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>
15 #include <asm/errata_list.h>
17 #if !IS_ENABLED(CONFIG_PREEMPTION)
18 .set resume_kernel, restore_all
21 ENTRY(handle_exception)
23 * If coming from userspace, preserve the user thread pointer and load
24 * the kernel thread pointer. If we came from the kernel, the scratch
25 * register will contain 0, and we should continue on the current TP.
27 csrrw tp, CSR_SCRATCH, tp
28 bnez tp, _save_context
32 REG_S sp, TASK_TI_KERNEL_SP(tp)
34 REG_S sp, TASK_TI_USER_SP(tp)
35 REG_L sp, TASK_TI_KERNEL_SP(tp)
36 addi sp, sp, -(PT_SIZE_ON_STACK)
68 * Disable user-mode memory access as it should only be set in the
69 * actual user copy routines.
71 * Disable the FPU to detect illegal usage of floating point in kernel
76 REG_L s0, TASK_TI_USER_SP(tp)
77 csrrc s1, CSR_STATUS, t0
83 REG_S s1, PT_STATUS(sp)
85 REG_S s3, PT_BADADDR(sp)
86 REG_S s4, PT_CAUSE(sp)
90 * Set the scratch register to 0, so that if a recursive exception
91 * occurs, the exception vector knows it came from the kernel
95 /* Load the global pointer */
98 la gp, __global_pointer$
101 #ifdef CONFIG_TRACE_IRQFLAGS
102 call trace_hardirqs_off
105 #ifdef CONFIG_CONTEXT_TRACKING
106 /* If previous state is in user mode, call context_tracking_user_exit. */
109 bnez a0, skip_context_tracking
110 call context_tracking_user_exit
111 skip_context_tracking:
115 * MSB of cause differentiates between
116 * interrupts and exceptions
120 la ra, ret_from_exception
122 /* Handle interrupts */
123 move a0, sp /* pt_regs */
124 la a1, handle_arch_irq
129 * Exceptions run with interrupts enabled or disabled depending on the
130 * state of SR_PIE in m/sstatus.
134 /* kprobes, entered via ebreak, must have interrupts disabled. */
135 li t0, EXC_BREAKPOINT
137 #ifdef CONFIG_TRACE_IRQFLAGS
138 call trace_hardirqs_on
140 csrs CSR_STATUS, SR_IE
143 la ra, ret_from_exception
144 /* Handle syscalls */
146 beq s4, t0, handle_syscall
148 /* Handle other exceptions */
149 slli t0, s4, RISCV_LGPTR
150 la t1, excp_vect_table
151 la t2, excp_vect_table_end
152 move a0, sp /* pt_regs */
154 /* Check if exception code lies within bounds */
162 #ifdef CONFIG_RISCV_M_MODE
164 * When running is M-Mode (no MMU config), MPIE does not get set.
165 * As a result, we need to force enable interrupts here because
166 * handle_exception did not do set SR_IE as it always sees SR_PIE
169 csrs CSR_STATUS, SR_IE
171 #if defined(CONFIG_TRACE_IRQFLAGS) || defined(CONFIG_CONTEXT_TRACKING)
172 /* Recover a0 - a7 for system calls */
182 /* save the initial A0 value (needed in signal handlers) */
183 REG_S a0, PT_ORIG_A0(sp)
185 * Advance SEPC to avoid executing the original
186 * scall instruction on sret
190 /* Trace syscalls, but only if requested by the user. */
191 REG_L t0, TASK_TI_FLAGS(tp)
192 andi t0, t0, _TIF_SYSCALL_WORK
193 bnez t0, handle_syscall_trace_enter
195 /* Check to make sure we don't jump to a bogus syscall number. */
197 la s0, sys_ni_syscall
199 * Syscall number held in a7.
200 * If syscall number is above allowed value, redirect to ni_syscall.
204 la s0, sys_call_table
205 slli t0, a7, RISCV_LGPTR
212 /* Set user a0 to kernel a0 */
215 * We didn't execute the actual syscall.
