xref: /openbmc/linux/arch/arc/kernel/entry.S (revision 13347c10)
1/* SPDX-License-Identifier: GPL-2.0-only */
2/*
3 * Common Low Level Interrupts/Traps/Exceptions(non-TLB) Handling for ARC
4 * (included from entry-<isa>.S
5 *
6 * Copyright (C) 2014-15 Synopsys, Inc. (www.synopsys.com)
7 * Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com)
8 */
9
10/*------------------------------------------------------------------
11 *    Function                            ABI
12 *------------------------------------------------------------------
13 *
14 *  Arguments                           r0 - r7
15 *  Caller Saved Registers              r0 - r12
16 *  Callee Saved Registers              r13- r25
17 *  Global Pointer (gp)                 r26
18 *  Frame Pointer (fp)                  r27
19 *  Stack Pointer (sp)                  r28
20 *  Branch link register (blink)        r31
21 *------------------------------------------------------------------
22 */
23
24;################### Special Sys Call Wrappers ##########################
25
26ENTRY(sys_clone_wrapper)
27	SAVE_CALLEE_SAVED_USER
28	bl  @sys_clone
29	DISCARD_CALLEE_SAVED_USER
30
31	GET_CURR_THR_INFO_FLAGS   r10
32	and.f 0, r10, _TIF_SYSCALL_WORK
33	bnz   tracesys_exit
34
35	b .Lret_from_system_call
36END(sys_clone_wrapper)
37
38ENTRY(sys_clone3_wrapper)
39	SAVE_CALLEE_SAVED_USER
40	bl  @sys_clone3
41	DISCARD_CALLEE_SAVED_USER
42
43	GET_CURR_THR_INFO_FLAGS   r10
44	and.f 0, r10, _TIF_SYSCALL_WORK
45	bnz   tracesys_exit
46
47	b .Lret_from_system_call
48END(sys_clone3_wrapper)
49
50ENTRY(ret_from_fork)
51	; when the forked child comes here from the __switch_to function
52	; r0 has the last task pointer.
53	; put last task in scheduler queue
54	jl   @schedule_tail
55
56	ld   r9, [sp, PT_status32]
57	brne r9, 0, 1f
58
59	jl.d [r14]		; kernel thread entry point
60	mov  r0, r13		; (see PF_KTHREAD block in copy_thread)
61
621:
63	; Return to user space
64	; 1. Any forked task (Reach here via BRne above)
65	; 2. First ever init task (Reach here via return from JL above)
66	;    This is the historic "kernel_execve" use-case, to return to init
67	;    user mode, in a round about way since that is always done from
68	;    a kernel thread which is executed via JL above but always returns
69	;    out whenever kernel_execve (now inline do_fork()) is involved
70	b    ret_from_exception
71END(ret_from_fork)
72
73;################### Non TLB Exception Handling #############################
74
75; ---------------------------------------------
76; Instruction Error Exception Handler
77; ---------------------------------------------
78
79ENTRY(instr_service)
80
81	EXCEPTION_PROLOGUE
82
83	bl  do_insterror_or_kprobe
84	b   ret_from_exception
85END(instr_service)
86
87; ---------------------------------------------
88; Machine Check Exception Handler
89; ---------------------------------------------
90
91ENTRY(EV_MachineCheck)
92
93	EXCEPTION_PROLOGUE_KEEP_AE	; ECR returned in r10
94
95	lr  r0, [efa]
96	mov r1, sp
97
98	; MC excpetions disable MMU
99	ARC_MMU_REENABLE r3
100
101	lsr  	r3, r10, 8
102	bmsk 	r3, r3, 7
103	brne    r3, ECR_C_MCHK_DUP_TLB, 1f
104
105	bl      do_tlb_overlap_fault
106	b       ret_from_exception
107
1081:
109	; DEAD END: can't do much, display Regs and HALT
110	SAVE_CALLEE_SAVED_USER
111
112	GET_CURR_TASK_FIELD_PTR   TASK_THREAD, r10
113	st  sp, [r10, THREAD_CALLEE_REG]
114
115	j  do_machine_check_fault
116
117END(EV_MachineCheck)
118
119; ---------------------------------------------
120; Privilege Violation Exception Handler
121; ---------------------------------------------
122ENTRY(EV_PrivilegeV)
123
124	EXCEPTION_PROLOGUE
125
126	bl  do_privilege_fault
127	b   ret_from_exception
128END(EV_PrivilegeV)
129
130; ---------------------------------------------
131; Extension Instruction Exception Handler
132; ---------------------------------------------
133ENTRY(EV_Extension)
134
135	EXCEPTION_PROLOGUE
136
137	bl  do_extension_fault
138	b   ret_from_exception
139END(EV_Extension)
140
141;################ Trap Handling (Syscall, Breakpoint) ##################
142
143; ---------------------------------------------
144; syscall Tracing
145; ---------------------------------------------
146tracesys:
147	; safekeep EFA (r12) if syscall tracer wanted PC
148	; for traps, ERET is pre-commit so points to next-PC
149	GET_CURR_TASK_FIELD_PTR   TASK_THREAD, r11
150	st  r12, [r11, THREAD_FAULT_ADDR]	; thread.fault_address
151
152	; PRE syscall trace hook
153	mov r0, sp				; pt_regs
154	bl  @syscall_trace_enter
155
156	; Tracing code now returns the syscall num (orig or modif)
157	mov r8, r0
158
159	; Do the Sys Call as we normally would.
