2 * Low-level exception handling code
4 * Copyright (C) 2012 ARM Ltd.
5 * Authors: Catalin Marinas <catalin.marinas@arm.com>
6 * Will Deacon <will.deacon@arm.com>
8 * This program is free software; you can redistribute it and/or modify
9 * it under the terms of the GNU General Public License version 2 as
10 * published by the Free Software Foundation.
12 * This program is distributed in the hope that it will be useful,
13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 * GNU General Public License for more details.
17 * You should have received a copy of the GNU General Public License
18 * along with this program. If not, see <http://www.gnu.org/licenses/>.
21 #include <linux/init.h>
22 #include <linux/linkage.h>
24 #include <asm/assembler.h>
25 #include <asm/asm-offsets.h>
26 #include <asm/errno.h>
28 #include <asm/thread_info.h>
29 #include <asm/unistd.h>
32 * Context tracking subsystem. Used to instrument transitions
33 * between user and kernel mode.
35 .macro ct_user_exit, syscall = 0
36 #ifdef CONFIG_CONTEXT_TRACKING
37 bl context_tracking_user_exit
40 * Save/restore needed during syscalls. Restore syscall arguments from
41 * the values already saved on stack during kernel_entry.
44 ldp x2, x3, [sp, #S_X2]
45 ldp x4, x5, [sp, #S_X4]
46 ldp x6, x7, [sp, #S_X6]
52 #ifdef CONFIG_CONTEXT_TRACKING
53 bl context_tracking_user_enter
66 .macro kernel_entry, el, regsize = 64
67 sub sp, sp, #S_FRAME_SIZE
69 mov w0, w0 // zero upper 32 bits of x0
71 stp x0, x1, [sp, #16 * 0]
72 stp x2, x3, [sp, #16 * 1]
73 stp x4, x5, [sp, #16 * 2]
74 stp x6, x7, [sp, #16 * 3]
75 stp x8, x9, [sp, #16 * 4]
76 stp x10, x11, [sp, #16 * 5]
77 stp x12, x13, [sp, #16 * 6]
78 stp x14, x15, [sp, #16 * 7]
79 stp x16, x17, [sp, #16 * 8]
80 stp x18, x19, [sp, #16 * 9]
81 stp x20, x21, [sp, #16 * 10]
82 stp x22, x23, [sp, #16 * 11]
83 stp x24, x25, [sp, #16 * 12]
84 stp x26, x27, [sp, #16 * 13]
85 stp x28, x29, [sp, #16 * 14]
89 get_thread_info tsk // Ensure MDSCR_EL1.SS is clear,
90 ldr x19, [tsk, #TI_FLAGS] // since we can unmask debug
91 disable_step_tsk x19, x20 // exceptions when scheduling.
93 add x21, sp, #S_FRAME_SIZE
97 stp lr, x21, [sp, #S_LR]
98 stp x22, x23, [sp, #S_PC]
101 * Set syscallno to -1 by default (overridden later if real syscall).
105 str x21, [sp, #S_SYSCALLNO]
109 * Registers that may be useful after this macro is invoked:
113 * x23 - aborted PSTATE
117 .macro kernel_exit, el, ret = 0
118 ldp x21, x22, [sp, #S_PC] // load ELR, SPSR
121 ldr x23, [sp, #S_SP] // load return stack pointer
124 msr elr_el1, x21 // set up the return data
127 ldr x1, [sp, #S_X1] // preserve x0 (syscall return)
129 ldp x0, x1, [sp, #16 * 0]
131 ldp x2, x3, [sp, #16 * 1]
132 ldp x4, x5, [sp, #16 * 2]
133 ldp x6, x7, [sp, #16 * 3]
134 ldp x8, x9, [sp, #16 * 4]
135 ldp x10, x11, [sp, #16 * 5]
136 ldp x12, x13, [sp, #16 * 6]
137 ldp x14, x15, [sp, #16 * 7]
138 ldp x16, x17, [sp, #16 * 8]
139 ldp x18, x19, [sp, #16 * 9]
140 ldp x20, x21, [sp, #16 * 10]
141 ldp x22, x23, [sp, #16 * 11]
142 ldp x24, x25, [sp, #16 * 12]
143 ldp x26, x27, [sp, #16 * 13]
144 ldp x28, x29, [sp, #16 * 14]
146 add sp, sp, #S_FRAME_SIZE // restore sp
147 eret // return to kernel
150 .macro get_thread_info, rd
152 and \rd, \rd, #~(THREAD_SIZE - 1) // top of stack
156 * These are the registers used in the syscall handler, and allow us to
157 * have in theory up to 7 arguments to a function - x0 to x6.
