| blob | fa2c08e3c05e6ee74ea0258b62cdf6580f98a385 |
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 */
15 #include <linux/init.h>
16 #include <linux/linkage.h>
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>
24 .text
25 .altmacro
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
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
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)
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
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
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
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)
144 REG_L x2, PT_SP(sp)
145 .endm
147 ENTRY(handle_exception)
148 SAVE_ALL
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
156 /* Load the global pointer */
157 .option push
158 .option norelax
159 la gp, __global_pointer$
160 .option pop
162 la ra, ret_from_exception
163 /*
164 * MSB of cause differentiates between
165 * interrupts and exceptions
166 */
167 bge s4, zero, 1f
169 /* Handle interrupts */
170 move a0, sp /* pt_regs */
171 move a1, s4 /* scause */
172 tail do_IRQ
173 1:
174 /* Exceptions run with interrupts enabled */
175 csrs sstatus, SR_SIE
177 /* Handle syscalls */
178 li t0, EXC_SYSCALL
179 beq s4, t0, handle_syscall
181 /* Handle other exceptions */
182 slli t0, s4, RISCV_LGPTR
183 la t1, excp_vect_table
184 la t2, excp_vect_table_end
185 move a0, sp /* pt_regs */
186 add t0, t1, t0
187 /* Check if exception code lies within bounds */
188 bgeu t0, t2, 1f
189 REG_L t0, 0(t0)
190 jr t0
191 1:
192 tail do_trap_unknown
194 handle_syscall:
195 /* save the initial A0 value (needed in signal handlers) */
196 REG_S a0, PT_ORIG_A0(sp)
197 /*
198 * Advance SEPC to avoid executing the original
199 * scall instruction on sret
200 */
201 addi s2, s2, 0x4
202 REG_S s2, PT_SEPC(sp)
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
207 check_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)
217 1:
218 jalr s0
220 ret_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
228 ret_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
234 resume_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
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)
244 /*
245 * Save TP into sscratch, so we can find the kernel data structures
246 * again.
247 */
248 csrw sscratch, tp
250 restore_all:
251 RESTORE_ALL
252 sret
254 work_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
259 work_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
265 work_resched:
266 tail schedule
268 /* Slow paths for ptrace. */
269 handle_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
281 handle_syscall_trace_exit:
282 move a0, sp
283 call do_syscall_trace_exit
284 j ret_from_exception
286 END(handle_exception)
288 ENTRY(ret_from_fork)
289 la ra, ret_from_exception
290 tail schedule_tail
291 ENDPROC(ret_from_fork)
293 ENTRY(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
299 ENDPROC(ret_from_kernel_thread)
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 */
312 ENTRY(__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
358 ENDPROC(__switch_to)
360 ENTRY(__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
401 ENDPROC(__fstate_save)
403 ENTRY(__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
444 ENDPROC(__fstate_restore)
447 .section ".rodata"
448 /* Exception vector table */
449 ENTRY(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 */
466 excp_vect_table_end:
467 END(excp_vect_table)