| blob | 40db0f9188b69e9e4323405c8c44e9a3fe153890 |
1 /* SPDX-License-Identifier: GPL-2.0 */
2 #include <linux/init.h>
3 #include <linux/linkage.h>
5 #include <asm/assembler.h>
6 #include <asm/asm-offsets.h>
7 #include <asm/errno.h>
8 #include <asm/thread_info.h>
9 #include <asm/uaccess-asm.h>
10 #include <asm/v7m.h>
12 @ Bad Abort numbers
13 @ -----------------
14 @
15 #define BAD_PREFETCH 0
16 #define BAD_DATA 1
17 #define BAD_ADDREXCPTN 2
18 #define BAD_IRQ 3
19 #define BAD_UNDEFINSTR 4
21 @
22 @ Most of the stack format comes from struct pt_regs, but with
23 @ the addition of 8 bytes for storing syscall args 5 and 6.
24 @ This _must_ remain a multiple of 8 for EABI.
25 @
26 #define S_OFF 8
28 /*
29 * The SWI code relies on the fact that R0 is at the bottom of the stack
30 * (due to slow/fast restore user regs).
31 */
32 #if S_R0 != 0
33 #error "Please fix"
34 #endif
36 .macro zero_fp
37 #ifdef CONFIG_FRAME_POINTER
38 mov fp, #0
39 #endif
40 .endm
42 #ifdef CONFIG_ALIGNMENT_TRAP
43 #define ATRAP(x...) x
44 #else
45 #define ATRAP(x...)
46 #endif
48 .macro alignment_trap, rtmp1, rtmp2, label
49 #ifdef CONFIG_ALIGNMENT_TRAP
50 mrc p15, 0, \rtmp2, c1, c0, 0
51 ldr \rtmp1, \label
52 ldr \rtmp1, [\rtmp1]
53 teq \rtmp1, \rtmp2
54 mcrne p15, 0, \rtmp1, c1, c0, 0
55 #endif
56 .endm
58 #ifdef CONFIG_CPU_V7M
59 /*
60 * ARMv7-M exception entry/exit macros.
61 *
62 * xPSR, ReturnAddress(), LR (R14), R12, R3, R2, R1, and R0 are
63 * automatically saved on the current stack (32 words) before
64 * switching to the exception stack (SP_main).
65 *
66 * If exception is taken while in user mode, SP_main is
67 * empty. Otherwise, SP_main is aligned to 64 bit automatically
68 * (CCR.STKALIGN set).
69 *
70 * Linux assumes that the interrupts are disabled when entering an
71 * exception handler and it may BUG if this is not the case. Interrupts
72 * are disabled during entry and reenabled in the exit macro.
73 *
74 * v7m_exception_slow_exit is used when returning from SVC or PendSV.
75 * When returning to kernel mode, we don't return from exception.
76 */
77 .macro v7m_exception_entry
78 @ determine the location of the registers saved by the core during
79 @ exception entry. Depending on the mode the cpu was in when the
80 @ exception happend that is either on the main or the process stack.
81 @ Bit 2 of EXC_RETURN stored in the lr register specifies which stack
82 @ was used.
83 tst lr, #EXC_RET_STACK_MASK
84 mrsne r12, psp
85 moveq r12, sp
87 @ we cannot rely on r0-r3 and r12 matching the value saved in the
88 @ exception frame because of tail-chaining. So these have to be
89 @ reloaded.
90 ldmia r12!, {r0-r3}
92 @ Linux expects to have irqs off. Do it here before taking stack space
93 cpsid i
95 sub sp, #PT_REGS_SIZE-S_IP
96 stmdb sp!, {r0-r11}
98 @ load saved r12, lr, return address and xPSR.
99 @ r0-r7 are used for signals and never touched from now on. Clobbering
100 @ r8-r12 is OK.
101 mov r9, r12
102 ldmia r9!, {r8, r10-r12}
104 @ calculate the original stack pointer value.
105 @ r9 currently points to the memory location just above the auto saved
106 @ xPSR.
107 @ The cpu might automatically 8-byte align the stack. Bit 9
108 @ of the saved xPSR specifies if stack aligning took place. In this case
109 @ another 32-bit value is included in the stack.
