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kernel-fxtec-pro1x/arch/arc/kernel/entry.S
Vineet Gupta 5c39c0ab5e ARC: [Review] Preparing to fix incorrect syscall restarts due to signals 
To avoid multiple syscall restarts (multiple signals) or no restart at
all (sigreturn), we need just an extra bit of state "literally 1 bit" in
struct pt_regs. orig_r8 is the best place to do this, however given the
way it is encoded currently, we can't add anything simplistically.

Current orig_r8:
* syscalls   -> 1 to NR_SYSCALLS
* Exceptions -> NR_SYSCALLS + 1
* Break-point-> NR_SYSCALLS + 2

In new scheme it is a bit-field
* lower short word contains the  exact event type (and a new bit to represent
   restart semantics : if syscall was already / can't be restarted)
* upper short word optionally containing the syscall num - needed by
  likes of tracehooks etc

This patch only changes how orig_r8 is organised and nothing should
change behaviourily.

Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
Cc: Al Viro <viro@ZenIV.linux.org.uk>
2013-02-15 23:15:49 +05:30

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/*
* 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:
; stop_pc info by gdb needs this info
st orig_r8_IS_BRKPT, [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
; 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
#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
; If kernel thread, jump to it's entry-point
ld r9, [sp, PT_status32]
brne r9, 0, 1f
jl.d [r14]
mov r0, r13 ; arg to payload
1:
; special case of kernel_thread entry point returning back due to
; kernel_execve() - pretend return from syscall to ret to userland
b ret_from_exception
ARC_EXIT ret_from_fork
;################### Special Sys Call Wrappers ##########################
; TBD: call do_fork directly from here
ARC_ENTRY sys_fork_wrapper
SAVE_CALLEE_SAVED_USER
bl @sys_fork
DISCARD_CALLEE_SAVED_USER
b ret_from_system_call
ARC_EXIT sys_fork_wrapper
ARC_ENTRY sys_vfork_wrapper
SAVE_CALLEE_SAVED_USER
bl @sys_vfork
DISCARD_CALLEE_SAVED_USER
b ret_from_system_call
ARC_EXIT sys_vfork_wrapper
ARC_ENTRY sys_clone_wrapper
SAVE_CALLEE_SAVED_USER
bl @sys_clone
DISCARD_CALLEE_SAVED_USER
b ret_from_system_call
ARC_EXIT sys_clone_wrapper
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