xref: /openbmc/linux/arch/arc/kernel/entry-compact.S (revision 13347c10)
1/* SPDX-License-Identifier: GPL-2.0-only */
2/*
3 * Low Level Interrupts/Traps/Exceptions(non-TLB) Handling for ARCompact ISA
4 *
5 * Copyright (C) 2014-15 Synopsys, Inc. (www.synopsys.com)
6 * Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com)
7 *
8 * vineetg: May 2011
9 *  -Userspace unaligned access emulation
10 *
11 * vineetg: Feb 2011 (ptrace low level code fixes)
12 *  -traced syscall return code (r0) was not saved into pt_regs for restoring
13 *   into user reg-file when traded task rets to user space.
14 *  -syscalls needing arch-wrappers (mainly for passing sp as pt_regs)
15 *   were not invoking post-syscall trace hook (jumping directly into
16 *   ret_from_system_call)
17 *
18 * vineetg: Nov 2010:
19 *  -Vector table jumps (@8 bytes) converted into branches (@4 bytes)
20 *  -To maintain the slot size of 8 bytes/vector, added nop, which is
21 *   not executed at runtime.
22 *
23 * vineetg: Nov 2009 (Everything needed for TIF_RESTORE_SIGMASK)
24 *  -do_signal()invoked upon TIF_RESTORE_SIGMASK as well
25 *  -Wrappers for sys_{,rt_}sigsuspend() no longer needed as they don't
26 *   need ptregs anymore
27 *
28 * Vineetg: Oct 2009
29 *  -In a rare scenario, Process gets a Priv-V exception and gets scheduled
30 *   out. Since we don't do FAKE RTIE for Priv-V, CPU exception state remains
31 *   active (AE bit enabled).  This causes a double fault for a subseq valid
32 *   exception. Thus FAKE RTIE needed in low level Priv-Violation handler.
33 *   Instr Error could also cause similar scenario, so same there as well.
34 *
35 * Vineetg: March 2009 (Supporting 2 levels of Interrupts)
36 *
37 * Vineetg: Aug 28th 2008: Bug #94984
38 *  -Zero Overhead Loop Context shd be cleared when entering IRQ/EXcp/Trap
39 *   Normally CPU does this automatically, however when doing FAKE rtie,
40 *   we need to explicitly do this. The problem in macros
41 *   FAKE_RET_FROM_EXCPN and FAKE_RET_FROM_EXCPN_LOCK_IRQ was that this bit
42 *   was being "CLEARED" rather then "SET". Since it is Loop INHIBIT Bit,
43 *   setting it and not clearing it clears ZOL context
44 *
45 * Vineetg: May 16th, 2008
46 *  - r25 now contains the Current Task when in kernel
47 *
48 * Vineetg: Dec 22, 2007
49 *    Minor Surgery of Low Level ISR to make it SMP safe
50 *    - MMU_SCRATCH0 Reg used for freeing up r9 in Level 1 ISR
51 *    - _current_task is made an array of NR_CPUS
52 *    - Access of _current_task wrapped inside a macro so that if hardware
53 *       team agrees for a dedicated reg, no other code is touched
54 *
55 * Amit Bhor, Rahul Trivedi, Kanika Nema, Sameer Dhavale : Codito Tech 2004
56 */
57
58#include <linux/errno.h>
59#include <linux/linkage.h>	/* {ENTRY,EXIT} */
60#include <asm/entry.h>
61#include <asm/irqflags.h>
62
63	.cpu A7
64
65;############################ Vector Table #################################
66
67.macro VECTOR  lbl
68#if 1   /* Just in case, build breaks */
69	j   \lbl
70#else
71	b   \lbl
72	nop
73#endif
74.endm
75
76	.section .vector, "ax",@progbits
77	.align 4
78
79/* Each entry in the vector table must occupy 2 words. Since it is a jump
80 * across sections (.vector to .text) we are guaranteed that 'j somewhere'
81 * will use the 'j limm' form of the instruction as long as somewhere is in
82 * a section other than .vector.
