscall(tc->readIntReg(INTREG_RAX), tc, fault);
+}
+
+void
+X86_64LinuxProcess::clone(ThreadContext *old_tc, ThreadContext *new_tc,
+                          Process *process, RegVal flags)
 {
     X86_64Process::clone(old_tc, new_tc, (X86_64Process*)process, flags);
 }
@@ -926,8 +933,22 @@ I386LinuxProcess::I386LinuxProcess(ProcessParams * params, ObjectFile *objFile)
                   sizeof(syscallDescs32) / sizeof(SyscallDesc))
 {}
 
-void I386LinuxProcess::clone(ThreadContext *old_tc, ThreadContext *new_tc,
-                             Process *process, RegVal flags)
+void
+I386LinuxProcess::syscall(ThreadContext *tc, Fault *fault)
+{
+    PCState pc = tc->pcState();
+    Addr eip = pc.pc();
+    if (eip >= vsyscallPage.base &&
+            eip < vsyscallPage.base + vsyscallPage.size) {
+        pc.npc(vsyscallPage.base + vsyscallPage.vsysexitOffset);
+        tc->pcState(pc);
+    }
+    doSyscall(tc->readIntReg(INTREG_RAX), tc, fault);
+}
+
+void
+I386LinuxProcess::clone(ThreadContext *old_tc, ThreadContext *new_tc,
+                        Process *process, RegVal flags)
 {
     I386Process::clone(old_tc, new_tc, (I386Process*)process, flags);
 }
diff --git a/src/arch/x86/linux/process.hh b/src/arch/x86/linux/process.hh
index d4c9b0cf6..5f3135dd9 100644
--- a/src/arch/x86/linux/process.hh
+++ b/src/arch/x86/linux/process.hh
@@ -54,6 +54,7 @@ class X86_64LinuxProcess : public X86_64Process
   public:
     /// Constructor.
     X86_64LinuxProcess(ProcessParams * params, ObjectFile *objFile);
+    void syscall(ThreadContext *tc, Fault *fault) override;
     void clone(ThreadContext *old_tc, ThreadContext *new_tc, Process *process,
                RegVal flags);
 };
@@ -63,6 +64,7 @@ class I386LinuxProcess : public I386Process
   public:
     /// Constructor.
     I386LinuxProcess(ProcessParams * params, ObjectFile *objFile);
+    void syscall(ThreadContext *tc, Fault *fault) override;
     void clone(ThreadContext *old_tc, ThreadContext *new_tc, Process *process,
                RegVal flags);
 };
diff --git a/src/arch/x86/process.cc b/src/arch/x86/process.cc
index f0e8ead98..df22f238a 100644
--- a/src/arch/x86/process.cc
+++ b/src/arch/x86/process.cc
@@ -146,19 +146,6 @@ X86_64Process::X86_64Process(ProcessParams *params, ObjectFile *objFile,
                                      next_thread_stack_base, mmap_end);
 }
 
-void
-I386Process::syscall(int64_t callnum, ThreadContext *tc, Fault *fault)
-{
-    PCState pc = tc->pcState();
-    Addr eip = pc.pc();
-    if (eip >= vsyscallPage.base &&
-            eip < vsyscallPage.base + vsyscallPage.size) {
-        pc.npc(vsyscallPage.base + vsyscallPage.vsysexitOffset);
-        tc->pcState(pc);
-    }
-    X86Process::syscall(callnum, tc, fault);
-}
-
 
 I386Process::I386Process(ProcessParams *params, ObjectFile *objFile,
                          SyscallDesc *_syscallDescs, int _numSyscallDescs)
diff --git a/src/arch/x86/process.hh b/src/arch/x86/process.hh
index 37545e9d9..4c424cd7d 100644
--- a/src/arch/x86/process.hh
+++ b/src/arch/x86/process.hh
@@ -176,8 +176,6 @@ namespace X86ISA
         void argsInit(int pageSize);
         void initState() override;
 
