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    Subject[PATCH 13/17] RISC-V: Task implementation
    Date
    From
    This patch contains the implementation of tasks on RISC-V, most of which
    is involved in task switching.

    Signed-off-by: Palmer Dabbelt <palmer@dabbelt.com>
    ---
    arch/riscv/include/asm/asm-offsets.h | 1 +
    arch/riscv/include/asm/current.h | 45 ++++
    arch/riscv/include/asm/kprobes.h | 22 ++
    arch/riscv/include/asm/processor.h | 97 ++++++++
    arch/riscv/include/asm/switch_to.h | 69 ++++++
    arch/riscv/include/asm/thread_info.h | 93 +++++++
    arch/riscv/kernel/asm-offsets.c | 322 ++++++++++++++++++++++++
    arch/riscv/kernel/entry.S | 457 +++++++++++++++++++++++++++++++++++
    arch/riscv/kernel/process.c | 129 ++++++++++
    9 files changed, 1235 insertions(+)
    create mode 100644 arch/riscv/include/asm/asm-offsets.h
    create mode 100644 arch/riscv/include/asm/current.h
    create mode 100644 arch/riscv/include/asm/kprobes.h
    create mode 100644 arch/riscv/include/asm/processor.h
    create mode 100644 arch/riscv/include/asm/switch_to.h
    create mode 100644 arch/riscv/include/asm/thread_info.h
    create mode 100644 arch/riscv/kernel/asm-offsets.c
    create mode 100644 arch/riscv/kernel/entry.S
    create mode 100644 arch/riscv/kernel/process.c

    diff --git a/arch/riscv/include/asm/asm-offsets.h b/arch/riscv/include/asm/asm-offsets.h
    new file mode 100644
    index 000000000000..d370ee36a182
    --- /dev/null
    +++ b/arch/riscv/include/asm/asm-offsets.h
    @@ -0,0 +1 @@
    +#include <generated/asm-offsets.h>
    diff --git a/arch/riscv/include/asm/current.h b/arch/riscv/include/asm/current.h
    new file mode 100644
    index 000000000000..2cf6336ef600
    --- /dev/null
    +++ b/arch/riscv/include/asm/current.h
    @@ -0,0 +1,45 @@
    +/*
    + * Based on arm/arm64/include/asm/current.h
    + *
    + * Copyright (C) 2016 ARM
    + * 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, version 2.
    + *
    + * 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.
    + */
    +
    +
    +#ifndef __ASM_CURRENT_H
    +#define __ASM_CURRENT_H
    +
    +#include <linux/bug.h>
    +#include <linux/compiler.h>
    +
    +#ifndef __ASSEMBLY__
    +
    +struct task_struct;
    +
    +/*
    + * This only works because "struct thread_info" is at offset 0 from "struct
    + * task_struct". This constraint seems to be necessary on other architectures
    + * as well, but __switch_to enforces it. We can't check TASK_TI here because
    + * <asm/asm-offsets.h> includes this, and I can't get the definition of "struct
    + * task_struct" here due to some header ordering problems.
    + */
    +static __always_inline struct task_struct *get_current(void)
    +{
    + register struct task_struct *tp __asm__("tp");
    + return tp;
    +}
    +
    +#define current get_current()
    +
    +#endif /* __ASSEMBLY__ */
    +
    +#endif /* __ASM_CURRENT_H */
    diff --git a/arch/riscv/include/asm/kprobes.h b/arch/riscv/include/asm/kprobes.h
    new file mode 100644
    index 000000000000..c7eb010d1528
    --- /dev/null
    +++ b/arch/riscv/include/asm/kprobes.h
    @@ -0,0 +1,22 @@
    +/*
    + * Copied from arch/arm64/include/asm/kprobes.h
    + *
    + * Copyright (C) 2013 Linaro Limited
    + * 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 version 2 as
    + * published by the Free Software Foundation.
    + *
    + * 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.
    + */
    +
    +#ifndef _RISCV_KPROBES_H
    +#define _RISCV_KPROBES_H
    +
    +#include <asm-generic/kprobes.h>
    +
    +#endif /* _RISCV_KPROBES_H */
    diff --git a/arch/riscv/include/asm/processor.h b/arch/riscv/include/asm/processor.h
    new file mode 100644
    index 000000000000..3fe4af8147d2
    --- /dev/null
    +++ b/arch/riscv/include/asm/processor.h
    @@ -0,0 +1,97 @@
    +/*
    + * Copyright (C) 2012 Regents of the University of California
    + *
    + * 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, version 2.
    + *
    + * 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.
    + */
    +
    +#ifndef _ASM_RISCV_PROCESSOR_H
    +#define _ASM_RISCV_PROCESSOR_H
    +
    +#include <linux/const.h>
    +
    +#include <asm/ptrace.h>
    +
    +/*
    + * This decides where the kernel will search for a free chunk of vm
    + * space during mmap's.
    + */
    +#define TASK_UNMAPPED_BASE PAGE_ALIGN(TASK_SIZE >> 1)
    +
    +#define STACK_TOP TASK_SIZE
    +#define STACK_TOP_MAX STACK_TOP
    +#define STACK_ALIGN 16
    +
    +#ifndef __ASSEMBLY__
    +
    +struct task_struct;
    +struct pt_regs;
    +
    +/*
    + * Default implementation of macro that returns current
    + * instruction pointer ("program counter").
