xref: /openbmc/linux/arch/arm/kernel/entry-common.S (revision 3ddc8b84) 
1/* SPDX-License-Identifier: GPL-2.0-only */
2/*
3 *  linux/arch/arm/kernel/entry-common.S
4 *
5 *  Copyright (C) 2000 Russell King
6 */
7
8#include <asm/assembler.h>
9#include <asm/unistd.h>
10#include <asm/ftrace.h>
11#include <asm/unwind.h>
12#include <asm/page.h>
13#ifdef CONFIG_AEABI
14#include <asm/unistd-oabi.h>
15#endif
16
17	.equ	NR_syscalls, __NR_syscalls
18
19#include "entry-header.S"
20
21saved_psr	.req	r8
22#if defined(CONFIG_TRACE_IRQFLAGS) || defined(CONFIG_CONTEXT_TRACKING_USER)
23saved_pc	.req	r9
24#define TRACE(x...) x
25#else
26saved_pc	.req	lr
27#define TRACE(x...)
28#endif
29
30	.section .entry.text,"ax",%progbits
31	.align	5
32#if !(IS_ENABLED(CONFIG_TRACE_IRQFLAGS) || IS_ENABLED(CONFIG_CONTEXT_TRACKING_USER) || \
33	IS_ENABLED(CONFIG_DEBUG_RSEQ))
34/*
35 * This is the fast syscall return path.  We do as little as possible here,
36 * such as avoiding writing r0 to the stack.  We only use this path if we
37 * have tracing, context tracking and rseq debug disabled - the overheads
38 * from those features make this path too inefficient.
39 */
40ret_fast_syscall:
41__ret_fast_syscall:
42 UNWIND(.fnstart	)
43 UNWIND(.cantunwind	)
44	disable_irq_notrace			@ disable interrupts
45	ldr	r1, [tsk, #TI_FLAGS]		@ re-check for syscall tracing
46	movs	r1, r1, lsl #16
47	bne	fast_work_pending
48
49	restore_user_regs fast = 1, offset = S_OFF
50 UNWIND(.fnend		)
51ENDPROC(ret_fast_syscall)
52
53	/* Ok, we need to do extra processing, enter the slow path. */
54fast_work_pending:
55	str	r0, [sp, #S_R0+S_OFF]!		@ returned r0
56	/* fall through to work_pending */
57#else
58/*
59 * The "replacement" ret_fast_syscall for when tracing, context tracking,
60 * or rseq debug is enabled.  As we will need to call out to some C functions,
61 * we save r0 first to avoid needing to save registers around each C function
62 * call.
63 */
64ret_fast_syscall:
65__ret_fast_syscall:
66 UNWIND(.fnstart	)
67 UNWIND(.cantunwind	)
68	str	r0, [sp, #S_R0 + S_OFF]!	@ save returned r0
69#if IS_ENABLED(CONFIG_DEBUG_RSEQ)
70	/* do_rseq_syscall needs interrupts enabled. */
71	mov	r0, sp				@ 'regs'
72	bl	do_rseq_syscall
73#endif
74	disable_irq_notrace			@ disable interrupts
75	ldr	r1, [tsk, #TI_FLAGS]		@ re-check for syscall tracing
76	movs	r1, r1, lsl #16
77	beq	no_work_pending
78 UNWIND(.fnend		)
79ENDPROC(ret_fast_syscall)
80
81	/* Slower path - fall through to work_pending */
82#endif
83
84	tst	r1, #_TIF_SYSCALL_WORK
85	bne	__sys_trace_return_nosave
86slow_work_pending:
87	mov	r0, sp				@ 'regs'
88	mov	r2, why				@ 'syscall'
89	bl	do_work_pending
90	cmp	r0, #0
91	beq	no_work_pending
92	movlt	scno, #(__NR_restart_syscall - __NR_SYSCALL_BASE)
93	str	scno, [tsk, #TI_ABI_SYSCALL]	@ make sure tracers see update
94	ldmia	sp, {r0 - r6}			@ have to reload r0 - r6
95	b	local_restart			@ ... and off we go
96ENDPROC(ret_fast_syscall)
97
98/*
99 * "slow" syscall return path.  "why" tells us if this was a real syscall.
100 * IRQs may be enabled here, so always disable them.  Note that we use the
101 * "notrace" version to avoid calling into the tracing code unnecessarily.
102 * do_work_pending() will update this state if necessary.
