| /* 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> |
| |
| .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, 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) |
| .endm |
| |
| /* |
| * Prepares to return from a system call or exception by restoring all |
| * registers from the stack. |
| */ |
| .macro RESTORE_ALL |
| 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) |
| .endm |
| |
| #if !IS_ENABLED(CONFIG_PREEMPT) |
| .set resume_kernel, restore_all |
| #endif |
| |
| ENTRY(handle_exception) |
| SAVE_ALL |
| |
| /* |
| * 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 |
| |
| la ra, ret_from_exception |
| /* |
| * MSB of cause differentiates between |
| * interrupts and exceptions |
| */ |
| bge s4, zero, 1f |
| |
| /* Handle interrupts */ |
| move a0, sp /* pt_regs */ |
| tail do_IRQ |
| 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 |
| csrs CSR_STATUS, SR_IE |
| |
| 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_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 |
| /* |
| * The tracer can change syscall number to valid/invalid value. |
| * We use syscall_set_nr helper in syscall_trace_enter thus we |
| * cannot trust the current value in a7 and have to reload from |
| * the current task pt_regs. |
| */ |
| REG_L a7, PT_A7(sp) |
| /* |
| * Syscall number held in a7. |
| * If syscall number is above allowed value, redirect to ni_syscall. |
| */ |
| bge a7, t0, 1f |
| /* |
| * Check if syscall is rejected by tracer or seccomp, i.e., a7 == -1. |
| * If yes, we pretend it was executed. |
| */ |
| li t1, -1 |
| beq a7, t1, ret_from_syscall_rejected |
| blt a7, t1, 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_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 |
| |
| /* 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: |
| RESTORE_ALL |
| #ifdef CONFIG_RISCV_M_MODE |
| mret |
| #else |
| sret |
| #endif |
| |
| #if IS_ENABLED(CONFIG_PREEMPT) |
| 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 |
| 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) |
| |
| #ifndef CONFIG_MMU |
| #define do_page_fault do_trap_unknown |
| #endif |
| |
| .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) |
| |
| #ifndef CONFIG_MMU |
| ENTRY(__user_rt_sigreturn) |
| li a7, __NR_rt_sigreturn |
| scall |
| END(__user_rt_sigreturn) |
| #endif |