111 tst r12, V7M_xPSR_FRAMEPTRALIGN
112 addne r9, r9, #4
114 @ store saved r12 using str to have a register to hold the base for stm
115 str r8, [sp, #S_IP]
116 add r8, sp, #S_SP
117 @ store r13-r15, xPSR
118 stmia r8!, {r9-r12}
119 @ store old_r0
120 str r0, [r8]
121 .endm
123 /*
124 * PENDSV and SVCALL are configured to have the same exception
125 * priorities. As a kernel thread runs at SVCALL execution priority it
126 * can never be preempted and so we will never have to return to a
127 * kernel thread here.
128 */
129 .macro v7m_exception_slow_exit ret_r0
130 cpsid i
131 ldr lr, =exc_ret
132 ldr lr, [lr]
134 @ read original r12, sp, lr, pc and xPSR
135 add r12, sp, #S_IP
136 ldmia r12, {r1-r5}
138 @ an exception frame is always 8-byte aligned. To tell the hardware if
139 @ the sp to be restored is aligned or not set bit 9 of the saved xPSR
140 @ accordingly.
141 tst r2, #4
142 subne r2, r2, #4
143 orrne r5, V7M_xPSR_FRAMEPTRALIGN
144 biceq r5, V7M_xPSR_FRAMEPTRALIGN
146 @ ensure bit 0 is cleared in the PC, otherwise behaviour is
147 @ unpredictable
148 bic r4, #1
150 @ write basic exception frame
151 stmdb r2!, {r1, r3-r5}
152 ldmia sp, {r1, r3-r5}
153 .if \ret_r0
154 stmdb r2!, {r0, r3-r5}
155 .else
156 stmdb r2!, {r1, r3-r5}
157 .endif
159 @ restore process sp
160 msr psp, r2
162 @ restore original r4-r11
163 ldmia sp!, {r0-r11}
165 @ restore main sp
166 add sp, sp, #PT_REGS_SIZE-S_IP
168 cpsie i
169 bx lr
170 .endm
171 #endif /* CONFIG_CPU_V7M */
173 @
174 @ Store/load the USER SP and LR registers by switching to the SYS
175 @ mode. Useful in Thumb-2 mode where "stm/ldm rd, {sp, lr}^" is not
176 @ available. Should only be called from SVC mode
177 @
178 .macro store_user_sp_lr, rd, rtemp, offset = 0
179 mrs \rtemp, cpsr
180 eor \rtemp, \rtemp, #(SVC_MODE ^ SYSTEM_MODE)
181 msr cpsr_c, \rtemp @ switch to the SYS mode
183 str sp, [\rd, #\offset] @ save sp_usr
184 str lr, [\rd, #\offset + 4] @ save lr_usr
186 eor \rtemp, \rtemp, #(SVC_MODE ^ SYSTEM_MODE)
187 msr cpsr_c, \rtemp @ switch back to the SVC mode
188 .endm
190 .macro load_user_sp_lr, rd, rtemp, offset = 0
191 mrs \rtemp, cpsr
192 eor \rtemp, \rtemp, #(SVC_MODE ^ SYSTEM_MODE)
193 msr cpsr_c, \rtemp @ switch to the SYS mode
195 ldr sp, [\rd, #\offset] @ load sp_usr
196 ldr lr, [\rd, #\offset + 4] @ load lr_usr
198 eor \rtemp, \rtemp, #(SVC_MODE ^ SYSTEM_MODE)
199 msr cpsr_c, \rtemp @ switch back to the SVC mode
200 .endm
203 .macro svc_exit, rpsr, irq = 0
204 .if \irq != 0
205 @ IRQs already off
206 #ifdef CONFIG_TRACE_IRQFLAGS
207 @ The parent context IRQs must have been enabled to get here in
208 @ the first place, so there's no point checking the PSR I bit.
