ARC: Low level IRQ/Trap/Exception Handling
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
Cc: Al Viro <viro@ZenIV.linux.org.uk>
diff --git a/arch/arc/kernel/entry.S b/arch/arc/kernel/entry.S
new file mode 100644
index 0000000..a4acc9e
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+++ b/arch/arc/kernel/entry.S
@@ -0,0 +1,571 @@
+/*
+ * 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: 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: 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: 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 **********************
+VECTOR handle_interrupt_level1
+
+VECTOR handle_interrupt_level1
+
+VECTOR handle_interrupt_level1
+
+VECTOR handle_interrupt_level1
+
+.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 <linux/linkage.h> /* ARC_{EXTRY,EXIT} */
+#include <asm/entry.h> /* SAVE_ALL_{INT1,INT2,TRAP...} */
+#include <asm/errno.h>
+#include <asm/arcregs.h>
+#include <asm/irqflags.h>
+
+;##################### Scratch Mem for IRQ stack switching #############
+
+ .section .data ; NOT .global
+ .align 32
+ .type int1_saved_reg, @object
+ .size int1_saved_reg, 4
+int1_saved_reg:
+ .zero 4
+
+; ---------------------------------------------
+ .section .text, "ax",@progbits
+
+res_service: ; processor restart
+ flag 0x1 ; not implemented
+ nop
+ nop
+
+reserved: ; processor restart
+ rtie ; jump to processor initializations
+
+;##################### Interrupt Handling ##############################
+
+; ---------------------------------------------
+; Level 1 ISR
+; ---------------------------------------------
+ARC_ENTRY handle_interrupt_level1
+
+ /* free up r9 as scratchpad */
+ st r9, [@int1_saved_reg]
+
+ ;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
+
+ 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
+ARC_EXIT handle_interrupt_level1
+
+;################### Non TLB Exception Handling #############################
+
+; ---------------------------------------------
+; Instruction Error Exception Handler
+; ---------------------------------------------
+
+ARC_ENTRY instr_service
+
+ EXCPN_PROLOG_FREEUP_REG r9
+
+ lr r9, [erstatus]
+
+ SWITCH_TO_KERNEL_STK
+ SAVE_ALL_SYS
+
+ lr r0, [ecr]
+ lr r1, [efa]
+
+ mov r2, sp
+
+ FAKE_RET_FROM_EXCPN r9
+
+ bl do_insterror_or_kprobe
+ b ret_from_exception
+ARC_EXIT instr_service
+
+; ---------------------------------------------
+; Memory Error Exception Handler
+; ---------------------------------------------
+
+ARC_ENTRY mem_service
+
+ EXCPN_PROLOG_FREEUP_REG r9
+
+ lr r9, [erstatus]
+
+ SWITCH_TO_KERNEL_STK
+ SAVE_ALL_SYS
+
+ lr r0, [ecr]
+ lr r1, [efa]
+ mov r2, sp
+ bl do_memory_error
+ b ret_from_exception
+ARC_EXIT mem_service
+
+; ---------------------------------------------
+; Machine Check Exception Handler
+; ---------------------------------------------
+
+ARC_ENTRY EV_MachineCheck
+
+ EXCPN_PROLOG_FREEUP_REG r9
+ lr r9, [erstatus]
+
+ SWITCH_TO_KERNEL_STK
+ SAVE_ALL_SYS
+
+ lr r0, [ecr]
+ lr r1, [efa]
+ mov r2, sp
+
+ brne r0, 0x200100, 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
+
+ARC_EXIT EV_MachineCheck
+
+; ---------------------------------------------
+; Protection Violation Exception Handler
+; ---------------------------------------------
+
+ARC_ENTRY EV_TLBProtV
+
+ EXCPN_PROLOG_FREEUP_REG r9
+
+ ;Which mode (user/kernel) was the system in when Exception occured
+ lr r9, [erstatus]
+
+ SWITCH_TO_KERNEL_STK
+ SAVE_ALL_SYS
+
+ ;---------(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 r3, [ecr]
+ lr r4, [efa]
+
+ ; --------(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
+
+ ;------ (5) Type of Protection Violation? ----------
+ ;
+ ; ProtV Hardware Exception is triggered for Access Faults of 2 types
+ ; -Access Violaton (WRITE to READ ONLY Page) - for linux COW
+ ; -Unaligned Access (READ/WRITE on odd boundary)
+ ;
+ cmp r3, 0x230400 ; Misaligned data access ?
