1 files changed, 472 insertions, 0 deletions
diff --git a/arch/riscv/kernel/entry.S b/arch/riscv/kernel/entry.S
new file mode 100644
index 000000000..d9de22686
--- /dev/null
+++ b/arch/riscv/kernel/entry.S
@@ -0,0 +1,472 @@
+/*
+ * 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 user-mode memory access as it should only be set in the
+	 * actual user copy routines.
+	 *
+	 * Disable the FPU to detect illegal usage of floating point in kernel
+	 * space.
+	 */
+	li t0, SR_SUM | 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 */
+	move a0, sp /* pt_regs */
+	move a1, s4 /* scause */
+	tail do_IRQ
+1:
+	/* Exceptions run with interrupts enabled or disabled
+	   depending on the state of sstatus.SR_SPIE */
+	andi t0, s1, SR_SPIE
+	beqz t0, 1f
+	csrs sstatus, SR_SIE
+
+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:
+	 /* save the initial A0 value (needed in signal handlers) */
+	REG_S a0, PT_ORIG_A0(sp)
+	/*
+	 * Advance SEPC to avoid executing the original
+	 * scall instruction on sret
+	 */
+	addi s2, s2, 0x4
+	REG_S s2, PT_SEPC(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_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_SIE
+	andi s0, s0, SR_SPP
+	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_SIE /* 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)
+	/* Swap the CPU entry around. */
+	lw a3, TASK_TI_CPU(a0)
+	lw a4, TASK_TI_CPU(a1)
+	sw a3, TASK_TI_CPU(a1)
+	sw a4, TASK_TI_CPU(a0)
+#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"
+	.align LGREG
+	/* 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)