    + */
    +#define current_text_addr() ({ __label__ _l; _l: &&_l; })
    +
    +/* CPU-specific state of a task */
    +struct thread_struct {
    + /* Callee-saved registers */
    + unsigned long ra;
    + unsigned long sp; /* Kernel mode stack */
    + unsigned long s[12]; /* s[0]: frame pointer */
    + struct __riscv_d_ext_state fstate;
    +};
    +
    +#define INIT_THREAD { \
    + .sp = sizeof(init_stack) + (long)&init_stack, \
    +}
    +
    +#define task_pt_regs(tsk) \
    + ((struct pt_regs *)(task_stack_page(tsk) + THREAD_SIZE \
    + - ALIGN(sizeof(struct pt_regs), STACK_ALIGN)))
    +
    +#define KSTK_EIP(tsk) (task_pt_regs(tsk)->sepc)
    +#define KSTK_ESP(tsk) (task_pt_regs(tsk)->sp)
    +
    +
    +/* Do necessary setup to start up a newly executed thread. */
    +extern void start_thread(struct pt_regs *regs,
    + unsigned long pc, unsigned long sp);
    +
    +/* Free all resources held by a thread. */
    +static inline void release_thread(struct task_struct *dead_task)
    +{
    +}
    +
    +extern unsigned long get_wchan(struct task_struct *p);
    +
    +
    +static inline void cpu_relax(void)
    +{
    +#ifdef __riscv_muldiv
    + int dummy;
    + /* In lieu of a halt instruction, induce a long-latency stall. */
    + __asm__ __volatile__ ("div %0, %0, zero" : "=r" (dummy));
    +#endif
    + barrier();
    +}
    +
    +static inline void wait_for_interrupt(void)
    +{
    + __asm__ __volatile__ ("wfi");
    +}
    +
    +struct device_node;
    +extern int riscv_of_processor_hart(struct device_node *node);
    +
    +extern void riscv_fill_hwcap(void);
    +
    +#endif /* __ASSEMBLY__ */
    +
    +#endif /* _ASM_RISCV_PROCESSOR_H */
    diff --git a/arch/riscv/include/asm/switch_to.h b/arch/riscv/include/asm/switch_to.h
    new file mode 100644
    index 000000000000..dd6b05bff75b
    --- /dev/null
    +++ b/arch/riscv/include/asm/switch_to.h
    @@ -0,0 +1,69 @@
    +/*
    + * Copyright (C) 2012 Regents of the University of California
    + *
    + * 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, version 2.
    + *
    + * 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.
    + */
    +
    +#ifndef _ASM_RISCV_SWITCH_TO_H
    +#define _ASM_RISCV_SWITCH_TO_H
    +
    +#include <asm/processor.h>
    +#include <asm/ptrace.h>
    +#include <asm/csr.h>
    +
    +extern void __fstate_save(struct task_struct *save_to);
    +extern void __fstate_restore(struct task_struct *restore_from);
    +
    +static inline void __fstate_clean(struct pt_regs *regs)
    +{
    + regs->sstatus |= (regs->sstatus & ~(SR_FS)) | SR_FS_CLEAN;
    +}
    +
    +static inline void fstate_save(struct task_struct *task,
    + struct pt_regs *regs)
    +{
    + if ((regs->sstatus & SR_FS) == SR_FS_DIRTY) {
    + __fstate_save(task);
    + __fstate_clean(regs);
    + }
    +}
    +
    +static inline void fstate_restore(struct task_struct *task,
    + struct pt_regs *regs)
    +{
    + if ((regs->sstatus & SR_FS) != SR_FS_OFF) {
    + __fstate_restore(task);
    + __fstate_clean(regs);
    + }
    +}
    +
    +static inline void __switch_to_aux(struct task_struct *prev,
    + struct task_struct *next)
    +{
    + struct pt_regs *regs;
    +
    + regs = task_pt_regs(prev);
    + if (unlikely(regs->sstatus & SR_SD))
    + fstate_save(prev, regs);
    + fstate_restore(next, task_pt_regs(next));
    +}
    +
    +extern struct task_struct *__switch_to(struct task_struct *,
    + struct task_struct *);
    +
    +#define switch_to(prev, next, last) \
    +do { \
    + struct task_struct *__prev = (prev); \
    + struct task_struct *__next = (next); \
    + __switch_to_aux(__prev, __next); \
    + ((last) = __switch_to(__prev, __next)); \
    +} while (0)
    +
    +#endif /* _ASM_RISCV_SWITCH_TO_H */
    diff --git a/arch/riscv/include/asm/thread_info.h b/arch/riscv/include/asm/thread_info.h
    new file mode 100644
    index 000000000000..ad13bea17b5d
    --- /dev/null
    +++ b/arch/riscv/include/asm/thread_info.h
    @@ -0,0 +1,93 @@
    +/*
    + * Copyright (C) 2009 Chen Liqin <liqin.chen@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, version 2.
    + *
    + * 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.
    + */
    +
    +#ifndef _ASM_RISCV_THREAD_INFO_H
    +#define _ASM_RISCV_THREAD_INFO_H
    +
    +#include <asm/page.h>
    +#include <linux/const.h>
    +
    +/* thread information allocation */
    +#define THREAD_SIZE_ORDER (1)
    +#define THREAD_SIZE (PAGE_SIZE << THREAD_SIZE_ORDER)
    +
    +#ifndef __ASSEMBLY__
    +
    +#include <asm/processor.h>
    +#include <asm/csr.h>
    +
    +typedef unsigned long mm_segment_t;
    +
    +/*
    + * low level task data that entry.S needs immediate access to
    + * - this struct should fit entirely inside of one cache line
    + * - if the members of this struct changes, the assembly constants
    + * in asm-offsets.c must be updated accordingly
    + * - thread_info is included in task_struct at an offset of 0. This means that
    + * tp points to both thread_info and task_struct.
    + */
    +struct thread_info {
    + unsigned long flags; /* low level flags */
    + int preempt_count; /* 0=>preemptible, <0=>BUG */
    + mm_segment_t addr_limit;
    + /*
    + * These stack pointers are overwritten on every system call or
    + * exception. SP is also saved to the stack it can be recovered when
    + * overwritten.
    + */
    + long kernel_sp; /* Kernel stack pointer */
    + long user_sp; /* User stack pointer */
    +};
    +
    +/*
    + * macros/functions for gaining access to the thread information structure
    + *
    + * preempt_count needs to be 1 initially, until the scheduler is functional.
