/* * Low-level exception handling code * * Copyright (C) 2012 ARM Ltd. * Authors: Catalin Marinas <catalin.marinas@arm.com> * Will Deacon <will.deacon@arm.com> * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License version 2 as * published by the Free Software Foundation. * * This program is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU General Public License for more details. * * You should have received a copy of the GNU General Public License * along with this program. If not, see <http://www.gnu.org/licenses/>. */ #include <linux/init.h> #include <linux/linkage.h> #include <asm/assembler.h> #include <asm/asm-offsets.h> #include <asm/errno.h> #include <asm/esr.h> #include <asm/ptrace.h> #include <asm/thread_info.h> #include <asm/unistd.h> /* * Bad Abort numbers *----------------- */ #define BAD_SYNC 0 #define BAD_IRQ 1 #define BAD_FIQ 2 #define BAD_ERROR 3 .macro kernel_entry, el, regsize = 64 sub sp, sp, #S_FRAME_SIZE - S_LR // room for LR, SP, SPSR, ELR .if \regsize == 32 mov w0, w0 // zero upper 32 bits of x0 .endif push x28, x29 push x26, x27 push x24, x25 push x22, x23 push x20, x21 push x18, x19 push x16, x17 push x14, x15 push x12, x13 push x10, x11 push x8, x9 push x6, x7 push x4, x5 push x2, x3 push x0, x1 .if \el == 0 mrs x21, sp_el0 .else add x21, sp, #S_FRAME_SIZE .endif mrs x22, elr_el1 mrs x23, spsr_el1 stp lr, x21, [sp, #S_LR] stp x22, x23, [sp, #S_PC] /* * Set syscallno to -1 by default (overridden later if real syscall). */ .if \el == 0 mvn x21, xzr str x21, [sp, #S_SYSCALLNO] .endif /* * Registers that may be useful after this macro is invoked: * * x21 - aborted SP * x22 - aborted PC * x23 - aborted PSTATE */ .endm .macro kernel_exit, el, ret = 0 ldp x21, x22, [sp, #S_PC] // load ELR, SPSR .if \el == 0 ldr x23, [sp, #S_SP] // load return stack pointer .endif .if \ret ldr x1, [sp, #S_X1] // preserve x0 (syscall return) add sp, sp, S_X2 .else pop x0, x1 .endif pop x2, x3 // load the rest of the registers pop x4, x5 pop x6, x7 pop x8, x9 msr elr_el1, x21 // set up the return data msr spsr_el1, x22 .if \el == 0 msr sp_el0, x23 .endif pop x10, x11 pop x12, x13 pop x14, x15 pop x16, x17 pop x18, x19 pop x20, x21 pop x22, x23 pop x24, x25 pop x26, x27 pop x28, x29 ldr lr, [sp], #S_FRAME_SIZE - S_LR // load LR and restore SP eret // return to kernel .endm .macro get_thread_info, rd mov \rd, sp and \rd, \rd, #~((1 << 13) - 1) // top of 8K stack .endm /* * These are the registers used in the syscall handler, and allow us to * have in theory up to 7 arguments to a function - x0 to x6. * * x7 is reserved for the system call number in 32-bit mode. */ sc_nr .req x25 // number of system calls scno .req x26 // syscall number stbl .req x27 // syscall table pointer tsk .req x28 // current thread_info /* * Interrupt handling. */ .macro irq_handler ldr x1, handle_arch_irq mov x0, sp blr x1 .endm .text /* * Exception vectors. */ .align 11 ENTRY(vectors) ventry el1_sync_invalid // Synchronous EL1t ventry el1_irq_invalid // IRQ EL1t ventry el1_fiq_invalid // FIQ EL1t ventry el1_error_invalid // Error EL1t ventry el1_sync // Synchronous EL1h ventry el1_irq // IRQ EL1h ventry el1_fiq_invalid // FIQ EL1h ventry el1_error_invalid // Error EL1h ventry el0_sync // Synchronous 64-bit EL0 ventry el0_irq // IRQ 64-bit EL0 ventry el0_fiq_invalid // FIQ 64-bit EL0 ventry el0_error_invalid // Error 64-bit EL0 #ifdef CONFIG_COMPAT ventry el0_sync_compat // Synchronous 32-bit EL0 ventry el0_irq_compat // IRQ 32-bit EL0 ventry el0_fiq_invalid_compat // FIQ 32-bit EL0 ventry el0_error_invalid_compat // Error 32-bit EL0 #else ventry el0_sync_invalid // Synchronous 32-bit EL0 ventry el0_irq_invalid // IRQ 32-bit EL0 ventry el0_fiq_invalid // FIQ 32-bit EL0 ventry el0_error_invalid // Error 32-bit EL0 #endif END(vectors) /* * Invalid mode handlers */ .macro inv_entry, el, reason, regsize = 64 kernel_entry el, \regsize mov x0, sp mov x1, #\reason mrs x2, esr_el1 b bad_mode .endm el0_sync_invalid: inv_entry 0, BAD_SYNC ENDPROC(el0_sync_invalid) el0_irq_invalid: inv_entry 0, BAD_IRQ ENDPROC(el0_irq_invalid) el0_fiq_invalid: inv_entry 0, BAD_FIQ ENDPROC(el0_fiq_invalid) el0_error_invalid: inv_entry 0, BAD_ERROR ENDPROC(el0_error_invalid) #ifdef CONFIG_COMPAT el0_fiq_invalid_compat: inv_entry 0, BAD_FIQ, 32 ENDPROC(el0_fiq_invalid_compat) el0_error_invalid_compat: inv_entry 0, BAD_ERROR, 32 ENDPROC(el0_error_invalid_compat) #endif el1_sync_invalid: inv_entry 1, BAD_SYNC ENDPROC(el1_sync_invalid) el1_irq_invalid: inv_entry 1, BAD_IRQ ENDPROC(el1_irq_invalid) el1_fiq_invalid: inv_entry 1, BAD_FIQ ENDPROC(el1_fiq_invalid) el1_error_invalid: inv_entry 1, BAD_ERROR ENDPROC(el1_error_invalid) /* * EL1 mode handlers. */ .align 6 el1_sync: kernel_entry 1 mrs x1, esr_el1 // read the syndrome register lsr x24, x1, #ESR_EL1_EC_SHIFT // exception class cmp x24, #ESR_EL1_EC_DABT_EL1 // data abort in EL1 b.eq el1_da cmp x24, #ESR_EL1_EC_SYS64 // configurable trap b.eq el1_undef cmp x24, #ESR_EL1_EC_SP_ALIGN // stack alignment exception b.eq el1_sp_pc cmp x24, #ESR_EL1_EC_PC_ALIGN // pc alignment exception b.eq el1_sp_pc cmp x24, #ESR_EL1_EC_UNKNOWN // unknown exception in EL1 b.eq el1_undef cmp x24, #ESR_EL1_EC_BREAKPT_EL1 // debug exception in EL1 b.ge el1_dbg b el1_inv el1_da: /* * Data abort handling */ mrs x0, far_el1 enable_dbg_if_not_stepping x2 // re-enable interrupts if they were enabled in the aborted context tbnz x23, #7, 1f // PSR_I_BIT enable_irq 1: mov x2, sp // struct pt_regs bl do_mem_abort // disable interrupts before pulling preserved data off the stack disable_irq kernel_exit 1 el1_sp_pc: /* * Stack or PC alignment exception handling */ mrs x0, far_el1 mov x1, x25 mov x2, sp b do_sp_pc_abort el1_undef: /* * Undefined instruction */ mov x0, sp b do_undefinstr el1_dbg: /* * Debug exception handling */ tbz x24, #0, el1_inv // EL1 only mrs x0, far_el1 mov x2, sp // struct pt_regs bl do_debug_exception