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) 114ASM_NOKPROBE(handle_exception) 115 116/* 117 * The ret_from_exception must be called with interrupt disabled. Here is the 118 * caller list: 119 * - handle_exception 120 * - ret_from_fork 121 */ 122SYM_CODE_START_NOALIGN(ret_from_exception) 123 REG_L s0, PT_STATUS(sp) 124#ifdef CONFIG_RISCV_M_MODE 125 /* the MPP value is too large to be used as an immediate arg for addi */ 126 li t0, SR_MPP 127 and s0, s0, t0 128#else 129 andi s0, s0, SR_SPP 130#endif 131 bnez s0, 1f 132 133 /* Save unwound kernel stack pointer in thread_info */ 134 addi s0, sp, PT_SIZE_ON_STACK 135 REG_S s0, TASK_TI_KERNEL_SP(tp) 136 137 /* Save the kernel shadow call stack pointer */ 138 scs_save_current 139 140 /* 141 * Save TP into the scratch register , so we can find the kernel data 142 * structures again. 143 */ 144 csrw CSR_SCRATCH, tp 1451: 146#ifdef CONFIG_RISCV_ISA_V_PREEMPTIVE 147 move a0, sp 148 call riscv_v_context_nesting_end 149#endif 150 REG_L a0, PT_STATUS(sp) 151 /* 152 * The current load reservation is effectively part of the processor's 153 * state, in the sense that load reservations cannot be shared between 154 * different hart contexts. We can't actually save and restore a load 155 * reservation, so instead here we clear any existing reservation -- 156 * it's always legal for implementations to clear load reservations at 157 * any point (as long as the forward progress guarantee is kept, but 158 * we'll ignore that here). 159 * 160 * Dangling load reservations can be the result of taking a trap in the 161 * middle of an LR/SC sequence, but can also be the result of a taken 162 * forward branch around an SC -- which is how we implement CAS. As a 163 * result we need to clear reservations between the last CAS and the 164 * jump back to the new context. While it is unlikely the store 165 * completes, implementations are allowed to expand reservations to be 166 * arbitrarily large. 167 */ 168 REG_L a2, PT_EPC(sp) 169 REG_SC x0, a2, PT_EPC(sp) 170 171 csrw CSR_STATUS, a0 172 csrw CSR_EPC, a2 173 174 REG_L x1, PT_RA(sp) 175 REG_L x3, PT_GP(sp) 176 REG_L x4, PT_TP(sp) 177 REG_L x5, PT_T0(sp) 178 restore_from_x6_to_x31 179 180 REG_L x2, PT_SP(sp) 181 182#ifdef CONFIG_RISCV_M_MODE 183 mret 184#else 185 sret 186#endif 187SYM_CODE_END(ret_from_exception) 188ASM_NOKPROBE(ret_from_exception) 189 190#ifdef CONFIG_VMAP_STACK 191SYM_CODE_START_LOCAL(handle_kernel_stack_overflow) 192 /* we reach here from kernel context, sscratch must be 0 */ 193 csrrw x31, CSR_SCRATCH, x31 194 asm_per_cpu sp, overflow_stack, x31 195 li x31, OVERFLOW_STACK_SIZE 196 add sp, sp, x31 197 /* zero out x31 again and restore x31 */ 198 xor x31, x31, x31 199 csrrw x31, CSR_SCRATCH, x31 200 201 addi sp, sp, -(PT_SIZE_ON_STACK) 202 203 //save context to overflow stack 204 REG_S x1, PT_RA(sp) 205 REG_S x3, PT_GP(sp) 206 REG_S x5, PT_T0(sp) 207 save_from_x6_to_x31 208 209 REG_L s0, TASK_TI_KERNEL_SP(tp) 210 csrr s1, CSR_STATUS 211 csrr s2, CSR_EPC 212 csrr s3, CSR_TVAL 213 csrr s4, CSR_CAUSE 214 csrr s5, CSR_SCRATCH 215 REG_S s0, PT_SP(sp) 216 REG_S s1, PT_STATUS(sp) 217 REG_S s2, PT_EPC(sp) 218 REG_S s3, PT_BADADDR(sp) 219 REG_S s4, PT_CAUSE(sp) 220 REG_S s5, PT_TP(sp) 221 move a0, sp 222 tail handle_bad_stack 223SYM_CODE_END(handle_kernel_stack_overflow) 224ASM_NOKPROBE(handle_kernel_stack_overflow) 225#endif 226 227SYM_CODE_START(ret_from_fork) 228 call schedule_tail 229 beqz s0, 1f /* not from kernel thread */ 230 /* Call fn(arg) */ 231 move a0, s1 232 jalr s0 2331: 234 move a0, sp /* pt_regs */ 235 la ra, ret_from_exception 236 tail syscall_exit_to_user_mode 237SYM_CODE_END(ret_from_fork) 238 239#ifdef CONFIG_IRQ_STACKS 240/* 241 * void call_on_irq_stack(struct pt_regs *regs, 242 * void (*func)(struct pt_regs *)); 243 * 244 * Calls func(regs) using the per-CPU IRQ stack. 