1/* 2 * Copyright (C) 2012 Regents of the University of California 3 * Copyright (C) 2017 SiFive 4 * 5 * This program is free software; you can redistribute it and/or 6 * modify it under the terms of the GNU General Public License 7 * as published by the Free Software Foundation, version 2. 8 * 9 * This program is distributed in the hope that it will be useful, 10 * but WITHOUT ANY WARRANTY; without even the implied warranty of 11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 12 * GNU General Public License for more details. 13 */ 14 15#include <linux/init.h> 16#include <linux/linkage.h> 17 18#include <asm/asm.h> 19#include <asm/csr.h> 20#include <asm/unistd.h> 21#include <asm/thread_info.h> 22#include <asm/asm-offsets.h> 23 24 .text 25 .altmacro 26 27/* 28 * Prepares to enter a system call or exception by saving all registers to the 29 * stack. 30 */ 31 .macro SAVE_ALL 32 LOCAL _restore_kernel_tpsp 33 LOCAL _save_context 34 35 /* 36 * If coming from userspace, preserve the user thread pointer and load 37 * the kernel thread pointer. If we came from the kernel, sscratch 38 * will contain 0, and we should continue on the current TP. 39 */ 40 csrrw tp, sscratch, tp 41 bnez tp, _save_context 42 43_restore_kernel_tpsp: 44 csrr tp, sscratch 45 REG_S sp, TASK_TI_KERNEL_SP(tp) 46_save_context: 47 REG_S sp, TASK_TI_USER_SP(tp) 48 REG_L sp, TASK_TI_KERNEL_SP(tp) 49 addi sp, sp, -(PT_SIZE_ON_STACK) 50 REG_S x1, PT_RA(sp) 51 REG_S x3, PT_GP(sp) 52 REG_S x5, PT_T0(sp) 53 REG_S x6, PT_T1(sp) 54 REG_S x7, PT_T2(sp) 55 REG_S x8, PT_S0(sp) 56 REG_S x9, PT_S1(sp) 57 REG_S x10, PT_A0(sp) 58 REG_S x11, PT_A1(sp) 59 REG_S x12, PT_A2(sp) 60 REG_S x13, PT_A3(sp) 61 REG_S x14, PT_A4(sp) 62 REG_S x15, PT_A5(sp) 63 REG_S x16, PT_A6(sp) 64 REG_S x17, PT_A7(sp) 65 REG_S x18, PT_S2(sp) 66 REG_S x19, PT_S3(sp) 67 REG_S x20, PT_S4(sp) 68 REG_S x21, PT_S5(sp) 69 REG_S x22, PT_S6(sp) 70 REG_S x23, PT_S7(sp) 71 REG_S x24, PT_S8(sp) 72 REG_S x25, PT_S9(sp) 73 REG_S x26, PT_S10(sp) 74 REG_S x27, PT_S11(sp) 75 REG_S x28, PT_T3(sp) 76 REG_S x29, PT_T4(sp) 77 REG_S x30, PT_T5(sp) 78 REG_S x31, PT_T6(sp) 79 80 /* 81 * Disable user-mode memory access as it should only be set in the 82 * actual user copy routines. 83 * 84 * Disable the FPU to detect illegal usage of floating point in kernel 85 * space. 86 */ 87 li t0, SR_SUM | SR_FS 88 89 REG_L s0, TASK_TI_USER_SP(tp) 90 csrrc s1, sstatus, t0 91 csrr s2, sepc 92 csrr s3, sbadaddr 93 csrr s4, scause 94 csrr s5, sscratch 95 REG_S s0, PT_SP(sp) 96 REG_S s1, PT_SSTATUS(sp) 97 REG_S s2, PT_SEPC(sp) 98 REG_S s3, PT_SBADADDR(sp) 99 REG_S s4, PT_SCAUSE(sp) 100 REG_S s5, PT_TP(sp) 101 .endm 102 103/* 104 * Prepares to return from a system call or exception by restoring all 105 * registers from the stack. 