2 * Copyright (C) 2012 Regents of the University of California
3 * Copyright (C) 2017 SiFive
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.
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.
15 #include <linux/init.h>
16 #include <linux/linkage.h>
20 #include <asm/unistd.h>
21 #include <asm/thread_info.h>
22 #include <asm/asm-offsets.h>
28 * Prepares to enter a system call or exception by saving all registers to the
32 LOCAL _restore_kernel_tpsp
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.
40 csrrw tp, sscratch, tp
41 bnez tp, _save_context
45 REG_S sp, TASK_TI_KERNEL_SP(tp)
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)
81 * Disable user-mode memory access as it should only be set in the
82 * actual user copy routines.
84 * Disable the FPU to detect illegal usage of floating point in kernel
89 REG_L s0, TASK_TI_USER_SP(tp)
96 REG_S s1, PT_SSTATUS(sp)
98 REG_S s3, PT_SBADADDR(sp)
99 REG_S s4, PT_SCAUSE(sp)
104 * Prepares to return from a system call or exception by restoring all
105 * registers from the stack.
108 REG_L a0, PT_SSTATUS(sp)
109 REG_L a2, PT_SEPC(sp)
137 REG_L x26, PT_S10(sp)
138 REG_L x27, PT_S11(sp)
147 ENTRY(handle_exception)
151 * Set sscratch register to 0, so that if a recursive exception
152 * occurs, the exception vector knows it came from the kernel
156 /* Load the global pointer */
159 la gp, __global_pointer$
162 la ra, ret_from_exception
164 * MSB of cause differentiates between
165 * interrupts and exceptions
169 /* Handle interrupts */
170 move a0, sp /* pt_regs */
171 move a1, s4 /* scause */
174 /* Exceptions run with interrupts enabled */
177 /* Handle syscalls */
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 */
187 /* Check if exception code lies within bounds */
195 /* save the initial A0 value (needed in signal handlers) */
196 REG_S a0, PT_ORIG_A0(sp)
198 * Advance SEPC to avoid executing the original
199 * scall instruction on sret
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
208 /* Check to make sure we don't jump to a bogus syscall number. */
210 la s0, sys_ni_syscall
211 /* Syscall number held in a7 */
213 la s0, sys_call_table
214 slli t0, a7, RISCV_LGPTR
221 /* Set user a0 to kernel a0 */
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
229 REG_L s0, PT_SSTATUS(sp)
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)
245 * Save TP into sscratch, so we can find the kernel data structures
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
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
268 /* Slow paths for ptrace. */
269 handle_syscall_trace_enter:
271 call do_syscall_trace_enter
281 handle_syscall_trace_exit:
283 call do_syscall_trace_exit
286 END(handle_exception)
289 la ra, ret_from_exception
291 ENDPROC(ret_from_fork)
293 ENTRY(ret_from_kernel_thread)
296 la ra, ret_from_exception
299 ENDPROC(ret_from_kernel_thread)
303 * Integer register context switch
304 * The callee-saved registers must be saved and restored.
306 * a0: previous task_struct (must be preserved across the switch)
307 * a1: next task_struct
309 * The value of a0 and a1 must be preserved by this function, as that's how
310 * arguments are passed to schedule_tail.
313 /* Save context into prev->thread */
314 li a4, TASK_THREAD_RA
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)
352 #error "TASK_TI != 0: tp will contain a 'struct thread_info', not a 'struct task_struct' so get_current() won't work."
361 /* Exception vector table */
362 ENTRY(excp_vect_table)
363 RISCV_PTR do_trap_insn_misaligned
364 RISCV_PTR do_trap_insn_fault
365 RISCV_PTR do_trap_insn_illegal
366 RISCV_PTR do_trap_break
367 RISCV_PTR do_trap_load_misaligned
368 RISCV_PTR do_trap_load_fault
369 RISCV_PTR do_trap_store_misaligned
370 RISCV_PTR do_trap_store_fault
371 RISCV_PTR do_trap_ecall_u /* system call, gets intercepted */
372 RISCV_PTR do_trap_ecall_s
373 RISCV_PTR do_trap_unknown
374 RISCV_PTR do_trap_ecall_m
375 RISCV_PTR do_page_fault /* instruction page fault */
376 RISCV_PTR do_page_fault /* load page fault */
377 RISCV_PTR do_trap_unknown
378 RISCV_PTR do_page_fault /* store page fault */