/* * Low Level Interrupts/Traps/Exceptions(non-TLB) Handling for ARC * * Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.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. * * vineetg: May 2011 * -Userspace unaligned access emulation * * vineetg: Feb 2011 (ptrace low level code fixes) * -traced syscall return code (r0) was not saved into pt_regs for restoring * into user reg-file when traded task rets to user space. * -syscalls needing arch-wrappers (mainly for passing sp as pt_regs) * were not invoking post-syscall trace hook (jumping directly into * ret_from_system_call) * * vineetg: Nov 2010: * -Vector table jumps (@8 bytes) converted into branches (@4 bytes) * -To maintain the slot size of 8 bytes/vector, added nop, which is * not executed at runtime. * * vineetg: Nov 2009 (Everything needed for TIF_RESTORE_SIGMASK) * -do_signal()invoked upon TIF_RESTORE_SIGMASK as well * -Wrappers for sys_{,rt_}sigsuspend() nolonger needed as they don't * need ptregs anymore * * Vineetg: Oct 2009 * -In a rare scenario, Process gets a Priv-V exception and gets scheduled * out. Since we don't do FAKE RTIE for Priv-V, CPU excpetion state remains * active (AE bit enabled). This causes a double fault for a subseq valid * exception. Thus FAKE RTIE needed in low level Priv-Violation handler. * Instr Error could also cause similar scenario, so same there as well. * * Vineetg: March 2009 (Supporting 2 levels of Interrupts) * * Vineetg: Aug 28th 2008: Bug #94984 * -Zero Overhead Loop Context shd be cleared when entering IRQ/EXcp/Trap * Normally CPU does this automatically, however when doing FAKE rtie, * we need to explicitly do this. The problem in macros * FAKE_RET_FROM_EXCPN and FAKE_RET_FROM_EXCPN_LOCK_IRQ was that this bit * was being "CLEARED" rather then "SET". Since it is Loop INHIBIT Bit, * setting it and not clearing it clears ZOL context * * Vineetg: May 16th, 2008 * - r25 now contains the Current Task when in kernel * * Vineetg: Dec 22, 2007 * Minor Surgery of Low Level ISR to make it SMP safe * - MMU_SCRATCH0 Reg used for freeing up r9 in Level 1 ISR * - _current_task is made an array of NR_CPUS * - Access of _current_task wrapped inside a macro so that if hardware * team agrees for a dedicated reg, no other code is touched * * Amit Bhor, Rahul Trivedi, Kanika Nema, Sameer Dhavale : Codito Tech 2004 */ /*------------------------------------------------------------------ * 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 * Interrupt link register (ilink1) r29 * Interrupt link register (ilink2) r30 * Branch link register (blink) r31 *------------------------------------------------------------------ */ .cpu A7 ;############################ Vector Table ################################# .macro VECTOR lbl #if 1 /* Just in case, build breaks */ j \lbl #else b \lbl nop #endif .endm .section .vector, "ax",@progbits .align 4 /* Each entry in the vector table must occupy 2 words. Since it is a jump * across sections (.vector to .text) we are gauranteed that 'j somewhere' * will use the 'j limm' form of the intrsuction as long as somewhere is in * a section other than .vector. */ ; ********* Critical System Events ********************** VECTOR res_service ; 0x0, Restart Vector (0x0) VECTOR mem_service ; 0x8, Mem exception (0x1) VECTOR instr_service ; 0x10, Instrn Error (0x2) ; ******************** Device ISRs ********************** #ifdef CONFIG_ARC_IRQ3_LV2 VECTOR handle_interrupt_level2 #else VECTOR handle_interrupt_level1 #endif VECTOR handle_interrupt_level1 #ifdef CONFIG_ARC_IRQ5_LV2 VECTOR handle_interrupt_level2 #else VECTOR handle_interrupt_level1 #endif #ifdef CONFIG_ARC_IRQ6_LV2 VECTOR handle_interrupt_level2 #else VECTOR handle_interrupt_level1 #endif .rept 25 VECTOR handle_interrupt_level1 ; Other devices .endr /* FOR ARC600: timer = 0x3, uart = 0x8, emac = 0x10 */ ; ******************** Exceptions ********************** VECTOR EV_MachineCheck ; 0x100, Fatal Machine check (0x20) VECTOR EV_TLBMissI ; 0x108, Intruction TLB miss (0x21) VECTOR EV_TLBMissD ; 0x110, Data TLB miss (0x22) VECTOR EV_TLBProtV ; 0x118, Protection Violation (0x23) ; or Misaligned Access VECTOR EV_PrivilegeV ; 0x120, Privilege Violation (0x24) VECTOR EV_Trap ; 0x128, Trap exception (0x25) VECTOR EV_Extension ; 0x130, Extn Intruction Excp (0x26) .rept 24 VECTOR reserved ; Reserved Exceptions .endr #include /* {EXTRY,EXIT} */ #include /* SAVE_ALL_{INT1,INT2,SYS...} */ #include #include #include ;##################### Scratch Mem for IRQ stack switching ############# ARCFP_DATA int1_saved_reg .align 32 .type int1_saved_reg, @object .size int1_saved_reg, 4 int1_saved_reg: .zero 4 /* Each Interrupt level needs its own scratch */ #ifdef CONFIG_ARC_COMPACT_IRQ_LEVELS ARCFP_DATA int2_saved_reg .type int2_saved_reg, @object .size int2_saved_reg, 4 int2_saved_reg: .zero 4 #endif ; --------------------------------------------- .section .text, "ax",@progbits res_service: ; processor restart flag 0x1 ; not implemented nop nop reserved: ; processor restart rtie ; jump to processor initializations ;##################### Interrupt Handling ############################## #ifdef CONFIG_ARC_COMPACT_IRQ_LEVELS ; --------------------------------------------- ; Level 2 ISR: Can interrupt a Level 1 ISR ; --------------------------------------------- ENTRY(handle_interrupt_level2) ; TODO-vineetg for SMP this wont work ; free up r9 as scratchpad st r9, [@int2_saved_reg] ;Which mode (user/kernel) was the system in when intr occured lr r9, [status32_l2] SWITCH_TO_KERNEL_STK SAVE_ALL_INT2 ;------------------------------------------------------ ; if L2 IRQ interrupted a L1 ISR, disable preemption ;------------------------------------------------------ ld r9, [sp, PT_status32] ; get statu32_l2 (saved in pt_regs) bbit0 r9, STATUS_A1_BIT, 1f ; L1 not active when L2 IRQ, so normal ; A1 is set in status32_l2 ; bump thread_info->preempt_count (Disable preemption) GET_CURR_THR_INFO_FROM_SP r10 ld r9, [r10, THREAD_INFO_PREEMPT_COUNT] add r9, r9, 1 st r9, [r10, THREAD_INFO_PREEMPT_COUNT] 1: ;------------------------------------------------------ ; setup params for Linux common ISR and invoke it ;------------------------------------------------------ lr r0, [icause2] and r0, r0, 0x1f bl.d @arch_do_IRQ mov r1, sp mov r8,0x2 sr r8, [AUX_IRQ_LV12] ; clear bit in Sticky Status Reg b ret_from_exception END(handle_interrupt_level2) #endif ; --------------------------------------------- ; Level 1 ISR ; --------------------------------------------- ENTRY(handle_interrupt_level1) /* free up r9 as scratchpad */ #ifdef CONFIG_SMP sr r9, [ARC_REG_SCRATCH_DATA0] #else st r9, [@int1_saved_reg] #endif ;Which mode (user/kernel) was the system in when intr occured lr r9, [status32_l1] SWITCH_TO_KERNEL_STK SAVE_ALL_INT1 lr r0, [icause1] and r0, r0, 0x1f #ifdef CONFIG_TRACE_IRQFLAGS ; icause1 needs to be read early, before calling tracing, which ; can clobber scratch regs, hence use of stack to stash it push r0 TRACE_ASM_IRQ_DISABLE pop r0 #endif bl.d @arch_do_IRQ mov r1, sp mov r8,0x1 sr r8, [AUX_IRQ_LV12] ; clear bit in Sticky Status Reg b ret_from_exception END(handle_interrupt_level1) ;################### Non TLB Exception Handling ############################# ; --------------------------------------------- ; Instruction Error Exception Handler ; --------------------------------------------- ENTRY(instr_service) EXCEPTION_PROLOGUE lr r0, [efa] mov r1, sp FAKE_RET_FROM_EXCPN r9 bl do_insterror_or_kprobe b ret_from_exception END(instr_service) ; --------------------------------------------- ; Memory Error Exception Handler ; --------------------------------------------- ENTRY(mem_service) EXCEPTION_PROLOGUE