v4.19.13 snapshot.
diff --git a/arch/riscv/kernel/process.c b/arch/riscv/kernel/process.c
new file mode 100644
index 0000000..d7c6ca7
--- /dev/null
+++ b/arch/riscv/kernel/process.c
@@ -0,0 +1,129 @@
+/*
+ * Copyright (C) 2009 Sunplus Core Technology Co., Ltd.
+ * Chen Liqin <liqin.chen@sunplusct.com>
+ * Lennox Wu <lennox.wu@sunplusct.com>
+ * Copyright (C) 2012 Regents of the University of California
+ * Copyright (C) 2017 SiFive
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see the file COPYING, or write
+ * to the Free Software Foundation, Inc.,
+ */
+
+#include <linux/kernel.h>
+#include <linux/sched.h>
+#include <linux/sched/task_stack.h>
+#include <linux/tick.h>
+#include <linux/ptrace.h>
+#include <linux/uaccess.h>
+
+#include <asm/unistd.h>
+#include <asm/processor.h>
+#include <asm/csr.h>
+#include <asm/string.h>
+#include <asm/switch_to.h>
+
+extern asmlinkage void ret_from_fork(void);
+extern asmlinkage void ret_from_kernel_thread(void);
+
+void arch_cpu_idle(void)
+{
+ wait_for_interrupt();
+ local_irq_enable();
+}
+
+void show_regs(struct pt_regs *regs)
+{
+ show_regs_print_info(KERN_DEFAULT);
+
+ pr_cont("sepc: " REG_FMT " ra : " REG_FMT " sp : " REG_FMT "\n",
+ regs->sepc, regs->ra, regs->sp);
+ pr_cont(" gp : " REG_FMT " tp : " REG_FMT " t0 : " REG_FMT "\n",
+ regs->gp, regs->tp, regs->t0);
+ pr_cont(" t1 : " REG_FMT " t2 : " REG_FMT " s0 : " REG_FMT "\n",
+ regs->t1, regs->t2, regs->s0);
+ pr_cont(" s1 : " REG_FMT " a0 : " REG_FMT " a1 : " REG_FMT "\n",
+ regs->s1, regs->a0, regs->a1);
+ pr_cont(" a2 : " REG_FMT " a3 : " REG_FMT " a4 : " REG_FMT "\n",
+ regs->a2, regs->a3, regs->a4);
+ pr_cont(" a5 : " REG_FMT " a6 : " REG_FMT " a7 : " REG_FMT "\n",
+ regs->a5, regs->a6, regs->a7);
+ pr_cont(" s2 : " REG_FMT " s3 : " REG_FMT " s4 : " REG_FMT "\n",
+ regs->s2, regs->s3, regs->s4);
+ pr_cont(" s5 : " REG_FMT " s6 : " REG_FMT " s7 : " REG_FMT "\n",
+ regs->s5, regs->s6, regs->s7);
+ pr_cont(" s8 : " REG_FMT " s9 : " REG_FMT " s10: " REG_FMT "\n",
+ regs->s8, regs->s9, regs->s10);
+ pr_cont(" s11: " REG_FMT " t3 : " REG_FMT " t4 : " REG_FMT "\n",
+ regs->s11, regs->t3, regs->t4);
+ pr_cont(" t5 : " REG_FMT " t6 : " REG_FMT "\n",
+ regs->t5, regs->t6);
+
+ pr_cont("sstatus: " REG_FMT " sbadaddr: " REG_FMT " scause: " REG_FMT "\n",
+ regs->sstatus, regs->sbadaddr, regs->scause);
+}
+
+void start_thread(struct pt_regs *regs, unsigned long pc,
+ unsigned long sp)
+{
+ regs->sstatus = SR_SPIE /* User mode, irqs on */ | SR_FS_INITIAL;
+ regs->sepc = pc;
+ regs->sp = sp;
+ set_fs(USER_DS);
+}
+
+void flush_thread(void)
+{
+ /*
+ * Reset FPU context
+ * frm: round to nearest, ties to even (IEEE default)
+ * fflags: accrued exceptions cleared
+ */
+ memset(¤t->thread.fstate, 0, sizeof(current->thread.fstate));
+}
+
+int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src)
+{
+ fstate_save(src, task_pt_regs(src));
+ *dst = *src;
+ return 0;
+}
+
+int copy_thread(unsigned long clone_flags, unsigned long usp,
+ unsigned long arg, struct task_struct *p)
+{
+ struct pt_regs *childregs = task_pt_regs(p);
+
+ /* p->thread holds context to be restored by __switch_to() */
+ if (unlikely(p->flags & PF_KTHREAD)) {
+ /* Kernel thread */
+ const register unsigned long gp __asm__ ("gp");
+ memset(childregs, 0, sizeof(struct pt_regs));
+ childregs->gp = gp;
+ childregs->sstatus = SR_SPP | SR_SPIE; /* Supervisor, irqs on */
+
+ p->thread.ra = (unsigned long)ret_from_kernel_thread;
+ p->thread.s[0] = usp; /* fn */
+ p->thread.s[1] = arg;
+ } else {
+ *childregs = *(current_pt_regs());
+ if (usp) /* User fork */
+ childregs->sp = usp;
+ if (clone_flags & CLONE_SETTLS)
+ childregs->tp = childregs->a5;
+ childregs->a0 = 0; /* Return value of fork() */
+ p->thread.ra = (unsigned long)ret_from_fork;
+ }
+ p->thread.sp = (unsigned long)childregs; /* kernel sp */
+ return 0;
+}