216 * Seccomp already set return value for the current task pt_regs.
217 * (If it was configured with SECCOMP_RET_ERRNO/TRACE)
219 ret_from_syscall_rejected:
220 /* Trace syscalls, but only if requested by the user. */
221 REG_L t0, TASK_TI_FLAGS(tp)
222 andi t0, t0, _TIF_SYSCALL_WORK
223 bnez t0, handle_syscall_trace_exit
226 REG_L s0, PT_STATUS(sp)
227 csrc CSR_STATUS, SR_IE
228 #ifdef CONFIG_TRACE_IRQFLAGS
229 call trace_hardirqs_off
231 #ifdef CONFIG_RISCV_M_MODE
232 /* the MPP value is too large to be used as an immediate arg for addi */
238 bnez s0, resume_kernel
241 /* Interrupts must be disabled here so flags are checked atomically */
242 REG_L s0, TASK_TI_FLAGS(tp) /* current_thread_info->flags */
243 andi s1, s0, _TIF_WORK_MASK
244 bnez s1, work_pending
246 #ifdef CONFIG_CONTEXT_TRACKING
247 call context_tracking_user_enter
250 /* Save unwound kernel stack pointer in thread_info */
251 addi s0, sp, PT_SIZE_ON_STACK
252 REG_S s0, TASK_TI_KERNEL_SP(tp)
255 * Save TP into the scratch register , so we can find the kernel data
261 #ifdef CONFIG_TRACE_IRQFLAGS
262 REG_L s1, PT_STATUS(sp)
265 call trace_hardirqs_on
268 call trace_hardirqs_off
271 REG_L a0, PT_STATUS(sp)
273 * The current load reservation is effectively part of the processor's
274 * state, in the sense that load reservations cannot be shared between
275 * different hart contexts. We can't actually save and restore a load
276 * reservation, so instead here we clear any existing reservation --
277 * it's always legal for implementations to clear load reservations at
278 * any point (as long as the forward progress guarantee is kept, but
279 * we'll ignore that here).
281 * Dangling load reservations can be the result of taking a trap in the
282 * middle of an LR/SC sequence, but can also be the result of a taken
283 * forward branch around an SC -- which is how we implement CAS. As a
284 * result we need to clear reservations between the last CAS and the
285 * jump back to the new context. While it is unlikely the store
286 * completes, implementations are allowed to expand reservations to be
290 REG_SC x0, a2, PT_EPC(sp)
319 REG_L x26, PT_S10(sp)
320 REG_L x27, PT_S11(sp)
328 #ifdef CONFIG_RISCV_M_MODE
334 #if IS_ENABLED(CONFIG_PREEMPTION)
336 REG_L s0, TASK_TI_PREEMPT_COUNT(tp)
338 REG_L s0, TASK_TI_FLAGS(tp)
339 andi s0, s0, _TIF_NEED_RESCHED
341 call preempt_schedule_irq
346 /* Enter slow path for supplementary processing */
347 la ra, ret_from_exception
348 andi s1, s0, _TIF_NEED_RESCHED
349 bnez s1, work_resched
351 /* Handle pending signals and notify-resume requests */
352 csrs CSR_STATUS, SR_IE /* Enable interrupts for do_notify_resume() */
353 move a0, sp /* pt_regs */
354 move a1, s0 /* current_thread_info->flags */
355 tail do_notify_resume
359 /* Slow paths for ptrace. */
360 handle_syscall_trace_enter:
362 call do_syscall_trace_enter
372 bnez t0, ret_from_syscall_rejected
374 handle_syscall_trace_exit:
376 call do_syscall_trace_exit
379 END(handle_exception)
382 la ra, ret_from_exception
384 ENDPROC(ret_from_fork)
386 ENTRY(ret_from_kernel_thread)
389 la ra, ret_from_exception
392 ENDPROC(ret_from_kernel_thread)
396 * Integer register context switch
397 * The callee-saved registers must be saved and restored.
