xref: /openbmc/linux/arch/arc/kernel/entry.S (revision 39f75da7) 
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(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	btst r10, TIF_SYSCALL_TRACE
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	lr  r0, [efa]
84	mov r1, sp
85
86	FAKE_RET_FROM_EXCPN
87
88	bl  do_insterror_or_kprobe
89	b   ret_from_exception
90END(instr_service)
91
92; ---------------------------------------------
93; Machine Check Exception Handler
94; ---------------------------------------------
95
96ENTRY(EV_MachineCheck)
97
98	EXCEPTION_PROLOGUE
99
100	lr  r2, [ecr]
101	lr  r0, [efa]
102	mov r1, sp
103
104	; hardware auto-disables MMU, re-enable it to allow kernel vaddr
105	; access for say stack unwinding of modules for crash dumps
106	lr	r3, [ARC_REG_PID]
107	or	r3, r3, MMU_ENABLE
108	sr	r3, [ARC_REG_PID]
109
110	lsr  	r3, r2, 8
111	bmsk 	r3, r3, 7
112	brne    r3, ECR_C_MCHK_DUP_TLB, 1f
113
114	bl      do_tlb_overlap_fault
115	b       ret_from_exception
116
1171:
118	; DEAD END: can't do much, display Regs and HALT
119	SAVE_CALLEE_SAVED_USER
120
121	GET_CURR_TASK_FIELD_PTR   TASK_THREAD, r10
122	st  sp, [r10, THREAD_CALLEE_REG]
123
124	j  do_machine_check_fault
125
126END(EV_MachineCheck)
127
128; ---------------------------------------------
129; Privilege Violation Exception Handler
130; ---------------------------------------------
131ENTRY(EV_PrivilegeV)
132
133	EXCEPTION_PROLOGUE
134
135	lr  r0, [efa]
136	mov r1, sp
137
138	FAKE_RET_FROM_EXCPN
139
140	bl  do_privilege_fault
141	b   ret_from_exception
142END(EV_PrivilegeV)
143
144; ---------------------------------------------
145; Extension Instruction Exception Handler
146; ---------------------------------------------
147ENTRY(EV_Extension)
148
149	EXCEPTION_PROLOGUE
150
151	lr  r0, [efa]
152	mov r1, sp
153
154	FAKE_RET_FROM_EXCPN
155
156	bl  do_extension_fault
157	b   ret_from_exception
158END(EV_Extension)
159
160;################ Trap Handling (Syscall, Breakpoint) ##################
161
162; ---------------------------------------------
163; syscall Tracing
164; ---------------------------------------------
165tracesys:
166	; save EFA in case tracer wants the PC of traced task
167	; using ERET won't work since next-PC has already committed
168	GET_CURR_TASK_FIELD_PTR   TASK_THREAD, r11
169	st  r12, [r11, THREAD_FAULT_ADDR]	; thread.fault_address
170
171	; PRE Sys Call Ptrace hook
172	mov r0, sp			; pt_regs needed
173	bl  @syscall_trace_entry
174
175	; Tracing code now returns the syscall num (orig or modif)
176	mov r8, r0
177
178	; Do the Sys Call as we normally would.
179	; Validate the Sys Call number
180	cmp     r8,  NR_syscalls - 1
181	mov.hi  r0, -ENOSYS
182	bhi     tracesys_exit
183
184	; Restore the sys-call args. Mere invocation of the hook abv could have
185	; clobbered them (since they are in scratch regs). The tracer could also
186	; have deliberately changed the syscall args: r0-r7
187	ld  r0, [sp, PT_r0]
188	ld  r1, [sp, PT_r1]
189	ld  r2, [sp, PT_r2]
190	ld  r3, [sp, PT_r3]
191	ld  r4, [sp, PT_r4]
192	ld  r5, [sp, PT_r5]
193	ld  r6, [sp, PT_r6]
194	ld  r7, [sp, PT_r7]
195	ld.as   r9, [sys_call_table, r8]
196	jl      [r9]        ; Entry into Sys Call Handler
197
198tracesys_exit:
199	st  r0, [sp, PT_r0]     ; sys call return value in pt_regs
200
201	;POST Sys Call Ptrace Hook
202	bl  @syscall_trace_exit
203	b   ret_from_exception ; NOT ret_from_system_call at is saves r0 which
204	; we'd done before calling post hook above
205
206; ---------------------------------------------
207; Breakpoint TRAP
208; ---------------------------------------------
209trap_with_param:
210	mov r0, r12	; EFA in case ptracer/gdb wants stop_pc
211	mov r1, sp
212
213	; Save callee regs in case gdb wants to have a look
214	; SP will grow up by size of CALLEE Reg-File
215	; NOTE: clobbers r12
216	SAVE_CALLEE_SAVED_USER
217
218	; save location of saved Callee Regs @ thread_struct->pc
219	GET_CURR_TASK_FIELD_PTR   TASK_THREAD, r10
220	st  sp, [r10, THREAD_CALLEE_REG]
221
222	; Call the trap handler
223	bl  do_non_swi_trap
224
225	; unwind stack to discard Callee saved Regs
226	DISCARD_CALLEE_SAVED_USER
227
228	b   ret_from_exception
229
230; ---------------------------------------------
231; syscall TRAP
232; ABI: (r0-r7) upto 8 args, (r8) syscall number
233; ---------------------------------------------
234
235ENTRY(EV_Trap)
236
237	EXCEPTION_PROLOGUE
238
239	lr  r12, [efa]
240
241	FAKE_RET_FROM_EXCPN
242
243	;============ TRAP 1   :breakpoints
244	; Check ECR for trap with arg (PROLOGUE ensures r10 has ECR)
245	bmsk.f 0, r10, 7
246	bnz    trap_with_param
247
248	;============ TRAP  (no param): syscall top level
249
250	; If syscall tracing ongoing, invoke pre-post-hooks
251	GET_CURR_THR_INFO_FLAGS   r10
252	btst r10, TIF_SYSCALL_TRACE
253	bnz tracesys  ; this never comes back
254
255	;============ Normal syscall case
256
257	; syscall num shd not exceed the total system calls avail
258	cmp     r8,  NR_syscalls - 1
259	mov.hi  r0, -ENOSYS
260	bhi     .Lret_from_system_call
261
262	; Offset into the syscall_table and call handler
263	ld.as   r9,[sys_call_table, r8]
264	jl      [r9]        ; Entry into Sys Call Handler
265
266.Lret_from_system_call:
267
268	st  r0, [sp, PT_r0]     ; sys call return value in pt_regs
269
270	; fall through to ret_from_exception
271END(EV_Trap)
272
273;############# Return from Intr/Excp/Trap (Linux Specifics) ##############
274;
275; If ret to user mode do we need to handle signals, schedule() et al.
