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

source code of linux/arch/arm/kernel/entry-common.S