1/* SPDX-License-Identifier: GPL-2.0-only */ 2/* 3 * Copyright (C) 2012 Regents of the University of California 4 * Copyright (C) 2017 SiFive 5 */ 6 7#include <linux/init.h> 8#include <linux/linkage.h> 9 10#include <asm/asm.h> 11#include <asm/csr.h> 12#include <asm/scs.h> 13#include <asm/unistd.h> 14#include <asm/page.h> 15#include <asm/thread_info.h> 16#include <asm/asm-offsets.h> 17#include <asm/errata_list.h> 18#include <linux/sizes.h> 19 20 .section .irqentry.text, "ax" 21 22SYM_CODE_START(handle_exception) 23 /* 24 * If coming from userspace, preserve the user thread pointer and load 25 * the kernel thread pointer. If we came from the kernel, the scratch 26 * register will contain 0, and we should continue on the current TP. 27 */ 28 csrrw tp, CSR_SCRATCH, tp 29 bnez tp, .Lsave_context 30 31.Lrestore_kernel_tpsp: 32 csrr tp, CSR_SCRATCH 33 REG_S sp, TASK_TI_KERNEL_SP(tp) 34 35#ifdef CONFIG_VMAP_STACK 36 addi sp, sp, -(PT_SIZE_ON_STACK) 37 srli sp, sp, THREAD_SHIFT 38 andi sp, sp, 0x1 39 bnez sp, handle_kernel_stack_overflow 40 REG_L sp, TASK_TI_KERNEL_SP(tp) 41#endif 42 43.Lsave_context: 44 REG_S sp, TASK_TI_USER_SP(tp) 45 REG_L sp, TASK_TI_KERNEL_SP(tp) 46 addi sp, sp, -(PT_SIZE_ON_STACK) 47 REG_S x1, PT_RA(sp) 48 REG_S x3, PT_GP(sp) 49 REG_S x5, PT_T0(sp) 50 save_from_x6_to_x31 51 52 /* 53 * Disable user-mode memory access as it should only be set in the 54 * actual user copy routines. 55 * 56 * Disable the FPU/Vector to detect illegal usage of floating point 57 * or vector in kernel space. 58 */ 59 li t0, SR_SUM | SR_FS_VS 60 61 REG_L s0, TASK_TI_USER_SP(tp) 62 csrrc s1, CSR_STATUS, t0 63 csrr s2, CSR_EPC 64 csrr s3, CSR_TVAL 65 csrr s4, CSR_CAUSE 66 csrr s5, CSR_SCRATCH 67 REG_S s0, PT_SP(sp) 68 REG_S s1, PT_STATUS(sp) 69 REG_S s2, PT_EPC(sp) 70 REG_S s3, PT_BADADDR(sp) 71 REG_S s4, PT_CAUSE(sp) 72 REG_S s5, PT_TP(sp) 73 74 /* 75 * Set the scratch register to 0, so that if a recursive exception 76 * occurs, the exception vector knows it came from the kernel 77 */ 78 csrw CSR_SCRATCH, x0 79 80 /* Load the global pointer */ 81 load_global_pointer 82 83 /* Load the kernel shadow call stack pointer if coming from userspace */ 84 scs_load_current_if_task_changed s5 85 86#ifdef CONFIG_RISCV_ISA_V_PREEMPTIVE 87 move a0, sp 88 call riscv_v_context_nesting_start 89#endif 90 move a0, sp /* pt_regs */ 91 la ra, ret_from_exception 92 93 /* 94 * MSB of cause differentiates between 95 * interrupts and exceptions 96 */ 97 bge s4, zero, 1f 98 99 /* Handle interrupts */ 100 tail do_irq 1011: 102 /* Handle other exceptions */ 103 slli t0, s4, RISCV_LGPTR 104 la t1, excp_vect_table 105 la t2, excp_vect_table_end 106 add t0, t1, t0 107 /* Check if exception code lies within bounds */ 108 bgeu t0, t2, 1f 109 REG_L t0, 0(t0) 110 jr t0 1111: 112 tail do_trap_unknown 113SYM_CODE_END(handle_exception) 114 115/* 116 * The ret_from_exception must be called with interrupt disabled. Here is the 117 * caller list: 118 * - handle_exception 119 * - ret_from_fork 120 */ 121SYM_CODE_START_NOALIGN(ret_from_exception) 122 REG_L s0, PT_STATUS(sp) 123#ifdef CONFIG_RISCV_M_MODE 124 /* the MPP value is too large to be used as an immediate arg for addi */ 125 li t0, SR_MPP 126 and s0, s0, t0 127#else 128 andi s0, s0, SR_SPP 129#endif 130 bnez s0, 1f 131 132 /* Save unwound kernel stack pointer in thread_info */ 133 addi s0, sp, PT_SIZE_ON_STACK 134 REG_S s0, TASK_TI_KERNEL_SP(tp) 135 136 /* Save the kernel shadow call stack pointer */ 137 scs_save_current 138 139 /* 140 * Save TP into the scratch register , so we can find the kernel data 141 * structures again. 