diff --git a/src/sim/syscall_abi.hh b/src/sim/syscall_abi.hh
new file mode 100644
index 0000000000..f6eade50e9
--- /dev/null
+++ b/src/sim/syscall_abi.hh
@@ -0,0 +1,128 @@
+/*
+ * Copyright 2019 Google, Inc.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met: redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer;
+ * redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the distribution;
+ * neither the name of the copyright holders nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef __SIM_SYSCALL_ABI_HH__
+#define __SIM_SYSCALL_ABI_HH__
+
+#include "base/types.hh"
+#include "cpu/thread_context.hh"
+#include "sim/guest_abi.hh"
+#include "sim/syscall_return.hh"
+
+class SyscallDesc;
+
+namespace GuestABI
+{
+
+// Does this normally 64 bit data type shrink down to 32 bits for 32 bit ABIs?
+template <typename T, typename Enabled=void>
+struct IsConforming : public std::false_type {};
+
+template <>
+struct IsConforming<Addr> : public std::true_type {};
+
+} // namespace GuestABI
+
+struct GenericSyscallABI
+{
+    using Position = int;
+};
+
+struct GenericSyscallABI64 : public GenericSyscallABI
+{};
+
+struct GenericSyscallABI32 : public GenericSyscallABI
+{
+    // Is this argument too big for a single register?
+    template <typename T, typename Enabled=void>
+    struct IsWide;
+
+    template <typename T>
+    struct IsWide<T, typename std::enable_if<
+        std::is_integral<T>::value &&
+        (sizeof(T) < sizeof(uint64_t) ||
+         GuestABI::IsConforming<T>::value)>::type>
+    {
+        static const bool value = false;
+    };
+
+    template <typename T>
+    struct IsWide<T, typename std::enable_if<
+        std::is_integral<T>::value &&
+        sizeof(T) == sizeof(uint64_t) &&
+        !GuestABI::IsConforming<T>::value>::type>
+    {
+        static const bool value = true;
+    };
+
+    // Read two registers and merge them into one value.
+    static uint64_t
+    mergeRegs(ThreadContext *tc, RegIndex low_idx, RegIndex high_idx)
+    {
+        RegVal low = tc->readIntReg(low_idx);
+        RegVal high = tc->readIntReg(high_idx);
+        return insertBits(low, 63, 32, high);
+    }
+};
+
+namespace GuestABI
+{
+
+// For 64 bit systems, return syscall args directly.
+template <typename ABI, typename Arg>
+struct Argument<ABI, Arg,
+    typename std::enable_if<
+        std::is_base_of<GenericSyscallABI64, ABI>::value &&
+        std::is_integral<Arg>::value>::type>
+{
+    static Arg
+    get(ThreadContext *tc, typename ABI::Position &position)
+    {
+        panic_if(position >= ABI::ArgumentRegs.size(),
+                "Ran out of syscall argument registers.");
+        return tc->readIntReg(ABI::ArgumentRegs[position++]);
+    }
+};
+
+// For 32 bit systems, return small enough syscall args directly. Large
+// arguments aren't handled generically.
+template <typename ABI, typename Arg>
+struct Argument<ABI, Arg,
+    typename std::enable_if<!ABI::template IsWide<Arg>::value>::type>
+{
+    static Arg
+    get(ThreadContext *tc, typename ABI::Position &position)
+    {
+        panic_if(position >= ABI::ArgumentRegs.size(),
+                "Ran out of syscall argument registers.");
+        return bits(tc->readIntReg(ABI::ArgumentRegs[position++]), 31, 0);
+    }
+};
+
+} // namespace GuestABI
+
+#endif // __SIM_SYSCALL_ABI_HH__