106 */ 107 .macro RESTORE_ALL 108 REG_L a0, PT_SSTATUS(sp) 109 REG_L a2, PT_SEPC(sp) 110 csrw sstatus, a0 111 csrw sepc, a2 112 113 REG_L x1, PT_RA(sp) 114 REG_L x3, PT_GP(sp) 115 REG_L x4, PT_TP(sp) 116 REG_L x5, PT_T0(sp) 117 REG_L x6, PT_T1(sp) 118 REG_L x7, PT_T2(sp) 119 REG_L x8, PT_S0(sp) 120 REG_L x9, PT_S1(sp) 121 REG_L x10, PT_A0(sp) 122 REG_L x11, PT_A1(sp) 123 REG_L x12, PT_A2(sp) 124 REG_L x13, PT_A3(sp) 125 REG_L x14, PT_A4(sp) 126 REG_L x15, PT_A5(sp) 127 REG_L x16, PT_A6(sp) 128 REG_L x17, PT_A7(sp) 129 REG_L x18, PT_S2(sp) 130 REG_L x19, PT_S3(sp) 131 REG_L x20, PT_S4(sp) 132 REG_L x21, PT_S5(sp) 133 REG_L x22, PT_S6(sp) 134 REG_L x23, PT_S7(sp) 135 REG_L x24, PT_S8(sp) 136 REG_L x25, PT_S9(sp) 137 REG_L x26, PT_S10(sp) 138 REG_L x27, PT_S11(sp) 139 REG_L x28, PT_T3(sp) 140 REG_L x29, PT_T4(sp) 141 REG_L x30, PT_T5(sp) 142 REG_L x31, PT_T6(sp) 143 144 REG_L x2, PT_SP(sp) 145 .endm 146 147ENTRY(handle_exception) 148 SAVE_ALL 149 150 /* 151 * Set sscratch register to 0, so that if a recursive exception 152 * occurs, the exception vector knows it came from the kernel 153 */ 154 csrw sscratch, x0 155 156 /* Load the global pointer */ 157.option push 158.option norelax 159 la gp, __global_pointer$ 160.option pop 161 162 la ra, ret_from_exception 163 /* 164 * MSB of cause differentiates between 165 * interrupts and exceptions 166 */ 167 bge s4, zero, 1f 168 169 /* Handle interrupts */ 170 slli a0, s4, 1 171 srli a0, a0, 1 172 move a1, sp /* pt_regs */ 173 tail do_IRQ 1741: 175 /* Handle syscalls */ 176 li t0, EXC_SYSCALL 177 beq s4, t0, handle_syscall 178 179 /* Handle other exceptions */ 180 slli t0, s4, RISCV_LGPTR 181 la t1, excp_vect_table 182 la t2, excp_vect_table_end 183 move a0, sp /* pt_regs */ 184 add t0, t1, t0 185 /* Check if exception code lies within bounds */ 186 bgeu t0, t2, 1f 187 REG_L t0, 0(t0) 188 jr t0 1891: 190 tail do_trap_unknown 191 192handle_syscall: 193 /* save the initial A0 value (needed in signal handlers) */ 194 REG_S a0, PT_ORIG_A0(sp) 195 /* 196 * Advance SEPC to avoid executing the original 197 * scall instruction on sret 198 */ 199 addi s2, s2, 0x4 200 REG_S s2, PT_SEPC(sp) 201 /* System calls run with interrupts enabled */ 202 csrs sstatus, SR_SIE 203 /* Trace syscalls, but only if requested by the user. */ 204 REG_L t0, TASK_TI_FLAGS(tp) 205 andi t0, t0, _TIF_SYSCALL_TRACE 206 bnez t0, handle_syscall_trace_enter 207check_syscall_nr: 