142 */ 143 csrw CSR_SCRATCH, tp 1441: 145#ifdef CONFIG_RISCV_ISA_V_PREEMPTIVE 146 move a0, sp 147 call riscv_v_context_nesting_end 148#endif 149 REG_L a0, PT_STATUS(sp) 150 /* 151 * The current load reservation is effectively part of the processor's 152 * state, in the sense that load reservations cannot be shared between 153 * different hart contexts. We can't actually save and restore a load 154 * reservation, so instead here we clear any existing reservation -- 155 * it's always legal for implementations to clear load reservations at 156 * any point (as long as the forward progress guarantee is kept, but 157 * we'll ignore that here). 158 * 159 * Dangling load reservations can be the result of taking a trap in the 160 * middle of an LR/SC sequence, but can also be the result of a taken 161 * forward branch around an SC -- which is how we implement CAS. As a 162 * result we need to clear reservations between the last CAS and the 163 * jump back to the new context. While it is unlikely the store 164 * completes, implementations are allowed to expand reservations to be 165 * arbitrarily large. 166 */ 167 REG_L a2, PT_EPC(sp) 168 REG_SC x0, a2, PT_EPC(sp) 169 170 csrw CSR_STATUS, a0 171 csrw CSR_EPC, a2 172 173 REG_L x1, PT_RA(sp) 174 REG_L x3, PT_GP(sp) 175 REG_L x4, PT_TP(sp) 176 REG_L x5, PT_T0(sp) 177 restore_from_x6_to_x31 178 179 REG_L x2, PT_SP(sp) 180 181#ifdef CONFIG_RISCV_M_MODE 182 mret 183#else 184 sret 185#endif 186SYM_CODE_END(ret_from_exception) 187 188#ifdef CONFIG_VMAP_STACK 189SYM_CODE_START_LOCAL(handle_kernel_stack_overflow) 190 /* we reach here from kernel context, sscratch must be 0 */ 191 csrrw x31, CSR_SCRATCH, x31 192 asm_per_cpu sp, overflow_stack, x31 193 li x31, OVERFLOW_STACK_SIZE 194 add sp, sp, x31 195 /* zero out x31 again and restore x31 */ 196 xor x31, x31, x31 197 csrrw x31, CSR_SCRATCH, x31 198 199 addi sp, sp, -(PT_SIZE_ON_STACK) 200 201 //save context to overflow stack 202 REG_S x1, PT_RA(sp) 203 REG_S x3, PT_GP(sp) 204 REG_S x5, PT_T0(sp) 205 save_from_x6_to_x31 206 207 REG_L s0, TASK_TI_KERNEL_SP(tp) 208 csrr s1, CSR_STATUS 209 csrr s2, CSR_EPC 210 csrr s3, CSR_TVAL 211 csrr s4, CSR_CAUSE 212 csrr s5, CSR_SCRATCH 213 REG_S s0, PT_SP(sp) 214 REG_S s1, PT_STATUS(sp) 215 REG_S s2, PT_EPC(sp) 216 REG_S s3, PT_BADADDR(sp) 217 REG_S s4, PT_CAUSE(sp) 218 REG_S s5, PT_TP(sp) 219 move a0, sp 220 tail handle_bad_stack 221SYM_CODE_END(handle_kernel_stack_overflow) 222#endif 223 224SYM_CODE_START(ret_from_fork) 225 call schedule_tail 226 beqz s0, 1f /* not from kernel thread */ 227 /* Call fn(arg) */ 228 move a0, s1 229 jalr s0 2301: 231 move a0, sp /* pt_regs */ 232 la ra, ret_from_exception 233 tail syscall_exit_to_user_mode 234SYM_CODE_END(ret_from_fork) 235 236#ifdef CONFIG_IRQ_STACKS 237/* 238 * void call_on_irq_stack(struct pt_regs *regs, 239 * void (*func)(struct pt_regs *)); 240 * 241 * Calls func(regs) using the per-CPU IRQ stack. 