xref: /openbmc/linux/arch/arc/kernel/entry.S (revision e7253313) 
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	btst r10, TIF_SYSCALL_TRACE
33	bnz  tracesys_exit
34
35	b .Lret_from_system_call
36END(sys_clone_wrapper)
37
38ENTRY(ret_from_fork)
39	; when the forked child comes here from the __switch_to function
40	; r0 has the last task pointer.
41	; put last task in scheduler queue
42	jl   @schedule_tail
43
44	ld   r9, [sp, PT_status32]
45	brne r9, 0, 1f
46
47	jl.d [r14]		; kernel thread entry point
48	mov  r0, r13		; (see PF_KTHREAD block in copy_thread)
49
501:
51	; Return to user space
52	; 1. Any forked task (Reach here via BRne above)
53	; 2. First ever init task (Reach here via return from JL above)
54	;    This is the historic "kernel_execve" use-case, to return to init
55	;    user mode, in a round about way since that is always done from
56	;    a kernel thread which is executed via JL above but always returns
57	;    out whenever kernel_execve (now inline do_fork()) is involved
58	b    ret_from_exception
59END(ret_from_fork)
60
61;################### Non TLB Exception Handling #############################
62
63; ---------------------------------------------
64; Instruction Error Exception Handler
65; ---------------------------------------------
66
67ENTRY(instr_service)
68
69	EXCEPTION_PROLOGUE
70
71	lr  r0, [efa]
72	mov r1, sp
73
74	FAKE_RET_FROM_EXCPN
75
76	bl  do_insterror_or_kprobe
77	b   ret_from_exception
78END(instr_service)
79
80; ---------------------------------------------
81; Machine Check Exception Handler
82; ---------------------------------------------
83
84ENTRY(EV_MachineCheck)
85
86	EXCEPTION_PROLOGUE
87
88	lr  r2, [ecr]
89	lr  r0, [efa]
90	mov r1, sp
91
92	; hardware auto-disables MMU, re-enable it to allow kernel vaddr
93	; access for say stack unwinding of modules for crash dumps
94	lr	r3, [ARC_REG_PID]
95	or	r3, r3, MMU_ENABLE
96	sr	r3, [ARC_REG_PID]
97
98	lsr  	r3, r2, 8
99	bmsk 	r3, r3, 7
100	brne    r3, ECR_C_MCHK_DUP_TLB, 1f
101
102	bl      do_tlb_overlap_fault
103	b       ret_from_exception
104
1051:
106	; DEAD END: can't do much, display Regs and HALT
107	SAVE_CALLEE_SAVED_USER
108
109	GET_CURR_TASK_FIELD_PTR   TASK_THREAD, r10
110	st  sp, [r10, THREAD_CALLEE_REG]
111
112	j  do_machine_check_fault
113
114END(EV_MachineCheck)
115
116; ---------------------------------------------
117; Privilege Violation Exception Handler
118; ---------------------------------------------
119ENTRY(EV_PrivilegeV)
120
121	EXCEPTION_PROLOGUE
122
123	lr  r0, [efa]
124	mov r1, sp
125
126	FAKE_RET_FROM_EXCPN
127
128	bl  do_privilege_fault
129	b   ret_from_exception
130END(EV_PrivilegeV)
131
132; ---------------------------------------------
133; Extension Instruction Exception Handler
134; ---------------------------------------------
135ENTRY(EV_Extension)
136
137	EXCEPTION_PROLOGUE
138
139	lr  r0, [efa]
140	mov r1, sp
141
142	FAKE_RET_FROM_EXCPN
143
144	bl  do_extension_fault
145	b   ret_from_exception
146END(EV_Extension)
147
148;################ Trap Handling (Syscall, Breakpoint) ##################
149
150; ---------------------------------------------
151; syscall Tracing
152; ---------------------------------------------
153tracesys:
154	; save EFA in case tracer wants the PC of traced task
155	; using ERET won't work since next-PC has already committed
156	lr  r12, [efa]
157	GET_CURR_TASK_FIELD_PTR   TASK_THREAD, r11
158	st  r12, [r11, THREAD_FAULT_ADDR]	; thread.fault_address
159
160	; PRE Sys Call Ptrace hook
161	mov r0, sp			; pt_regs needed
162	bl  @syscall_trace_entry
163
164	; Tracing code now returns the syscall num (orig or modif)
165	mov r8, r0
166
167	; Do the Sys Call as we normally would.