103 */
104ENTRY(ret_to_user)
105ret_slow_syscall:
106#if IS_ENABLED(CONFIG_DEBUG_RSEQ)
107	/* do_rseq_syscall needs interrupts enabled. */
108	enable_irq_notrace			@ enable interrupts
109	mov	r0, sp				@ 'regs'
110	bl	do_rseq_syscall
111#endif
112	disable_irq_notrace			@ disable interrupts
113ENTRY(ret_to_user_from_irq)
114	ldr	r1, [tsk, #TI_FLAGS]
115	movs	r1, r1, lsl #16
116	bne	slow_work_pending
117no_work_pending:
118	asm_trace_hardirqs_on save = 0
119
120	ct_user_enter save = 0
121
122	restore_user_regs fast = 0, offset = 0
123ENDPROC(ret_to_user_from_irq)
124ENDPROC(ret_to_user)
125
126/*
127 * This is how we return from a fork.
128 */
129ENTRY(ret_from_fork)
130	bl	schedule_tail
131	cmp	r5, #0
132	movne	r0, r4
133	badrne	lr, 1f
134	retne	r5
1351:	get_thread_info tsk
136	b	ret_slow_syscall
137ENDPROC(ret_from_fork)
138
139/*=============================================================================
140 * SWI handler
141 *-----------------------------------------------------------------------------
142 */
143
144	.align	5
145#ifdef CONFIG_HARDEN_BRANCH_HISTORY
146ENTRY(vector_bhb_loop8_swi)
147	sub	sp, sp, #PT_REGS_SIZE
148	stmia	sp, {r0 - r12}
149	mov	r8, #8
1501:	b	2f
1512:	subs	r8, r8, #1
152	bne	1b
153	dsb	nsh
154	isb
155	b	3f
156ENDPROC(vector_bhb_loop8_swi)
157
158	.align	5
159ENTRY(vector_bhb_bpiall_swi)
160	sub	sp, sp, #PT_REGS_SIZE
161	stmia	sp, {r0 - r12}
162	mcr	p15, 0, r8, c7, c5, 6	@ BPIALL
163	isb
164	b	3f
165ENDPROC(vector_bhb_bpiall_swi)
166#endif
167	.align	5
168ENTRY(vector_swi)
169#ifdef CONFIG_CPU_V7M
170	v7m_exception_entry
171#else
172	sub	sp, sp, #PT_REGS_SIZE
173	stmia	sp, {r0 - r12}			@ Calling r0 - r12
1743:
175 ARM(	add	r8, sp, #S_PC		)
176 ARM(	stmdb	r8, {sp, lr}^		)	@ Calling sp, lr
177 THUMB(	mov	r8, sp			)
178 THUMB(	store_user_sp_lr r8, r10, S_SP	)	@ calling sp, lr
179	mrs	saved_psr, spsr			@ called from non-FIQ mode, so ok.
180 TRACE(	mov	saved_pc, lr		)
181	str	saved_pc, [sp, #S_PC]		@ Save calling PC
182	str	saved_psr, [sp, #S_PSR]		@ Save CPSR
183	str	r0, [sp, #S_OLD_R0]		@ Save OLD_R0
184#endif
185	reload_current r10, ip
186	zero_fp
187	alignment_trap r10, ip, cr_alignment
188	asm_trace_hardirqs_on save=0
189	enable_irq_notrace
190	ct_user_exit save=0
191
192	/*
193	 * Get the system call number.
194	 */
195
196#if defined(CONFIG_OABI_COMPAT)
197
198	/*
199	 * If we have CONFIG_OABI_COMPAT then we need to look at the swi
200	 * value to determine if it is an EABI or an old ABI call.
201	 */
202#ifdef CONFIG_ARM_THUMB
203	tst	saved_psr, #PSR_T_BIT
204	movne	r10, #0				@ no thumb OABI emulation
205 USER(	ldreq	r10, [saved_pc, #-4]	)	@ get SWI instruction
206#else
207 USER(	ldr	r10, [saved_pc, #-4]	)	@ get SWI instruction
208#endif
209 ARM_BE8(rev	r10, r10)			@ little endian instruction
210
211#elif defined(CONFIG_AEABI)
212
213	/*
214	 * Pure EABI user space always put syscall number into scno (r7).
