From 112e1cdfca116a56e852515e7da374ddb5d53c8b Mon Sep 17 00:00:00 2001
From: Gabe Black <gabeblack@google.com>
Date: Fri, 6 Dec 2019 17:46:38 -0800
Subject: [PATCH] x86: Define a local ABI for system calls.

These ABIs (one 32 bit and one 64 bit) take advantage of the
GenericSyscallABI and X86Linux::SyscallABI partial ABIs set up earlier.

This removes x86's dependence on the getSyscallArg and setSyscallReturn
Process methods.

Change-Id: Ia07834cea1afa827d77e590af5397e2a1e0e2099
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/23443
Reviewed-by: Bobby R. Bruce <bbruce@ucdavis.edu>
Maintainer: Gabe Black <gabeblack@google.com>
Tested-by: kokoro <noreply+kokoro@google.com>
---
 src/arch/x86/linux/linux.hh   |  9 +++++----
 src/arch/x86/linux/process.cc | 12 ++++++++++--
 src/arch/x86/linux/process.hh | 35 +++++++++++++++++++++++++++++++++++
 3 files changed, 50 insertions(+), 6 deletions(-)

diff --git a/src/arch/x86/linux/linux.hh b/src/arch/x86/linux/linux.hh
index 7fb362784..e373dafbb 100644
--- a/src/arch/x86/linux/linux.hh
+++ b/src/arch/x86/linux/linux.hh
@@ -65,9 +65,7 @@ class X86Linux : public Linux
             ctc->setIntReg(X86ISA::StackPointerReg, stack);
     }
 
-    class SyscallABI
-    {
-    };
+    class SyscallABI {};
 };
 
 namespace GuestABI
@@ -81,7 +79,10 @@ struct Result<ABI, SyscallReturn,
     static void
     store(ThreadContext *tc, const SyscallReturn &ret)
     {
-        tc->setIntReg(ABI::ReturnValueReg, ret.encodedValue());
+        if (ret.suppressed() || ret.needsRetry())
+            return;
+
+        tc->setIntReg(X86ISA::INTREG_RAX, ret.encodedValue());
     }
 };
 
diff --git a/src/arch/x86/linux/process.cc b/src/arch/x86/linux/process.cc
index ee3f4cc9c..36a75d79c 100644
--- a/src/arch/x86/linux/process.cc
+++ b/src/arch/x86/linux/process.cc
@@ -250,7 +250,11 @@ setThreadArea32Func(SyscallDesc *desc, int callnum, ThreadContext *tc,
     return 0;
 }
 
-static SyscallDescABI<DefaultSyscallABI> syscallDescs64[] = {
+const std::vector<IntRegIndex> X86_64LinuxProcess::SyscallABI::ArgumentRegs = {
+    INTREG_RDI, INTREG_RSI, INTREG_RDX, INTREG_R10W, INTREG_R8W, INTREG_R9W
+};
+
+static SyscallDescABI<X86_64LinuxProcess::SyscallABI> syscallDescs64[] = {
     /*   0 */ { "read", readFunc<X86Linux64> },
     /*   1 */ { "write", writeFunc<X86Linux64> },
     /*   2 */ { "open", openFunc<X86Linux64> },
@@ -590,7 +594,11 @@ X86_64LinuxProcess::clone(ThreadContext *old_tc, ThreadContext *new_tc,
     X86_64Process::clone(old_tc, new_tc, (X86_64Process*)process, flags);
 }
 
-static SyscallDescABI<DefaultSyscallABI> syscallDescs32[] = {
+const std::vector<IntRegIndex> I386LinuxProcess::SyscallABI::ArgumentRegs = {
+    INTREG_EBX, INTREG_ECX, INTREG_EDX, INTREG_ESI, INTREG_EDI, INTREG_EBP
+};
+
+static SyscallDescABI<I386LinuxProcess::SyscallABI> syscallDescs32[] = {
     /*   0 */ { "restart_syscall" },
     /*   1 */ { "exit", exitFunc },
     /*   2 */ { "fork" },
diff --git a/src/arch/x86/linux/process.hh b/src/arch/x86/linux/process.hh
index 53e8c4793..a236a9e12 100644
--- a/src/arch/x86/linux/process.hh
+++ b/src/arch/x86/linux/process.hh
@@ -41,6 +41,7 @@
 #include "arch/x86/linux/linux.hh"
 #include "arch/x86/process.hh"
 #include "sim/process.hh"
+#include "sim/syscall_abi.hh"
 
 struct ProcessParams;
 struct ThreadContext;
@@ -55,6 +56,11 @@ class X86_64LinuxProcess : public X86_64Process
     void syscall(ThreadContext *tc, Fault *fault) override;
     void clone(ThreadContext *old_tc, ThreadContext *new_tc, Process *process,
                RegVal flags) override;
+
+    struct SyscallABI : public GenericSyscallABI64, public X86Linux::SyscallABI
+    {
+        static const std::vector<IntRegIndex> ArgumentRegs;
+    };
 };
 
 class I386LinuxProcess : public I386Process
@@ -65,7 +71,36 @@ class I386LinuxProcess : public I386Process
     void syscall(ThreadContext *tc, Fault *fault) override;
     void clone(ThreadContext *old_tc, ThreadContext *new_tc, Process *process,
                RegVal flags) override;
+
+    struct SyscallABI : public GenericSyscallABI32, public X86Linux::SyscallABI
+    {
+        static const std::vector<IntRegIndex> ArgumentRegs;
+    };
 };
 
 } // namespace X86ISA
+
+namespace GuestABI
+{
+
+template <typename Arg>
+struct Argument<X86ISA::I386LinuxProcess::SyscallABI, Arg,
+    typename std::enable_if<
+        X86ISA::I386LinuxProcess::SyscallABI::IsWide<Arg>::value>::type>
+{
+    using ABI = X86ISA::I386LinuxProcess::SyscallABI;
+
+    static Arg
+    get(ThreadContext *tc, typename ABI::Position &position)
+    {
+        panic_if(position + 1 >= ABI::ArgumentRegs.size(),
+                "Ran out of syscall argument registers.");
+        auto low = ABI::ArgumentRegs[position++];
+        auto high = ABI::ArgumentRegs[position++];
+        return (Arg)ABI::mergeRegs(tc, low, high);
+    }
+};
+
+} // namespace GuestABI
+
 #endif // __X86_LINUX_PROCESS_HH__
-- 
2.30.2