245 */ 246SYM_FUNC_START(call_on_irq_stack) 247 /* Create a frame record to save ra and s0 (fp) */ 248 addi sp, sp, -STACKFRAME_SIZE_ON_STACK 249 REG_S ra, STACKFRAME_RA(sp) 250 REG_S s0, STACKFRAME_FP(sp) 251 addi s0, sp, STACKFRAME_SIZE_ON_STACK 252 253 /* Switch to the per-CPU shadow call stack */ 254 scs_save_current 255 scs_load_irq_stack t0 256 257 /* Switch to the per-CPU IRQ stack and call the handler */ 258 load_per_cpu t0, irq_stack_ptr, t1 259 li t1, IRQ_STACK_SIZE 260 add sp, t0, t1 261 jalr a1 262 263 /* Switch back to the thread shadow call stack */ 264 scs_load_current 265 266 /* Switch back to the thread stack and restore ra and s0 */ 267 addi sp, s0, -STACKFRAME_SIZE_ON_STACK 268 REG_L ra, STACKFRAME_RA(sp) 269 REG_L s0, STACKFRAME_FP(sp) 270 addi sp, sp, STACKFRAME_SIZE_ON_STACK 271 272 ret 273SYM_FUNC_END(call_on_irq_stack) 274#endif /* CONFIG_IRQ_STACKS */ 275 276/* 277 * Integer register context switch 278 * The callee-saved registers must be saved and restored. 279 * 280 * a0: previous task_struct (must be preserved across the switch) 281 * a1: next task_struct 282 * 283 * The value of a0 and a1 must be preserved by this function, as that's how 284 * arguments are passed to schedule_tail. 285 */ 286SYM_FUNC_START(__switch_to) 287 /* Save context into prev->thread */ 288 li a4, TASK_THREAD_RA 289 add a3, a0, a4 290 add a4, a1, a4 291 REG_S ra, TASK_THREAD_RA_RA(a3) 292 REG_S sp, TASK_THREAD_SP_RA(a3) 293 REG_S s0, TASK_THREAD_S0_RA(a3) 294 REG_S s1, TASK_THREAD_S1_RA(a3) 295 REG_S s2, TASK_THREAD_S2_RA(a3) 296 REG_S s3, TASK_THREAD_S3_RA(a3) 297 REG_S s4, TASK_THREAD_S4_RA(a3) 298 REG_S s5, TASK_THREAD_S5_RA(a3) 299 REG_S s6, TASK_THREAD_S6_RA(a3) 300 REG_S s7, TASK_THREAD_S7_RA(a3) 301 REG_S s8, TASK_THREAD_S8_RA(a3) 302 REG_S s9, TASK_THREAD_S9_RA(a3) 303 REG_S s10, TASK_THREAD_S10_RA(a3) 304 REG_S s11, TASK_THREAD_S11_RA(a3) 305 /* Save the kernel shadow call stack pointer */ 306 scs_save_current 307 /* Restore context from next->thread */ 308 REG_L ra, TASK_THREAD_RA_RA(a4) 309 REG_L sp, TASK_THREAD_SP_RA(a4) 310 REG_L s0, TASK_THREAD_S0_RA(a4) 311 REG_L s1, TASK_THREAD_S1_RA(a4) 312 REG_L s2, TASK_THREAD_S2_RA(a4) 313 REG_L s3, TASK_THREAD_S3_RA(a4) 314 REG_L s4, TASK_THREAD_S4_RA(a4) 315 REG_L s5, TASK_THREAD_S5_RA(a4) 316 REG_L s6, TASK_THREAD_S6_RA(a4) 317 REG_L s7, TASK_THREAD_S7_RA(a4) 318 REG_L s8, TASK_THREAD_S8_RA(a4) 319 REG_L s9, TASK_THREAD_S9_RA(a4) 320 REG_L s10, TASK_THREAD_S10_RA(a4) 321 REG_L s11, TASK_THREAD_S11_RA(a4) 322 /* The offset of thread_info in task_struct is zero. */ 323 move tp, a1 324 /* Switch to the next shadow call stack */ 325 scs_load_current 326 ret 327SYM_FUNC_END(__switch_to) 328 329#ifndef CONFIG_MMU 330#define do_page_fault do_trap_unknown 331#endif 332 333 .section ".rodata" 334 .align LGREG 335 /* Exception vector table */ 336SYM_DATA_START_LOCAL(excp_vect_table) 337 RISCV_PTR do_trap_insn_misaligned 338 ALT_INSN_FAULT(RISCV_PTR do_trap_insn_fault) 339 RISCV_PTR do_trap_insn_illegal 340 RISCV_PTR do_trap_break 341 RISCV_PTR do_trap_load_misaligned 342 RISCV_PTR do_trap_load_fault 343 RISCV_PTR do_trap_store_misaligned 344 RISCV_PTR do_trap_store_fault 345 RISCV_PTR do_trap_ecall_u /* system call */ 346 RISCV_PTR do_trap_ecall_s 347 RISCV_PTR do_trap_unknown 348 RISCV_PTR do_trap_ecall_m 349 /* instruciton page fault */ 350 ALT_PAGE_FAULT(RISCV_PTR do_page_fault) 351 RISCV_PTR do_page_fault /* load page fault */ 352 RISCV_PTR do_trap_unknown 353 RISCV_PTR do_page_fault /* store page fault */ 354SYM_DATA_END_LABEL(excp_vect_table, SYM_L_LOCAL, excp_vect_table_end) 355 356#ifndef CONFIG_MMU 357SYM_DATA_START(__user_rt_sigreturn) 358 li a7, __NR_rt_sigreturn 359 ecall 360SYM_DATA_END(__user_rt_sigreturn) 361#endif 362