159 * x7 is reserved for the system call number in 32-bit mode.
161 sc_nr .req x25 // number of system calls
162 scno .req x26 // syscall number
163 stbl .req x27 // syscall table pointer
164 tsk .req x28 // current thread_info
167 * Interrupt handling.
170 adrp x1, handle_arch_irq
171 ldr x1, [x1, #:lo12:handle_arch_irq]
184 ventry el1_sync_invalid // Synchronous EL1t
185 ventry el1_irq_invalid // IRQ EL1t
186 ventry el1_fiq_invalid // FIQ EL1t
187 ventry el1_error_invalid // Error EL1t
189 ventry el1_sync // Synchronous EL1h
190 ventry el1_irq // IRQ EL1h
191 ventry el1_fiq_invalid // FIQ EL1h
192 ventry el1_error_invalid // Error EL1h
194 ventry el0_sync // Synchronous 64-bit EL0
195 ventry el0_irq // IRQ 64-bit EL0
196 ventry el0_fiq_invalid // FIQ 64-bit EL0
197 ventry el0_error_invalid // Error 64-bit EL0
200 ventry el0_sync_compat // Synchronous 32-bit EL0
201 ventry el0_irq_compat // IRQ 32-bit EL0
202 ventry el0_fiq_invalid_compat // FIQ 32-bit EL0
203 ventry el0_error_invalid_compat // Error 32-bit EL0
205 ventry el0_sync_invalid // Synchronous 32-bit EL0
206 ventry el0_irq_invalid // IRQ 32-bit EL0
207 ventry el0_fiq_invalid // FIQ 32-bit EL0
208 ventry el0_error_invalid // Error 32-bit EL0
213 * Invalid mode handlers
215 .macro inv_entry, el, reason, regsize = 64
216 kernel_entry el, \regsize
224 inv_entry 0, BAD_SYNC
225 ENDPROC(el0_sync_invalid)
229 ENDPROC(el0_irq_invalid)
233 ENDPROC(el0_fiq_invalid)
236 inv_entry 0, BAD_ERROR
237 ENDPROC(el0_error_invalid)
240 el0_fiq_invalid_compat:
241 inv_entry 0, BAD_FIQ, 32
242 ENDPROC(el0_fiq_invalid_compat)
244 el0_error_invalid_compat:
245 inv_entry 0, BAD_ERROR, 32
246 ENDPROC(el0_error_invalid_compat)
250 inv_entry 1, BAD_SYNC
251 ENDPROC(el1_sync_invalid)
255 ENDPROC(el1_irq_invalid)
259 ENDPROC(el1_fiq_invalid)
262 inv_entry 1, BAD_ERROR
263 ENDPROC(el1_error_invalid)
271 mrs x1, esr_el1 // read the syndrome register
272 lsr x24, x1, #ESR_EL1_EC_SHIFT // exception class
273 cmp x24, #ESR_EL1_EC_DABT_EL1 // data abort in EL1
275 cmp x24, #ESR_EL1_EC_SYS64 // configurable trap
277 cmp x24, #ESR_EL1_EC_SP_ALIGN // stack alignment exception
279 cmp x24, #ESR_EL1_EC_PC_ALIGN // pc alignment exception
281 cmp x24, #ESR_EL1_EC_UNKNOWN // unknown exception in EL1
283 cmp x24, #ESR_EL1_EC_BREAKPT_EL1 // debug exception in EL1
288 * Data abort handling
292 // re-enable interrupts if they were enabled in the aborted context
293 tbnz x23, #7, 1f // PSR_I_BIT
296 mov x2, sp // struct pt_regs
299 // disable interrupts before pulling preserved data off the stack
304 * Stack or PC alignment exception handling
312 * Undefined instruction
319 * Debug exception handling
321 cmp x24, #ESR_EL1_EC_BRK64 // if BRK64
322 cinc x24, x24, eq // set bit '0'
323 tbz x24, #0, el1_inv // EL1 only
325 mov x2, sp // struct pt_regs
326 bl do_debug_exception
329 // TODO: add support for undefined instructions in kernel mode
341 #ifdef CONFIG_TRACE_IRQFLAGS
342 bl trace_hardirqs_off
347 #ifdef CONFIG_PREEMPT
349 ldr w24, [tsk, #TI_PREEMPT] // get preempt count
350 cbnz w24, 1f // preempt count != 0
351 ldr x0, [tsk, #TI_FLAGS] // get flags
352 tbz x0, #TIF_NEED_RESCHED, 1f // needs rescheduling?