kernel_exit 1 el1_inv: // TODO: add support for undefined instructions in kernel mode mov x0, sp mov x1, #BAD_SYNC mrs x2, esr_el1 b bad_mode ENDPROC(el1_sync) .align 6 el1_irq: kernel_entry 1 enable_dbg_if_not_stepping x0 #ifdef CONFIG_TRACE_IRQFLAGS bl trace_hardirqs_off #endif #ifdef CONFIG_PREEMPT get_thread_info tsk ldr x24, [tsk, #TI_PREEMPT] // get preempt count add x0, x24, #1 // increment it str x0, [tsk, #TI_PREEMPT] #endif irq_handler #ifdef CONFIG_PREEMPT str x24, [tsk, #TI_PREEMPT] // restore preempt count cbnz x24, 1f // preempt count != 0 ldr x0, [tsk, #TI_FLAGS] // get flags tbz x0, #TIF_NEED_RESCHED, 1f // needs rescheduling? bl el1_preempt 1: #endif #ifdef CONFIG_TRACE_IRQFLAGS bl trace_hardirqs_on #endif kernel_exit 1 ENDPROC(el1_irq) #ifdef CONFIG_PREEMPT el1_preempt: mov x24, lr 1: enable_dbg bl preempt_schedule_irq // irq en/disable is done inside ldr x0, [tsk, #TI_FLAGS] // get new tasks TI_FLAGS tbnz x0, #TIF_NEED_RESCHED, 1b // needs rescheduling? ret x24 #endif /* * EL0 mode handlers. */ .align 6 el0_sync: kernel_entry 0 mrs x25, esr_el1 // read the syndrome register lsr x24, x25, #ESR_EL1_EC_SHIFT // exception class cmp x24, #ESR_EL1_EC_SVC64 // SVC in 64-bit state b.eq el0_svc adr lr, ret_from_exception cmp x24, #ESR_EL1_EC_DABT_EL0 // data abort in EL0 b.eq el0_da cmp x24, #ESR_EL1_EC_IABT_EL0 // instruction abort in EL0 b.eq el0_ia cmp x24, #ESR_EL1_EC_FP_ASIMD // FP/ASIMD access b.eq el0_fpsimd_acc cmp x24, #ESR_EL1_EC_FP_EXC64 // FP/ASIMD exception b.eq el0_fpsimd_exc cmp x24, #ESR_EL1_EC_SYS64 // configurable trap b.eq el0_undef cmp x24, #ESR_EL1_EC_SP_ALIGN // stack alignment exception b.eq el0_sp_pc cmp x24, #ESR_EL1_EC_PC_ALIGN // pc alignment exception b.eq el0_sp_pc cmp x24, #ESR_EL1_EC_UNKNOWN // unknown exception in EL0 b.eq el0_undef cmp x24, #ESR_EL1_EC_BREAKPT_EL0 // debug exception in EL0 b.ge el0_dbg b el0_inv #ifdef CONFIG_COMPAT .align 6 el0_sync_compat: kernel_entry 0, 32 mrs x25, esr_el1 // read the syndrome register lsr x24, x25, #ESR_EL1_EC_SHIFT // exception class cmp x24, #ESR_EL1_EC_SVC32 // SVC in 32-bit state b.eq el0_svc_compat adr lr, ret_from_exception cmp x24, #ESR_EL1_EC_DABT_EL0 // data abort in EL0 b.eq el0_da cmp x24, #ESR_EL1_EC_IABT_EL0 // instruction abort in EL0 b.eq el0_ia cmp x24, #ESR_EL1_EC_FP_ASIMD // FP/ASIMD access b.eq el0_fpsimd_acc cmp x24, #ESR_EL1_EC_FP_EXC32 // FP/ASIMD exception b.eq el0_fpsimd_exc cmp x24, #ESR_EL1_EC_UNKNOWN // unknown exception in EL0 b.eq el0_undef cmp x24, #ESR_EL1_EC_CP15_32 // CP15 MRC/MCR trap b.eq el0_undef cmp x24, #ESR_EL1_EC_CP15_64 // CP15 MRRC/MCRR trap b.eq el0_undef cmp x24, #ESR_EL1_EC_CP14_MR // CP14 MRC/MCR trap b.eq el0_undef cmp x24, #ESR_EL1_EC_CP14_LS // CP14 LDC/STC trap b.eq el0_undef cmp x24, #ESR_EL1_EC_CP14_64 // CP14 MRRC/MCRR trap b.eq el0_undef cmp x24, #ESR_EL1_EC_BREAKPT_EL0 // debug exception in EL0 b.ge el0_dbg b el0_inv el0_svc_compat: /* * AArch32 syscall handling */ adr stbl, compat_sys_call_table // load compat syscall table pointer uxtw scno, w7 // syscall number in w7 (r7) mov sc_nr, #__NR_compat_syscalls b el0_svc_naked .align 6 el0_irq_compat: kernel_entry 0, 32 b el0_irq_naked #endif el0_da: /* * Data abort handling */ mrs x0, far_el1 bic x0, x0, #(0xff << 56) disable_step x1 isb enable_dbg // enable interrupts before calling the main handler enable_irq mov x1, x25 mov x2, sp b do_mem_abort el0_ia: /* * Instruction abort handling */ mrs x0, far_el1 disable_step x1 isb enable_dbg // enable interrupts before calling the main handler enable_irq orr x1, x25, #1 << 24 // use reserved ISS bit for instruction aborts mov x2, sp b do_mem_abort el0_fpsimd_acc: /* * Floating Point or Advanced SIMD access */ mov x0, x25 mov x1, sp b do_fpsimd_acc el0_fpsimd_exc: /* * Floating Point or Advanced SIMD exception */ mov x0, x25 mov x1, sp b do_fpsimd_exc el0_sp_pc: /* * Stack or PC alignment exception handling */ mrs x0, far_el1 disable_step x1 isb enable_dbg // enable interrupts before calling the main handler enable_irq mov x1, x25 mov x2, sp b do_sp_pc_abort el0_undef: /* * Undefined instruction */ mov x0, sp b do_undefinstr el0_dbg: /* * Debug exception handling */ tbnz x24, #0, el0_inv // EL0 only mrs x0, far_el1 disable_step x1 mov x1, x25 mov x2, sp b do_debug_exception el0_inv: mov x0, sp mov x1, #BAD_SYNC mrs x2, esr_el1 b bad_mode ENDPROC(el0_sync) .align 6 el0_irq: kernel_entry 0 el0_irq_naked: disable_step x1 isb enable_dbg #ifdef CONFIG_TRACE_IRQFLAGS bl trace_hardirqs_off #endif get_thread_info tsk #ifdef CONFIG_PREEMPT ldr x24, [tsk, #TI_PREEMPT] // get preempt count add x23, x24, #1 // increment it str x23, [tsk, #TI_PREEMPT] #endif irq_handler #ifdef CONFIG_PREEMPT ldr x0, [tsk, #TI_PREEMPT] str x24, [tsk, #TI_PREEMPT] cmp x0, x23 b.eq 1f mov x1, #0 str x1, [x1] // BUG 1: #endif #ifdef CONFIG_TRACE_IRQFLAGS bl trace_hardirqs_on #endif b ret_to_user ENDPROC(el0_irq) /* * This is the return code to user mode for abort handlers */ ret_from_exception: get_thread_info tsk b ret_to_user ENDPROC(ret_from_exception) /* * Register switch for AArch64. The callee-saved registers need to be saved * and restored. On entry: * x0 = previous task_struct (must be preserved across the switch) * x1 = next task_struct * Previous and next are guaranteed not to be the same. * */ ENTRY(cpu_switch_to) add x8, x0, #THREAD_CPU_CONTEXT mov x9, sp stp x19, x20, [x8], #16 // store callee-saved registers stp x21, x22, [x8], #16 stp x23, x24, [x8], #16 stp x25, x26, [x8], #16 stp x27, x28, [x8], #16 stp x29, x9, [x8], #16 str lr, [x8] add x8, x1, #THREAD_CPU_CONTEXT ldp x19, x20, [x8], #16 // restore callee-saved registers ldp x21, x22, [x8], #16 ldp x23, x24, [x8], #16 ldp x25, x26, [x8], #16 ldp x27, x28, [x8], #16 ldp x29, x9, [x8], #16 ldr lr, [x8] mov sp, x9 ret ENDPROC(cpu_switch_to) /* * This is the fast syscall return path. We do as little as possible here, * and this includes