ARC: Low level IRQ/Trap/Exception Handling

Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
Cc: Al Viro <viro@ZenIV.linux.org.uk>

1 files changed, 571 insertions, 0 deletions

diff --git a/arch/arc/kernel/entry.S b/arch/arc/kernel/entry.S
new file mode 100644
index 00000000000..a4acc9ee131
--- /dev/null
+++ 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