356 #ifdef CONFIG_TRACE_IRQFLAGS
362 #ifdef CONFIG_PREEMPT
365 1: bl preempt_schedule_irq // irq en/disable is done inside
366 ldr x0, [tsk, #TI_FLAGS] // get new tasks TI_FLAGS
367 tbnz x0, #TIF_NEED_RESCHED, 1b // needs rescheduling?
377 mrs x25, esr_el1 // read the syndrome register
378 lsr x24, x25, #ESR_EL1_EC_SHIFT // exception class
379 cmp x24, #ESR_EL1_EC_SVC64 // SVC in 64-bit state
381 cmp x24, #ESR_EL1_EC_DABT_EL0 // data abort in EL0
383 cmp x24, #ESR_EL1_EC_IABT_EL0 // instruction abort in EL0
385 cmp x24, #ESR_EL1_EC_FP_ASIMD // FP/ASIMD access
387 cmp x24, #ESR_EL1_EC_FP_EXC64 // FP/ASIMD exception
389 cmp x24, #ESR_EL1_EC_SYS64 // configurable trap
391 cmp x24, #ESR_EL1_EC_SP_ALIGN // stack alignment exception
393 cmp x24, #ESR_EL1_EC_PC_ALIGN // pc alignment exception
395 cmp x24, #ESR_EL1_EC_UNKNOWN // unknown exception in EL0
397 cmp x24, #ESR_EL1_EC_BREAKPT_EL0 // debug exception in EL0
405 mrs x25, esr_el1 // read the syndrome register
406 lsr x24, x25, #ESR_EL1_EC_SHIFT // exception class
407 cmp x24, #ESR_EL1_EC_SVC32 // SVC in 32-bit state
409 cmp x24, #ESR_EL1_EC_DABT_EL0 // data abort in EL0
411 cmp x24, #ESR_EL1_EC_IABT_EL0 // instruction abort in EL0
413 cmp x24, #ESR_EL1_EC_FP_ASIMD // FP/ASIMD access
415 cmp x24, #ESR_EL1_EC_FP_EXC32 // FP/ASIMD exception
417 cmp x24, #ESR_EL1_EC_UNKNOWN // unknown exception in EL0
419 cmp x24, #ESR_EL1_EC_CP15_32 // CP15 MRC/MCR trap
421 cmp x24, #ESR_EL1_EC_CP15_64 // CP15 MRRC/MCRR trap
423 cmp x24, #ESR_EL1_EC_CP14_MR // CP14 MRC/MCR trap
425 cmp x24, #ESR_EL1_EC_CP14_LS // CP14 LDC/STC trap
427 cmp x24, #ESR_EL1_EC_CP14_64 // CP14 MRRC/MCRR trap
429 cmp x24, #ESR_EL1_EC_BREAKPT_EL0 // debug exception in EL0
434 * AArch32 syscall handling
436 adr stbl, compat_sys_call_table // load compat syscall table pointer
437 uxtw scno, w7 // syscall number in w7 (r7)
438 mov sc_nr, #__NR_compat_syscalls
449 * Data abort handling
452 // enable interrupts before calling the main handler
455 bic x0, x26, #(0xff << 56)
462 * Instruction abort handling
465 // enable interrupts before calling the main handler
469 orr x1, x25, #1 << 24 // use reserved ISS bit for instruction aborts
475 * Floating Point or Advanced SIMD access
485 * Floating Point or Advanced SIMD exception
495 * Stack or PC alignment exception handling
498 // enable interrupts before calling the main handler
507 * Undefined instruction
509 // enable interrupts before calling the main handler
517 * Debug exception handling
519 tbnz x24, #0, el0_inv // EL0 only
523 bl do_debug_exception
542 #ifdef CONFIG_TRACE_IRQFLAGS
543 bl trace_hardirqs_off
549 #ifdef CONFIG_TRACE_IRQFLAGS
556 * Register switch for AArch64. The callee-saved registers need to be saved
557 * and restored. On entry:
558 * x0 = previous task_struct (must be preserved across the switch)
559 * x1 = next task_struct
560 * Previous and next are guaranteed not to be the same.