saving x0 back into the kernel stack. */ ret_fast_syscall: disable_irq // disable interrupts ldr x1, [tsk, #TI_FLAGS] and x2, x1, #_TIF_WORK_MASK cbnz x2, fast_work_pending tbz x1, #TIF_SINGLESTEP, fast_exit disable_dbg enable_step x2 fast_exit: kernel_exit 0, ret = 1 /* * Ok, we need to do extra processing, enter the slow path. */ fast_work_pending: str x0, [sp, #S_X0] // returned x0 work_pending: tbnz x1, #TIF_NEED_RESCHED, work_resched /* TIF_SIGPENDING, TIF_NOTIFY_RESUME or TIF_FOREIGN_FPSTATE case */ ldr x2, [sp, #S_PSTATE] mov x0, sp // 'regs' tst x2, #PSR_MODE_MASK // user mode regs? b.ne no_work_pending // returning to kernel enable_irq // enable interrupts for do_notify_resume() bl do_notify_resume b ret_to_user work_resched: enable_dbg bl schedule /* * "slow" syscall return path. */ ret_to_user: disable_irq // disable interrupts ldr x1, [tsk, #TI_FLAGS] and x2, x1, #_TIF_WORK_MASK cbnz x2, work_pending tbz x1, #TIF_SINGLESTEP, no_work_pending disable_dbg enable_step x2 no_work_pending: kernel_exit 0, ret = 0 ENDPROC(ret_to_user) /* * This is how we return from a fork. */ ENTRY(ret_from_fork) bl schedule_tail cbz x19, 1f // not a kernel thread mov x0, x20 blr x19 1: get_thread_info tsk b ret_to_user ENDPROC(ret_from_fork) /* * SVC handler. */ .align 6 el0_svc: adrp stbl, sys_call_table // load syscall table pointer uxtw scno, w8 // syscall number in w8 mov sc_nr, #__NR_syscalls el0_svc_naked: // compat entry point stp x0, scno, [sp, #S_ORIG_X0] // save the original x0 and syscall number disable_step x16 isb enable_dbg enable_irq get_thread_info tsk ldr x16, [tsk, #TI_FLAGS] // check for syscall hooks tst x16, #_TIF_SYSCALL_WORK b.ne __sys_trace adr lr, ret_fast_syscall // return address cmp scno, sc_nr // check upper syscall limit b.hs ni_sys ldr x16, [stbl, scno, lsl #3] // address in the syscall table br x16 // call sys_* routine ni_sys: mov x0, sp b do_ni_syscall ENDPROC(el0_svc) /* * This is the really slow path. We're going to be doing context * switches, and waiting for our parent to respond. */ __sys_trace: mov x0, sp bl syscall_trace_enter adr lr, __sys_trace_return // return address cmp w0, #RET_SKIP_SYSCALL_TRACE // skip syscall and tracing? b.eq ret_to_user cmp w0, #RET_SKIP_SYSCALL // skip syscall? b.eq __sys_trace_return_skipped uxtw scno, w0 // syscall number (possibly new) mov x1, sp // pointer to regs cmp scno, sc_nr // check upper syscall limit b.hs ni_sys ldp x0, x1, [sp] // restore the syscall args ldp x2, x3, [sp, #S_X2] ldp x4, x5, [sp, #S_X4] ldp x6, x7, [sp, #S_X6] ldr x16, [stbl, scno, lsl #3] // address in the syscall table br x16 // call sys_* routine __sys_trace_return: str x0, [sp] // save returned x0 __sys_trace_return_skipped: // x0 already in regs[0] mov x0, sp bl syscall_trace_exit b ret_to_user /* * Special system call wrappers. */ ENTRY(sys_rt_sigreturn_wrapper) mov x0, sp b sys_rt_sigreturn ENDPROC(sys_rt_sigreturn_wrapper) ENTRY(handle_arch_irq) .quad 0