xref: /openbmc/linux/arch/arm/kernel/entry-common.S (revision 12cecbf9) 
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/memory.h>
13#ifdef CONFIG_AEABI
14#include <asm/unistd-oabi.h>
15#endif
16
17	.equ	NR_syscalls, __NR_syscalls
18
19	.macro  arch_ret_to_user, tmp
20#ifdef CONFIG_ARCH_IOP32X
21	mrc	p15, 0, \tmp, c15, c1, 0
22	tst	\tmp, #(1 << 6)
23	bicne	\tmp, \tmp, #(1 << 6)
24	mcrne	p15, 0, \tmp, c15, c1, 0	@ Disable cp6 access
25#endif
26	.endm
27
28#include "entry-header.S"
29
30saved_psr	.req	r8
31#if defined(CONFIG_TRACE_IRQFLAGS) || defined(CONFIG_CONTEXT_TRACKING_USER)
32saved_pc	.req	r9
33#define TRACE(x...) x
34#else
35saved_pc	.req	lr
36#define TRACE(x...)
37#endif
38
39	.section .entry.text,"ax",%progbits
40	.align	5
41#if !(IS_ENABLED(CONFIG_TRACE_IRQFLAGS) || IS_ENABLED(CONFIG_CONTEXT_TRACKING_USER) || \
42	IS_ENABLED(CONFIG_DEBUG_RSEQ))
43/*
44 * This is the fast syscall return path.  We do as little as possible here,
45 * such as avoiding writing r0 to the stack.  We only use this path if we
46 * have tracing, context tracking and rseq debug disabled - the overheads
47 * from those features make this path too inefficient.
48 */
49ret_fast_syscall:
50__ret_fast_syscall:
51 UNWIND(.fnstart	)
52 UNWIND(.cantunwind	)
53	disable_irq_notrace			@ disable interrupts
54	ldr	r1, [tsk, #TI_FLAGS]		@ re-check for syscall tracing
55	movs	r1, r1, lsl #16
56	bne	fast_work_pending
57
58
59	/* perform architecture specific actions before user return */
60	arch_ret_to_user r1
61
62	restore_user_regs fast = 1, offset = S_OFF
63 UNWIND(.fnend		)
64ENDPROC(ret_fast_syscall)
65
66	/* Ok, we need to do extra processing, enter the slow path. */
67fast_work_pending:
68	str	r0, [sp, #S_R0+S_OFF]!		@ returned r0
69	/* fall through to work_pending */
70#else
71/*
72 * The "replacement" ret_fast_syscall for when tracing, context tracking,
73 * or rseq debug is enabled.  As we will need to call out to some C functions,
74 * we save r0 first to avoid needing to save registers around each C function
75 * call.
76 */
77ret_fast_syscall:
78__ret_fast_syscall:
79 UNWIND(.fnstart	)
80 UNWIND(.cantunwind	)
81	str	r0, [sp, #S_R0 + S_OFF]!	@ save returned r0
82#if IS_ENABLED(CONFIG_DEBUG_RSEQ)
83	/* do_rseq_syscall needs interrupts enabled. */
84	mov	r0, sp				@ 'regs'
85	bl	do_rseq_syscall
86#endif
87	disable_irq_notrace			@ disable interrupts
88	ldr	r1, [tsk, #TI_FLAGS]		@ re-check for syscall tracing
89	movs	r1, r1, lsl #16
90	beq	no_work_pending
91 UNWIND(.fnend		)
92ENDPROC(ret_fast_syscall)
93
94	/* Slower path - fall through to work_pending */
95#endif
96
97	tst	r1, #_TIF_SYSCALL_WORK
98	bne	__sys_trace_return_nosave
99slow_work_pending:
100	mov	r0, sp				@ 'regs'
101	mov	r2, why				@ 'syscall'
102	bl	do_work_pending
103	cmp	r0, #0
104	beq	no_work_pending
105	movlt	scno, #(__NR_restart_syscall - __NR_SYSCALL_BASE)
106	ldmia	sp, {r0 - r6}			@ have to reload r0 - r6
107	b	local_restart			@ ... and off we go
108ENDPROC(ret_fast_syscall)
109
110/*
111 * "slow" syscall return path.  "why" tells us if this was a real syscall.
112 * IRQs may be enabled here, so always disable them.  Note that we use the
113 * "notrace" version to avoid calling into the tracing code unnecessarily.
114 * do_work_pending() will update this state if necessary.