564 add x8, x0, #THREAD_CPU_CONTEXT
566 stp x19, x20, [x8], #16 // store callee-saved registers
567 stp x21, x22, [x8], #16
568 stp x23, x24, [x8], #16
569 stp x25, x26, [x8], #16
570 stp x27, x28, [x8], #16
571 stp x29, x9, [x8], #16
573 add x8, x1, #THREAD_CPU_CONTEXT
574 ldp x19, x20, [x8], #16 // restore callee-saved registers
575 ldp x21, x22, [x8], #16
576 ldp x23, x24, [x8], #16
577 ldp x25, x26, [x8], #16
578 ldp x27, x28, [x8], #16
579 ldp x29, x9, [x8], #16
583 ENDPROC(cpu_switch_to)
586 * This is the fast syscall return path. We do as little as possible here,
587 * and this includes saving x0 back into the kernel stack.
590 disable_irq // disable interrupts
591 ldr x1, [tsk, #TI_FLAGS]
592 and x2, x1, #_TIF_WORK_MASK
593 cbnz x2, fast_work_pending
594 enable_step_tsk x1, x2
595 kernel_exit 0, ret = 1
598 * Ok, we need to do extra processing, enter the slow path.
601 str x0, [sp, #S_X0] // returned x0
603 tbnz x1, #TIF_NEED_RESCHED, work_resched
604 /* TIF_SIGPENDING, TIF_NOTIFY_RESUME or TIF_FOREIGN_FPSTATE case */
605 ldr x2, [sp, #S_PSTATE]
607 tst x2, #PSR_MODE_MASK // user mode regs?
608 b.ne no_work_pending // returning to kernel
609 enable_irq // enable interrupts for do_notify_resume()
616 * "slow" syscall return path.
619 disable_irq // disable interrupts
620 ldr x1, [tsk, #TI_FLAGS]
621 and x2, x1, #_TIF_WORK_MASK
622 cbnz x2, work_pending
623 enable_step_tsk x1, x2
625 kernel_exit 0, ret = 0
629 * This is how we return from a fork.
633 cbz x19, 1f // not a kernel thread
636 1: get_thread_info tsk
638 ENDPROC(ret_from_fork)
645 adrp stbl, sys_call_table // load syscall table pointer
646 uxtw scno, w8 // syscall number in w8
647 mov sc_nr, #__NR_syscalls
648 el0_svc_naked: // compat entry point
649 stp x0, scno, [sp, #S_ORIG_X0] // save the original x0 and syscall number
653 ldr x16, [tsk, #TI_FLAGS] // check for syscall hooks
654 tst x16, #_TIF_SYSCALL_WORK
656 cmp scno, sc_nr // check upper syscall limit
658 ldr x16, [stbl, scno, lsl #3] // address in the syscall table
659 blr x16 // call sys_* routine
668 * This is the really slow path. We're going to be doing context
669 * switches, and waiting for our parent to respond.
672 mov w0, #-1 // set default errno for
673 cmp scno, x0 // user-issued syscall(-1)
678 bl syscall_trace_enter
679 cmp w0, #-1 // skip the syscall?
680 b.eq __sys_trace_return_skipped
681 uxtw scno, w0 // syscall number (possibly new)
682 mov x1, sp // pointer to regs
683 cmp scno, sc_nr // check upper syscall limit
685 ldp x0, x1, [sp] // restore the syscall args
686 ldp x2, x3, [sp, #S_X2]
687 ldp x4, x5, [sp, #S_X4]
688 ldp x6, x7, [sp, #S_X6]
689 ldr x16, [stbl, scno, lsl #3] // address in the syscall table
690 blr x16 // call sys_* routine
693 str x0, [sp, #S_X0] // save returned x0
694 __sys_trace_return_skipped:
696 bl syscall_trace_exit
705 * Special system call wrappers.
707 ENTRY(sys_rt_sigreturn_wrapper)
710 ENDPROC(sys_rt_sigreturn_wrapper)