160	cmp     r8,  NR_syscalls - 1
161	mov.hi  r0, -ENOSYS
162	bhi     tracesys_exit
163
164	; Restore the sys-call args. Mere invocation of the hook abv could have
165	; clobbered them (since they are in scratch regs). The tracer could also
166	; have deliberately changed the syscall args: r0-r7
167	ld  r0, [sp, PT_r0]
168	ld  r1, [sp, PT_r1]
169	ld  r2, [sp, PT_r2]
170	ld  r3, [sp, PT_r3]
171	ld  r4, [sp, PT_r4]
172	ld  r5, [sp, PT_r5]
173	ld  r6, [sp, PT_r6]
174	ld  r7, [sp, PT_r7]
175	ld.as   r9, [sys_call_table, r8]
176	jl      [r9]
177
178tracesys_exit:
179	st  r0, [sp, PT_r0]
180
181	; POST syscall trace hook
182	mov r0, sp		; pt_regs needed
183	bl  @syscall_trace_exit
184
185	; don't call ret_from_system_call as it saves r0, already done above
186	b   ret_from_exception
187
188; ---------------------------------------------
189; Breakpoint TRAP
190; ---------------------------------------------
191trap_with_param:
192	mov r0, r12	; EFA in case ptracer/gdb wants stop_pc
193	mov r1, sp	; pt_regs
194
195	; save callee regs in case tracer/gdb wants to peek
196	SAVE_CALLEE_SAVED_USER
197
198	; safekeep ref to callee regs
199	GET_CURR_TASK_FIELD_PTR   TASK_THREAD, r10
200	st  sp, [r10, THREAD_CALLEE_REG]
201
202	; call the non syscall trap handler
203	bl  do_non_swi_trap
204
205	; unwind stack to discard callee regs
206	DISCARD_CALLEE_SAVED_USER
207
208	b   ret_from_exception
209
210; ---------------------------------------------
211; syscall TRAP
212; ABI: (r0-r7) upto 8 args, (r8) syscall number
213; ---------------------------------------------
214
215ENTRY(EV_Trap)
216
217	EXCEPTION_PROLOGUE_KEEP_AE
218
219	lr  r12, [efa]
220
221	FAKE_RET_FROM_EXCPN
222
223	;============ TRAP N : breakpoints, kprobes etc
224	bmsk.f 0, r10, 7
225	bnz    trap_with_param
226
227	;============ TRAP 0 (no param): syscall
228
229	; syscall tracing ongoing, invoke pre-post-hooks around syscall
230	GET_CURR_THR_INFO_FLAGS   r10
231	and.f 0, r10, _TIF_SYSCALL_WORK
232	bnz   tracesys  ; this never comes back
233
234	;============ Normal syscall case
235
236	cmp     r8,  NR_syscalls - 1
237	mov.hi  r0, -ENOSYS
238	bhi     .Lret_from_system_call
239
240	ld.as   r9,[sys_call_table, r8]
241	jl      [r9]
242
243.Lret_from_system_call:
244	st  r0, [sp, PT_r0]     ; sys call return value in pt_regs
245
246	; fall through to ret_from_exception
247END(EV_Trap)
248
249;############# Return from Intr/Excp/Trap (Linux Specifics) ##############
250;
251; If ret to user mode do we need to handle signals, schedule() et al.