208 /* Check to make sure we don't jump to a bogus syscall number. */ 209 li t0, __NR_syscalls 210 la s0, sys_ni_syscall 211 /* Syscall number held in a7 */ 212 bgeu a7, t0, 1f 213 la s0, sys_call_table 214 slli t0, a7, RISCV_LGPTR 215 add s0, s0, t0 216 REG_L s0, 0(s0) 2171: 218 jalr s0 219 220ret_from_syscall: 221 /* Set user a0 to kernel a0 */ 222 REG_S a0, PT_A0(sp) 223 /* Trace syscalls, but only if requested by the user. */ 224 REG_L t0, TASK_TI_FLAGS(tp) 225 andi t0, t0, _TIF_SYSCALL_TRACE 226 bnez t0, handle_syscall_trace_exit 227 228ret_from_exception: 229 REG_L s0, PT_SSTATUS(sp) 230 csrc sstatus, SR_SIE 231 andi s0, s0, SR_SPP 232 bnez s0, restore_all 233 234resume_userspace: 235 /* Interrupts must be disabled here so flags are checked atomically */ 236 REG_L s0, TASK_TI_FLAGS(tp) /* current_thread_info->flags */ 237 andi s1, s0, _TIF_WORK_MASK 238 bnez s1, work_pending 239 240 /* Save unwound kernel stack pointer in thread_info */ 241 addi s0, sp, PT_SIZE_ON_STACK 242 REG_S s0, TASK_TI_KERNEL_SP(tp) 243 244 /* 245 * Save TP into sscratch, so we can find the kernel data structures 246 * again. 247 */ 248 csrw sscratch, tp 249 250restore_all: 251 RESTORE_ALL 252 sret 253 254work_pending: 255 /* Enter slow path for supplementary processing */ 256 la ra, ret_from_exception 257 andi s1, s0, _TIF_NEED_RESCHED 258 bnez s1, work_resched 259work_notifysig: 260 /* Handle pending signals and notify-resume requests */ 261 csrs sstatus, SR_SIE /* Enable interrupts for do_notify_resume() */ 262 move a0, sp /* pt_regs */ 263 move a1, s0 /* current_thread_info->flags */ 264 tail do_notify_resume 265work_resched: 266 tail schedule 267 268/* Slow paths for ptrace. */ 269handle_syscall_trace_enter: 270 move a0, sp 271 call do_syscall_trace_enter 272 REG_L a0, PT_A0(sp) 273 REG_L a1, PT_A1(sp) 274 REG_L a2, PT_A2(sp) 275 REG_L a3, PT_A3(sp) 276 REG_L a4, PT_A4(sp) 277 REG_L a5, PT_A5(sp) 278 REG_L a6, PT_A6(sp) 279 REG_L a7, PT_A7(sp) 280 j check_syscall_nr 281handle_syscall_trace_exit: 282 move a0, sp 283 call do_syscall_trace_exit 284 j ret_from_exception 285 286END(handle_exception) 287 288ENTRY(ret_from_fork) 289 la ra, ret_from_exception 290 tail schedule_tail 291ENDPROC(ret_from_fork) 292 293ENTRY(ret_from_kernel_thread) 294 call schedule_tail 295 /* Call fn(arg) */ 296 la ra, ret_from_exception 297 move a0, s1 298 jr s0 299ENDPROC(ret_from_kernel_thread) 300 301 302/* 303 * Integer register context switch 304 * The callee-saved registers must be saved and restored. 