215	 */
216#elif defined(CONFIG_ARM_THUMB)
217	/* Legacy ABI only, possibly thumb mode. */
218	tst	saved_psr, #PSR_T_BIT		@ this is SPSR from save_user_regs
219	addne	scno, r7, #__NR_SYSCALL_BASE	@ put OS number in
220 USER(	ldreq	scno, [saved_pc, #-4]	)
221
222#else
223	/* Legacy ABI only. */
224 USER(	ldr	scno, [saved_pc, #-4]	)	@ get SWI instruction
225#endif
226
227	/* saved_psr and saved_pc are now dead */
228
229	uaccess_disable tbl
230	get_thread_info tsk
231
232	adr	tbl, sys_call_table		@ load syscall table pointer
233
234#if defined(CONFIG_OABI_COMPAT)
235	/*
236	 * If the swi argument is zero, this is an EABI call and we do nothing.
237	 *
238	 * If this is an old ABI call, get the syscall number into scno and
239	 * get the old ABI syscall table address.
240	 */
241	bics	r10, r10, #0xff000000
242	strne	r10, [tsk, #TI_ABI_SYSCALL]
243	streq	scno, [tsk, #TI_ABI_SYSCALL]
244	eorne	scno, r10, #__NR_OABI_SYSCALL_BASE
245	ldrne	tbl, =sys_oabi_call_table
246#elif !defined(CONFIG_AEABI)
247	bic	scno, scno, #0xff000000		@ mask off SWI op-code
248	str	scno, [tsk, #TI_ABI_SYSCALL]
249	eor	scno, scno, #__NR_SYSCALL_BASE	@ check OS number
250#else
251	str	scno, [tsk, #TI_ABI_SYSCALL]
252#endif
253	/*
254	 * Reload the registers that may have been corrupted on entry to
255	 * the syscall assembly (by tracing or context tracking.)
256	 */
257 TRACE(	ldmia	sp, {r0 - r3}		)
258
259local_restart:
260	ldr	r10, [tsk, #TI_FLAGS]		@ check for syscall tracing
261	stmdb	sp!, {r4, r5}			@ push fifth and sixth args
262
263	tst	r10, #_TIF_SYSCALL_WORK		@ are we tracing syscalls?
264	bne	__sys_trace
265
266	invoke_syscall tbl, scno, r10, __ret_fast_syscall
267
268	add	r1, sp, #S_OFF
2692:	cmp	scno, #(__ARM_NR_BASE - __NR_SYSCALL_BASE)
270	eor	r0, scno, #__NR_SYSCALL_BASE	@ put OS number back
271	bcs	arm_syscall
272	mov	why, #0				@ no longer a real syscall
273	b	sys_ni_syscall			@ not private func
274
275#if defined(CONFIG_OABI_COMPAT) || !defined(CONFIG_AEABI)
276	/*
277	 * We failed to handle a fault trying to access the page
278	 * containing the swi instruction, but we're not really in a
279	 * position to return -EFAULT. Instead, return back to the
280	 * instruction and re-enter the user fault handling path trying
281	 * to page it in. This will likely result in sending SEGV to the
282	 * current task.
283	 */
2849001:
285	sub	lr, saved_pc, #4
286	str	lr, [sp, #S_PC]
287	get_thread_info tsk
288	b	ret_fast_syscall
289#endif
290ENDPROC(vector_swi)
291	.ltorg
292
293	/*
294	 * This is the really slow path.  We're going to be doing
295	 * context switches, and waiting for our parent to respond.
296	 */
297__sys_trace:
298	add	r0, sp, #S_OFF
299	bl	syscall_trace_enter
300	mov	scno, r0
301	invoke_syscall tbl, scno, r10, __sys_trace_return, reload=1
302	cmp	scno, #-1			@ skip the syscall?
303	bne	2b
304	add	sp, sp, #S_OFF			@ restore stack
305
306__sys_trace_return_nosave:
307	enable_irq_notrace
308	mov	r0, sp
309	bl	syscall_trace_exit
310	b	ret_slow_syscall
311
312__sys_trace_return:
313	str	r0, [sp, #S_R0 + S_OFF]!	@ save returned r0
314	mov	r0, sp
315	bl	syscall_trace_exit
316	b	ret_slow_syscall
317
318	.macro	syscall_table_start, sym
319	.equ	__sys_nr, 0
320	.type	\sym, #object
321ENTRY(\sym)
322	.endm
323
324	.macro	syscall, nr, func
325	.ifgt	__sys_nr - \nr
326	.error	"Duplicated/unorded system call entry"
327	.endif
328	.rept	\nr - __sys_nr
329	.long	sys_ni_syscall
330	.endr
331	.long	\func
332	.equ	__sys_nr, \nr + 1
333	.endm
334
335	.macro	syscall_table_end, sym
336	.ifgt	__sys_nr - __NR_syscalls
337	.error	"System call table too big"
338	.endif
339	.rept	__NR_syscalls - __sys_nr
340	.long	sys_ni_syscall
341	.endr
342	.size	\sym, . - \sym
343	.endm
344
345#define __SYSCALL_WITH_COMPAT(nr, native, compat)	__SYSCALL(nr, native)
346#define __SYSCALL(nr, func) syscall nr, func
347
348/*
349 * This is the syscall table declaration for native ABI syscalls.