    + */
    +#define INIT_THREAD_INFO(tsk) \
    +{ \
    + .flags = 0, \
    + .preempt_count = INIT_PREEMPT_COUNT, \
    + .addr_limit = KERNEL_DS, \
    +}
    +
    +#define init_stack (init_thread_union.stack)
    +
    +#endif /* !__ASSEMBLY__ */
    +
    +/*
    + * thread information flags
    + * - these are process state flags that various assembly files may need to
    + * access
    + * - pending work-to-be-done flags are in lowest half-word
    + * - other flags in upper half-word(s)
    + */
    +#define TIF_SYSCALL_TRACE 0 /* syscall trace active */
    +#define TIF_NOTIFY_RESUME 1 /* callback before returning to user */
    +#define TIF_SIGPENDING 2 /* signal pending */
    +#define TIF_NEED_RESCHED 3 /* rescheduling necessary */
    +#define TIF_RESTORE_SIGMASK 4 /* restore signal mask in do_signal() */
    +#define TIF_MEMDIE 5 /* is terminating due to OOM killer */
    +#define TIF_SYSCALL_TRACEPOINT 6 /* syscall tracepoint instrumentation */
    +
    +#define _TIF_SYSCALL_TRACE (1 << TIF_SYSCALL_TRACE)
    +#define _TIF_NOTIFY_RESUME (1 << TIF_NOTIFY_RESUME)
    +#define _TIF_SIGPENDING (1 << TIF_SIGPENDING)
    +#define _TIF_NEED_RESCHED (1 << TIF_NEED_RESCHED)
    +
    +#define _TIF_WORK_MASK \
    + (_TIF_NOTIFY_RESUME | _TIF_SIGPENDING | _TIF_NEED_RESCHED)
    +
    +#endif /* _ASM_RISCV_THREAD_INFO_H */
    diff --git a/arch/riscv/kernel/asm-offsets.c b/arch/riscv/kernel/asm-offsets.c
    new file mode 100644
    index 000000000000..33ed16137a23
    --- /dev/null
    +++ b/arch/riscv/kernel/asm-offsets.c
    @@ -0,0 +1,322 @@
    +/*
    + * 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, version 2.
    + *
    + * 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.
    + */
    +
    +#define GENERATING_ASM_OFFSETS
    +
    +#include <linux/kbuild.h>
    +#include <linux/sched.h>
    +#include <asm/thread_info.h>
    +#include <asm/ptrace.h>
    +
    +void asm_offsets(void)
    +{
    + OFFSET(TASK_THREAD_RA, task_struct, thread.ra);
    + OFFSET(TASK_THREAD_SP, task_struct, thread.sp);
    + OFFSET(TASK_THREAD_S0, task_struct, thread.s[0]);
    + OFFSET(TASK_THREAD_S1, task_struct, thread.s[1]);
    + OFFSET(TASK_THREAD_S2, task_struct, thread.s[2]);
    + OFFSET(TASK_THREAD_S3, task_struct, thread.s[3]);
    + OFFSET(TASK_THREAD_S4, task_struct, thread.s[4]);
    + OFFSET(TASK_THREAD_S5, task_struct, thread.s[5]);
    + OFFSET(TASK_THREAD_S6, task_struct, thread.s[6]);
    + OFFSET(TASK_THREAD_S7, task_struct, thread.s[7]);
    + OFFSET(TASK_THREAD_S8, task_struct, thread.s[8]);
    + OFFSET(TASK_THREAD_S9, task_struct, thread.s[9]);
    + OFFSET(TASK_THREAD_S10, task_struct, thread.s[10]);
    + OFFSET(TASK_THREAD_S11, task_struct, thread.s[11]);
    + OFFSET(TASK_THREAD_SP, task_struct, thread.sp);
    + OFFSET(TASK_STACK, task_struct, stack);
    + OFFSET(TASK_TI, task_struct, thread_info);
    + OFFSET(TASK_TI_FLAGS, task_struct, thread_info.flags);
    + OFFSET(TASK_TI_KERNEL_SP, task_struct, thread_info.kernel_sp);
    + OFFSET(TASK_TI_USER_SP, task_struct, thread_info.user_sp);
    +
    + OFFSET(TASK_THREAD_F0, task_struct, thread.fstate.f[0]);
    + OFFSET(TASK_THREAD_F1, task_struct, thread.fstate.f[1]);
    + OFFSET(TASK_THREAD_F2, task_struct, thread.fstate.f[2]);
    + OFFSET(TASK_THREAD_F3, task_struct, thread.fstate.f[3]);
    + OFFSET(TASK_THREAD_F4, task_struct, thread.fstate.f[4]);
    + OFFSET(TASK_THREAD_F5, task_struct, thread.fstate.f[5]);
    + OFFSET(TASK_THREAD_F6, task_struct, thread.fstate.f[6]);
    + OFFSET(TASK_THREAD_F7, task_struct, thread.fstate.f[7]);
    + OFFSET(TASK_THREAD_F8, task_struct, thread.fstate.f[8]);
    + OFFSET(TASK_THREAD_F9, task_struct, thread.fstate.f[9]);
    + OFFSET(TASK_THREAD_F10, task_struct, thread.fstate.f[10]);
    + OFFSET(TASK_THREAD_F11, task_struct, thread.fstate.f[11]);
    + OFFSET(TASK_THREAD_F12, task_struct, thread.fstate.f[12]);
    + OFFSET(TASK_THREAD_F13, task_struct, thread.fstate.f[13]);
    + OFFSET(TASK_THREAD_F14, task_struct, thread.fstate.f[14]);
    + OFFSET(TASK_THREAD_F15, task_struct, thread.fstate.f[15]);
    + OFFSET(TASK_THREAD_F16, task_struct, thread.fstate.f[16]);
    + OFFSET(TASK_THREAD_F17, task_struct, thread.fstate.f[17]);
    + OFFSET(TASK_THREAD_F18, task_struct, thread.fstate.f[18]);
    + OFFSET(TASK_THREAD_F19, task_struct, thread.fstate.f[19]);
    + OFFSET(TASK_THREAD_F20, task_struct, thread.fstate.f[20]);
    + OFFSET(TASK_THREAD_F21, task_struct, thread.fstate.f[21]);
    + OFFSET(TASK_THREAD_F22, task_struct, thread.fstate.f[22]);
    + OFFSET(TASK_THREAD_F23, task_struct, thread.fstate.f[23]);
    + OFFSET(TASK_THREAD_F24, task_struct, thread.fstate.f[24]);
    + OFFSET(TASK_THREAD_F25, task_struct, thread.fstate.f[25]);
    + OFFSET(TASK_THREAD_F26, task_struct, thread.fstate.f[26]);
    + OFFSET(TASK_THREAD_F27, task_struct, thread.fstate.f[27]);
    + OFFSET(TASK_THREAD_F28, task_struct, thread.fstate.f[28]);
