1 /* SPDX-License-Identifier: GPL-2.0-only */
3 * Copyright (C) 2012 Regents of the University of California
4 * Copyright (C) 2017 SiFive
7 #include <linux/init.h>
8 #include <linux/linkage.h>
12 #include <asm/unistd.h>
13 #include <asm/thread_info.h>
14 #include <asm/asm-offsets.h>
20 * Prepares to enter a system call or exception by saving all registers to the
24 LOCAL _restore_kernel_tpsp
28 * If coming from userspace, preserve the user thread pointer and load
29 * the kernel thread pointer. If we came from the kernel, sscratch
30 * will contain 0, and we should continue on the current TP.
32 csrrw tp, CSR_SSCRATCH, tp
33 bnez tp, _save_context
37 REG_S sp, TASK_TI_KERNEL_SP(tp)
39 REG_S sp, TASK_TI_USER_SP(tp)
40 REG_L sp, TASK_TI_KERNEL_SP(tp)
41 addi sp, sp, -(PT_SIZE_ON_STACK)
73 * Disable user-mode memory access as it should only be set in the
74 * actual user copy routines.
76 * Disable the FPU to detect illegal usage of floating point in kernel
81 REG_L s0, TASK_TI_USER_SP(tp)
82 csrrc s1, CSR_SSTATUS, t0
88 REG_S s1, PT_SSTATUS(sp)
90 REG_S s3, PT_SBADADDR(sp)
91 REG_S s4, PT_SCAUSE(sp)
96 * Prepares to return from a system call or exception by restoring all
97 * registers from the stack.
100 REG_L a0, PT_SSTATUS(sp)
101 REG_L a2, PT_SEPC(sp)
129 REG_L x26, PT_S10(sp)
130 REG_L x27, PT_S11(sp)
139 #if !IS_ENABLED(CONFIG_PREEMPT)
140 .set resume_kernel, restore_all
143 ENTRY(handle_exception)
147 * Set sscratch register to 0, so that if a recursive exception
148 * occurs, the exception vector knows it came from the kernel
150 csrw CSR_SSCRATCH, x0
152 /* Load the global pointer */
155 la gp, __global_pointer$
158 la ra, ret_from_exception
160 * MSB of cause differentiates between
161 * interrupts and exceptions
165 /* Handle interrupts */
166 move a0, sp /* pt_regs */
169 /* Exceptions run with interrupts enabled */
170 csrs CSR_SSTATUS, SR_SIE
172 /* Handle syscalls */
174 beq s4, t0, handle_syscall
176 /* Handle other exceptions */
177 slli t0, s4, RISCV_LGPTR
178 la t1, excp_vect_table
179 la t2, excp_vect_table_end
180 move a0, sp /* pt_regs */
182 /* Check if exception code lies within bounds */
190 /* save the initial A0 value (needed in signal handlers) */
191 REG_S a0, PT_ORIG_A0(sp)
193 * Advance SEPC to avoid executing the original
194 * scall instruction on sret
197 REG_S s2, PT_SEPC(sp)
198 /* Trace syscalls, but only if requested by the user. */
199 REG_L t0, TASK_TI_FLAGS(tp)
200 andi t0, t0, _TIF_SYSCALL_WORK
201 bnez t0, handle_syscall_trace_enter
203 /* Check to make sure we don't jump to a bogus syscall number. */
205 la s0, sys_ni_syscall
206 /* Syscall number held in a7 */
208 la s0, sys_call_table
209 slli t0, a7, RISCV_LGPTR
216 /* Set user a0 to kernel a0 */
218 /* Trace syscalls, but only if requested by the user. */
219 REG_L t0, TASK_TI_FLAGS(tp)
220 andi t0, t0, _TIF_SYSCALL_WORK
221 bnez t0, handle_syscall_trace_exit
224 REG_L s0, PT_SSTATUS(sp)
225 csrc CSR_SSTATUS, SR_SIE
227 bnez s0, resume_kernel
230 /* Interrupts must be disabled here so flags are checked atomically */
231 REG_L s0, TASK_TI_FLAGS(tp) /* current_thread_info->flags */
232 andi s1, s0, _TIF_WORK_MASK
233 bnez s1, work_pending
235 /* Save unwound kernel stack pointer in thread_info */
236 addi s0, sp, PT_SIZE_ON_STACK
237 REG_S s0, TASK_TI_KERNEL_SP(tp)
240 * Save TP into sscratch, so we can find the kernel data structures
243 csrw CSR_SSCRATCH, tp
249 #if IS_ENABLED(CONFIG_PREEMPT)
251 REG_L s0, TASK_TI_PREEMPT_COUNT(tp)
254 REG_L s0, TASK_TI_FLAGS(tp)
255 andi s0, s0, _TIF_NEED_RESCHED
257 call preempt_schedule_irq
262 /* Enter slow path for supplementary processing */
263 la ra, ret_from_exception
264 andi s1, s0, _TIF_NEED_RESCHED
265 bnez s1, work_resched
267 /* Handle pending signals and notify-resume requests */
268 csrs CSR_SSTATUS, SR_SIE /* Enable interrupts for do_notify_resume() */
269 move a0, sp /* pt_regs */
270 move a1, s0 /* current_thread_info->flags */
271 tail do_notify_resume
275 /* Slow paths for ptrace. */
276 handle_syscall_trace_enter:
278 call do_syscall_trace_enter
288 handle_syscall_trace_exit:
290 call do_syscall_trace_exit
293 END(handle_exception)
296 la ra, ret_from_exception
298 ENDPROC(ret_from_fork)
300 ENTRY(ret_from_kernel_thread)
303 la ra, ret_from_exception
306 ENDPROC(ret_from_kernel_thread)
310 * Integer register context switch
311 * The callee-saved registers must be saved and restored.