305 * 306 * a0: previous task_struct (must be preserved across the switch) 307 * a1: next task_struct 308 * 309 * The value of a0 and a1 must be preserved by this function, as that's how 310 * arguments are passed to schedule_tail. 311 */ 312ENTRY(__switch_to) 313 /* Save context into prev->thread */ 314 li a4, TASK_THREAD_RA 315 add a3, a0, a4 316 add a4, a1, a4 317 REG_S ra, TASK_THREAD_RA_RA(a3) 318 REG_S sp, TASK_THREAD_SP_RA(a3) 319 REG_S s0, TASK_THREAD_S0_RA(a3) 320 REG_S s1, TASK_THREAD_S1_RA(a3) 321 REG_S s2, TASK_THREAD_S2_RA(a3) 322 REG_S s3, TASK_THREAD_S3_RA(a3) 323 REG_S s4, TASK_THREAD_S4_RA(a3) 324 REG_S s5, TASK_THREAD_S5_RA(a3) 325 REG_S s6, TASK_THREAD_S6_RA(a3) 326 REG_S s7, TASK_THREAD_S7_RA(a3) 327 REG_S s8, TASK_THREAD_S8_RA(a3) 328 REG_S s9, TASK_THREAD_S9_RA(a3) 329 REG_S s10, TASK_THREAD_S10_RA(a3) 330 REG_S s11, TASK_THREAD_S11_RA(a3) 331 /* Restore context from next->thread */ 332 REG_L ra, TASK_THREAD_RA_RA(a4) 333 REG_L sp, TASK_THREAD_SP_RA(a4) 334 REG_L s0, TASK_THREAD_S0_RA(a4) 335 REG_L s1, TASK_THREAD_S1_RA(a4) 336 REG_L s2, TASK_THREAD_S2_RA(a4) 337 REG_L s3, TASK_THREAD_S3_RA(a4) 338 REG_L s4, TASK_THREAD_S4_RA(a4) 339 REG_L s5, TASK_THREAD_S5_RA(a4) 340 REG_L s6, TASK_THREAD_S6_RA(a4) 341 REG_L s7, TASK_THREAD_S7_RA(a4) 342 REG_L s8, TASK_THREAD_S8_RA(a4) 343 REG_L s9, TASK_THREAD_S9_RA(a4) 344 REG_L s10, TASK_THREAD_S10_RA(a4) 345 REG_L s11, TASK_THREAD_S11_RA(a4) 346 /* Swap the CPU entry around. */ 347 lw a3, TASK_TI_CPU(a0) 348 lw a4, TASK_TI_CPU(a1) 349 sw a3, TASK_TI_CPU(a1) 350 sw a4, TASK_TI_CPU(a0) 351#if TASK_TI != 0 352#error "TASK_TI != 0: tp will contain a 'struct thread_info', not a 'struct task_struct' so get_current() won't work." 353 addi tp, a1, TASK_TI 354#else 355 move tp, a1 356#endif 357 ret 358ENDPROC(__switch_to) 359 360ENTRY(__fstate_save) 361 li a2, TASK_THREAD_F0 362 add a0, a0, a2 363 li t1, SR_FS 364 csrs sstatus, t1 365 frcsr t0 366 fsd f0, TASK_THREAD_F0_F0(a0) 367 fsd f1, TASK_THREAD_F1_F0(a0) 368 fsd f2, TASK_THREAD_F2_F0(a0) 369 fsd f3, TASK_THREAD_F3_F0(a0) 370 fsd f4, TASK_THREAD_F4_F0(a0) 371 fsd f5, TASK_THREAD_F5_F0(a0) 372 fsd f6, TASK_THREAD_F6_F0(a0) 373 fsd f7, TASK_THREAD_F7_F0(a0) 374 fsd f8, TASK_THREAD_F8_F0(a0) 375 fsd f9, TASK_THREAD_F9_F0(a0) 376 fsd f10, TASK_THREAD_F10_F0(a0) 377 fsd f11, TASK_THREAD_F11_F0(a0) 378 fsd f12, TASK_THREAD_F12_F0(a0) 379 fsd f13, TASK_THREAD_F13_F0(a0) 380 fsd f14, TASK_THREAD_F14_F0(a0) 381 fsd f15, TASK_THREAD_F15_F0(a0) 382 fsd f16, TASK_THREAD_F16_F0(a0) 383 fsd f17, TASK_THREAD_F17_F0(a0) 384 fsd f18, TASK_THREAD_F18_F0(a0) 385 fsd f19, TASK_THREAD_F19_F0(a0) 386 fsd f20, TASK_THREAD_F20_F0(a0) 387 fsd