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linux/arch/riscv/kernel/entry.S
Palmer Dabbelt 7db91e57a0 RISC-V: Task implementation 
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>
2017-09-26 15:26:46 -07:00

465 lines
11 KiB
ArmAsm
Raw Blame History

/*
* 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:
/* 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)
/* 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)
/* 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"
/* 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)
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