    + OFFSET(TASK_THREAD_F29, task_struct, thread.fstate.f[29]);
    + OFFSET(TASK_THREAD_F30, task_struct, thread.fstate.f[30]);
    + OFFSET(TASK_THREAD_F31, task_struct, thread.fstate.f[31]);
    + OFFSET(TASK_THREAD_FCSR, task_struct, thread.fstate.fcsr);
    +
    + DEFINE(PT_SIZE, sizeof(struct pt_regs));
    + OFFSET(PT_SEPC, pt_regs, sepc);
    + OFFSET(PT_RA, pt_regs, ra);
    + OFFSET(PT_FP, pt_regs, s0);
    + OFFSET(PT_S0, pt_regs, s0);
    + OFFSET(PT_S1, pt_regs, s1);
    + OFFSET(PT_S2, pt_regs, s2);
    + OFFSET(PT_S3, pt_regs, s3);
    + OFFSET(PT_S4, pt_regs, s4);
    + OFFSET(PT_S5, pt_regs, s5);
    + OFFSET(PT_S6, pt_regs, s6);
    + OFFSET(PT_S7, pt_regs, s7);
    + OFFSET(PT_S8, pt_regs, s8);
    + OFFSET(PT_S9, pt_regs, s9);
    + OFFSET(PT_S10, pt_regs, s10);
    + OFFSET(PT_S11, pt_regs, s11);
    + OFFSET(PT_SP, pt_regs, sp);
    + OFFSET(PT_TP, pt_regs, tp);
    + OFFSET(PT_A0, pt_regs, a0);
    + OFFSET(PT_A1, pt_regs, a1);
    + OFFSET(PT_A2, pt_regs, a2);
    + OFFSET(PT_A3, pt_regs, a3);
    + OFFSET(PT_A4, pt_regs, a4);
    + OFFSET(PT_A5, pt_regs, a5);
    + OFFSET(PT_A6, pt_regs, a6);
    + OFFSET(PT_A7, pt_regs, a7);
    + OFFSET(PT_T0, pt_regs, t0);
    + OFFSET(PT_T1, pt_regs, t1);
    + OFFSET(PT_T2, pt_regs, t2);
    + OFFSET(PT_T3, pt_regs, t3);
    + OFFSET(PT_T4, pt_regs, t4);
    + OFFSET(PT_T5, pt_regs, t5);
    + OFFSET(PT_T6, pt_regs, t6);
    + OFFSET(PT_GP, pt_regs, gp);
    + OFFSET(PT_SSTATUS, pt_regs, sstatus);
    + OFFSET(PT_SBADADDR, pt_regs, sbadaddr);
    + OFFSET(PT_SCAUSE, pt_regs, scause);
    +
    + /*
    + * THREAD_{F,X}* might be larger than a S-type offset can handle, but
    + * these are used in performance-sensitive assembly so we can't resort
    + * to loading the long immediate every time.
    + */
    + DEFINE(TASK_THREAD_RA_RA,
    + offsetof(struct task_struct, thread.ra)
    + - offsetof(struct task_struct, thread.ra)
    + );
    + DEFINE(TASK_THREAD_SP_RA,
    + offsetof(struct task_struct, thread.sp)
    + - offsetof(struct task_struct, thread.ra)
    + );
    + DEFINE(TASK_THREAD_S0_RA,
    + offsetof(struct task_struct, thread.s[0])
    + - offsetof(struct task_struct, thread.ra)
    + );
    + DEFINE(TASK_THREAD_S1_RA,
    + offsetof(struct task_struct, thread.s[1])
    + - offsetof(struct task_struct, thread.ra)
    + );
    + DEFINE(TASK_THREAD_S2_RA,
    + offsetof(struct task_struct, thread.s[2])
    + - offsetof(struct task_struct, thread.ra)
    + );
    + DEFINE(TASK_THREAD_S3_RA,
    + offsetof(struct task_struct, thread.s[3])
    + - offsetof(struct task_struct, thread.ra)
    + );
    + DEFINE(TASK_THREAD_S4_RA,
    + offsetof(struct task_struct, thread.s[4])
    + - offsetof(struct task_struct, thread.ra)
    + );
    + DEFINE(TASK_THREAD_S5_RA,
    + offsetof(struct task_struct, thread.s[5])
    + - offsetof(struct task_struct, thread.ra)
    + );
    + DEFINE(TASK_THREAD_S6_RA,
    + offsetof(struct task_struct, thread.s[6])
    + - offsetof(struct task_struct, thread.ra)
    + );
    + DEFINE(TASK_THREAD_S7_RA,
    + offsetof(struct task_struct, thread.s[7])
    + - offsetof(struct task_struct, thread.ra)
    + );
    + DEFINE(TASK_THREAD_S8_RA,
    + offsetof(struct task_struct, thread.s[8])
    + - offsetof(struct task_struct, thread.ra)
    + );
    + DEFINE(TASK_THREAD_S9_RA,
    + offsetof(struct task_struct, thread.s[9])
    + - offsetof(struct task_struct, thread.ra)
    + );
    + DEFINE(TASK_THREAD_S10_RA,
    + offsetof(struct task_struct, thread.s[10])
    + - offsetof(struct task_struct, thread.ra)
    + );
    + DEFINE(TASK_THREAD_S11_RA,
    + offsetof(struct task_struct, thread.s[11])
    + - offsetof(struct task_struct, thread.ra)
    + );
    +
    + DEFINE(TASK_THREAD_F0_F0,
    + offsetof(struct task_struct, thread.fstate.f[0])
    + - offsetof(struct task_struct, thread.fstate.f[0])
    + );
    + DEFINE(TASK_THREAD_F1_F0,
    + offsetof(struct task_struct, thread.fstate.f[1])
    + - offsetof(struct task_struct, thread.fstate.f[0])
    + );
    + DEFINE(TASK_THREAD_F2_F0,
    + offsetof(struct task_struct, thread.fstate.f[2])
    + - offsetof(struct task_struct, thread.fstate.f[0])
    + );
    + DEFINE(TASK_THREAD_F3_F0,
    + offsetof(struct task_struct, thread.fstate.f[3])
    + - offsetof(struct task_struct, thread.fstate.f[0])
    + );
    + DEFINE(TASK_THREAD_F4_F0,
    + offsetof(struct task_struct, thread.fstate.f[4])
    + - offsetof(struct task_struct, thread.fstate.f[0])
    + );
    + DEFINE(TASK_THREAD_F5_F0,
    + offsetof(struct task_struct, thread.fstate.f[5])
    + - offsetof(struct task_struct, thread.fstate.f[0])
    + );
    + DEFINE(TASK_THREAD_F6_F0,
    + offsetof(struct task_struct, thread.fstate.f[6])
    + - offsetof(struct task_struct, thread.fstate.f[0])
    + );
    + DEFINE(TASK_THREAD_F7_F0,
    + offsetof(struct task_struct, thread.fstate.f[7])
    + - offsetof(struct task_struct, thread.fstate.f[0])
    + );
    + DEFINE(TASK_THREAD_F8_F0,