-        void syscall(int64_t callnum, ThreadContext *tc,
-                     Fault *fault) override;
         RegVal getSyscallArg(ThreadContext *tc, int &i) override;
         RegVal getSyscallArg(ThreadContext *tc, int &i, int width) override;
         void clone(ThreadContext *old_tc, ThreadContext *new_tc,
diff --git a/src/arch/x86/pseudo_inst.cc b/src/arch/x86/pseudo_inst.cc
index 62d8b25c5..68bc74acc 100644
--- a/src/arch/x86/pseudo_inst.cc
+++ b/src/arch/x86/pseudo_inst.cc
@@ -50,7 +50,7 @@ m5Syscall(ThreadContext *tc)
     DPRINTF(PseudoInst, "PseudoInst::m5Syscall()\n");
 
     Fault fault;
-    tc->syscall(tc->readIntReg(INTREG_RAX), &fault);
+    tc->syscall(&fault);
 }
 
 /*
diff --git a/src/cpu/checker/cpu.hh b/src/cpu/checker/cpu.hh
index 8db6aa376..e50afebf5 100644
--- a/src/cpu/checker/cpu.hh
+++ b/src/cpu/checker/cpu.hh
@@ -581,7 +581,7 @@ class CheckerCPU : public BaseCPU, public ExecContext
     void wakeup(ThreadID tid) override { }
     // Assume that the normal CPU's call to syscall was successful.
     // The checker's state would have already been updated by the syscall.
-    void syscall(int64_t callnum, Fault *fault) override { }
+    void syscall(Fault *fault) override { }
 
     void
     handleError()
diff --git a/src/cpu/checker/thread_context.hh b/src/cpu/checker/thread_context.hh
index dbdfa80cd..0fb75562a 100644
--- a/src/cpu/checker/thread_context.hh
+++ b/src/cpu/checker/thread_context.hh
@@ -184,9 +184,9 @@ class CheckerThreadContext : public ThreadContext
 
     /** Executes a syscall in SE mode. */
     void
-    syscall(int64_t callnum, Fault *fault) override
+    syscall(Fault *fault) override
     {
-        return actualTC->syscall(callnum, fault);
+        return actualTC->syscall(fault);
     }
 
     Status status() const override { return actualTC->status(); }
diff --git a/src/cpu/exec_context.hh b/src/cpu/exec_context.hh
index a2b392492..80f3edaee 100644
--- a/src/cpu/exec_context.hh
+++ b/src/cpu/exec_context.hh
@@ -304,9 +304,9 @@ class ExecContext {
      */
 
     /**
-     * Executes a syscall specified by the callnum.
+     * Executes a syscall.
      */
-    virtual void syscall(int64_t callnum, Fault *fault) = 0;
+    virtual void syscall(Fault *fault) = 0;
 
     /** @} */
 
diff --git a/src/cpu/minor/exec_context.hh b/src/cpu/minor/exec_context.hh
index 66e313eb3..184dd2910 100644
--- a/src/cpu/minor/exec_context.hh
+++ b/src/cpu/minor/exec_context.hh
@@ -387,9 +387,9 @@ class ExecContext : public ::ExecContext
     }
 
     void
-    syscall(int64_t callnum, Fault *fault) override
+    syscall(Fault *fault) override
     {
-        thread.syscall(callnum, fault);
+        thread.syscall(fault);
     }
 
     ThreadContext *tcBase() override { return thread.getTC(); }
diff --git a/src/cpu/o3/cpu.cc b/src/cpu/o3/cpu.cc
index c843db3a0..996f6360b 100644
--- a/src/cpu/o3/cpu.cc
+++ b/src/cpu/o3/cpu.cc
@@ -918,7 +918,7 @@ FullO3CPU<Impl>::trap(const Fault &fault, ThreadID tid,
 
 template <class Impl>
 void
-FullO3CPU<Impl>::syscall(int64_t callnum, ThreadID tid, Fault *fault)
+FullO3CPU<Impl>::syscall(ThreadID tid, Fault *fault)
 {
     DPRINTF(O3CPU, "[tid:%i] Executing syscall().\n\n", tid);
 