350 * With EABI a couple syscalls are obsolete and defined as sys_ni_syscall.
351 */
352	syscall_table_start sys_call_table
353#ifdef CONFIG_AEABI
354#include <calls-eabi.S>
355#else
356#include <calls-oabi.S>
357#endif
358	syscall_table_end sys_call_table
359
360/*============================================================================
361 * Special system call wrappers
362 */
363@ r0 = syscall number
364@ r8 = syscall table
365sys_syscall:
366		bic	scno, r0, #__NR_OABI_SYSCALL_BASE
367		cmp	scno, #__NR_syscall - __NR_SYSCALL_BASE
368		cmpne	scno, #NR_syscalls	@ check range
369#ifdef CONFIG_CPU_SPECTRE
370		movhs	scno, #0
371		csdb
372#endif
373		stmialo	sp, {r5, r6}		@ shuffle args
374		movlo	r0, r1
375		movlo	r1, r2
376		movlo	r2, r3
377		movlo	r3, r4
378		ldrlo	pc, [tbl, scno, lsl #2]
379		b	sys_ni_syscall
380ENDPROC(sys_syscall)
381
382sys_sigreturn_wrapper:
383		add	r0, sp, #S_OFF
384		mov	why, #0		@ prevent syscall restart handling
385		b	sys_sigreturn
386ENDPROC(sys_sigreturn_wrapper)
387
388sys_rt_sigreturn_wrapper:
389		add	r0, sp, #S_OFF
390		mov	why, #0		@ prevent syscall restart handling
391		b	sys_rt_sigreturn
392ENDPROC(sys_rt_sigreturn_wrapper)
393
394sys_statfs64_wrapper:
395		teq	r1, #88
396		moveq	r1, #84
397		b	sys_statfs64
398ENDPROC(sys_statfs64_wrapper)
399
400sys_fstatfs64_wrapper:
401		teq	r1, #88
402		moveq	r1, #84
403		b	sys_fstatfs64
404ENDPROC(sys_fstatfs64_wrapper)
405
406/*
407 * Note: off_4k (r5) is always units of 4K.  If we can't do the requested
408 * offset, we return EINVAL.
409 */
410sys_mmap2:
411		str	r5, [sp, #4]
412		b	sys_mmap_pgoff
413ENDPROC(sys_mmap2)
414
415#ifdef CONFIG_OABI_COMPAT
416
417/*
418 * These are syscalls with argument register differences
419 */
420
421sys_oabi_pread64:
422		stmia	sp, {r3, r4}
423		b	sys_pread64
424ENDPROC(sys_oabi_pread64)
425
426sys_oabi_pwrite64:
427		stmia	sp, {r3, r4}
428		b	sys_pwrite64
429ENDPROC(sys_oabi_pwrite64)
430
431sys_oabi_truncate64:
432		mov	r3, r2
433		mov	r2, r1
434		b	sys_truncate64
435ENDPROC(sys_oabi_truncate64)
436
437sys_oabi_ftruncate64:
438		mov	r3, r2
439		mov	r2, r1
440		b	sys_ftruncate64
441ENDPROC(sys_oabi_ftruncate64)
442
443sys_oabi_readahead:
444		str	r3, [sp]
445		mov	r3, r2
446		mov	r2, r1
447		b	sys_readahead
448ENDPROC(sys_oabi_readahead)
449
450/*
451 * Let's declare a second syscall table for old ABI binaries
452 * using the compatibility syscall entries.
453 */
454	syscall_table_start sys_oabi_call_table
455#undef __SYSCALL_WITH_COMPAT
456#define __SYSCALL_WITH_COMPAT(nr, native, compat)	__SYSCALL(nr, compat)
457#include <calls-oabi.S>
458	syscall_table_end sys_oabi_call_table
459
460#endif
461
462