/* SPDX-License-Identifier: GPL-2.0-only */ /* * Common Low Level Interrupts/Traps/Exceptions(non-TLB) Handling for ARC * (included from entry-.S * * Copyright (C) 2014-15 Synopsys, Inc. (www.synopsys.com) * Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com) */ /*------------------------------------------------------------------ * Function ABI *------------------------------------------------------------------ * * Arguments r0 - r7 * Caller Saved Registers r0 - r12 * Callee Saved Registers r13- r25 * Global Pointer (gp) r26 * Frame Pointer (fp) r27 * Stack Pointer (sp) r28 * Branch link register (blink) r31 *------------------------------------------------------------------ */ ;################### Special Sys Call Wrappers ########################## ENTRY(sys_clone_wrapper) SAVE_CALLEE_SAVED_USER bl @sys_clone DISCARD_CALLEE_SAVED_USER GET_CURR_THR_INFO_FLAGS r10 btst r10, TIF_SYSCALL_TRACE bnz tracesys_exit b .Lret_from_system_call END(sys_clone_wrapper) ENTRY(sys_clone3_wrapper) SAVE_CALLEE_SAVED_USER bl @sys_clone3 DISCARD_CALLEE_SAVED_USER GET_CURR_THR_INFO_FLAGS r10 btst r10, TIF_SYSCALL_TRACE bnz tracesys_exit b .Lret_from_system_call END(sys_clone3_wrapper) ENTRY(ret_from_fork) ; when the forked child comes here from the __switch_to function ; r0 has the last task pointer. ; put last task in scheduler queue jl @schedule_tail ld r9, [sp, PT_status32] brne r9, 0, 1f jl.d [r14] ; kernel thread entry point mov r0, r13 ; (see PF_KTHREAD block in copy_thread) 1: ; Return to user space ; 1. Any forked task (Reach here via BRne above) ; 2. First ever init task (Reach here via return from JL above) ; This is the historic "kernel_execve" use-case, to return to init ; user mode, in a round about way since that is always done from ; a kernel thread which is executed via JL above but always returns ; out whenever kernel_execve (now inline do_fork()) is involved b ret_from_exception END(ret_from_fork) ;################### Non TLB Exception Handling ############################# ; --------------------------------------------- ; Instruction Error Exception Handler ; --------------------------------------------- ENTRY(instr_service) EXCEPTION_PROLOGUE lr r0, [efa] mov r1, sp FAKE_RET_FROM_EXCPN bl do_insterror_or_kprobe b ret_from_exception END(instr_service) ; --------------------------------------------- ; Machine Check Exception Handler ; --------------------------------------------- ENTRY(EV_MachineCheck) EXCEPTION_PROLOGUE lr r2, [ecr] lr r0, [efa] mov r1, sp ; hardware auto-disables MMU, re-enable it to allow kernel vaddr ; access for say stack unwinding of modules for crash dumps lr r3, [ARC_REG_PID] or r3, r3, MMU_ENABLE sr r3, [ARC_REG_PID] lsr r3, r2, 8 bmsk r3, r3, 7 brne r3, ECR_C_MCHK_DUP_TLB, 1f bl do_tlb_overlap_fault b ret_from_exception 1: ; DEAD END: can't do much, display Regs and HALT SAVE_CALLEE_SAVED_USER GET_CURR_TASK_FIELD_PTR TASK_THREAD, r10 st sp, [r10, THREAD_CALLEE_REG] j do_machine_check_fault END(EV_MachineCheck) ; --------------------------------------------- ; Privilege Violation Exception Handler ; --------------------------------------------- ENTRY(EV_PrivilegeV) EXCEPTION_PROLOGUE lr r0, [efa] mov r1, sp FAKE_RET_FROM_EXCPN bl do_privilege_fault b ret_from_exception END(EV_PrivilegeV) ; --------------------------------------------- ; Extension Instruction Exception Handler ; --------------------------------------------- ENTRY(EV_Extension) EXCEPTION_PROLOGUE lr r0, [efa] mov r1, sp FAKE_RET_FROM_EXCPN bl do_extension_fault b ret_from_exception END(EV_Extension) ;################ Trap Handling (Syscall, Breakpoint) ################## ; --------------------------------------------- ; syscall Tracing ; --------------------------------------------- tracesys: ; save EFA in case tracer wants the PC of traced task ; using ERET won't work since next-PC has already committed GET_CURR_TASK_FIELD_PTR TASK_THREAD, r11 st r12, [r11, THREAD_FAULT_ADDR] ; thread.fault_address ; PRE Sys Call Ptrace hook mov r0, sp ; pt_regs needed bl @syscall_trace_entry ; Tracing code now returns the syscall num (orig or modif) mov r8, r0 ; Do the Sys Call as we normally would. ; Validate the Sys Call number cmp r8, NR_syscalls mov.hi r0, -ENOSYS bhi tracesys_exit ; Restore the sys-call args. Mere invocation of the hook abv could have ; clobbered them (since they are in scratch regs). The tracer could also ; have deliberately changed the syscall args: r0-r7 ld r0, [sp, PT_r0] ld r1, [sp, PT_r1] ld r2, [sp, PT_r2] ld r3, [sp, PT_r3] ld r4, [sp, PT_r4] ld r5, [sp, PT_r5] ld r6, [sp, PT_r6] ld r7, [sp, PT_r7] ld.as r9, [sys_call_table, r8] jl [r9] ; Entry into Sys Call Handler tracesys_exit: st r0, [sp, PT_r0] ; sys