    + offsetof(struct task_struct, thread.fstate.f[8])
    + - offsetof(struct task_struct, thread.fstate.f[0])
    + );
    + DEFINE(TASK_THREAD_F9_F0,
    + offsetof(struct task_struct, thread.fstate.f[9])
    + - offsetof(struct task_struct, thread.fstate.f[0])
    + );
    + DEFINE(TASK_THREAD_F10_F0,
    + offsetof(struct task_struct, thread.fstate.f[10])
    + - offsetof(struct task_struct, thread.fstate.f[0])
    + );
    + DEFINE(TASK_THREAD_F11_F0,
    + offsetof(struct task_struct, thread.fstate.f[11])
    + - offsetof(struct task_struct, thread.fstate.f[0])
    + );
    + DEFINE(TASK_THREAD_F12_F0,
    + offsetof(struct task_struct, thread.fstate.f[12])
    + - offsetof(struct task_struct, thread.fstate.f[0])
    + );
    + DEFINE(TASK_THREAD_F13_F0,
    + offsetof(struct task_struct, thread.fstate.f[13])
    + - offsetof(struct task_struct, thread.fstate.f[0])
    + );
    + DEFINE(TASK_THREAD_F14_F0,
    + offsetof(struct task_struct, thread.fstate.f[14])
    + - offsetof(struct task_struct, thread.fstate.f[0])
    + );
    + DEFINE(TASK_THREAD_F15_F0,
    + offsetof(struct task_struct, thread.fstate.f[15])
    + - offsetof(struct task_struct, thread.fstate.f[0])
    + );
    + DEFINE(TASK_THREAD_F16_F0,
    + offsetof(struct task_struct, thread.fstate.f[16])
    + - offsetof(struct task_struct, thread.fstate.f[0])
    + );
    + DEFINE(TASK_THREAD_F17_F0,
    + offsetof(struct task_struct, thread.fstate.f[17])
    + - offsetof(struct task_struct, thread.fstate.f[0])
    + );
    + DEFINE(TASK_THREAD_F18_F0,
    + offsetof(struct task_struct, thread.fstate.f[18])
    + - offsetof(struct task_struct, thread.fstate.f[0])
    + );
    + DEFINE(TASK_THREAD_F19_F0,
    + offsetof(struct task_struct, thread.fstate.f[19])
    + - offsetof(struct task_struct, thread.fstate.f[0])
    + );
    + DEFINE(TASK_THREAD_F20_F0,
    + offsetof(struct task_struct, thread.fstate.f[20])
    + - offsetof(struct task_struct, thread.fstate.f[0])
    + );
    + DEFINE(TASK_THREAD_F21_F0,
    + offsetof(struct task_struct, thread.fstate.f[21])
    + - offsetof(struct task_struct, thread.fstate.f[0])
    + );
    + DEFINE(TASK_THREAD_F22_F0,
    + offsetof(struct task_struct, thread.fstate.f[22])
    + - offsetof(struct task_struct, thread.fstate.f[0])
    + );
    + DEFINE(TASK_THREAD_F23_F0,
    + offsetof(struct task_struct, thread.fstate.f[23])
    + - offsetof(struct task_struct, thread.fstate.f[0])
    + );
    + DEFINE(TASK_THREAD_F24_F0,
    + offsetof(struct task_struct, thread.fstate.f[24])
    + - offsetof(struct task_struct, thread.fstate.f[0])
    + );
    + DEFINE(TASK_THREAD_F25_F0,
    + offsetof(struct task_struct, thread.fstate.f[25])
    + - offsetof(struct task_struct, thread.fstate.f[0])
    + );
    + DEFINE(TASK_THREAD_F26_F0,
    + offsetof(struct task_struct, thread.fstate.f[26])
    + - offsetof(struct task_struct, thread.fstate.f[0])
    + );
    + DEFINE(TASK_THREAD_F27_F0,
    + offsetof(struct task_struct, thread.fstate.f[27])
    + - offsetof(struct task_struct, thread.fstate.f[0])
    + );
    + DEFINE(TASK_THREAD_F28_F0,
    + offsetof(struct task_struct, thread.fstate.f[28])
    + - offsetof(struct task_struct, thread.fstate.f[0])
    + );
    + DEFINE(TASK_THREAD_F29_F0,
    + offsetof(struct task_struct, thread.fstate.f[29])
    + - offsetof(struct task_struct, thread.fstate.f[0])
    + );
    + DEFINE(TASK_THREAD_F30_F0,
    + offsetof(struct task_struct, thread.fstate.f[30])
    + - offsetof(struct task_struct, thread.fstate.f[0])
    + );
    + DEFINE(TASK_THREAD_F31_F0,
    + offsetof(struct task_struct, thread.fstate.f[31])
    + - offsetof(struct task_struct, thread.fstate.f[0])
    + );
    + DEFINE(TASK_THREAD_FCSR_F0,
    + offsetof(struct task_struct, thread.fstate.fcsr)
    + - offsetof(struct task_struct, thread.fstate.f[0])
    + );
    +
    + /* The assembler needs access to THREAD_SIZE as well. */
    + DEFINE(ASM_THREAD_SIZE, THREAD_SIZE);
    +
    + /*
    + * We allocate a pt_regs on the stack when entering the kernel. This
    + * ensures the alignment is sane.
    + */
    + DEFINE(PT_SIZE_ON_STACK, ALIGN(sizeof(struct pt_regs), STACK_ALIGN));
    +
    + OFFSET(TASK_CPU, task_struct, cpu);
    +}
    diff --git a/arch/riscv/kernel/entry.S b/arch/riscv/kernel/entry.S
    new file mode 100644
    index 000000000000..af280d43a7ed
    --- /dev/null
    +++ b/arch/riscv/kernel/entry.S
    @@ -0,0 +1,457 @@
    +/*
    + * 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, version 2.
    + *
    + * 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.
    + */
    +
    +#include <linux/init.h>
    +#include <linux/linkage.h>
    +
    +#include <asm/asm.h>
    +#include <asm/csr.h>
    +#include <asm/unistd.h>
    +#include <asm/thread_info.h>
    +#include <asm/asm-offsets.h>
    +
    + .text
    + .altmacro
    +
    +/*
    + * Prepares to enter a system call or exception by saving all registers to the
    + * stack.