209 bl trace_hardirqs_on
210 #endif
211 .else
212 @ IRQs off again before pulling preserved data off the stack
213 disable_irq_notrace
214 #ifdef CONFIG_TRACE_IRQFLAGS
215 tst \rpsr, #PSR_I_BIT
216 bleq trace_hardirqs_on
217 tst \rpsr, #PSR_I_BIT
218 blne trace_hardirqs_off
219 #endif
220 .endif
221 uaccess_exit tsk, r0, r1
223 #ifndef CONFIG_THUMB2_KERNEL
224 @ ARM mode SVC restore
225 msr spsr_cxsf, \rpsr
226 #if defined(CONFIG_CPU_V6) || defined(CONFIG_CPU_32v6K)
227 @ We must avoid clrex due to Cortex-A15 erratum #830321
228 sub r0, sp, #4 @ uninhabited address
229 strex r1, r2, [r0] @ clear the exclusive monitor
230 #endif
231 ldmia sp, {r0 - pc}^ @ load r0 - pc, cpsr
232 #else
233 @ Thumb mode SVC restore
234 ldr lr, [sp, #S_SP] @ top of the stack
235 ldrd r0, r1, [sp, #S_LR] @ calling lr and pc
237 @ We must avoid clrex due to Cortex-A15 erratum #830321
238 strex r2, r1, [sp, #S_LR] @ clear the exclusive monitor
240 stmdb lr!, {r0, r1, \rpsr} @ calling lr and rfe context
241 ldmia sp, {r0 - r12}
242 mov sp, lr
243 ldr lr, [sp], #4
244 rfeia sp!
245 #endif
246 .endm
248 @
249 @ svc_exit_via_fiq - like svc_exit but switches to FIQ mode before exit
250 @
251 @ This macro acts in a similar manner to svc_exit but switches to FIQ
252 @ mode to restore the final part of the register state.
253 @
254 @ We cannot use the normal svc_exit procedure because that would
255 @ clobber spsr_svc (FIQ could be delivered during the first few
256 @ instructions of vector_swi meaning its contents have not been
257 @ saved anywhere).
258 @
259 @ Note that, unlike svc_exit, this macro also does not allow a caller
260 @ supplied rpsr. This is because the FIQ exceptions are not re-entrant
261 @ and the handlers cannot call into the scheduler (meaning the value
262 @ on the stack remains correct).
263 @
264 .macro svc_exit_via_fiq
265 uaccess_exit tsk, r0, r1
266 #ifndef CONFIG_THUMB2_KERNEL
267 @ ARM mode restore
268 mov r0, sp
269 ldmib r0, {r1 - r14} @ abort is deadly from here onward (it will
270 @ clobber state restored below)
271 msr cpsr_c, #FIQ_MODE | PSR_I_BIT | PSR_F_BIT
272 add r8, r0, #S_PC
273 ldr r9, [r0, #S_PSR]
274 msr spsr_cxsf, r9
275 ldr r0, [r0, #S_R0]
276 ldmia r8, {pc}^
277 #else
278 @ Thumb mode restore
279 add r0, sp, #S_R2
280 ldr lr, [sp, #S_LR]
281 ldr sp, [sp, #S_SP] @ abort is deadly from here onward (it will
282 @ clobber state restored below)
283 ldmia r0, {r2 - r12}
284 mov r1, #FIQ_MODE | PSR_I_BIT | PSR_F_BIT
285 msr cpsr_c, r1
286 sub r0, #S_R2
287 add r8, r0, #S_PC
288 ldmia r0, {r0 - r1}
289 rfeia r8
290 #endif
291 .endm
294 .macro restore_user_regs, fast = 0, offset = 0
295 uaccess_enable r1, isb=0
296 #ifndef CONFIG_THUMB2_KERNEL
297 @ ARM mode restore
298 mov r2, sp
299 ldr r1, [r2, #\offset + S_PSR] @ get calling cpsr
300 ldr lr, [r2, #\offset + S_PC]! @ get pc
301 tst r1, #PSR_I_BIT | 0x0f
302 bne 1f
303 msr spsr_cxsf, r1 @ save in spsr_svc
304 #if defined(CONFIG_CPU_V6) || defined(CONFIG_CPU_32v6K)
305 @ We must avoid clrex due to Cortex-A15 erratum #830321
306 strex r1, r2, [r2] @ clear the exclusive monitor
307 #endif
308 .if \fast
309 ldmdb r2, {r1 - lr}^ @ get calling r1 - lr
310 .else
311 ldmdb r2, {r0 - lr}^ @ get calling r0 - lr
312 .endif
313 mov r0, r0 @ ARMv5T and earlier require a nop
314 @ after ldm {}^
315 add sp, sp, #\offset + PT_REGS_SIZE
316 movs pc, lr @ return & move spsr_svc into cpsr
317 1: bug "Returning to usermode but unexpected PSR bits set?", \@
318 #elif defined(CONFIG_CPU_V7M)
319 @ V7M restore.