313 * a0: previous task_struct (must be preserved across the switch)
314 * a1: next task_struct
316 * The value of a0 and a1 must be preserved by this function, as that's how
317 * arguments are passed to schedule_tail.
320 /* Save context into prev->thread */
321 li a4, TASK_THREAD_RA
324 REG_S ra, TASK_THREAD_RA_RA(a3)
325 REG_S sp, TASK_THREAD_SP_RA(a3)
326 REG_S s0, TASK_THREAD_S0_RA(a3)
327 REG_S s1, TASK_THREAD_S1_RA(a3)
328 REG_S s2, TASK_THREAD_S2_RA(a3)
329 REG_S s3, TASK_THREAD_S3_RA(a3)
330 REG_S s4, TASK_THREAD_S4_RA(a3)
331 REG_S s5, TASK_THREAD_S5_RA(a3)
332 REG_S s6, TASK_THREAD_S6_RA(a3)
333 REG_S s7, TASK_THREAD_S7_RA(a3)
334 REG_S s8, TASK_THREAD_S8_RA(a3)
335 REG_S s9, TASK_THREAD_S9_RA(a3)
336 REG_S s10, TASK_THREAD_S10_RA(a3)
337 REG_S s11, TASK_THREAD_S11_RA(a3)
338 /* Restore context from next->thread */
339 REG_L ra, TASK_THREAD_RA_RA(a4)
340 REG_L sp, TASK_THREAD_SP_RA(a4)
341 REG_L s0, TASK_THREAD_S0_RA(a4)
342 REG_L s1, TASK_THREAD_S1_RA(a4)
343 REG_L s2, TASK_THREAD_S2_RA(a4)
344 REG_L s3, TASK_THREAD_S3_RA(a4)
345 REG_L s4, TASK_THREAD_S4_RA(a4)
346 REG_L s5, TASK_THREAD_S5_RA(a4)
347 REG_L s6, TASK_THREAD_S6_RA(a4)
348 REG_L s7, TASK_THREAD_S7_RA(a4)
349 REG_L s8, TASK_THREAD_S8_RA(a4)
350 REG_L s9, TASK_THREAD_S9_RA(a4)
351 REG_L s10, TASK_THREAD_S10_RA(a4)
352 REG_L s11, TASK_THREAD_S11_RA(a4)
353 /* Swap the CPU entry around. */
354 lw a3, TASK_TI_CPU(a0)
355 lw a4, TASK_TI_CPU(a1)
356 sw a3, TASK_TI_CPU(a1)
357 sw a4, TASK_TI_CPU(a0)
359 #error "TASK_TI != 0: tp will contain a 'struct thread_info', not a 'struct task_struct' so get_current() won't work."
368 /* Exception vector table */
369 ENTRY(excp_vect_table)
370 RISCV_PTR do_trap_insn_misaligned
371 RISCV_PTR do_trap_insn_fault
372 RISCV_PTR do_trap_insn_illegal
373 RISCV_PTR do_trap_break
374 RISCV_PTR do_trap_load_misaligned
375 RISCV_PTR do_trap_load_fault
376 RISCV_PTR do_trap_store_misaligned
377 RISCV_PTR do_trap_store_fault
378 RISCV_PTR do_trap_ecall_u /* system call, gets intercepted */
379 RISCV_PTR do_trap_ecall_s
380 RISCV_PTR do_trap_unknown
381 RISCV_PTR do_trap_ecall_m
382 RISCV_PTR do_page_fault /* instruction page fault */
383 RISCV_PTR do_page_fault /* load page fault */
384 RISCV_PTR do_trap_unknown
385 RISCV_PTR do_page_fault /* store page fault */