    + */
    + .macro SAVE_ALL
    + LOCAL _restore_kernel_tpsp
    + LOCAL _save_context
    +
    + /*
    + * If coming from userspace, preserve the user thread pointer and load
    + * the kernel thread pointer. If we came from the kernel, sscratch
    + * will contain 0, and we should continue on the current TP.
    + */
    + csrrw tp, sscratch, tp
    + bnez tp, _save_context
    +
    +_restore_kernel_tpsp:
    + csrr tp, sscratch
    + REG_S sp, TASK_TI_KERNEL_SP(tp)
    +_save_context:
    + REG_S sp, TASK_TI_USER_SP(tp)
    + REG_L sp, TASK_TI_KERNEL_SP(tp)
    + addi sp, sp, -(PT_SIZE_ON_STACK)
    + REG_S x1, PT_RA(sp)
    + REG_S x3, PT_GP(sp)
    + REG_S x5, PT_T0(sp)
    + REG_S x6, PT_T1(sp)
    + REG_S x7, PT_T2(sp)
    + REG_S x8, PT_S0(sp)
    + REG_S x9, PT_S1(sp)
    + REG_S x10, PT_A0(sp)
    + REG_S x11, PT_A1(sp)
    + REG_S x12, PT_A2(sp)
    + REG_S x13, PT_A3(sp)
    + REG_S x14, PT_A4(sp)
    + REG_S x15, PT_A5(sp)
    + REG_S x16, PT_A6(sp)
    + REG_S x17, PT_A7(sp)
    + REG_S x18, PT_S2(sp)
    + REG_S x19, PT_S3(sp)
    + REG_S x20, PT_S4(sp)
    + REG_S x21, PT_S5(sp)
    + REG_S x22, PT_S6(sp)
    + REG_S x23, PT_S7(sp)
    + REG_S x24, PT_S8(sp)
    + REG_S x25, PT_S9(sp)
    + REG_S x26, PT_S10(sp)
    + REG_S x27, PT_S11(sp)
    + REG_S x28, PT_T3(sp)
    + REG_S x29, PT_T4(sp)
    + REG_S x30, PT_T5(sp)
    + REG_S x31, PT_T6(sp)
    +
    + /*
    + * Disable FPU to detect illegal usage of
    + * floating point in kernel space
    + */
    + li t0, SR_FS
    +
    + REG_L s0, TASK_TI_USER_SP(tp)
    + csrrc s1, sstatus, t0
    + csrr s2, sepc
    + csrr s3, sbadaddr
    + csrr s4, scause
    + csrr s5, sscratch
    + REG_S s0, PT_SP(sp)
    + REG_S s1, PT_SSTATUS(sp)
    + REG_S s2, PT_SEPC(sp)
    + REG_S s3, PT_SBADADDR(sp)
    + REG_S s4, PT_SCAUSE(sp)
    + REG_S s5, PT_TP(sp)
    + .endm
    +
    +/*
    + * Prepares to return from a system call or exception by restoring all
    + * registers from the stack.
    + */
    + .macro RESTORE_ALL
    + REG_L a0, PT_SSTATUS(sp)
    + REG_L a2, PT_SEPC(sp)
    + csrw sstatus, a0
    + csrw sepc, a2
    +
    + REG_L x1, PT_RA(sp)
    + REG_L x3, PT_GP(sp)
    + REG_L x4, PT_TP(sp)
    + REG_L x5, PT_T0(sp)
    + REG_L x6, PT_T1(sp)
    + REG_L x7, PT_T2(sp)
    + REG_L x8, PT_S0(sp)
    + REG_L x9, PT_S1(sp)
    + REG_L x10, PT_A0(sp)
    + REG_L x11, PT_A1(sp)
    + REG_L x12, PT_A2(sp)
    + REG_L x13, PT_A3(sp)
    + REG_L x14, PT_A4(sp)
    + REG_L x15, PT_A5(sp)
    + REG_L x16, PT_A6(sp)
    + REG_L x17, PT_A7(sp)
    + REG_L x18, PT_S2(sp)
    + REG_L x19, PT_S3(sp)
    + REG_L x20, PT_S4(sp)
    + REG_L x21, PT_S5(sp)
    + REG_L x22, PT_S6(sp)
    + REG_L x23, PT_S7(sp)
    + REG_L x24, PT_S8(sp)
    + REG_L x25, PT_S9(sp)
    + REG_L x26, PT_S10(sp)
    + REG_L x27, PT_S11(sp)
    + REG_L x28, PT_T3(sp)
    + REG_L x29, PT_T4(sp)
    + REG_L x30, PT_T5(sp)
    + REG_L x31, PT_T6(sp)
    +
    + REG_L x2, PT_SP(sp)
    + .endm
    +
    +ENTRY(handle_exception)
    + SAVE_ALL
    +
    + /*
    + * Set sscratch register to 0, so that if a recursive exception
    + * occurs, the exception vector knows it came from the kernel
    + */
    + csrw sscratch, x0
    +
    + /* Load the global pointer */
    +.option push
    +.option norelax
    + la gp, __global_pointer$
    +.option pop
    +
    + la ra, ret_from_exception
    + /*
    + * MSB of cause differentiates between
    + * interrupts and exceptions
    + */
    + bge s4, zero, 1f
    +
    + /* Handle interrupts */
    + slli a0, s4, 1
    + srli a0, a0, 1
    + move a1, sp /* pt_regs */
    + tail do_IRQ
    +1:
    + /* Handle syscalls */
    + li t0, EXC_SYSCALL
    + beq s4, t0, handle_syscall
    +
    + /* Handle other exceptions */
    + slli t0, s4, RISCV_LGPTR
    + la t1, excp_vect_table
    + la t2, excp_vect_table_end
    + move a0, sp /* pt_regs */
    + add t0, t1, t0
    + /* Check if exception code lies within bounds */
    + bgeu t0, t2, 1f
    + REG_L t0, 0(t0)
    + jr t0
    +1:
    + tail do_trap_unknown
    +
    +handle_syscall:
    + /*
    + * Advance SEPC to avoid executing the original
    + * scall instruction on sret
    + */
    + addi s2, s2, 0x4
    + REG_S s2, PT_SEPC(sp)
    + /* System calls run with interrupts enabled */
    + csrs sstatus, SR_IE
    + /* Trace syscalls, but only if requested by the user. */
    + REG_L t0, TASK_TI_FLAGS(tp)
    + andi t0, t0, _TIF_SYSCALL_TRACE
    + bnez t0, handle_syscall_trace_enter
    +check_syscall_nr:
    + /* Check to make sure we don't jump to a bogus syscall number. */
    + li t0, __NR_syscalls
    + la s0, sys_ni_syscall
    + /* Syscall number held in a7 */
    + bgeu a7, t0, 1f
    + la s0, sys_call_table
    + slli t0, a7, RISCV_LGPTR
    + add s0, s0, t0
    + REG_L s0, 0(s0)
    +1:
    + jalr s0
    +
    +ret_from_syscall:
    + /* Set user a0 to kernel a0 */
    + REG_S a0, PT_A0(sp)
    + /* Trace syscalls, but only if requested by the user. */
    + REG_L t0, TASK_TI_FLAGS(tp)
    + andi t0, t0, _TIF_SYSCALL_TRACE
    + bnez t0, handle_syscall_trace_exit
    +
    +ret_from_exception:
    + REG_L s0, PT_SSTATUS(sp)
    + csrc sstatus, SR_IE
    + andi s0, s0, SR_PS
    + bnez s0, restore_all
    +
    +resume_userspace:
    + /* Interrupts must be disabled here so flags are checked atomically */
    + REG_L s0, TASK_TI_FLAGS(tp) /* current_thread_info->flags */
    + andi s1, s0, _TIF_WORK_MASK
    + bnez s1, work_pending
    +
    + /* Save unwound kernel stack pointer in thread_info */
    + addi s0, sp, PT_SIZE_ON_STACK
    + REG_S s0, TASK_TI_KERNEL_SP(tp)
    +
    + /*
    + * Save TP into sscratch, so we can find the kernel data structures
    + * again.
