arch,sim-se: Handle syscall retry/suppression in the syscall desc.

Rather than make each ISA include boilerplate to ignore a
SyscallReturn's value when it's marked as suppressed or needing a retry,
put that code into the SyscallDesc::doSyscall method instead.

That has two benefits. First, it removes a decent amount of code
duplication which is nice from a maintenance perspective. Second, it
puts the SyscallDesc in charge of figuring out what to do once a system
call implementation finishes. That will let it schedule a retry of the
system call for instance, without worrying about what the ISA is doing
with the SyscallReturn behind its back.

Jira Issue: https://gem5.atlassian.net/browse/GEM5-1123

Change-Id: I3732a98c8e0d0b2b94d61313960aa0782c0b971f
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/54023
Maintainer: Gabe Black <gabe.black@gmail.com>
Tested-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: Giacomo Travaglini <giacomo.travaglini@arm.com>

src/arch/arm/freebsd/se_workload.hh

@@ -82,9 +82,6 @@ struct Result<ABI, SyscallReturn,
     static void
     store(ThreadContext *tc, const SyscallReturn &ret)
     {
-        if (ret.suppressed() || ret.needsRetry())
-            return;
-
         RegVal val;
         if (ret.successful()) {
             tc->setCCReg(ArmISA::CCREG_C, 0);

src/arch/arm/linux/se_workload.hh

@@ -74,9 +74,6 @@ struct Result<ABI, SyscallReturn,
     static void
     store(ThreadContext *tc, const SyscallReturn &ret)
     {
-        if (ret.suppressed() || ret.needsRetry())
-            return;
-
         tc->setIntReg(ArmISA::ReturnValueReg, ret.encodedValue());
         if (ret.count() > 1)
             tc->setIntReg(ArmISA::SyscallPseudoReturnReg, ret.value2());

src/arch/mips/se_workload.hh

@@ -77,9 +77,6 @@ struct Result<MipsISA::SEWorkload::SyscallABI, SyscallReturn>
     static void
     store(ThreadContext *tc, const SyscallReturn &ret)
     {
-        if (ret.suppressed() || ret.needsRetry())
-            return;
-
         if (ret.successful()) {
             // no error
             tc->setIntReg(MipsISA::SyscallSuccessReg, 0);

src/arch/power/se_workload.hh

@@ -77,9 +77,6 @@ struct Result<PowerISA::SEWorkload::SyscallABI, SyscallReturn>
     static void
     store(ThreadContext *tc, const SyscallReturn &ret)
     {
-        if (ret.suppressed() || ret.needsRetry())
-            return;
-
         PowerISA::Cr cr = tc->readIntReg(PowerISA::INTREG_CR);
         if (ret.successful()) {
             cr.cr0.so = 0;

src/arch/riscv/se_workload.hh

@@ -75,9 +75,6 @@ struct Result<RiscvISA::SEWorkload::SyscallABI, SyscallReturn>
     static void
     store(ThreadContext *tc, const SyscallReturn &ret)
     {
-        if (ret.suppressed() || ret.needsRetry())
-            return;
-
         if (ret.successful()) {
             // no error
             tc->setIntReg(RiscvISA::ReturnValueReg, ret.returnValue());

src/arch/sparc/se_workload.hh

@@ -89,9 +89,6 @@ struct Result<ABI, SyscallReturn,
     static void
     store(ThreadContext *tc, const SyscallReturn &ret)
     {
-        if (ret.suppressed() || ret.needsRetry())
-            return;
-
         // check for error condition.  SPARC syscall convention is to
         // indicate success/failure in reg the carry bit of the ccr
         // and put the return value itself in the standard return value reg.

src/arch/x86/linux/linux.hh

@@ -86,9 +86,6 @@ struct Result<ABI, SyscallReturn,
     static void
     store(ThreadContext *tc, const SyscallReturn &ret)
     {
-        if (ret.suppressed() || ret.needsRetry())
-            return;
-
         tc->setIntReg(X86ISA::INTREG_RAX, ret.encodedValue());
     }
 };

src/sim/syscall_desc.cc

@@ -44,12 +44,14 @@ SyscallDesc::doSyscall(ThreadContext *tc)
 
     SyscallReturn retval = executor(this, tc);
 
-    if (retval.needsRetry())
+    if (retval.needsRetry()) {
         DPRINTF_SYSCALL(Base, "Needs retry.\n", name());
-    else if (retval.suppressed())
+    } else if (retval.suppressed()) {
         DPRINTF_SYSCALL(Base, "No return value.\n", name());
-    else
+    } else {
+        returnInto(tc, retval);
         DPRINTF_SYSCALL(Base, "Returned %d.\n", retval.encodedValue());
+    }
 }
 
 } // namespace gem5

src/sim/syscall_desc.hh

@@ -141,7 +141,7 @@ class SyscallDescABI : public SyscallDesc
 
             // Use invokeSimcall to gather the other arguments based on the
             // given ABI and pass them to the syscall implementation.
-            return invokeSimcall<ABI, SyscallReturn, Args...>(tc,
+            return invokeSimcall<ABI, false, SyscallReturn, Args...>(tc,
                     std::function<SyscallReturn(ThreadContext *, Args...)>(
                         partial));
         };