sim-se: Refactor clone to avoid most ifdefs

Some parts of clone are architecture dependent. In some cases, we are
able to use architecture-specific helper functions or register
aliases. However, there is still some architecture-specific that is
protected by ifdefs in the common clone implementation.

Move these architecture-specific bits to the architecture-specific OS
class instead to avoid these ifdefs and make the code a bit more
readable.

Change-Id: Ia0903d738d0ba890863bddfa77e3b717db7f45de
Signed-off-by: Andreas Sandberg <andreas.sandberg@arm.com>
Cc: Giacomo Travaglini <giacomo.travaglini@arm.com>
Cc: Javier Setoain <javier.setoain@arm.com>
Cc: Brandon Potter <Brandon.Potter@amd.com>
Reviewed-on: https://gem5-review.googlesource.com/c/15435
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>
Maintainer: Brandon Potter <Brandon.Potter@amd.com>

src/arch/riscv/linux/linux.hh

@@ -31,6 +31,7 @@
 #ifndef __ARCH_RISCV_LINUX_LINUX_HH__
 #define __ARCH_RISCV_LINUX_LINUX_HH__
 
+#include "arch/riscv/utility.hh"
 #include "kern/linux/linux.hh"
 
 class RiscvLinux : public Linux
@@ -187,6 +188,17 @@ class RiscvLinux : public Linux
         uint64_t freehigh;
         uint32_t mem_unit;
     } tgt_sysinfo;
+
+    static void
+    archClone(uint64_t flags,
+              Process *pp, Process *cp,
+              ThreadContext *ptc, ThreadContext *ctc,
+              uint64_t stack, uint64_t tls)
+    {
+        RiscvISA::copyRegs(ptc, ctc);
+        if (stack)
+            ctc->setIntReg(RiscvISA::StackPointerReg, stack);
+    }
 };
 
 #endif