242 */ 243SYM_FUNC_START(call_on_irq_stack) 244 /* Create a frame record to save ra and s0 (fp) */ 245 addi sp, sp, -STACKFRAME_SIZE_ON_STACK 246 REG_S ra, STACKFRAME_RA(sp) 247 REG_S s0, STACKFRAME_FP(sp) 248 addi s0, sp, STACKFRAME_SIZE_ON_STACK 249 250 /* Switch to the per-CPU shadow call stack */ 251 scs_save_current 252 scs_load_irq_stack t0 253 254 /* Switch to the per-CPU IRQ stack and call the handler */ 255 load_per_cpu t0, irq_stack_ptr, t1 256 li t1, IRQ_STACK_SIZE 257 add sp, t0, t1 258 jalr a1 259 260 /* Switch back to the thread shadow call stack */ 261 scs_load_current 262 263 /* Switch back to the thread stack and restore ra and s0 */ 264 addi sp, s0, -STACKFRAME_SIZE_ON_STACK 265 REG_L ra, STACKFRAME_RA(sp) 266 REG_L s0, STACKFRAME_FP(sp) 267 addi sp, sp, STACKFRAME_SIZE_ON_STACK 268 269 ret 270SYM_FUNC_END(call_on_irq_stack) 271#endif /* CONFIG_IRQ_STACKS */ 272 273/* 274 * Integer register context switch 275 * The callee-saved registers must be saved and restored. 276 * 277 * a0: previous task_struct (must be preserved across the switch) 278 * a1: next task_struct 279 * 280 * The value of a0 and a1 must be preserved by this function, as that's how 281 * arguments are passed to schedule_tail. 282 */ 283SYM_FUNC_START(__switch_to) 284 /* Save context into prev->thread */ 285 li a4, TASK_THREAD_RA 286 add a3, a0, a4 287 add a4, a1, a4 288 REG_S ra, TASK_THREAD_RA_RA(a3) 289 REG_S sp, TASK_THREAD_SP_RA(a3) 290 REG_S s0, TASK_THREAD_S0_RA(a3) 291 REG_S s1, TASK_THREAD_S1_RA(a3) 292 REG_S s2, TASK_THREAD_S2_RA(a3) 293 REG_S s3, TASK_THREAD_S3_RA(a3) 294 REG_S s4, TASK_THREAD_S4_RA(a3) 295 REG_S s5, TASK_THREAD_S5_RA(a3) 296 REG_S s6, TASK_THREAD_S6_RA(a3) 297 REG_S s7, TASK_THREAD_S7_RA(a3) 298 REG_S s8, TASK_THREAD_S8_RA(a3) 299 REG_S s9, TASK_THREAD_S9_RA(a3) 300 REG_S s10, TASK_THREAD_S10_RA(a3) 301 REG_S s11, TASK_THREAD_S11_RA(a3) 302 /* Save the kernel shadow call stack pointer */ 303 scs_save_current 304 /* Restore context from next->thread */ 305 REG_L ra, TASK_THREAD_RA_RA(a4) 306 REG_L sp, TASK_THREAD_SP_RA(a4) 307 REG_L s0, TASK_THREAD_S0_RA(a4) 308 REG_L s1, TASK_THREAD_S1_RA(a4) 309 REG_L s2, TASK_THREAD_S2_RA(a4) 310 REG_L s3, TASK_THREAD_S3_RA(a4) 311 REG_L s4, TASK_THREAD_S4_RA(a4) 312 REG_L s5, TASK_THREAD_S5_RA(a4) 313 REG_L s6, TASK_THREAD_S6_RA(a4) 314 REG_L s7, TASK_THREAD_S7_RA(a4) 315 REG_L s8, TASK_THREAD_S8_RA(a4) 316 REG_L s9, TASK_THREAD_S9_RA(a4) 317 REG_L s10, TASK_THREAD_S10_RA(a4) 318 REG_L s11, TASK_THREAD_S11_RA(a4) 319 /* The offset of thread_info in task_struct is zero. */ 320 move tp, a1 321 /* Switch to the next shadow call stack */ 322 scs_load_current 323 ret 324SYM_FUNC_END(__switch_to) 325 326#ifndef CONFIG_MMU 327#define do_page_fault do_trap_unknown 328#endif 329 330 .section ".rodata" 331 .align LGREG 332 /* Exception vector table */ 333SYM_DATA_START_LOCAL(excp_vect_table) 334 RISCV_PTR do_trap_insn_misaligned 335 ALT_INSN_FAULT(RISCV_PTR do_trap_insn_fault) 336 RISCV_PTR do_trap_insn_illegal 337 RISCV_PTR do_trap_break 338 RISCV_PTR do_trap_load_misaligned 339 RISCV_PTR do_trap_load_fault 340 RISCV_PTR do_trap_store_misaligned 341 RISCV_PTR do_trap_store_fault 342 RISCV_PTR do_trap_ecall_u /* system call */ 343 RISCV_PTR do_trap_ecall_s 344 RISCV_PTR do_trap_unknown 345 RISCV_PTR do_trap_ecall_m 346 /* instruciton page fault */ 347 ALT_PAGE_FAULT(RISCV_PTR do_page_fault) 348 RISCV_PTR do_page_fault /* load page fault */ 349 RISCV_PTR do_trap_unknown 350 RISCV_PTR do_page_fault /* store page fault */ 351SYM_DATA_END_LABEL(excp_vect_table, SYM_L_LOCAL, excp_vect_table_end) 352 353#ifndef CONFIG_MMU 354SYM_DATA_START(__user_rt_sigreturn) 355 li a7, __NR_rt_sigreturn 356 ecall 357SYM_DATA_END(__user_rt_sigreturn) 358#endif 359