168	; Validate the Sys Call number
169	cmp     r8,  NR_syscalls
170	mov.hi  r0, -ENOSYS
171	bhi     tracesys_exit
172
173	; Restore the sys-call args. Mere invocation of the hook abv could have
174	; clobbered them (since they are in scratch regs). The tracer could also
175	; have deliberately changed the syscall args: r0-r7
176	ld  r0, [sp, PT_r0]
177	ld  r1, [sp, PT_r1]
178	ld  r2, [sp, PT_r2]
179	ld  r3, [sp, PT_r3]
180	ld  r4, [sp, PT_r4]
181	ld  r5, [sp, PT_r5]
182	ld  r6, [sp, PT_r6]
183	ld  r7, [sp, PT_r7]
184	ld.as   r9, [sys_call_table, r8]
185	jl      [r9]        ; Entry into Sys Call Handler
186
187tracesys_exit:
188	st  r0, [sp, PT_r0]     ; sys call return value in pt_regs
189
190	;POST Sys Call Ptrace Hook
191	bl  @syscall_trace_exit
192	b   ret_from_exception ; NOT ret_from_system_call at is saves r0 which
193	; we'd done before calling post hook above
194
195; ---------------------------------------------
196; Breakpoint TRAP
197; ---------------------------------------------
198trap_with_param:
199
200	; stop_pc info by gdb needs this info
201	lr  r0, [efa]
202	mov r1, sp
203
204	; Now that we have read EFA, it is safe to do "fake" rtie
205	;   and get out of CPU exception mode
206	FAKE_RET_FROM_EXCPN
207
208	; Save callee regs in case gdb wants to have a look
209	; SP will grow up by size of CALLEE Reg-File
210	; NOTE: clobbers r12
211	SAVE_CALLEE_SAVED_USER
212
213	; save location of saved Callee Regs @ thread_struct->pc
214	GET_CURR_TASK_FIELD_PTR   TASK_THREAD, r10
215	st  sp, [r10, THREAD_CALLEE_REG]
216
217	; Call the trap handler
218	bl  do_non_swi_trap
219
220	; unwind stack to discard Callee saved Regs
221	DISCARD_CALLEE_SAVED_USER
222
223	b   ret_from_exception
224
225; ---------------------------------------------
226; syscall TRAP
227; ABI: (r0-r7) upto 8 args, (r8) syscall number
228; ---------------------------------------------
229
230ENTRY(EV_Trap)
231
232	EXCEPTION_PROLOGUE
233
234	;============ TRAP 1   :breakpoints
235	; Check ECR for trap with arg (PROLOGUE ensures r10 has ECR)
236	bmsk.f 0, r10, 7
237	bnz    trap_with_param
238
239	;============ TRAP  (no param): syscall top level
240
241	; First return from Exception to pure K mode (Exception/IRQs renabled)
242	FAKE_RET_FROM_EXCPN
243
244	; If syscall tracing ongoing, invoke pre-post-hooks
245	GET_CURR_THR_INFO_FLAGS   r10
246	btst r10, TIF_SYSCALL_TRACE
247	bnz tracesys  ; this never comes back
248
249	;============ Normal syscall case
250
251	; syscall num shd not exceed the total system calls avail
252	cmp     r8,  NR_syscalls
253	mov.hi  r0, -ENOSYS
254	bhi     .Lret_from_system_call
255
256	; Offset into the syscall_table and call handler
257	ld.as   r9,[sys_call_table, r8]
258	jl      [r9]        ; Entry into Sys Call Handler
259
260.Lret_from_system_call:
261
262	st  r0, [sp, PT_r0]     ; sys call return value in pt_regs
263
264	; fall through to ret_from_exception
265END(EV_Trap)
266
267;############# Return from Intr/Excp/Trap (Linux Specifics) ##############
268;
269; If ret to user mode do we need to handle signals, schedule() et al.
