entry-arcv2.S
/*
* ARCv2 ISA based core Low Level Intr/Traps/Exceptions(non-TLB) Handling
*
* Copyright (C) 2013 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.
*/
#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>
; A maximum number of supported interrupts in the core interrupt controller.
; This number is not equal to the maximum interrupt number (256) because
; first 16 lines are reserved for exceptions and are not configurable.
#define NR_CPU_IRQS 240
.cpu HS
#define VECTOR .word
;############################ Vector Table #################################
.section .vector,"a",@progbits
.align 4
# Initial 16 slots are Exception Vectors
VECTOR res_service ; Reset Vector
VECTOR mem_service ; Mem exception
VECTOR instr_service ; Instrn Error
VECTOR EV_MachineCheck ; Fatal Machine check
VECTOR EV_TLBMissI ; Intruction TLB miss
VECTOR EV_TLBMissD ; Data TLB miss
VECTOR EV_TLBProtV ; Protection Violation
VECTOR EV_PrivilegeV ; Privilege Violation
VECTOR EV_SWI ; Software Breakpoint
VECTOR EV_Trap ; Trap exception
VECTOR EV_Extension ; Extn Instruction Exception
VECTOR EV_DivZero ; Divide by Zero
VECTOR EV_DCError ; Data Cache Error
VECTOR EV_Misaligned ; Misaligned Data Access
VECTOR reserved ; Reserved slots
VECTOR reserved ; Reserved slots
# Begin Interrupt Vectors
VECTOR handle_interrupt ; (16) Timer0
VECTOR handle_interrupt ; unused (Timer1)
VECTOR handle_interrupt ; unused (WDT)
VECTOR handle_interrupt ; (19) Inter core Interrupt (IPI)
VECTOR handle_interrupt ; (20) perf Interrupt
VECTOR handle_interrupt ; (21) Software Triggered Intr (Self IPI)
VECTOR handle_interrupt ; unused
VECTOR handle_interrupt ; (23) unused
# End of fixed IRQs
.rept NR_CPU_IRQS - 8
VECTOR handle_interrupt
.endr
.section .text, "ax",@progbits
reserved:
flag 1 ; Unexpected event, halt
;##################### Interrupt Handling ##############################
ENTRY(handle_interrupt)
INTERRUPT_PROLOGUE irq
# irq control APIs local_irq_save/restore/disable/enable fiddle with
# global interrupt enable bits in STATUS32 (.IE for 1 prio, .E[] for 2 prio)
# However a taken interrupt doesn't clear these bits. Thus irqs_disabled()
# query in hard ISR path would return false (since .IE is set) which would
# trips genirq interrupt handling asserts.
#
# So do a "soft" disable of interrutps here.
#
# Note this disable is only for consistent book-keeping as further interrupts
# will be disabled anyways even w/o this. Hardware tracks active interrupts
# seperately in AUX_IRQ_ACTIVE.active and will not take new interrupts
# unless this one returns (or higher prio becomes pending in 2-prio scheme)
IRQ_DISABLE
; icause is banked: one per priority level
; so a higher prio interrupt taken here won't clobber prev prio icause
lr r0, [ICAUSE]
mov blink, ret_from_exception
b.d arch_do_IRQ
mov r1, sp
END(handle_interrupt)
;################### Non TLB Exception Handling #############################
ENTRY(EV_SWI)
; TODO: implement this
EXCEPTION_PROLOGUE
b ret_from_exception
END(EV_SWI)
ENTRY(EV_DivZero)
; TODO: implement this
EXCEPTION_PROLOGUE
b ret_from_exception
END(EV_DivZero)
ENTRY(EV_DCError)
; TODO: implement this
EXCEPTION_PROLOGUE
b ret_from_exception
END(EV_DCError)
; ---------------------------------------------
; Memory Error Exception Handler
; - Unlike ARCompact, handles Bus errors for both User/Kernel mode,
; Instruction fetch or Data access, under a single Exception Vector
; ---------------------------------------------
ENTRY(mem_service)
EXCEPTION_PROLOGUE
lr r0, [efa]
mov r1, sp
FAKE_RET_FROM_EXCPN
bl do_memory_error
b ret_from_exception
END(mem_service)
ENTRY(EV_Misaligned)
EXCEPTION_PROLOGUE
lr r0, [efa] ; Faulting Data address
mov r1, sp
FAKE_RET_FROM_EXCPN
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_Misaligned)
; ---------------------------------------------
; Protection Violation Exception Handler
; ---------------------------------------------
ENTRY(EV_TLBProtV)
EXCEPTION_PROLOGUE
lr r0, [efa] ; Faulting Data address
mov r1, sp ; pt_regs
FAKE_RET_FROM_EXCPN
mov blink, ret_from_exception
b do_page_fault
END(EV_TLBProtV)
; From Linux standpoint Slow Path I/D TLB Miss is same a ProtV as they
; need to call do_page_fault().