252
253ENTRY(ret_from_exception)
254
255	; Pre-{IRQ,Trap,Exception} K/U mode from pt_regs->status32
256	ld  r8, [sp, PT_status32]   ; returning to User/Kernel Mode
257
258	bbit0  r8, STATUS_U_BIT, resume_kernel_mode
259
260	; Before returning to User mode check-for-and-complete any pending work
261	; such as rescheduling/signal-delivery etc.
262resume_user_mode_begin:
263
264	; Disable IRQs to ensures that chk for pending work itself is atomic
265	; (and we don't end up missing a NEED_RESCHED/SIGPENDING due to an
266	; interim IRQ).
267	IRQ_DISABLE	r10
268
269	; Fast Path return to user mode if no pending work
270	GET_CURR_THR_INFO_FLAGS   r9
271	and.f  0,  r9, _TIF_WORK_MASK
272	bz     .Lrestore_regs
273
274	; --- (Slow Path #1) task preemption ---
275	bbit0  r9, TIF_NEED_RESCHED, .Lchk_pend_signals
276	mov    blink, resume_user_mode_begin  ; tail-call to U mode ret chks
277	j      @schedule 	; BTST+Bnz causes relo error in link
278
279.Lchk_pend_signals:
280	IRQ_ENABLE	r10
281
282	; --- (Slow Path #2) pending signal  ---
283	mov r0, sp	; pt_regs for arg to do_signal()/do_notify_resume()
284
285	GET_CURR_THR_INFO_FLAGS   r9
286	and.f  0,  r9, _TIF_SIGPENDING|_TIF_NOTIFY_SIGNAL
287	bz .Lchk_notify_resume
288
289	; Normal Trap/IRQ entry only saves Scratch (caller-saved) regs
290	; in pt_reg since the "C" ABI (kernel code) will automatically
291	; save/restore callee-saved regs.
292	;
293	; However, here we need to explicitly save callee regs because
294	; (i)  If this signal causes coredump - full regfile needed
295	; (ii) If signal is SIGTRAP/SIGSTOP, task is being traced thus
296	;      tracer might call PEEKUSR(CALLEE reg)
297	;
298	; NOTE: SP will grow up by size of CALLEE Reg-File
299	SAVE_CALLEE_SAVED_USER
300
301	; save location of saved Callee Regs @ thread_struct->callee
302	GET_CURR_TASK_FIELD_PTR   TASK_THREAD, r10
303	st  sp, [r10, THREAD_CALLEE_REG]
304
305	bl  @do_signal
306
307	; Ideally we want to discard the Callee reg above, however if this was
308	; a tracing signal, tracer could have done a POKEUSR(CALLEE reg)
309	RESTORE_CALLEE_SAVED_USER
310
311	b      resume_user_mode_begin	; loop back to start of U mode ret
312
313	; --- (Slow Path #3) notify_resume ---
314.Lchk_notify_resume:
315	btst   r9, TIF_NOTIFY_RESUME
316	blnz   @do_notify_resume
317	b      resume_user_mode_begin	; unconditionally back to U mode ret chks
318					; for single exit point from this block
319
320resume_kernel_mode:
321
322	; Disable Interrupts from this point on
323	; CONFIG_PREEMPTION: This is a must for preempt_schedule_irq()
324	; !CONFIG_PREEMPTION: To ensure restore_regs is intr safe
325	IRQ_DISABLE	r9
326
327#ifdef CONFIG_PREEMPTION
328
329	; Can't preempt if preemption disabled
330	GET_CURR_THR_INFO_FROM_SP   r10
331	ld  r8, [r10, THREAD_INFO_PREEMPT_COUNT]
332	brne  r8, 0, .Lrestore_regs
333
334	; check if this task's NEED_RESCHED flag set
335	ld  r9, [r10, THREAD_INFO_FLAGS]
336	bbit0  r9, TIF_NEED_RESCHED, .Lrestore_regs
337
338	; Invoke PREEMPTION
339	jl      preempt_schedule_irq
340
341	; preempt_schedule_irq() always returns with IRQ disabled
342#endif
343
344	b	.Lrestore_regs
345
346##### DONT ADD CODE HERE - .Lrestore_regs actually follows in entry-<isa>.S
347
348