arch-riscv,sim: Support clone syscall in RISC-V

(1) This patch sets a correct order of clone syscall's arguments for
RISC-V. Linux kernel 4.15 uses CLONE_BACKWARDS flag by default for
RISC-V. The flag in the Linux kernel defines the list of clone syscall's
arguments in the following order:

  clone_flags   (flags)
  newsp         (newStack)
  parent_tidptr (ptidPtr)
  tls           (tlsPtr)
  child_tidptr  (ctidPtr)

Code reference:
  https://github.com/riscv/riscv-linux/blob/master/kernel/fork.c
  https://github.com/riscv/riscv-linux/blob/master/arch/riscv/Kconfig

(2) This patch copies a parent thread's register values to its child
thread in clone syscall.

Change-Id: I2eb1c8e80990861080ce7153503ed784fb2c7bdf
Reviewed-on: https://gem5-review.googlesource.com/6904
Maintainer: Brandon Potter <Brandon.Potter@amd.com>
Reviewed-by: Alec Roelke <ar4jc@virginia.edu>

diff --git a/src/sim/syscall_emul.hh b/src/sim/syscall_emul.hh
index 2ffd6d6ae1c21307142b1bdc1b426bb9f437f63f..ef61299a03bb5f3c5b2db6d9da0fd770ff0b8ad9 100644 (file)
--- a/src/sim/syscall_emul.hh
+++ b/src/sim/syscall_emul.hh
@@ -1241,11 +1241,23 @@ SyscallReturn
 cloneFunc(SyscallDesc *desc, int callnum, Process *p, ThreadContext *tc)
 {
     int index = 0;
+
     TheISA::IntReg flags = p->getSyscallArg(tc, index);
     TheISA::IntReg newStack = p->getSyscallArg(tc, index);
     Addr ptidPtr = p->getSyscallArg(tc, index);
+
+#if THE_ISA == RISCV_ISA
+    /**
+     * Linux kernel 4.15 sets CLONE_BACKWARDS flag for RISC-V.
+     * The flag defines the list of clone() arguments in the following
+     * order: flags -> newStack -> ptidPtr -> tlsPtr -> ctidPtr
+     */
+    Addr tlsPtr M5_VAR_USED = p->getSyscallArg(tc, index);
+    Addr ctidPtr = p->getSyscallArg(tc, index);
+#else
     Addr ctidPtr = p->getSyscallArg(tc, index);
     Addr tlsPtr M5_VAR_USED = p->getSyscallArg(tc, index);
+#endif
 
     if (((flags & OS::TGT_CLONE_SIGHAND)&& !(flags & OS::TGT_CLONE_VM)) ||
         ((flags & OS::TGT_CLONE_THREAD) && !(flags & OS::TGT_CLONE_SIGHAND)) ||
@@ -1340,7 +1352,7 @@ cloneFunc(SyscallDesc *desc, int callnum, Process *p, ThreadContext *tc)
     ctc->setMiscReg(TheISA::MISCREG_ASI, TheISA::ASI_PRIMARY);
     for (int y = 8; y < 32; y++)
         ctc->setIntReg(y, tc->readIntReg(y));
-#elif THE_ISA == ARM_ISA or THE_ISA == X86_ISA
+#elif THE_ISA == ARM_ISA or THE_ISA == X86_ISA or THE_ISA == RISCV_ISA
     TheISA::copyRegs(tc, ctc);
 #endif