    + */
    + csrw sscratch, tp
    +
    +restore_all:
    + RESTORE_ALL
    + sret
    +
    +work_pending:
    + /* Enter slow path for supplementary processing */
    + la ra, ret_from_exception
    + andi s1, s0, _TIF_NEED_RESCHED
    + bnez s1, work_resched
    +work_notifysig:
    + /* Handle pending signals and notify-resume requests */
    + csrs sstatus, SR_IE /* Enable interrupts for do_notify_resume() */
    + move a0, sp /* pt_regs */
    + move a1, s0 /* current_thread_info->flags */
    + tail do_notify_resume
    +work_resched:
    + tail schedule
    +
    +/* Slow paths for ptrace. */
    +handle_syscall_trace_enter:
    + move a0, sp
    + call do_syscall_trace_enter
    + REG_L a0, PT_A0(sp)
    + REG_L a1, PT_A1(sp)
    + REG_L a2, PT_A2(sp)
    + REG_L a3, PT_A3(sp)
    + REG_L a4, PT_A4(sp)
    + REG_L a5, PT_A5(sp)
    + REG_L a6, PT_A6(sp)
    + REG_L a7, PT_A7(sp)
    + j check_syscall_nr
    +handle_syscall_trace_exit:
    + move a0, sp
    + call do_syscall_trace_exit
    + j ret_from_exception
    +
    +END(handle_exception)
    +
    +ENTRY(ret_from_fork)
    + la ra, ret_from_exception
    + tail schedule_tail
    +ENDPROC(ret_from_fork)
    +
    +ENTRY(ret_from_kernel_thread)
    + call schedule_tail
    + /* Call fn(arg) */
    + la ra, ret_from_exception
    + move a0, s1
    + jr s0
    +ENDPROC(ret_from_kernel_thread)
    +
    +
    +/*
    + * Integer register context switch
    + * The callee-saved registers must be saved and restored.
    + *
    + * a0: previous task_struct (must be preserved across the switch)
    + * a1: next task_struct
    + *
    + * The value of a0 and a1 must be preserved by this function, as that's how
    + * arguments are passed to schedule_tail.
    + */
    +ENTRY(__switch_to)
    + /* Save context into prev->thread */
    + li a4, TASK_THREAD_RA
    + add a3, a0, a4
    + add a4, a1, a4
    + REG_S ra, TASK_THREAD_RA_RA(a3)
    + REG_S sp, TASK_THREAD_SP_RA(a3)
    + REG_S s0, TASK_THREAD_S0_RA(a3)
    + REG_S s1, TASK_THREAD_S1_RA(a3)
    + REG_S s2, TASK_THREAD_S2_RA(a3)
    + REG_S s3, TASK_THREAD_S3_RA(a3)
    + REG_S s4, TASK_THREAD_S4_RA(a3)
    + REG_S s5, TASK_THREAD_S5_RA(a3)
    + REG_S s6, TASK_THREAD_S6_RA(a3)
    + REG_S s7, TASK_THREAD_S7_RA(a3)
    + REG_S s8, TASK_THREAD_S8_RA(a3)
    + REG_S s9, TASK_THREAD_S9_RA(a3)
    + REG_S s10, TASK_THREAD_S10_RA(a3)
    + REG_S s11, TASK_THREAD_S11_RA(a3)
    + /* Restore context from next->thread */
    + REG_L ra, TASK_THREAD_RA_RA(a4)
    + REG_L sp, TASK_THREAD_SP_RA(a4)
    + REG_L s0, TASK_THREAD_S0_RA(a4)
    + REG_L s1, TASK_THREAD_S1_RA(a4)
    + REG_L s2, TASK_THREAD_S2_RA(a4)
    + REG_L s3, TASK_THREAD_S3_RA(a4)
    + REG_L s4, TASK_THREAD_S4_RA(a4)
    + REG_L s5, TASK_THREAD_S5_RA(a4)
    + REG_L s6, TASK_THREAD_S6_RA(a4)
    + REG_L s7, TASK_THREAD_S7_RA(a4)
    + REG_L s8, TASK_THREAD_S8_RA(a4)
    + REG_L s9, TASK_THREAD_S9_RA(a4)
    + REG_L s10, TASK_THREAD_S10_RA(a4)
    + REG_L s11, TASK_THREAD_S11_RA(a4)
    +#if TASK_TI != 0
    +#error "TASK_TI != 0: tp will contain a 'struct thread_info', not a 'struct task_struct' so get_current() won't work."