115 */
116ENTRY(ret_to_user)
117ret_slow_syscall:
118#if IS_ENABLED(CONFIG_DEBUG_RSEQ)
119	/* do_rseq_syscall needs interrupts enabled. */
120	enable_irq_notrace			@ enable interrupts
121	mov	r0, sp				@ 'regs'
122	bl	do_rseq_syscall
123#endif
124	disable_irq_notrace			@ disable interrupts
125ENTRY(ret_to_user_from_irq)
126	ldr	r1, [tsk, #TI_FLAGS]
127	movs	r1, r1, lsl #16
128	bne	slow_work_pending
129no_work_pending:
130	asm_trace_hardirqs_on save = 0
131
132	/* perform architecture specific actions before user return */
133	arch_ret_to_user r1
134	ct_user_enter save = 0
135
136	restore_user_regs fast = 0, offset = 0
137ENDPROC(ret_to_user_from_irq)
138ENDPROC(ret_to_user)
139
140/*
141 * This is how we return from a fork.
142 */
143ENTRY(ret_from_fork)
144	bl	schedule_tail
145	cmp	r5, #0
146	movne	r0, r4
147	badrne	lr, 1f
148	retne	r5
1491:	get_thread_info tsk
150	b	ret_slow_syscall
151ENDPROC(ret_from_fork)
152
153/*=============================================================================
154 * SWI handler
155 *-----------------------------------------------------------------------------
156 */
157
158	.align	5
159#ifdef CONFIG_HARDEN_BRANCH_HISTORY
160ENTRY(vector_bhb_loop8_swi)
161	sub	sp, sp, #PT_REGS_SIZE
162	stmia	sp, {r0 - r12}
163	mov	r8, #8
1641:	b	2f
1652:	subs	r8, r8, #1
166	bne	1b
167	dsb	nsh
168	isb
169	b	3f
170ENDPROC(vector_bhb_loop8_swi)
171
172	.align	5
173ENTRY(vector_bhb_bpiall_swi)
174	sub	sp, sp, #PT_REGS_SIZE
175	stmia	sp, {r0 - r12}
176	mcr	p15, 0, r8, c7, c5, 6	@ BPIALL
177	isb
178	b	3f
179ENDPROC(vector_bhb_bpiall_swi)
180#endif
181	.align	5
182ENTRY(vector_swi)
183#ifdef CONFIG_CPU_V7M
184	v7m_exception_entry
185#else
186	sub	sp, sp, #PT_REGS_SIZE
187	stmia	sp, {r0 - r12}			@ Calling r0 - r12
1883:
189 ARM(	add	r8, sp, #S_PC		)
190 ARM(	stmdb	r8, {sp, lr}^		)	@ Calling sp, lr
191 THUMB(	mov	r8, sp			)
192 THUMB(	store_user_sp_lr r8, r10, S_SP	)	@ calling sp, lr
193	mrs	saved_psr, spsr			@ called from non-FIQ mode, so ok.
194 TRACE(	mov	saved_pc, lr		)
195	str	saved_pc, [sp, #S_PC]		@ Save calling PC
196	str	saved_psr, [sp, #S_PSR]		@ Save CPSR
197	str	r0, [sp, #S_OLD_R0]		@ Save OLD_R0
198#endif
199	reload_current r10, ip
200	zero_fp
201	alignment_trap r10, ip, cr_alignment
202	asm_trace_hardirqs_on save=0
203	enable_irq_notrace
204	ct_user_exit save=0
205
206	/*
207	 * Get the system call number.
208	 */
209
210#if defined(CONFIG_OABI_COMPAT)
211
212	/*
213	 * If we have CONFIG_OABI_COMPAT then we need to look at the swi
214	 * value to determine if it is an EABI or an old ABI call.
215	 */
216#ifdef CONFIG_ARM_THUMB
217	tst	saved_psr, #PSR_T_BIT
218	movne	r10, #0				@ no thumb OABI emulation
219 USER(	ldreq	r10, [saved_pc, #-4]	)	@ get SWI instruction
220#else
221 USER(	ldr	r10, [saved_pc, #-4]	)	@ get SWI instruction
222#endif
223 ARM_BE8(rev	r10, r10)			@ little endian instruction
224
225#elif defined(CONFIG_AEABI)
226
227	/*
228	 * Pure EABI user space always put syscall number into scno (r7).