@@ -929,7 +929,7 @@ FullO3CPU<Impl>::syscall(int64_t callnum, ThreadID tid, Fault *fault)
     ++(this->thread[tid]->funcExeInst);
 
     // Execute the actual syscall.
-    this->thread[tid]->syscall(callnum, fault);
+    this->thread[tid]->syscall(fault);
 
     // Decrease funcExeInst by one as the normal commit will handle
     // incrementing it.
diff --git a/src/cpu/o3/cpu.hh b/src/cpu/o3/cpu.hh
index b06182d43..7c0ea5166 100644
--- a/src/cpu/o3/cpu.hh
+++ b/src/cpu/o3/cpu.hh
@@ -284,7 +284,7 @@ class FullO3CPU : public BaseO3CPU
     /** Executes a syscall.
      * @todo: Determine if this needs to be virtual.
      */
-    void syscall(int64_t callnum, ThreadID tid, Fault *fault);
+    void syscall(ThreadID tid, Fault *fault);
 
     /** Starts draining the CPU's pipeline of all instructions in
      * order to stop all memory accesses. */
diff --git a/src/cpu/o3/dyn_inst.hh b/src/cpu/o3/dyn_inst.hh
index 131ffd258..a136e9019 100644
--- a/src/cpu/o3/dyn_inst.hh
+++ b/src/cpu/o3/dyn_inst.hh
@@ -252,7 +252,7 @@ class BaseO3DynInst : public BaseDynInst<Impl>
     void trap(const Fault &fault);
 
     /** Emulates a syscall. */
-    void syscall(int64_t callnum, Fault *fault) override;
+    void syscall(Fault *fault) override;
 
   public:
 
diff --git a/src/cpu/o3/dyn_inst_impl.hh b/src/cpu/o3/dyn_inst_impl.hh
index 22d89ec0b..a9fc990ec 100644
--- a/src/cpu/o3/dyn_inst_impl.hh
+++ b/src/cpu/o3/dyn_inst_impl.hh
@@ -192,13 +192,13 @@ BaseO3DynInst<Impl>::trap(const Fault &fault)
 
 template <class Impl>
 void
-BaseO3DynInst<Impl>::syscall(int64_t callnum, Fault *fault)
+BaseO3DynInst<Impl>::syscall(Fault *fault)
 {
     // HACK: check CPU's nextPC before and after syscall. If it
     // changes, update this instruction's nextPC because the syscall
     // must have changed the nextPC.
     TheISA::PCState curPC = this->cpu->pcState(this->threadNumber);
-    this->cpu->syscall(callnum, this->threadNumber, fault);
+    this->cpu->syscall(this->threadNumber, fault);
     TheISA::PCState newPC = this->cpu->pcState(this->threadNumber);
     if (!(curPC == newPC)) {
         this->pcState(newPC);
diff --git a/src/cpu/o3/thread_context.hh b/src/cpu/o3/thread_context.hh
index c68f34c07..a01c05413 100644
--- a/src/cpu/o3/thread_context.hh
+++ b/src/cpu/o3/thread_context.hh
@@ -448,9 +448,9 @@ class O3ThreadContext : public ThreadContext
 
     /** Executes a syscall in SE mode. */
     void
-    syscall(int64_t callnum, Fault *fault) override
+    syscall(Fault *fault) override
     {
-        return cpu->syscall(callnum, thread->threadId(), fault);
+        return cpu->syscall(thread->threadId(), fault);
     }
 
     /** Reads the funcExeInst counter. */
diff --git a/src/cpu/o3/thread_state.hh b/src/cpu/o3/thread_state.hh
index a0c3a8171..024ebd074 100644
--- a/src/cpu/o3/thread_state.hh
+++ b/src/cpu/o3/thread_state.hh
@@ -148,10 +148,9 @@ struct O3ThreadState : public ThreadState {
     ThreadContext *getTC() { return tc; }
 