276
277ENTRY(ret_from_exception)
278
279	; Pre-{IRQ,Trap,Exception} K/U mode from pt_regs->status32
280	ld  r8, [sp, PT_status32]   ; returning to User/Kernel Mode
281
282	bbit0  r8, STATUS_U_BIT, resume_kernel_mode
283
284	; Before returning to User mode check-for-and-complete any pending work
285	; such as rescheduling/signal-delivery etc.
286resume_user_mode_begin:
287
288	; Disable IRQs to ensures that chk for pending work itself is atomic
289	; (and we don't end up missing a NEED_RESCHED/SIGPENDING due to an
290	; interim IRQ).
291	IRQ_DISABLE	r10
292
293	; Fast Path return to user mode if no pending work
294	GET_CURR_THR_INFO_FLAGS   r9
295	and.f  0,  r9, _TIF_WORK_MASK
296	bz     .Lrestore_regs
297
298	; --- (Slow Path #1) task preemption ---
299	bbit0  r9, TIF_NEED_RESCHED, .Lchk_pend_signals
300	mov    blink, resume_user_mode_begin  ; tail-call to U mode ret chks
301	j      @schedule 	; BTST+Bnz causes relo error in link
302
303.Lchk_pend_signals:
304	IRQ_ENABLE	r10
305
306	; --- (Slow Path #2) pending signal  ---
307	mov r0, sp	; pt_regs for arg to do_signal()/do_notify_resume()
308
309	GET_CURR_THR_INFO_FLAGS   r9
310	and.f  0,  r9, _TIF_SIGPENDING|_TIF_NOTIFY_SIGNAL
311	bz .Lchk_notify_resume
312
313	; Normal Trap/IRQ entry only saves Scratch (caller-saved) regs
314	; in pt_reg since the "C" ABI (kernel code) will automatically
315	; save/restore callee-saved regs.
316	;
317	; However, here we need to explicitly save callee regs because
318	; (i)  If this signal causes coredump - full regfile needed
319	; (ii) If signal is SIGTRAP/SIGSTOP, task is being traced thus
320	;      tracer might call PEEKUSR(CALLEE reg)
321	;
322	; NOTE: SP will grow up by size of CALLEE Reg-File
323	SAVE_CALLEE_SAVED_USER		; clobbers r12
324
325	; save location of saved Callee Regs @ thread_struct->callee
326	GET_CURR_TASK_FIELD_PTR   TASK_THREAD, r10
327	st  sp, [r10, THREAD_CALLEE_REG]
328
329	bl  @do_signal
330
331	; Ideally we want to discard the Callee reg above, however if this was
332	; a tracing signal, tracer could have done a POKEUSR(CALLEE reg)
333	RESTORE_CALLEE_SAVED_USER
334
335	b      resume_user_mode_begin	; loop back to start of U mode ret
336
337	; --- (Slow Path #3) notify_resume ---
338.Lchk_notify_resume:
339	btst   r9, TIF_NOTIFY_RESUME
340	blnz   @do_notify_resume
341	b      resume_user_mode_begin	; unconditionally back to U mode ret chks
342					; for single exit point from this block
343
344resume_kernel_mode:
345
346	; Disable Interrupts from this point on
347	; CONFIG_PREEMPTION: This is a must for preempt_schedule_irq()
348	; !CONFIG_PREEMPTION: To ensure restore_regs is intr safe
349	IRQ_DISABLE	r9
350
351#ifdef CONFIG_PREEMPTION
352
353	; Can't preempt if preemption disabled
354	GET_CURR_THR_INFO_FROM_SP   r10
355	ld  r8, [r10, THREAD_INFO_PREEMPT_COUNT]
356	brne  r8, 0, .Lrestore_regs
357
358	; check if this task's NEED_RESCHED flag set
359	ld  r9, [r10, THREAD_INFO_FLAGS]
360	bbit0  r9, TIF_NEED_RESCHED, .Lrestore_regs
361
362	; Invoke PREEMPTION
363	jl      preempt_schedule_irq
364
365	; preempt_schedule_irq() always returns with IRQ disabled
366#endif
367
368	b	.Lrestore_regs
369
370##### DONT ADD CODE HERE - .Lrestore_regs actually follows in entry-<isa>.S
371
372