83 */
84
85; ********* Critical System Events **********************
86VECTOR   res_service             ; 0x0, Reset Vector	(0x0)
87VECTOR   mem_service             ; 0x8, Mem exception   (0x1)
88VECTOR   instr_service           ; 0x10, Instrn Error   (0x2)
89
90; ******************** Device ISRs **********************
91#ifdef CONFIG_ARC_COMPACT_IRQ_LEVELS
92VECTOR   handle_interrupt_level2
93#else
94VECTOR   handle_interrupt_level1
95#endif
96
97.rept   28
98VECTOR   handle_interrupt_level1 ; Other devices
99.endr
100
101/* FOR ARC600: timer = 0x3, uart = 0x8, emac = 0x10 */
102
103; ******************** Exceptions **********************
104VECTOR   EV_MachineCheck         ; 0x100, Fatal Machine check   (0x20)
105VECTOR   EV_TLBMissI             ; 0x108, Instruction TLB miss  (0x21)
106VECTOR   EV_TLBMissD             ; 0x110, Data TLB miss         (0x22)
107VECTOR   EV_TLBProtV             ; 0x118, Protection Violation  (0x23)
108				 ;         or Misaligned Access
109VECTOR   EV_PrivilegeV           ; 0x120, Privilege Violation   (0x24)
110VECTOR   EV_Trap                 ; 0x128, Trap exception        (0x25)
111VECTOR   EV_Extension            ; 0x130, Extn Instruction Excp (0x26)
112
113.rept   24
114VECTOR   reserved                ; Reserved Exceptions
115.endr
116
117
118;##################### Scratch Mem for IRQ stack switching #############
119
120ARCFP_DATA int1_saved_reg
121	.align 32
122	.type   int1_saved_reg, @object
123	.size   int1_saved_reg, 4
124int1_saved_reg:
125	.zero 4
126
127/* Each Interrupt level needs its own scratch */
128ARCFP_DATA int2_saved_reg
129	.type   int2_saved_reg, @object
130	.size   int2_saved_reg, 4
131int2_saved_reg:
132	.zero 4
133
134; ---------------------------------------------
135	.section .text, "ax",@progbits
136
137
138reserved:
139	flag 1		; Unexpected event, halt
140
141;##################### Interrupt Handling ##############################
142
143#ifdef CONFIG_ARC_COMPACT_IRQ_LEVELS
144; ---------------------------------------------
145;  Level 2 ISR: Can interrupt a Level 1 ISR
146; ---------------------------------------------
147ENTRY(handle_interrupt_level2)
148
149	INTERRUPT_PROLOGUE 2
150
151	;------------------------------------------------------
152	; if L2 IRQ interrupted a L1 ISR, disable preemption
153	;
154	; This is to avoid a potential L1-L2-L1 scenario
155	;  -L1 IRQ taken
156	;  -L2 interrupts L1 (before L1 ISR could run)
157	;  -preemption off IRQ, user task in syscall picked to run
158	;  -RTIE to userspace
159	;	Returns from L2 context fine
160	;	But both L1 and L2 re-enabled, so another L1 can be taken
161	;	while prev L1 is still unserviced
162	;
163	;------------------------------------------------------
164
165	; L2 interrupting L1 implies both L2 and L1 active
166	; However both A2 and A1 are NOT set in STATUS32, thus
167	; need to check STATUS32_L2 to determine if L1 was active
168
169	ld r9, [sp, PT_status32]        ; get statu32_l2 (saved in pt_regs)
170	bbit0 r9, STATUS_A1_BIT, 1f     ; L1 not active when L2 IRQ, so normal
171
172	; bump thread_info->preempt_count (Disable preemption)
173	GET_CURR_THR_INFO_FROM_SP   r10
174	ld      r9, [r10, THREAD_INFO_PREEMPT_COUNT]
175	add     r9, r9, 1
176	st      r9, [r10, THREAD_INFO_PREEMPT_COUNT]
177
1781:
179	;------------------------------------------------------
180	; setup params for Linux common ISR and invoke it
181	;------------------------------------------------------
182	lr  r0, [icause2]
183	and r0, r0, 0x1f
184
185	bl.d  @arch_do_IRQ
186	mov r1, sp
187
188	mov r8,0x2
189	sr r8, [AUX_IRQ_LV12]       ; clear bit in Sticky Status Reg
190
191	b   ret_from_exception
192
193END(handle_interrupt_level2)
194
195#endif
196
197; ---------------------------------------------
198; User Mode Memory Bus Error Interrupt Handler
199; (Kernel mode memory errors handled via separate exception vectors)
200; ---------------------------------------------
201ENTRY(mem_service)
202
203	INTERRUPT_PROLOGUE 2
204
205	mov r0, ilink2
206	mov r1, sp
207
208	; User process needs to be killed with SIGBUS, but first need to get
209	; out of the L2 interrupt context (drop to pure kernel mode) and jump
210	; off to "C" code where SIGBUS in enqueued
211	lr  r3, [status32]
212	bclr r3, r3, STATUS_A2_BIT
213	or  r3, r3, (STATUS_E1_MASK|STATUS_E2_MASK)
214	sr  r3, [status32_l2]
215	mov ilink2, 1f
216	rtie
2171:
218	bl  do_memory_error
219	b   ret_from_exception
220END(mem_service)
221
222; ---------------------------------------------
223;  Level 1 ISR
224; ---------------------------------------------
225ENTRY(handle_interrupt_level1)
226
227	INTERRUPT_PROLOGUE 1
228
229	lr  r0, [icause1]
230	and r0, r0, 0x1f
231
232#ifdef CONFIG_TRACE_IRQFLAGS
233	; icause1 needs to be read early, before calling tracing, which
