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>
16 #if !IS_ENABLED(CONFIG_PREEMPTION)
17 .set resume_kernel, restore_all
20 ENTRY(handle_exception)
22 * If coming from userspace, preserve the user thread pointer and load
23 * the kernel thread pointer. If we came from the kernel, the scratch
24 * register will contain 0, and we should continue on the current TP.
26 csrrw tp, CSR_SCRATCH, tp
27 bnez tp, _save_context
31 REG_S sp, TASK_TI_KERNEL_SP(tp)
33 REG_S sp, TASK_TI_USER_SP(tp)
34 REG_L sp, TASK_TI_KERNEL_SP(tp)
35 addi sp, sp, -(PT_SIZE_ON_STACK)
67 * Disable user-mode memory access as it should only be set in the
68 * actual user copy routines.
70 * Disable the FPU to detect illegal usage of floating point in kernel
75 REG_L s0, TASK_TI_USER_SP(tp)
76 csrrc s1, CSR_STATUS, t0
82 REG_S s1, PT_STATUS(sp)
84 REG_S s3, PT_BADADDR(sp)
85 REG_S s4, PT_CAUSE(sp)
89 * Set the scratch register to 0, so that if a recursive exception
90 * occurs, the exception vector knows it came from the kernel
94 /* Load the global pointer */
97 la gp, __global_pointer$
100 #ifdef CONFIG_TRACE_IRQFLAGS
101 call trace_hardirqs_off
104 #ifdef CONFIG_CONTEXT_TRACKING
105 /* If previous state is in user mode, call context_tracking_user_exit. */
108 bnez a0, skip_context_tracking
109 call context_tracking_user_exit
110 skip_context_tracking:
114 * MSB of cause differentiates between
115 * interrupts and exceptions
119 la ra, ret_from_exception
121 /* Handle interrupts */
122 move a0, sp /* pt_regs */
123 la a1, handle_arch_irq
128 * Exceptions run with interrupts enabled or disabled depending on the
129 * state of SR_PIE in m/sstatus.
133 #ifdef CONFIG_TRACE_IRQFLAGS
134 call trace_hardirqs_on
136 csrs CSR_STATUS, SR_IE
139 la ra, ret_from_exception
140 /* Handle syscalls */
142 beq s4, t0, handle_syscall
144 /* Handle other exceptions */
145 slli t0, s4, RISCV_LGPTR
146 la t1, excp_vect_table
147 la t2, excp_vect_table_end
148 move a0, sp /* pt_regs */
150 /* Check if exception code lies within bounds */
158 #ifdef CONFIG_RISCV_M_MODE
160 * When running is M-Mode (no MMU config), MPIE does not get set.
161 * As a result, we need to force enable interrupts here because
162 * handle_exception did not do set SR_IE as it always sees SR_PIE
165 csrs CSR_STATUS, SR_IE
167 #if defined(CONFIG_TRACE_IRQFLAGS) || defined(CONFIG_CONTEXT_TRACKING)
168 /* Recover a0 - a7 for system calls */
178 /* save the initial A0 value (needed in signal handlers) */
179 REG_S a0, PT_ORIG_A0(sp)
181 * Advance SEPC to avoid executing the original
182 * scall instruction on sret
186 /* Trace syscalls, but only if requested by the user. */
187 REG_L t0, TASK_TI_FLAGS(tp)
188 andi t0, t0, _TIF_SYSCALL_WORK
189 bnez t0, handle_syscall_trace_enter
191 /* Check to make sure we don't jump to a bogus syscall number. */
193 la s0, sys_ni_syscall
195 * Syscall number held in a7.
196 * If syscall number is above allowed value, redirect to ni_syscall.
200 la s0, sys_call_table
201 slli t0, a7, RISCV_LGPTR
208 /* Set user a0 to kernel a0 */
211 * We didn't execute the actual syscall.
212 * Seccomp already set return value for the current task pt_regs.
213 * (If it was configured with SECCOMP_RET_ERRNO/TRACE)
215 ret_from_syscall_rejected:
216 /* Trace syscalls, but only if requested by the user. */
217 REG_L t0, TASK_TI_FLAGS(tp)
218 andi t0, t0, _TIF_SYSCALL_WORK
219 bnez t0, handle_syscall_trace_exit
222 REG_L s0, PT_STATUS(sp)
223 csrc CSR_STATUS, SR_IE
224 #ifdef CONFIG_TRACE_IRQFLAGS
225 call trace_hardirqs_off
227 #ifdef CONFIG_RISCV_M_MODE
228 /* the MPP value is too large to be used as an immediate arg for addi */
234 bnez s0, resume_kernel
237 /* Interrupts must be disabled here so flags are checked atomically */
238 REG_L s0, TASK_TI_FLAGS(tp) /* current_thread_info->flags */
239 andi s1, s0, _TIF_WORK_MASK
240 bnez s1, work_pending
242 #ifdef CONFIG_CONTEXT_TRACKING
243 call context_tracking_user_enter
246 /* Save unwound kernel stack pointer in thread_info */
247 addi s0, sp, PT_SIZE_ON_STACK
248 REG_S s0, TASK_TI_KERNEL_SP(tp)
251 * Save TP into the scratch register , so we can find the kernel data
257 #ifdef CONFIG_TRACE_IRQFLAGS
258 REG_L s1, PT_STATUS(sp)
261 call trace_hardirqs_on
264 call trace_hardirqs_off
267 REG_L a0, PT_STATUS(sp)
269 * The current load reservation is effectively part of the processor's
270 * state, in the sense that load reservations cannot be shared between
271 * different hart contexts. We can't actually save and restore a load
272 * reservation, so instead here we clear any existing reservation --
273 * it's always legal for implementations to clear load reservations at
274 * any point (as long as the forward progress guarantee is kept, but
275 * we'll ignore that here).