     /** Handles the syscall. */
-    void syscall(int64_t callnum, Fault *fault)
+    void syscall(Fault *fault)
     {
-        fatal_if(FullSystem, "System call emulation is unavailable!");
-        process->syscall(callnum, tc, fault);
+        process->syscall(tc, fault);
     }
 
     void dumpFuncProfile()
diff --git a/src/cpu/simple/exec_context.hh b/src/cpu/simple/exec_context.hh
index 4d26dfe2a..48a9f9423 100644
--- a/src/cpu/simple/exec_context.hh
+++ b/src/cpu/simple/exec_context.hh
@@ -497,9 +497,9 @@ class SimpleExecContext : public ExecContext {
      * Executes a syscall specified by the callnum.
      */
     void
-    syscall(int64_t callnum, Fault *fault) override
+    syscall(Fault *fault) override
     {
-        thread->syscall(callnum, fault);
+        thread->syscall(fault);
     }
 
     /** Returns a pointer to the ThreadContext. */
diff --git a/src/cpu/simple_thread.hh b/src/cpu/simple_thread.hh
index 387e74546..b4afcbbc8 100644
--- a/src/cpu/simple_thread.hh
+++ b/src/cpu/simple_thread.hh
@@ -609,10 +609,9 @@ class SimpleThread : public ThreadState, public ThreadContext
     }
 
     void
-    syscall(int64_t callnum, Fault *fault) override
+    syscall(Fault *fault) override
     {
-        fatal_if(FullSystem, "System call emulation is unavailable!");
-        process->syscall(callnum, this, fault);
+        process->syscall(this, fault);
     }
 
     RegVal readIntRegFlat(RegIndex idx) const override { return intRegs[idx]; }
diff --git a/src/cpu/thread_context.hh b/src/cpu/thread_context.hh
index a77ac4848..c14161d6f 100644
--- a/src/cpu/thread_context.hh
+++ b/src/cpu/thread_context.hh
@@ -307,7 +307,7 @@ class ThreadContext : public PCEventScope
     // Same with st cond failures.
     virtual Counter readFuncExeInst() const = 0;
 
-    virtual void syscall(int64_t callnum, Fault *fault) = 0;
+    virtual void syscall(Fault *fault) = 0;
 
     // This function exits the thread context in the CPU and returns
     // 1 if the CPU has no more active threads (meaning it's OK to exit);
diff --git a/src/sim/process.cc b/src/sim/process.cc
index db013aee0..e7f682aad 100644
--- a/src/sim/process.cc
+++ b/src/sim/process.cc
@@ -437,7 +437,7 @@ Process::map(Addr vaddr, Addr paddr, int size, bool cacheable)
 }
 
 void
-Process::syscall(int64_t callnum, ThreadContext *tc, Fault *fault)
+Process::doSyscall(int64_t callnum, ThreadContext *tc, Fault *fault)
 {
     numSyscalls++;
 
diff --git a/src/sim/process.hh b/src/sim/process.hh
index 5d4a9672e..70be3ab8a 100644
--- a/src/sim/process.hh
+++ b/src/sim/process.hh
@@ -63,6 +63,9 @@ class ThreadContext;
 
 class Process : public SimObject
 {
+  protected:
+    void doSyscall(int64_t callnum, ThreadContext *tc, Fault *fault);
+
   public:
     Process(ProcessParams *params, EmulationPageTable *pTable,
             ObjectFile *obj_file);
@@ -74,7 +77,7 @@ class Process : public SimObject
     void initState() override;
     DrainState drain() override;
 
-    virtual void syscall(int64_t callnum, ThreadContext *tc, Fault *fault);
+    virtual void syscall(ThreadContext *tc, Fault *fault) = 0;
     virtual RegVal getSyscallArg(ThreadContext *tc, int &i) = 0;
     virtual RegVal getSyscallArg(ThreadContext *tc, int &i, int width);
     virtual void setSyscallReturn(ThreadContext *tc,