; ECR in pt_regs provides whether access was R/W/X
.global call_do_page_fault
.set call_do_page_fault, EV_TLBProtV
;############# Common Handlers for ARCompact and ARCv2 ##############
#include "entry.S"
;############# Return from Intr/Excp/Trap (ARCv2 ISA 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
.Lrestore_regs:
restore_regs:
# Interrpts are actually disabled from this point on, but will get
# reenabled after we return from interrupt/exception.
# But irq tracer needs to be told now...
TRACE_ASM_IRQ_ENABLE
ld r0, [sp, PT_status32] ; U/K mode at time of entry
lr r10, [AUX_IRQ_ACT]
bmsk r11, r10, 15 ; AUX_IRQ_ACT.ACTIVE
breq r11, 0, .Lexcept_ret ; No intr active, ret from Exception
;####### Return from Intr #######
debug_marker_l1:
bbit1.nt r0, STATUS_DE_BIT, .Lintr_ret_to_delay_slot
.Lisr_ret_fast_path:
; Handle special case #1: (Entry via Exception, Return via IRQ)
;
; Exception in U mode, preempted in kernel, Intr taken (K mode), orig
; task now returning to U mode (riding the Intr)
; AUX_IRQ_ACTIVE won't have U bit set (since intr in K mode), hence SP
; won't be switched to correct U mode value (from AUX_SP)
; So force AUX_IRQ_ACT.U for such a case
btst r0, STATUS_U_BIT ; Z flag set if K (Z clear for U)
bset.nz r11, r11, AUX_IRQ_ACT_BIT_U ; NZ means U
sr r11, [AUX_IRQ_ACT]
INTERRUPT_EPILOGUE irq
rtie
;####### Return from Exception / pure kernel mode #######
.Lexcept_ret: ; Expects r0 has PT_status32
debug_marker_syscall:
EXCEPTION_EPILOGUE
rtie
;####### Return from Intr to insn in delay slot #######
; Handle special case #2: (Entry via Exception in Delay Slot, Return via IRQ)
;
; Intr returning to a Delay Slot (DS) insn
; (since IRQ NOT allowed in DS in ARCv2, this can only happen if orig
; entry was via Exception in DS which got preempted in kernel).
;
; IRQ RTIE won't reliably restore DE bit and/or BTA, needs workaround
;
; Solution is return from Intr w/o any delay slot quirks into a kernel trampoline
; and from pure kernel mode return to delay slot which handles DS bit/BTA correctly
.Lintr_ret_to_delay_slot:
debug_marker_ds:
ld r2, [@intr_to_DE_cnt]
add r2, r2, 1
st r2, [@intr_to_DE_cnt]
ld r2, [sp, PT_ret]
ld r3, [sp, PT_status32]
; STAT32 for Int return created from scratch
; (No delay dlot, disable Further intr in trampoline)
bic r0, r3, STATUS_U_MASK|STATUS_DE_MASK|STATUS_IE_MASK|STATUS_L_MASK
st r0, [sp, PT_status32]
mov r1, .Lintr_ret_to_delay_slot_2
st r1, [sp, PT_ret]
; Orig exception PC/STAT32 safekept @orig_r0 and @event stack slots
st r2, [sp, 0]
st r3, [sp, 4]
b .Lisr_ret_fast_path
.Lintr_ret_to_delay_slot_2:
; Trampoline to restore orig exception PC/STAT32/BTA/AUX_USER_SP
sub sp, sp, SZ_PT_REGS
st r9, [sp, -4]
ld r9, [sp, 0]
sr r9, [eret]
ld r9, [sp, 4]
sr r9, [erstatus]
; restore AUX_USER_SP if returning to U mode
bbit0 r9, STATUS_U_BIT, 1f
ld r9, [sp, PT_sp]
sr r9, [AUX_USER_SP]
1:
ld r9, [sp, 8]
sr r9, [erbta]
ld r9, [sp, -4]
add sp, sp, SZ_PT_REGS
; return from pure kernel mode to delay slot
rtie
END(ret_from_exception)