f21, TASK_THREAD_F21_F0(a0) 388 fsd f22, TASK_THREAD_F22_F0(a0) 389 fsd f23, TASK_THREAD_F23_F0(a0) 390 fsd f24, TASK_THREAD_F24_F0(a0) 391 fsd f25, TASK_THREAD_F25_F0(a0) 392 fsd f26, TASK_THREAD_F26_F0(a0) 393 fsd f27, TASK_THREAD_F27_F0(a0) 394 fsd f28, TASK_THREAD_F28_F0(a0) 395 fsd f29, TASK_THREAD_F29_F0(a0) 396 fsd f30, TASK_THREAD_F30_F0(a0) 397 fsd f31, TASK_THREAD_F31_F0(a0) 398 sw t0, TASK_THREAD_FCSR_F0(a0) 399 csrc sstatus, t1 400 ret 401ENDPROC(__fstate_save) 402 403ENTRY(__fstate_restore) 404 li a2, TASK_THREAD_F0 405 add a0, a0, a2 406 li t1, SR_FS 407 lw t0, TASK_THREAD_FCSR_F0(a0) 408 csrs sstatus, t1 409 fld f0, TASK_THREAD_F0_F0(a0) 410 fld f1, TASK_THREAD_F1_F0(a0) 411 fld f2, TASK_THREAD_F2_F0(a0) 412 fld f3, TASK_THREAD_F3_F0(a0) 413 fld f4, TASK_THREAD_F4_F0(a0) 414 fld f5, TASK_THREAD_F5_F0(a0) 415 fld f6, TASK_THREAD_F6_F0(a0) 416 fld f7, TASK_THREAD_F7_F0(a0) 417 fld f8, TASK_THREAD_F8_F0(a0) 418 fld f9, TASK_THREAD_F9_F0(a0) 419 fld f10, TASK_THREAD_F10_F0(a0) 420 fld f11, TASK_THREAD_F11_F0(a0) 421 fld f12, TASK_THREAD_F12_F0(a0) 422 fld f13, TASK_THREAD_F13_F0(a0) 423 fld f14, TASK_THREAD_F14_F0(a0) 424 fld f15, TASK_THREAD_F15_F0(a0) 425 fld f16, TASK_THREAD_F16_F0(a0) 426 fld f17, TASK_THREAD_F17_F0(a0) 427 fld f18, TASK_THREAD_F18_F0(a0) 428 fld f19, TASK_THREAD_F19_F0(a0) 429 fld f20, TASK_THREAD_F20_F0(a0) 430 fld f21, TASK_THREAD_F21_F0(a0) 431 fld f22, TASK_THREAD_F22_F0(a0) 432 fld f23, TASK_THREAD_F23_F0(a0) 433 fld f24, TASK_THREAD_F24_F0(a0) 434 fld f25, TASK_THREAD_F25_F0(a0) 435 fld f26, TASK_THREAD_F26_F0(a0) 436 fld f27, TASK_THREAD_F27_F0(a0) 437 fld f28, TASK_THREAD_F28_F0(a0) 438 fld f29, TASK_THREAD_F29_F0(a0) 439 fld f30, TASK_THREAD_F30_F0(a0) 440 fld f31, TASK_THREAD_F31_F0(a0) 441 fscsr t0 442 csrc sstatus, t1 443 ret 444ENDPROC(__fstate_restore) 445 446 447 .section ".rodata" 448 /* Exception vector table */ 449ENTRY(excp_vect_table) 450 RISCV_PTR do_trap_insn_misaligned 451 RISCV_PTR do_trap_insn_fault 452 RISCV_PTR do_trap_insn_illegal 453 RISCV_PTR do_trap_break 454 RISCV_PTR do_trap_load_misaligned 455 RISCV_PTR do_trap_load_fault 456 RISCV_PTR do_trap_store_misaligned 457 RISCV_PTR do_trap_store_fault 458 RISCV_PTR do_trap_ecall_u /* system call, gets intercepted */ 459 RISCV_PTR do_trap_ecall_s 460 RISCV_PTR do_trap_unknown 461 RISCV_PTR do_trap_ecall_m 462 RISCV_PTR do_page_fault /* instruction page fault */ 463 RISCV_PTR do_page_fault /* load page fault */ 464 RISCV_PTR do_trap_unknown 465 RISCV_PTR do_page_fault /* store page fault */ 466excp_vect_table_end: 467END(excp_vect_table) 468