229	 */
230#elif defined(CONFIG_ARM_THUMB)
231	/* Legacy ABI only, possibly thumb mode. */
232	tst	saved_psr, #PSR_T_BIT		@ this is SPSR from save_user_regs
233	addne	scno, r7, #__NR_SYSCALL_BASE	@ put OS number in
234 USER(	ldreq	scno, [saved_pc, #-4]	)
235
236#else
237	/* Legacy ABI only. */
238 USER(	ldr	scno, [saved_pc, #-4]	)	@ get SWI instruction
239#endif
240
241	/* saved_psr and saved_pc are now dead */
242
243	uaccess_disable tbl
244	get_thread_info tsk
245
246	adr	tbl, sys_call_table		@ load syscall table pointer
247
248#if defined(CONFIG_OABI_COMPAT)
249	/*
250	 * If the swi argument is zero, this is an EABI call and we do nothing.
251	 *
252	 * If this is an old ABI call, get the syscall number into scno and
253	 * get the old ABI syscall table address.
254	 */
255	bics	r10, r10, #0xff000000
256	strne	r10, [tsk, #TI_ABI_SYSCALL]
257	streq	scno, [tsk, #TI_ABI_SYSCALL]
258	eorne	scno, r10, #__NR_OABI_SYSCALL_BASE
259	ldrne	tbl, =sys_oabi_call_table
260#elif !defined(CONFIG_AEABI)
261	bic	scno, scno, #0xff000000		@ mask off SWI op-code
262	str	scno, [tsk, #TI_ABI_SYSCALL]
263	eor	scno, scno, #__NR_SYSCALL_BASE	@ check OS number
264#else
265	str	scno, [tsk, #TI_ABI_SYSCALL]
266#endif
267	/*
268	 * Reload the registers that may have been corrupted on entry to
269	 * the syscall assembly (by tracing or context tracking.)
270	 */
271 TRACE(	ldmia	sp, {r0 - r3}		)
272
273local_restart:
274	ldr	r10, [tsk, #TI_FLAGS]		@ check for syscall tracing
275	stmdb	sp!, {r4, r5}			@ push fifth and sixth args
276
277	tst	r10, #_TIF_SYSCALL_WORK		@ are we tracing syscalls?
278	bne	__sys_trace
279
280	invoke_syscall tbl, scno, r10, __ret_fast_syscall
281
282	add	r1, sp, #S_OFF
2832:	cmp	scno, #(__ARM_NR_BASE - __NR_SYSCALL_BASE)
284	eor	r0, scno, #__NR_SYSCALL_BASE	@ put OS number back
285	bcs	arm_syscall
286	mov	why, #0				@ no longer a real syscall
287	b	sys_ni_syscall			@ not private func
288
289#if defined(CONFIG_OABI_COMPAT) || !defined(CONFIG_AEABI)
290	/*
291	 * We failed to handle a fault trying to access the page
292	 * containing the swi instruction, but we're not really in a
293	 * position to return -EFAULT. Instead, return back to the
294	 * instruction and re-enter the user fault handling path trying
295	 * to page it in. This will likely result in sending SEGV to the
296	 * current task.
297	 */
2989001:
299	sub	lr, saved_pc, #4
300	str	lr, [sp, #S_PC]
301	get_thread_info tsk
302	b	ret_fast_syscall
303#endif
304ENDPROC(vector_swi)
305	.ltorg
306
307	/*
308	 * This is the really slow path.  We're going to be doing
309	 * context switches, and waiting for our parent to respond.
310	 */
311__sys_trace:
312	add	r0, sp, #S_OFF
313	bl	syscall_trace_enter
314	mov	scno, r0
315	invoke_syscall tbl, scno, r10, __sys_trace_return, reload=1
316	cmp	scno, #-1			@ skip the syscall?
317	bne	2b
318	add	sp, sp, #S_OFF			@ restore stack
319
320__sys_trace_return_nosave:
321	enable_irq_notrace
322	mov	r0, sp
323	bl	syscall_trace_exit
324	b	ret_slow_syscall
325
326__sys_trace_return:
327	str	r0, [sp, #S_R0 + S_OFF]!	@ save returned r0
328	mov	r0, sp
329	bl	syscall_trace_exit
330	b	ret_slow_syscall
331
332	.macro	syscall_table_start, sym
333	.equ	__sys_nr, 0
334	.type	\sym, #object
335ENTRY(\sym)
336	.endm
337
338	.macro	syscall, nr, func
339	.ifgt	__sys_nr - \nr
340	.error	"Duplicated/unorded system call entry"
341	.endif
342	.rept	\nr - __sys_nr
343	.long	sys_ni_syscall
344	.endr
345	.long	\func
346	.equ	__sys_nr, \nr + 1
347	.endm
348
349	.macro	syscall_table_end, sym
350	.ifgt	__sys_nr - __NR_syscalls
351	.error	"System call table too big"
352	.endif
353	.rept	__NR_syscalls - __sys_nr
354	.long	sys_ni_syscall
355	.endr
356	.size	\sym, . - \sym
357	.endm
358
359#define __SYSCALL_WITH_COMPAT(nr, native, compat)	__SYSCALL(nr, native)
360#define __SYSCALL(nr, func) syscall nr, func
361
362/*
363 * This is the syscall table declaration for native ABI syscalls.