    + addi tp, a1, TASK_TI
    +#else
    + move tp, a1
    +#endif
    + ret
    +ENDPROC(__switch_to)
    +
    +ENTRY(__fstate_save)
    + li a2, TASK_THREAD_F0
    + add a0, a0, a2
    + li t1, SR_FS
    + csrs sstatus, t1
    + frcsr t0
    + fsd f0, TASK_THREAD_F0_F0(a0)
    + fsd f1, TASK_THREAD_F1_F0(a0)
    + fsd f2, TASK_THREAD_F2_F0(a0)
    + fsd f3, TASK_THREAD_F3_F0(a0)
    + fsd f4, TASK_THREAD_F4_F0(a0)
    + fsd f5, TASK_THREAD_F5_F0(a0)
    + fsd f6, TASK_THREAD_F6_F0(a0)
    + fsd f7, TASK_THREAD_F7_F0(a0)
    + fsd f8, TASK_THREAD_F8_F0(a0)
    + fsd f9, TASK_THREAD_F9_F0(a0)
    + fsd f10, TASK_THREAD_F10_F0(a0)
    + fsd f11, TASK_THREAD_F11_F0(a0)
    + fsd f12, TASK_THREAD_F12_F0(a0)
    + fsd f13, TASK_THREAD_F13_F0(a0)
    + fsd f14, TASK_THREAD_F14_F0(a0)
    + fsd f15, TASK_THREAD_F15_F0(a0)
    + fsd f16, TASK_THREAD_F16_F0(a0)
    + fsd f17, TASK_THREAD_F17_F0(a0)
    + fsd f18, TASK_THREAD_F18_F0(a0)
    + fsd f19, TASK_THREAD_F19_F0(a0)
    + fsd f20, TASK_THREAD_F20_F0(a0)
    + fsd f21, TASK_THREAD_F21_F0(a0)
    + fsd f22, TASK_THREAD_F22_F0(a0)
    + fsd f23, TASK_THREAD_F23_F0(a0)
    + fsd f24, TASK_THREAD_F24_F0(a0)
    + fsd f25, TASK_THREAD_F25_F0(a0)
    + fsd f26, TASK_THREAD_F26_F0(a0)
    + fsd f27, TASK_THREAD_F27_F0(a0)
    + fsd f28, TASK_THREAD_F28_F0(a0)
    + fsd f29, TASK_THREAD_F29_F0(a0)
    + fsd f30, TASK_THREAD_F30_F0(a0)
    + fsd f31, TASK_THREAD_F31_F0(a0)
    + sw t0, TASK_THREAD_FCSR_F0(a0)
    + csrc sstatus, t1
    + ret
    +ENDPROC(__fstate_save)
    +
    +ENTRY(__fstate_restore)
    + li a2, TASK_THREAD_F0
    + add a0, a0, a2
    + li t1, SR_FS
    + lw t0, TASK_THREAD_FCSR_F0(a0)
    + csrs sstatus, t1
    + fld f0, TASK_THREAD_F0_F0(a0)
    + fld f1, TASK_THREAD_F1_F0(a0)
    + fld f2, TASK_THREAD_F2_F0(a0)
    + fld f3, TASK_THREAD_F3_F0(a0)
    + fld f4, TASK_THREAD_F4_F0(a0)
    + fld f5, TASK_THREAD_F5_F0(a0)
    + fld f6, TASK_THREAD_F6_F0(a0)
    + fld f7, TASK_THREAD_F7_F0(a0)
    + fld f8, TASK_THREAD_F8_F0(a0)
    + fld f9, TASK_THREAD_F9_F0(a0)
    + fld f10, TASK_THREAD_F10_F0(a0)
    + fld f11, TASK_THREAD_F11_F0(a0)
    + fld f12, TASK_THREAD_F12_F0(a0)
    + fld f13, TASK_THREAD_F13_F0(a0)
    + fld f14, TASK_THREAD_F14_F0(a0)
    + fld f15, TASK_THREAD_F15_F0(a0)
    + fld f16, TASK_THREAD_F16_F0(a0)
    + fld f17, TASK_THREAD_F17_F0(a0)
    + fld f18, TASK_THREAD_F18_F0(a0)
    + fld f19, TASK_THREAD_F19_F0(a0)
    + fld f20, TASK_THREAD_F20_F0(a0)
    + fld f21, TASK_THREAD_F21_F0(a0)
    + fld f22, TASK_THREAD_F22_F0(a0)
    + fld f23, TASK_THREAD_F23_F0(a0)
    + fld f24, TASK_THREAD_F24_F0(a0)
    + fld f25, TASK_THREAD_F25_F0(a0)
    + fld f26, TASK_THREAD_F26_F0(a0)
    + fld f27, TASK_THREAD_F27_F0(a0)
    + fld f28, TASK_THREAD_F28_F0(a0)
    + fld f29, TASK_THREAD_F29_F0(a0)
    + fld f30, TASK_THREAD_F30_F0(a0)
    + fld f31, TASK_THREAD_F31_F0(a0)
    + fscsr t0
    + csrc sstatus, t1
    + ret
    +ENDPROC(__fstate_restore)
    +
    +
    + .section ".rodata"
    + /* Exception vector table */
    +ENTRY(excp_vect_table)
    + RISCV_PTR do_trap_insn_misaligned
    + RISCV_PTR do_trap_insn_fault
    + RISCV_PTR do_trap_insn_illegal
    + RISCV_PTR do_trap_break
    + RISCV_PTR do_trap_load_misaligned
    + RISCV_PTR do_trap_load_fault
    + RISCV_PTR do_trap_store_misaligned
    + RISCV_PTR do_trap_store_fault
    + RISCV_PTR do_trap_ecall_u /* system call, gets intercepted */
    + RISCV_PTR do_trap_ecall_s
    + RISCV_PTR do_trap_unknown
    + RISCV_PTR do_trap_ecall_m
    + RISCV_PTR do_page_fault /* instruction page fault */
    + RISCV_PTR do_page_fault /* load page fault */
    + RISCV_PTR do_trap_unknown
    + RISCV_PTR do_page_fault /* store page fault */
    +excp_vect_table_end:
    +END(excp_vect_table)
    diff --git a/arch/riscv/kernel/process.c b/arch/riscv/kernel/process.c
    new file mode 100644
    index 000000000000..0d90dcc1fbd3
    --- /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 <asm/unistd.h>
    +#include <asm/uaccess.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_PIE /* 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(&current->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_PS | SR_PIE; /* 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;
    +}
    --
    2.13.0
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