277 * Dangling load reservations can be the result of taking a trap in the
278 * middle of an LR/SC sequence, but can also be the result of a taken
279 * forward branch around an SC -- which is how we implement CAS. As a
280 * result we need to clear reservations between the last CAS and the
281 * jump back to the new context. While it is unlikely the store
282 * completes, implementations are allowed to expand reservations to be
286 REG_SC x0, a2, PT_EPC(sp)
315 REG_L x26, PT_S10(sp)
316 REG_L x27, PT_S11(sp)
324 #ifdef CONFIG_RISCV_M_MODE
330 #if IS_ENABLED(CONFIG_PREEMPTION)
332 REG_L s0, TASK_TI_PREEMPT_COUNT(tp)
334 REG_L s0, TASK_TI_FLAGS(tp)
335 andi s0, s0, _TIF_NEED_RESCHED
337 call preempt_schedule_irq
342 /* Enter slow path for supplementary processing */
343 la ra, ret_from_exception
344 andi s1, s0, _TIF_NEED_RESCHED
345 bnez s1, work_resched
347 /* Handle pending signals and notify-resume requests */
348 csrs CSR_STATUS, SR_IE /* Enable interrupts for do_notify_resume() */
349 move a0, sp /* pt_regs */
350 move a1, s0 /* current_thread_info->flags */
351 tail do_notify_resume
355 /* Slow paths for ptrace. */
356 handle_syscall_trace_enter:
358 call do_syscall_trace_enter
368 bnez t0, ret_from_syscall_rejected
370 handle_syscall_trace_exit:
372 call do_syscall_trace_exit
375 END(handle_exception)
378 la ra, ret_from_exception
380 ENDPROC(ret_from_fork)
382 ENTRY(ret_from_kernel_thread)
385 la ra, ret_from_exception
388 ENDPROC(ret_from_kernel_thread)
392 * Integer register context switch
393 * The callee-saved registers must be saved and restored.
395 * a0: previous task_struct (must be preserved across the switch)
396 * a1: next task_struct
398 * The value of a0 and a1 must be preserved by this function, as that's how
399 * arguments are passed to schedule_tail.
402 /* Save context into prev->thread */
403 li a4, TASK_THREAD_RA
406 REG_S ra, TASK_THREAD_RA_RA(a3)
407 REG_S sp, TASK_THREAD_SP_RA(a3)
408 REG_S s0, TASK_THREAD_S0_RA(a3)
409 REG_S s1, TASK_THREAD_S1_RA(a3)
410 REG_S s2, TASK_THREAD_S2_RA(a3)
411 REG_S s3, TASK_THREAD_S3_RA(a3)
412 REG_S s4, TASK_THREAD_S4_RA(a3)
413 REG_S s5, TASK_THREAD_S5_RA(a3)
414 REG_S s6, TASK_THREAD_S6_RA(a3)
415 REG_S s7, TASK_THREAD_S7_RA(a3)
416 REG_S s8, TASK_THREAD_S8_RA(a3)
417 REG_S s9, TASK_THREAD_S9_RA(a3)
418 REG_S s10, TASK_THREAD_S10_RA(a3)
419 REG_S s11, TASK_THREAD_S11_RA(a3)
420 /* Restore context from next->thread */
421 REG_L ra, TASK_THREAD_RA_RA(a4)
422 REG_L sp, TASK_THREAD_SP_RA(a4)
423 REG_L s0, TASK_THREAD_S0_RA(a4)
424 REG_L s1, TASK_THREAD_S1_RA(a4)
425 REG_L s2, TASK_THREAD_S2_RA(a4)
426 REG_L s3, TASK_THREAD_S3_RA(a4)
427 REG_L s4, TASK_THREAD_S4_RA(a4)
428 REG_L s5, TASK_THREAD_S5_RA(a4)
429 REG_L s6, TASK_THREAD_S6_RA(a4)
430 REG_L s7, TASK_THREAD_S7_RA(a4)
431 REG_L s8, TASK_THREAD_S8_RA(a4)
432 REG_L s9, TASK_THREAD_S9_RA(a4)
433 REG_L s10, TASK_THREAD_S10_RA(a4)
434 REG_L s11, TASK_THREAD_S11_RA(a4)
435 /* Swap the CPU entry around. */
436 lw a3, TASK_TI_CPU(a0)
437 lw a4, TASK_TI_CPU(a1)
438 sw a3, TASK_TI_CPU(a1)
439 sw a4, TASK_TI_CPU(a0)
440 /* The offset of thread_info in task_struct is zero. */
446 #define do_page_fault do_trap_unknown
450 /* Exception vector table */
451 ENTRY(excp_vect_table)
452 RISCV_PTR do_trap_insn_misaligned
453 RISCV_PTR do_trap_insn_fault
454 RISCV_PTR do_trap_insn_illegal
455 RISCV_PTR do_trap_break
456 RISCV_PTR do_trap_load_misaligned
457 RISCV_PTR do_trap_load_fault
458 RISCV_PTR do_trap_store_misaligned
459 RISCV_PTR do_trap_store_fault
460 RISCV_PTR do_trap_ecall_u /* system call, gets intercepted */
461 RISCV_PTR do_trap_ecall_s
462 RISCV_PTR do_trap_unknown
463 RISCV_PTR do_trap_ecall_m
464 RISCV_PTR do_page_fault /* instruction page fault */
465 RISCV_PTR do_page_fault /* load page fault */
466 RISCV_PTR do_trap_unknown
467 RISCV_PTR do_page_fault /* store page fault */
472 ENTRY(__user_rt_sigreturn)
473 li a7, __NR_rt_sigreturn
475 END(__user_rt_sigreturn)