399 * a0: previous task_struct (must be preserved across the switch)
400 * a1: next task_struct
402 * The value of a0 and a1 must be preserved by this function, as that's how
403 * arguments are passed to schedule_tail.
406 /* Save context into prev->thread */
407 li a4, TASK_THREAD_RA
410 REG_S ra, TASK_THREAD_RA_RA(a3)
411 REG_S sp, TASK_THREAD_SP_RA(a3)
412 REG_S s0, TASK_THREAD_S0_RA(a3)
413 REG_S s1, TASK_THREAD_S1_RA(a3)
414 REG_S s2, TASK_THREAD_S2_RA(a3)
415 REG_S s3, TASK_THREAD_S3_RA(a3)
416 REG_S s4, TASK_THREAD_S4_RA(a3)
417 REG_S s5, TASK_THREAD_S5_RA(a3)
418 REG_S s6, TASK_THREAD_S6_RA(a3)
419 REG_S s7, TASK_THREAD_S7_RA(a3)
420 REG_S s8, TASK_THREAD_S8_RA(a3)
421 REG_S s9, TASK_THREAD_S9_RA(a3)
422 REG_S s10, TASK_THREAD_S10_RA(a3)
423 REG_S s11, TASK_THREAD_S11_RA(a3)
424 /* Restore context from next->thread */
425 REG_L ra, TASK_THREAD_RA_RA(a4)
426 REG_L sp, TASK_THREAD_SP_RA(a4)
427 REG_L s0, TASK_THREAD_S0_RA(a4)
428 REG_L s1, TASK_THREAD_S1_RA(a4)
429 REG_L s2, TASK_THREAD_S2_RA(a4)
430 REG_L s3, TASK_THREAD_S3_RA(a4)
431 REG_L s4, TASK_THREAD_S4_RA(a4)
432 REG_L s5, TASK_THREAD_S5_RA(a4)
433 REG_L s6, TASK_THREAD_S6_RA(a4)
434 REG_L s7, TASK_THREAD_S7_RA(a4)
435 REG_L s8, TASK_THREAD_S8_RA(a4)
436 REG_L s9, TASK_THREAD_S9_RA(a4)
437 REG_L s10, TASK_THREAD_S10_RA(a4)
438 REG_L s11, TASK_THREAD_S11_RA(a4)
439 /* Swap the CPU entry around. */
440 lw a3, TASK_TI_CPU(a0)
441 lw a4, TASK_TI_CPU(a1)
442 sw a3, TASK_TI_CPU(a1)
443 sw a4, TASK_TI_CPU(a0)
444 /* The offset of thread_info in task_struct is zero. */
450 #define do_page_fault do_trap_unknown
455 /* Exception vector table */
456 ENTRY(excp_vect_table)
457 RISCV_PTR do_trap_insn_misaligned
458 ALT_INSN_FAULT(RISCV_PTR do_trap_insn_fault)
459 RISCV_PTR do_trap_insn_illegal
460 RISCV_PTR do_trap_break
461 RISCV_PTR do_trap_load_misaligned
462 RISCV_PTR do_trap_load_fault
463 RISCV_PTR do_trap_store_misaligned
464 RISCV_PTR do_trap_store_fault
465 RISCV_PTR do_trap_ecall_u /* system call, gets intercepted */
466 RISCV_PTR do_trap_ecall_s
467 RISCV_PTR do_trap_unknown
468 RISCV_PTR do_trap_ecall_m
469 /* instruciton page fault */
470 ALT_PAGE_FAULT(RISCV_PTR do_page_fault)
471 RISCV_PTR do_page_fault /* load page fault */
472 RISCV_PTR do_trap_unknown
473 RISCV_PTR do_page_fault /* store page fault */
478 ENTRY(__user_rt_sigreturn)
479 li a7, __NR_rt_sigreturn
481 END(__user_rt_sigreturn)