arch-x86: Change guest ABI for x86 pseudo insts

Change the guest ABI for x86 pseudo instructions to explictly write rax.
This is required because for some reason, the KVM CPU overwrites rax
after the KVM MMIO sets the value.

Note: This is hacky. It will only work for the current implementations
of x86 m5 ops which have their return value in RAX. A comment is added
to the m5ops file to make this clear.

Change-Id: I9466bf050b26db3650cfe3d23008e0f77fda8bc0
Signed-off-by: Jason Lowe-Power <jason@lowepower.com>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/25664
Tested-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: Gabe Black <gabeblack@google.com>

diff --git a/src/arch/x86/mmapped_ipr.hh b/src/arch/x86/mmapped_ipr.hh
index 53690d91423a1eac0a5640619b9dacf6a623e5c4..32463f766cb10117871787ae6c36286279504e76 100644 (file)
--- a/src/arch/x86/mmapped_ipr.hh
+++ b/src/arch/x86/mmapped_ipr.hh
@@ -46,6 +46,7 @@
  * ISA-specific helper functions for memory mapped IPR accesses.
  */
 
+#include "arch/x86/pseudo_inst_abi.hh"
 #include "arch/x86/regs/misc.hh"
 #include "cpu/base.hh"
 #include "cpu/thread_context.hh"
@@ -63,7 +64,7 @@ namespace X86ISA
         if (m5opRange.contains(addr)) {
             uint8_t func;
             PseudoInst::decodeAddrOffset(addr - m5opRange.start(), func);
-            uint64_t ret = PseudoInst::pseudoInst<PseudoInstABI>(tc, func);
+            uint64_t ret = PseudoInst::pseudoInst<X86PseudoInstABI>(tc, func);
             pkt->setLE(ret);
         } else {
             Addr offset = addr & mask(3);
@@ -84,7 +85,7 @@ namespace X86ISA
         if (m5opRange.contains(addr)) {
             uint8_t func;
             PseudoInst::decodeAddrOffset(addr - m5opRange.start(), func);
-            PseudoInst::pseudoInst<PseudoInstABI>(tc, func);
+            PseudoInst::pseudoInst<X86PseudoInstABI>(tc, func);
         } else {
             Addr offset = addr & mask(3);
             MiscRegIndex index = (MiscRegIndex)(addr / sizeof(RegVal));

diff --git a/src/arch/x86/pseudo_inst_abi.hh b/src/arch/x86/pseudo_inst_abi.hh
new file mode 100644 (file)
index 0000000..5ac5efe
--- /dev/null
+++ b/src/arch/x86/pseudo_inst_abi.hh
@@ -0,0 +1,84 @@
+/*
+ * Copyright (c) 2020 The Regents of the University of California.
+ * All rights reserved.
+ *
+ * The license below extends only to copyright in the software and shall
+ * not be construed as granting a license to any other intellectual
+ * property including but not limited to intellectual property relating
+ * to a hardware implementation of the functionality of the software
+ * licensed hereunder.  You may use the software subject to the license
+ * terms below provided that you ensure that this notice is replicated
+ * unmodified and in its entirety in all distributions of the software,
+ * modified or unmodified, in source code or in binary form.
+ *
+ * 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.
+ */
+
+#include "arch/x86/registers.hh"
+#include "sim/guest_abi.hh"
+
+struct X86PseudoInstABI
+{
+    using Position = int;
+};
+
+namespace GuestABI
+{
+
+template <typename T>
+struct Result<X86PseudoInstABI, T>
+{
+    static void
+    store(ThreadContext *tc, const T &ret)
+    {
+        // This assumes that all pseudo ops have their return value set
+        // by the pseudo op instruction. This may need to be revisited if we
+        // modify the pseudo op ABI in util/m5/m5op_x86.S
+        tc->setIntReg(X86ISA::INTREG_RAX, ret);
+    }
+};
+
+template <>
+struct Argument<X86PseudoInstABI, uint64_t>
+{
+    static uint64_t
+    get(ThreadContext *tc, X86PseudoInstABI::Position &position)
+    {
+        // The first 6 integer arguments are passed in registers, the rest
+        // are passed on the stack.
+
+        panic_if(position >= 6, "Too many psuedo inst arguments.");
+
+        using namespace X86ISA;
+
+        const int int_reg_map[] = {
+            INTREG_RDI, INTREG_RSI, INTREG_RDX,
+            INTREG_RCX, INTREG_R8, INTREG_R9
+        };
+
+        return tc->readIntReg(int_reg_map[position++]);
+    }
+};
+
+} // namespace GuestABI

diff --git a/util/m5/m5op_x86.S b/util/m5/m5op_x86.S
index 2a8abbb6e26710c791cfedd6851901acc0ededfc..32229dc295ab6f340e17b58684ac8f40d25dbc91 100644 (file)
--- a/util/m5/m5op_x86.S
+++ b/util/m5/m5op_x86.S
@@ -32,6 +32,14 @@
 
 #include <gem5/asm/generic/m5ops.h>
 
+/*
+  Note: The ABI for pseudo ops using the M5OP_ADDR is defined in
+  src/arch/x86/pseudo_inst_abi.hh. If the ABI is changed below, it's likely
+  that the ABI in the arch directory will also need to be updated.
+
+  The ABI for the magic instruction-based pseudo ops is not affected by this.
+*/
+
 #if defined(M5OP_ADDR) && defined(M5OP_PIC)
 /* Use the memory mapped m5op interface */
 #define TWO_BYTE_OP(name, number)         \