234	; can clobber scratch regs, hence use of stack to stash it
235	push r0
236	TRACE_ASM_IRQ_DISABLE
237	pop  r0
238#endif
239
240	bl.d  @arch_do_IRQ
241	mov r1, sp
242
243	mov r8,0x1
244	sr r8, [AUX_IRQ_LV12]       ; clear bit in Sticky Status Reg
245
246	b   ret_from_exception
247END(handle_interrupt_level1)
248
249;################### Non TLB Exception Handling #############################
250
251; ---------------------------------------------
252; Protection Violation Exception Handler
253; ---------------------------------------------
254
255ENTRY(EV_TLBProtV)
256
257	EXCEPTION_PROLOGUE	; ECR returned in r10
258
259	;------ (5) Type of Protection Violation? ----------
260	;
261	; ProtV Hardware Exception is triggered for Access Faults of 2 types
262	;   -Access Violation	: 00_23_(00|01|02|03)_00
263	;			         x  r  w  r+w
264	;   -Unaligned Access	: 00_23_04_00
265	bbit1 r10, ECR_C_BIT_PROTV_MISALIG_DATA, 4f
266
267	;========= (6a) Access Violation Processing ========
268	bl  do_page_fault
269	b   ret_from_exception
270
271	;========== (6b) Non aligned access ============
2724:
273
274	SAVE_CALLEE_SAVED_USER
275	mov r2, sp              ; callee_regs
276
277	bl  do_misaligned_access
278
279	; TBD: optimize - do this only if a callee reg was involved
280	; either a dst of emulated LD/ST or src with address-writeback
281	RESTORE_CALLEE_SAVED_USER
282
283	b   ret_from_exception
284
285END(EV_TLBProtV)
286
287; Wrapper for Linux page fault handler called from EV_TLBMiss*
288; Very similar to ProtV handler case (6a) above, but avoids the extra checks
289; for Misaligned access
290;
291ENTRY(call_do_page_fault)
292
293	EXCEPTION_PROLOGUE
294
295	mov blink, ret_from_exception
296	b  do_page_fault
297
298END(call_do_page_fault)
299
300;############# Common Handlers for ARCompact and ARCv2 ##############
301
302#include "entry.S"
303
304;############# Return from Intr/Excp/Trap (ARC Specifics) ##############
305;
306; Restore the saved sys context (common exit-path for EXCPN/IRQ/Trap)
307; IRQ shd definitely not happen between now and rtie
308; All 2 entry points to here already disable interrupts
309
310.Lrestore_regs:
311
312	# Interrupts are actually disabled from this point on, but will get
313	# reenabled after we return from interrupt/exception.
314	# But irq tracer needs to be told now...
315	TRACE_ASM_IRQ_ENABLE
316
317	lr	r10, [status32]
318
319	; Restore REG File. In case multiple Events outstanding,
320	; use the same priority as rtie: EXCPN, L2 IRQ, L1 IRQ, None
321	; Note that we use realtime STATUS32 (not pt_regs->status32) to
322	; decide that.
323
324	and.f	0, r10, (STATUS_A1_MASK|STATUS_A2_MASK)
325	bz	.Lexcep_or_pure_K_ret
326
327	; Returning from Interrupts (Level 1 or 2)
328
329#ifdef CONFIG_ARC_COMPACT_IRQ_LEVELS
330
331	; Level 2 interrupt return Path - from hardware standpoint
332	bbit0  r10, STATUS_A2_BIT, not_level2_interrupt
333
334	;------------------------------------------------------------------
335	; However the context returning might not have taken L2 intr itself
336	; e.g. Task'A' user-code -> L2 intr -> schedule -> 'B' user-code ret
337	; Special considerations needed for the context which took L2 intr
338
339	ld   r9, [sp, PT_event]        ; Ensure this is L2 intr context
340	brne r9, event_IRQ2, 149f
341
342	;------------------------------------------------------------------
343	; if L2 IRQ interrupted an L1 ISR,  we'd disabled preemption earlier
344	; so that sched doesn't move to new task, causing L1 to be delayed
345	; undeterministically. Now that we've achieved that, let's reset
346	; things to what they were, before returning from L2 context
347	;----------------------------------------------------------------
348
349	ld r9, [sp, PT_status32]       ; get statu32_l2 (saved in pt_regs)
350	bbit0 r9, STATUS_A1_BIT, 149f  ; L1 not active when L2 IRQ, so normal
351
352	; decrement thread_info->preempt_count (re-enable preemption)
353	GET_CURR_THR_INFO_FROM_SP   r10
354	ld      r9, [r10, THREAD_INFO_PREEMPT_COUNT]
355
356	; paranoid check, given A1 was active when A2 happened, preempt count
357	; must not be 0 because we would have incremented it.
358	; If this does happen we simply HALT as it means a BUG !!!
359	cmp     r9, 0
360	bnz     2f
361	flag 1
362
3632:
364	sub     r9, r9, 1
365	st      r9, [r10, THREAD_INFO_PREEMPT_COUNT]
366
367149:
368	INTERRUPT_EPILOGUE 2	; return from level 2 interrupt
369debug_marker_l2:
370	rtie
371
372not_level2_interrupt:
373
374#endif
375
376	INTERRUPT_EPILOGUE 1	; return from level 1 interrupt
377debug_marker_l1:
378	rtie
379
380.Lexcep_or_pure_K_ret:
381
382	;this case is for syscalls or Exceptions or pure kernel mode
383
384	EXCEPTION_EPILOGUE
385debug_marker_syscall:
386	rtie
387
388END(ret_from_exception)
389