320 @ Note that we don't need to do clrex here as clearing the local
321 @ monitor is part of the exception entry and exit sequence.
322 .if \offset
323 add sp, #\offset
324 .endif
325 v7m_exception_slow_exit ret_r0 = \fast
326 #else
327 @ Thumb mode restore
328 mov r2, sp
329 load_user_sp_lr r2, r3, \offset + S_SP @ calling sp, lr
330 ldr r1, [sp, #\offset + S_PSR] @ get calling cpsr
331 ldr lr, [sp, #\offset + S_PC] @ get pc
332 add sp, sp, #\offset + S_SP
333 tst r1, #PSR_I_BIT | 0x0f
334 bne 1f
335 msr spsr_cxsf, r1 @ save in spsr_svc
337 @ We must avoid clrex due to Cortex-A15 erratum #830321
338 strex r1, r2, [sp] @ clear the exclusive monitor
340 .if \fast
341 ldmdb sp, {r1 - r12} @ get calling r1 - r12
342 .else
343 ldmdb sp, {r0 - r12} @ get calling r0 - r12
344 .endif
345 add sp, sp, #PT_REGS_SIZE - S_SP
346 movs pc, lr @ return & move spsr_svc into cpsr
347 1: bug "Returning to usermode but unexpected PSR bits set?", \@
348 #endif /* !CONFIG_THUMB2_KERNEL */
349 .endm
351 /*
352 * Context tracking subsystem. Used to instrument transitions
353 * between user and kernel mode.
354 */
355 .macro ct_user_exit, save = 1
356 #ifdef CONFIG_CONTEXT_TRACKING
357 .if \save
358 stmdb sp!, {r0-r3, ip, lr}
359 bl context_tracking_user_exit
360 ldmia sp!, {r0-r3, ip, lr}
361 .else
362 bl context_tracking_user_exit
363 .endif
364 #endif
365 .endm
367 .macro ct_user_enter, save = 1
368 #ifdef CONFIG_CONTEXT_TRACKING
369 .if \save
370 stmdb sp!, {r0-r3, ip, lr}
371 bl context_tracking_user_enter
372 ldmia sp!, {r0-r3, ip, lr}
373 .else
374 bl context_tracking_user_enter
375 .endif
376 #endif
377 .endm
379 .macro invoke_syscall, table, nr, tmp, ret, reload=0
380 #ifdef CONFIG_CPU_SPECTRE
381 mov \tmp, \nr
382 cmp \tmp, #NR_syscalls @ check upper syscall limit
383 movcs \tmp, #0
384 csdb
385 badr lr, \ret @ return address
386 .if \reload
387 add r1, sp, #S_R0 + S_OFF @ pointer to regs
388 ldmiacc r1, {r0 - r6} @ reload r0-r6
389 stmiacc sp, {r4, r5} @ update stack arguments
390 .endif
391 ldrcc pc, [\table, \tmp, lsl #2] @ call sys_* routine
392 #else
393 cmp \nr, #NR_syscalls @ check upper syscall limit
394 badr lr, \ret @ return address
395 .if \reload
396 add r1, sp, #S_R0 + S_OFF @ pointer to regs
397 ldmiacc r1, {r0 - r6} @ reload r0-r6
398 stmiacc sp, {r4, r5} @ update stack arguments
399 .endif
400 ldrcc pc, [\table, \nr, lsl #2] @ call sys_* routine
401 #endif
402 .endm
404 /*
405 * These are the registers used in the syscall handler, and allow us to
406 * have in theory up to 7 arguments to a function - r0 to r6.
407 *
408 * r7 is reserved for the system call number for thumb mode.
409 *
410 * Note that tbl == why is intentional.
411 *
412 * We must set at least "tsk" and "why" when calling ret_with_reschedule.
413 */
414 scno .req r7 @ syscall number
415 tbl .req r8 @ syscall table pointer
416 why .req r8 @ Linux syscall (!= 0)
417 tsk .req r9 @ current thread_info