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Diffstat (limited to '')
| -rw-r--r-- | arch/riscv/kernel/entry.S | 477 |
1 files changed, 477 insertions, 0 deletions
diff --git a/arch/riscv/kernel/entry.S b/arch/riscv/kernel/entry.S new file mode 100644 index 000000000..5214c578a --- /dev/null +++ b/arch/riscv/kernel/entry.S @@ -0,0 +1,477 @@ +/* SPDX-License-Identifier: GPL-2.0-only */ +/* + * Copyright (C) 2012 Regents of the University of California + * Copyright (C) 2017 SiFive + */ + +#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> + +#if !IS_ENABLED(CONFIG_PREEMPTION) +.set resume_kernel, restore_all +#endif + +ENTRY(handle_exception) + /* + * If coming from userspace, preserve the user thread pointer and load + * the kernel thread pointer. If we came from the kernel, the scratch + * register will contain 0, and we should continue on the current TP. + */ + csrrw tp, CSR_SCRATCH, tp + bnez tp, _save_context + +_restore_kernel_tpsp: + csrr tp, CSR_SCRATCH + 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, CSR_STATUS, t0 + csrr s2, CSR_EPC + csrr s3, CSR_TVAL + csrr s4, CSR_CAUSE + csrr s5, CSR_SCRATCH + REG_S s0, PT_SP(sp) + REG_S s1, PT_STATUS(sp) + REG_S s2, PT_EPC(sp) + REG_S s3, PT_BADADDR(sp) + REG_S s4, PT_CAUSE(sp) + REG_S s5, PT_TP(sp) + + /* + * Set the scratch register to 0, so that if a recursive exception + * occurs, the exception vector knows it came from the kernel + */ + csrw CSR_SCRATCH, x0 + + /* Load the global pointer */ +.option push +.option norelax + la gp, __global_pointer$ +.option pop + +#ifdef CONFIG_TRACE_IRQFLAGS + call __trace_hardirqs_off +#endif + +#ifdef CONFIG_CONTEXT_TRACKING + /* If previous state is in user mode, call context_tracking_user_exit. */ + li a0, SR_PP + and a0, s1, a0 + bnez a0, skip_context_tracking + call context_tracking_user_exit +skip_context_tracking: +#endif + + /* + * MSB of cause differentiates between + * interrupts and exceptions + */ + bge s4, zero, 1f + + la ra, ret_from_exception + + /* Handle interrupts */ + move a0, sp /* pt_regs */ + la a1, handle_arch_irq + REG_L a1, (a1) + jr a1 +1: + /* + * Exceptions run with interrupts enabled or disabled depending on the + * state of SR_PIE in m/sstatus. + */ + andi t0, s1, SR_PIE + beqz t0, 1f +#ifdef CONFIG_TRACE_IRQFLAGS + call __trace_hardirqs_on +#endif + csrs CSR_STATUS, SR_IE + +1: + la ra, ret_from_exception + /* 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: +#ifdef CONFIG_RISCV_M_MODE + /* + * When running is M-Mode (no MMU config), MPIE does not get set. + * As a result, we need to force enable interrupts here because + * handle_exception did not do set SR_IE as it always sees SR_PIE + * being cleared. + */ + csrs CSR_STATUS, SR_IE +#endif +#if defined(CONFIG_TRACE_IRQFLAGS) || defined(CONFIG_CONTEXT_TRACKING) + /* Recover a0 - a7 for system calls */ + 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) +#endif + /* 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_EPC(sp) + /* Trace syscalls, but only if requested by the user. */ + REG_L t0, TASK_TI_FLAGS(tp) + andi t0, t0, _TIF_SYSCALL_WORK + 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. + * If syscall number is above allowed value, redirect to ni_syscall. + */ + bgeu a7, t0, 1f + /* Call syscall */ + 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) + /* + * We didn't execute the actual syscall. + * Seccomp already set return value for the current task pt_regs. + * (If it was configured with SECCOMP_RET_ERRNO/TRACE) + */ +ret_from_syscall_rejected: + /* Trace syscalls, but only if requested by the user. */ + REG_L t0, TASK_TI_FLAGS(tp) + andi t0, t0, _TIF_SYSCALL_WORK + bnez t0, handle_syscall_trace_exit + +ret_from_exception: + REG_L s0, PT_STATUS(sp) + csrc CSR_STATUS, SR_IE +#ifdef CONFIG_TRACE_IRQFLAGS + call __trace_hardirqs_off +#endif +#ifdef CONFIG_RISCV_M_MODE + /* the MPP value is too large to be used as an immediate arg for addi */ + li t0, SR_MPP + and s0, s0, t0 +#else + andi s0, s0, SR_SPP +#endif + bnez s0, resume_kernel + +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 + +#ifdef CONFIG_CONTEXT_TRACKING + call context_tracking_user_enter +#endif + + /* 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 the scratch register , so we can find the kernel data + * structures again. + */ + csrw CSR_SCRATCH, tp + +restore_all: +#ifdef CONFIG_TRACE_IRQFLAGS + REG_L s1, PT_STATUS(sp) + andi t0, s1, SR_PIE + beqz t0, 1f + call __trace_hardirqs_on + j 2f +1: + call __trace_hardirqs_off +2: +#endif + REG_L a0, PT_STATUS(sp) + /* + * The current load reservation is effectively part of the processor's + * state, in the sense that load reservations cannot be shared between + * different hart contexts. We can't actually save and restore a load + * reservation, so instead here we clear any existing reservation -- + * it's always legal for implementations to clear load reservations at + * any point (as long as the forward progress guarantee is kept, but + * we'll ignore that here). + * + * Dangling load reservations can be the result of taking a trap in the + * middle of an LR/SC sequence, but can also be the result of a taken + * forward branch around an SC -- which is how we implement CAS. As a + * result we need to clear reservations between the last CAS and the + * jump back to the new context. While it is unlikely the store + * completes, implementations are allowed to expand reservations to be + * arbitrarily large. + */ + REG_L a2, PT_EPC(sp) + REG_SC x0, a2, PT_EPC(sp) + + csrw CSR_STATUS, a0 + csrw CSR_EPC, 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) + +#ifdef CONFIG_RISCV_M_MODE + mret +#else + sret +#endif + +#if IS_ENABLED(CONFIG_PREEMPTION) +resume_kernel: + REG_L s0, TASK_TI_PREEMPT_COUNT(tp) + bnez s0, restore_all + REG_L s0, TASK_TI_FLAGS(tp) + andi s0, s0, _TIF_NEED_RESCHED + beqz s0, restore_all + call preempt_schedule_irq + j restore_all +#endif + +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 CSR_STATUS, 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 + move t0, a0 + 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) + bnez t0, ret_from_syscall_rejected + 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) + /* The offset of thread_info in task_struct is zero. */ + move tp, a1 + ret +ENDPROC(__switch_to) + +#ifndef CONFIG_MMU +#define do_page_fault do_trap_unknown +#endif + + .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) + +#ifndef CONFIG_MMU +ENTRY(__user_rt_sigreturn) + li a7, __NR_rt_sigreturn + scall +END(__user_rt_sigreturn) +#endif |