364 * With EABI a couple syscalls are obsolete and defined as sys_ni_syscall.
365 */
366	syscall_table_start sys_call_table
367#ifdef CONFIG_AEABI
368#include <calls-eabi.S>
369#else
370#include <calls-oabi.S>
371#endif
372	syscall_table_end sys_call_table
373
374/*============================================================================
375 * Special system call wrappers
376 */
377@ r0 = syscall number
378@ r8 = syscall table
379sys_syscall:
380		bic	scno, r0, #__NR_OABI_SYSCALL_BASE
381		cmp	scno, #__NR_syscall - __NR_SYSCALL_BASE
382		cmpne	scno, #NR_syscalls	@ check range
383#ifdef CONFIG_CPU_SPECTRE
384		movhs	scno, #0
385		csdb
386#endif
387		stmialo	sp, {r5, r6}		@ shuffle args
388		movlo	r0, r1
389		movlo	r1, r2
390		movlo	r2, r3
391		movlo	r3, r4
392		ldrlo	pc, [tbl, scno, lsl #2]
393		b	sys_ni_syscall
394ENDPROC(sys_syscall)
395
396sys_sigreturn_wrapper:
397		add	r0, sp, #S_OFF
398		mov	why, #0		@ prevent syscall restart handling
399		b	sys_sigreturn
400ENDPROC(sys_sigreturn_wrapper)
401
402sys_rt_sigreturn_wrapper:
403		add	r0, sp, #S_OFF
404		mov	why, #0		@ prevent syscall restart handling
405		b	sys_rt_sigreturn
406ENDPROC(sys_rt_sigreturn_wrapper)
407
408sys_statfs64_wrapper:
409		teq	r1, #88
410		moveq	r1, #84
411		b	sys_statfs64
412ENDPROC(sys_statfs64_wrapper)
413
414sys_fstatfs64_wrapper:
415		teq	r1, #88
416		moveq	r1, #84
417		b	sys_fstatfs64
418ENDPROC(sys_fstatfs64_wrapper)
419
420/*
421 * Note: off_4k (r5) is always units of 4K.  If we can't do the requested
422 * offset, we return EINVAL.
423 */
424sys_mmap2:
425		str	r5, [sp, #4]
426		b	sys_mmap_pgoff
427ENDPROC(sys_mmap2)
428
429#ifdef CONFIG_OABI_COMPAT
430
431/*
432 * These are syscalls with argument register differences
433 */
434
435sys_oabi_pread64:
436		stmia	sp, {r3, r4}
437		b	sys_pread64
438ENDPROC(sys_oabi_pread64)
439
440sys_oabi_pwrite64:
441		stmia	sp, {r3, r4}
442		b	sys_pwrite64
443ENDPROC(sys_oabi_pwrite64)
444
445sys_oabi_truncate64:
446		mov	r3, r2
447		mov	r2, r1
448		b	sys_truncate64
449ENDPROC(sys_oabi_truncate64)
450
451sys_oabi_ftruncate64:
452		mov	r3, r2
453		mov	r2, r1
454		b	sys_ftruncate64
455ENDPROC(sys_oabi_ftruncate64)
456
457sys_oabi_readahead:
458		str	r3, [sp]
459		mov	r3, r2
460		mov	r2, r1
461		b	sys_readahead
462ENDPROC(sys_oabi_readahead)
463
464/*
465 * Let's declare a second syscall table for old ABI binaries
466 * using the compatibility syscall entries.
467 */
468	syscall_table_start sys_oabi_call_table
469#undef __SYSCALL_WITH_COMPAT
470#define __SYSCALL_WITH_COMPAT(nr, native, compat)	__SYSCALL(nr, compat)
471#include <calls-oabi.S>
472	syscall_table_end sys_oabi_call_table
473
474#endif
475
476