lr r0, [efa] mov r1, sp FAKE_RET_FROM_EXCPN r9 bl do_memory_error b ret_from_exception END(mem_service) ; --------------------------------------------- ; Machine Check Exception Handler ; --------------------------------------------- ENTRY(EV_MachineCheck) EXCEPTION_PROLOGUE lr r2, [ecr] lr r0, [efa] mov r1, sp 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) ; --------------------------------------------- ; Protection Violation Exception Handler ; --------------------------------------------- ENTRY(EV_TLBProtV) EXCEPTION_PROLOGUE ;---------(3) Save some more regs----------------- ; vineetg: Mar 6th: Random Seg Fault issue #1 ; ecr and efa were not saved in case an Intr sneaks in ; after fake rtie lr r2, [ecr] lr r0, [efa] ; Faulting Data address ; --------(4) Return from CPU Exception Mode --------- ; Fake a rtie, but rtie to next label ; That way, subsequently, do_page_fault ( ) executes in pure kernel ; mode with further Exceptions enabled FAKE_RET_FROM_EXCPN r9 mov r1, sp ;------ (5) Type of Protection Violation? ---------- ; ; ProtV Hardware Exception is triggered for Access Faults of 2 types ; -Access Violaton : 00_23_(00|01|02|03)_00 ; x r w r+w ; -Unaligned Access : 00_23_04_00 ; bbit1 r2, ECR_C_BIT_PROTV_MISALIG_DATA, 4f ;========= (6a) Access Violation Processing ======== bl do_page_fault b ret_from_exception ;========== (6b) Non aligned access ============ 4: SAVE_CALLEE_SAVED_USER mov r2, sp ; callee_regs bl do_misaligned_access ; TBD: optimize - do this only if a callee reg was involved ; either a dst of emulated LD/ST or src with address-writeback RESTORE_CALLEE_SAVED_USER b ret_from_exception END(EV_TLBProtV) ; --------------------------------------------- ; Privilege Violation Exception Handler ; --------------------------------------------- ENTRY(EV_PrivilegeV) EXCEPTION_PROLOGUE lr r0, [efa] mov r1, sp FAKE_RET_FROM_EXCPN r9 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 r9 bl do_extension_fault b ret_from_exception END(EV_Extension) ;######################### System Call Tracing ######################### tracesys: ; save EFA in case tracer wants the PC of traced task ; using ERET won't work since next-PC has already committed lr r12, [efa] 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 ;################### Break Point TRAP ########################## ; ======= (5b) Trap is due to Break-Point ========= trap_with_param: ; stop_pc info by gdb needs this info lr r0, [efa] mov r1, sp ; Now that we have read EFA, it is safe to do "fake" rtie ; and get out of CPU exception mode FAKE_RET_FROM_EXCPN r11 ; 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 ;##################### Trap Handling ############################## ; ; EV_Trap caused by TRAP_S and TRAP0 instructions. ;------------------------------------------------------------------ ; (1) System Calls ; :parameters in r0-r7. ; :r8 has the system call number ; (2) Break Points ;------------------------------------------------------------------ ENTRY(EV_Trap) EXCEPTION_PROLOGUE ;------- (4) What caused the Trap -------------- lr r12, [ecr] bmsk.f 0, r12, 7 bnz trap_with_param ; ======= (5a) Trap is due to System Call ======== ; Before doing anything, return from CPU Exception Mode FAKE_RET_FROM_EXCPN r11 ; If syscall tracing ongoing, invoke pre-pos-hooks GET_CURR_THR_INFO_FLAGS r10 btst r10, TIF_SYSCALL_TRACE bnz tracesys ; this never comes back ;============ This is normal System Call case ========== ; Sys-call num shd not exceed the total system calls avail cmp r8, NR_syscalls mov.hi r0, -ENOSYS bhi ret_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 ; fall through to ret_from_system_call END(EV_Trap) ENTRY(ret_from_system_call) st r0, [sp, PT_r0] ; sys call return value in pt_regs ; fall through yet again to ret_from_exception ;############# 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 restore_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 b @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 bbit0 r9, TIF_SIGPENDING, .