call return value in pt_regs ;POST Sys Call Ptrace Hook bl @syscall_trace_exit b ret_from_exception ; NOT ret_from_system_call at is saves r0 which ; we'd done before calling post hook above ; --------------------------------------------- ; Breakpoint TRAP ; --------------------------------------------- trap_with_param: mov r0, r12 ; EFA in case ptracer/gdb wants stop_pc mov r1, sp ; Save callee regs in case gdb wants to have a look ; SP will grow up by size of CALLEE Reg-File ; NOTE: clobbers r12 SAVE_CALLEE_SAVED_USER ; save location of saved Callee Regs @ thread_struct->pc GET_CURR_TASK_FIELD_PTR TASK_THREAD, r10 st sp, [r10, THREAD_CALLEE_REG] ; Call the trap handler bl do_non_swi_trap ; unwind stack to discard Callee saved Regs DISCARD_CALLEE_SAVED_USER b ret_from_exception ; --------------------------------------------- ; syscall TRAP ; ABI: (r0-r7) upto 8 args, (r8) syscall number ; --------------------------------------------- ENTRY(EV_Trap) EXCEPTION_PROLOGUE lr r12, [efa] FAKE_RET_FROM_EXCPN ;============ TRAP 1 :breakpoints ; Check ECR for trap with arg (PROLOGUE ensures r10 has ECR) bmsk.f 0, r10, 7 bnz trap_with_param ;============ TRAP (no param): syscall top level ; If syscall tracing ongoing, invoke pre-post-hooks GET_CURR_THR_INFO_FLAGS r10 btst r10, TIF_SYSCALL_TRACE bnz tracesys ; this never comes back ;============ Normal syscall case ; syscall num shd not exceed the total system calls avail cmp r8, NR_syscalls mov.hi r0, -ENOSYS bhi .Lret_from_system_call ; Offset into the syscall_table and call handler ld.as r9,[sys_call_table, r8] jl [r9] ; Entry into Sys Call Handler .Lret_from_system_call: st r0, [sp, PT_r0] ; sys call return value in pt_regs ; fall through to ret_from_exception END(EV_Trap) ;############# Return from Intr/Excp/Trap (Linux Specifics) ############## ; ; If ret to user mode do we need to handle signals, schedule() et al. ENTRY(ret_from_exception) ; Pre-{IRQ,Trap,Exception} K/U mode from pt_regs->status32 ld r8, [sp, PT_status32] ; returning to User/Kernel Mode bbit0 r8, STATUS_U_BIT, resume_kernel_mode ; Before returning to User mode check-for-and-complete any pending work ; such as rescheduling/signal-delivery etc. resume_user_mode_begin: ; Disable IRQs to ensures that chk for pending work itself is atomic ; (and we don't end up missing a NEED_RESCHED/SIGPENDING due to an ; interim IRQ). IRQ_DISABLE r10 ; Fast Path return to user mode if no pending work GET_CURR_THR_INFO_FLAGS r9 and.f 0, r9, _TIF_WORK_MASK bz .Lrestore_regs ; --- (Slow Path #1) task preemption --- bbit0 r9, TIF_NEED_RESCHED, .Lchk_pend_signals mov blink, resume_user_mode_begin ; tail-call to U mode ret chks j @schedule ; BTST+Bnz causes relo error in link .Lchk_pend_signals: IRQ_ENABLE r10 ; --- (Slow Path #2) pending signal --- mov r0, sp ; pt_regs for arg to do_signal()/do_notify_resume() GET_CURR_THR_INFO_FLAGS r9 and.f 0, r9, TIF_SIGPENDING|TIF_NOTIFY_SIGNAL bz .Lchk_notify_resume ; Normal Trap/IRQ entry only saves Scratch (caller-saved) regs ; in pt_reg since the "C" ABI (kernel code) will automatically ; save/restore callee-saved regs. ; ; However, here we need to explicitly save callee regs because ; (i) If this signal causes coredump - full regfile needed ; (ii) If signal is SIGTRAP/SIGSTOP, task is being traced thus ; tracer might call PEEKUSR(CALLEE reg) ; ; NOTE: SP will grow up by size of CALLEE Reg-File SAVE_CALLEE_SAVED_USER ; clobbers r12 ; save location of saved Callee Regs @ thread_struct->callee GET_CURR_TASK_FIELD_PTR TASK_THREAD, r10 st sp, [r10, THREAD_CALLEE_REG] bl @do_signal ; Ideally we want to discard the Callee reg above, however if this was ; a tracing signal, tracer could have done a POKEUSR(CALLEE reg) RESTORE_CALLEE_SAVED_USER b resume_user_mode_begin ; loop back to start of U mode ret ; --- (Slow Path #3) notify_resume --- .Lchk_notify_resume: btst r9, TIF_NOTIFY_RESUME blnz @do_notify_resume b resume_user_mode_begin ; unconditionally back to U mode ret chks ; for single exit point from this block resume_kernel_mode: ; Disable Interrupts from this point on ; CONFIG_PREEMPTION: This is a must for preempt_schedule_irq() ; !CONFIG_PREEMPTION: To ensure restore_regs is intr safe IRQ_DISABLE r9 #ifdef CONFIG_PREEMPTION ; Can't preempt if preemption disabled GET_CURR_THR_INFO_FROM_SP r10 ld r8, [r10, THREAD_INFO_PREEMPT_COUNT] brne r8, 0, .Lrestore_regs ; check if this task's NEED_RESCHED flag set ld r9, [r10, THREAD_INFO_FLAGS] bbit0 r9, TIF_NEED_RESCHED, .Lrestore_regs ; Invoke PREEMPTION jl preempt_schedule_irq ; preempt_schedule_irq() always returns with IRQ disabled #endif b .Lrestore_regs ##### DONT ADD CODE HERE - .Lrestore_regs actually follows in entry-.S