270
271ENTRY(ret_from_exception)
272
273	; Pre-{IRQ,Trap,Exception} K/U mode from pt_regs->status32
274	ld  r8, [sp, PT_status32]   ; returning to User/Kernel Mode
275
276	bbit0  r8, STATUS_U_BIT, resume_kernel_mode
277
278	; Before returning to User mode check-for-and-complete any pending work
279	; such as rescheduling/signal-delivery etc.
280resume_user_mode_begin:
281
282	; Disable IRQs to ensures that chk for pending work itself is atomic
283	; (and we don't end up missing a NEED_RESCHED/SIGPENDING due to an
284	; interim IRQ).
285	IRQ_DISABLE	r10
286
287	; Fast Path return to user mode if no pending work
288	GET_CURR_THR_INFO_FLAGS   r9
289	and.f  0,  r9, _TIF_WORK_MASK
290	bz     .Lrestore_regs
291
292	; --- (Slow Path #1) task preemption ---
293	bbit0  r9, TIF_NEED_RESCHED, .Lchk_pend_signals
294	mov    blink, resume_user_mode_begin  ; tail-call to U mode ret chks
295	j      @schedule 	; BTST+Bnz causes relo error in link
296
297.Lchk_pend_signals:
298	IRQ_ENABLE	r10
299
300	; --- (Slow Path #2) pending signal  ---
301	mov r0, sp	; pt_regs for arg to do_signal()/do_notify_resume()
302
303	GET_CURR_THR_INFO_FLAGS   r9
304	bbit0  r9, TIF_SIGPENDING, .Lchk_notify_resume
305
306	; Normal Trap/IRQ entry only saves Scratch (caller-saved) regs
307	; in pt_reg since the "C" ABI (kernel code) will automatically
308	; save/restore callee-saved regs.
309	;
310	; However, here we need to explicitly save callee regs because
311	; (i)  If this signal causes coredump - full regfile needed
312	; (ii) If signal is SIGTRAP/SIGSTOP, task is being traced thus
313	;      tracer might call PEEKUSR(CALLEE reg)
314	;
315	; NOTE: SP will grow up by size of CALLEE Reg-File
316	SAVE_CALLEE_SAVED_USER		; clobbers r12
317
318	; save location of saved Callee Regs @ thread_struct->callee
319	GET_CURR_TASK_FIELD_PTR   TASK_THREAD, r10
320	st  sp, [r10, THREAD_CALLEE_REG]
321
322	bl  @do_signal
323
324	; Ideally we want to discard the Callee reg above, however if this was
325	; a tracing signal, tracer could have done a POKEUSR(CALLEE reg)
326	RESTORE_CALLEE_SAVED_USER
327
328	b      resume_user_mode_begin	; loop back to start of U mode ret
329
330	; --- (Slow Path #3) notify_resume ---
331.Lchk_notify_resume:
332	btst   r9, TIF_NOTIFY_RESUME
333	blnz   @do_notify_resume
334	b      resume_user_mode_begin	; unconditionally back to U mode ret chks
335					; for single exit point from this block
336
337resume_kernel_mode:
338
339	; Disable Interrupts from this point on
340	; CONFIG_PREEMPT: This is a must for preempt_schedule_irq()
341	; !CONFIG_PREEMPT: To ensure restore_regs is intr safe
342	IRQ_DISABLE	r9
343
344#ifdef CONFIG_PREEMPT
345
346	; Can't preempt if preemption disabled
347	GET_CURR_THR_INFO_FROM_SP   r10
348	ld  r8, [r10, THREAD_INFO_PREEMPT_COUNT]
349	brne  r8, 0, .Lrestore_regs
350
351	; check if this task's NEED_RESCHED flag set
352	ld  r9, [r10, THREAD_INFO_FLAGS]
353	bbit0  r9, TIF_NEED_RESCHED, .Lrestore_regs
354
355	; Invoke PREEMPTION
356	jl      preempt_schedule_irq
357
358	; preempt_schedule_irq() always returns with IRQ disabled
359#endif
360
361	b	.Lrestore_regs
362
363##### DONT ADD CODE HERE - .Lrestore_regs actually follows in entry-<isa>.S
364
365