sim: Add GenericSyscallABI structs which can be used by the ISAs.

It's very common for system call arguments to be passed in a sequence
of registers, one argument per register. To avoid having that
implementation repeated over and over across the various ISAs and OSes,
these partial ABI implementations provide that mechanism they can just
pull in. They would need to define the sequence of registers to use,
and these would take care of the rest.

Unlike the temporary DefaultSyscallABI which defers to the Process
classes, these read registers from the ThreadContext directly.

Change-Id: Ic72eb8d784ecf4711b5eec76d958a87c70850fce
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/23441
Reviewed-by: Bobby R. Bruce <bbruce@ucdavis.edu>
Maintainer: Gabe Black <gabeblack@google.com>
Tested-by: kokoro <noreply+kokoro@google.com>

diff --git a/src/sim/syscall_abi.hh b/src/sim/syscall_abi.hh
new file mode 100644 (file)
index 0000000..f6eade5
--- /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__