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_PREEMPT: This is a must for preempt_schedule_irq() ; !CONFIG_PREEMPT: To ensure restore_regs is intr safe IRQ_DISABLE r9 #ifdef CONFIG_PREEMPT ; Can't preempt if preemption disabled GET_CURR_THR_INFO_FROM_SP r10 ld r8, [r10, THREAD_INFO_PREEMPT_COUNT] brne r8, 0, restore_regs ; check if this task's NEED_RESCHED flag set ld r9, [r10, THREAD_INFO_FLAGS] bbit0 r9, TIF_NEED_RESCHED, restore_regs ; Invoke PREEMPTION bl preempt_schedule_irq ; preempt_schedule_irq() always returns with IRQ disabled #endif ; fall through ;############# Return from Intr/Excp/Trap (ARC Specifics) ############## ; ; Restore the saved sys context (common exit-path for EXCPN/IRQ/Trap) ; IRQ shd definitely not happen between now and rtie ; All 2 entry points to here already disable interrupts restore_regs : TRACE_ASM_IRQ_ENABLE lr r10, [status32] ; Restore REG File. In case multiple Events outstanding, ; use the same priorty as rtie: EXCPN, L2 IRQ, L1 IRQ, None ; Note that we use realtime STATUS32 (not pt_regs->status32) to ; decide that. ; if Returning from Exception bbit0 r10, STATUS_AE_BIT, not_exception RESTORE_ALL_SYS rtie ; Not Exception so maybe Interrupts (Level 1 or 2) not_exception: #ifdef CONFIG_ARC_COMPACT_IRQ_LEVELS ; Level 2 interrupt return Path - from hardware standpoint bbit0 r10, STATUS_A2_BIT, not_level2_interrupt ;------------------------------------------------------------------ ; However the context returning might not have taken L2 intr itself ; e.g. Task'A' user-code -> L2 intr -> schedule -> 'B' user-code ret ; Special considerations needed for the context which took L2 intr ld r9, [sp, PT_event] ; Ensure this is L2 intr context brne r9, event_IRQ2, 149f ;------------------------------------------------------------------ ; if L2 IRQ interrupted an L1 ISR, we'd disabled preemption earlier ; so that sched doesn't move to new task, causing L1 to be delayed ; undeterministically. Now that we've achieved that, let's reset ; things to what they were, before returning from L2 context ;---------------------------------------------------------------- ld r9, [sp, PT_status32] ; get statu32_l2 (saved in pt_regs) bbit0 r9, STATUS_A1_BIT, 149f ; L1 not active when L2 IRQ, so normal ; decrement thread_info->preempt_count (re-enable preemption) GET_CURR_THR_INFO_FROM_SP r10 ld r9, [r10, THREAD_INFO_PREEMPT_COUNT] ; paranoid check, given A1 was active when A2 happened, preempt count ; must not be 0 because we would have incremented it. ; If this does happen we simply HALT as it means a BUG !!! cmp r9, 0 bnz 2f flag 1 2: sub r9, r9, 1 st r9, [r10, THREAD_INFO_PREEMPT_COUNT] 149: ;return from level 2 RESTORE_ALL_INT2 debug_marker_l2: rtie not_level2_interrupt: #endif bbit0 r10, STATUS_A1_BIT, not_level1_interrupt ;return from level 1 RESTORE_ALL_INT1 debug_marker_l1: rtie not_level1_interrupt: ;this case is for syscalls or Exceptions (with fake rtie) RESTORE_ALL_SYS debug_marker_syscall: rtie END(ret_from_exception) 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 bl @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) ;################### 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 ret_from_system_call END(sys_clone_wrapper) #ifdef CONFIG_ARC_DW2_UNWIND ; Workaround for bug 94179 (STAR ): ; Despite -fasynchronous-unwind-tables, linker is not making dwarf2 unwinder ; section (.debug_frame) as loadable. So we force it here. ; This also fixes STAR 9000487933 where the prev-workaround (objcopy --setflag) ; would not work after a clean build due to kernel build system dependencies. .section .debug_frame, "wa",@progbits #endif