+ beq 4f
+
+ ;========= (6a) Access Violation Processing ========
+ cmp r3, 0x230100
+ mov r1, 0x0 ; if LD exception ? write = 0
+ mov.ne r1, 0x1 ; else write = 1
+
+ mov r2, r4 ; faulting address
+ mov r0, sp ; pt_regs
+ bl do_page_fault
+ b ret_from_exception
+
+ ;========== (6b) Non aligned access ============
+4:
+ mov r0, r3 ; cause code
+ mov r1, r4 ; faulting address
+ mov r2, sp ; pt_regs
+
+ bl do_misaligned_access
+ b ret_from_exception
+
+ARC_EXIT EV_TLBProtV
+
+; ---------------------------------------------
+; Privilege Violation Exception Handler
+; ---------------------------------------------
+ARC_ENTRY EV_PrivilegeV
+
+ EXCPN_PROLOG_FREEUP_REG r9
+
+ lr r9, [erstatus]
+
+ SWITCH_TO_KERNEL_STK
+ SAVE_ALL_SYS
+
+ lr r0, [ecr]
+ lr r1, [efa]
+ mov r2, sp
+
+ FAKE_RET_FROM_EXCPN r9
+
+ bl do_privilege_fault
+ b ret_from_exception
+ARC_EXIT EV_PrivilegeV
+
+; ---------------------------------------------
+; Extension Instruction Exception Handler
+; ---------------------------------------------
+ARC_ENTRY EV_Extension
+
+ EXCPN_PROLOG_FREEUP_REG r9
+ lr r9, [erstatus]
+
+ SWITCH_TO_KERNEL_STK
+ SAVE_ALL_SYS
+
+ lr r0, [ecr]
+ lr r1, [efa]
+ mov r2, sp
+ bl do_extension_fault
+ b ret_from_exception
+ARC_EXIT EV_Extension
+
+;################### Break Point TRAP ##########################
+
+ ; ======= (5b) Trap is due to Break-Point =========
+
+trap_with_param:
+
+ ;make sure orig_r8 is a positive value
+ st NR_syscalls + 2, [sp, PT_orig_r8]
+
+ mov r0, r12
+ lr r1, [efa]
+ mov r2, sp
+
+ ; Now that we have read EFA, its 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
+;------------------------------------------------------------------
+
+ARC_ENTRY EV_Trap
+
+ ; Need at least 1 reg to code the early exception prolog
+ EXCPN_PROLOG_FREEUP_REG r9
+
+ ;Which mode (user/kernel) was the system in when intr occured
+ lr r9, [erstatus]
+
+ SWITCH_TO_KERNEL_STK
+ SAVE_ALL_TRAP
+
+ ;------- (4) What caused the Trap --------------
+ lr r12, [ecr]
+ and.f 0, r12, ECR_PARAM_MASK
+ bnz trap_with_param
+
+ ; ======= (5a) Trap is due to System Call ========
+
+ ; Before doing anything, return from CPU Exception Mode
+ FAKE_RET_FROM_EXCPN r11
+
+ ;============ 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
+ARC_EXIT EV_Trap
+
+ARC_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.
+
+ARC_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
+
+#ifdef CONFIG_PREEMPT
+ bbit0 r8, STATUS_U_BIT, resume_kernel_mode
+#else
+ bbit0 r8, STATUS_U_BIT, restore_regs
+#endif
+
+ ; 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()
+
+ bbit0 r9, TIF_SIGPENDING, .Lchk_notify_resume
+
+ ; save CALLEE Regs.
+ ; (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
+
+ ; unwind SP for cheap discard of Callee saved Regs
+ DISCARD_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
+
+#ifdef CONFIG_PREEMPT
+
+resume_kernel_mode:
+
+ ; 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
+
+ IRQ_DISABLE r9
+
+ ; 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
+
+restore_regs :
+
+ ; Disable Interrupts while restoring reg-file back
+ ; XXX can this be optimised out
+ IRQ_DISABLE_SAVE r9, r10 ;@r10 has prisitine (pre-disable) copy
+
+ ; 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:
+
+ 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
+
+ARC_EXIT ret_from_exception
+
+ARC_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
+ b @ret_from_exception
+ARC_EXIT ret_from_fork