/*
* Copyright (C) 2004-2006 Atmel Corporation
*
* 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.
*/
/*
* This file contains the low-level entry-points into the kernel, that is,
* exception handlers, debug trap handlers, interrupt handlers and the
* system call handler.
*/
#include <linux/errno.h>
#include <asm/asm.h>
#include <asm/hardirq.h>
#include <asm/irq.h>
#include <asm/ocd.h>
#include <asm/page.h>
#include <asm/pgtable.h>
#include <asm/ptrace.h>
#include <asm/sysreg.h>
#include <asm/thread_info.h>
#include <asm/unistd.h>
#ifdef CONFIG_PREEMPT
# define preempt_stop mask_interrupts
#else
# define preempt_stop
# define fault_resume_kernel fault_restore_all
#endif
#define __MASK(x) ((1 << (x)) - 1)
#define IRQ_MASK ((__MASK(SOFTIRQ_BITS) << SOFTIRQ_SHIFT) | \
(__MASK(HARDIRQ_BITS) << HARDIRQ_SHIFT))
.section .ex.text,"ax",@progbits
.align 2
exception_vectors:
bral handle_critical
.align 2
bral handle_critical
.align 2
bral do_bus_error_write
.align 2
bral do_bus_error_read
.align 2
bral do_nmi_ll
.align 2
bral handle_address_fault
.align 2
bral handle_protection_fault
.align 2
bral handle_debug
.align 2
bral do_illegal_opcode_ll
.align 2
bral do_illegal_opcode_ll
.align 2
bral do_illegal_opcode_ll
.align 2
bral do_fpe_ll
.align 2
bral do_illegal_opcode_ll
.align 2
bral handle_address_fault
.align 2
bral handle_address_fault
.align 2
bral handle_protection_fault
.align 2
bral handle_protection_fault
.align 2
bral do_dtlb_modified
#define tlbmiss_save pushm r0-r3
#define tlbmiss_restore popm r0-r3
.org 0x50
.global itlb_miss
itlb_miss:
tlbmiss_save
rjmp tlb_miss_common
.org 0x60
dtlb_miss_read:
tlbmiss_save
rjmp tlb_miss_common
.org 0x70
dtlb_miss_write:
tlbmiss_save
.global tlb_miss_common
.align 2
tlb_miss_common:
mfsr r0, SYSREG_TLBEAR
mfsr r1, SYSREG_PTBR
/*
* First level lookup: The PGD contains virtual pointers to
* the second-level page tables, but they may be NULL if not
* present.
*/
pgtbl_lookup:
lsr r2, r0, PGDIR_SHIFT
ld.w r3, r1[r2 << 2]
bfextu r1, r0, PAGE_SHIFT, PGDIR_SHIFT - PAGE_SHIFT
cp.w r3, 0
breq page_table_not_present
/* Second level lookup */
ld.w r2, r3[r1 << 2]
mfsr r0, SYSREG_TLBARLO
bld r2, _PAGE_BIT_PRESENT
brcc page_not_present
/* Mark the page as accessed */
sbr r2, _PAGE_BIT_ACCESSED
st.w r3[r1 << 2], r2
/* Drop software flags */
andl r2, _PAGE_FLAGS_HARDWARE_MASK & 0xffff
mtsr SYSREG_TLBELO, r2
/* Figure out which entry we want to replace */
mfsr r1, SYSREG_MMUCR
clz r2, r0
brcc 1f
mov r3, -1 /* All entries have been accessed, */
mov r2, 0 /* so start at 0 */
mtsr SYSREG_TLBARLO, r3 /* and reset TLBAR */
1: bfins r1, r2, SYSREG_DRP_OFFSET, SYSREG_DRP_SIZE
mtsr SYSREG_MMUCR, r1
tlbw
tlbmiss_restore
rete
/* The slow path of the TLB miss handler */
.align 2
page_table_not_present:
/* Do we need to synchronize with swapper_pg_dir? */
bld r0, 31
brcs sync_with_swapper_pg_dir
page_not_present:
tlbmiss_restore
sub sp, 4
stmts --sp, r0-lr
call save_full_context_ex
mfsr r12, SYSREG_ECR
mov r11, sp
call do_page_fault
rjmp ret_from_exception
.align 2
sync_with_swapper_pg_dir:
/*
* If swapper_pg_dir contains a non-NULL second-level page
* table pointer, copy it into the current PGD. If not, we
* must handle it as a full-blown page fault.
*
* Jumping back to pgtbl_lookup causes an unnecessary lookup,
* but it is guaranteed to be a cache hit, it won't happen
* very often, and we absolutely do not want to sacrifice any
* performance in the fast path in order to improve this.
*/
mov r1, lo(swapper_pg_dir)
orh r1, hi(swapper_pg_dir)
ld.w r3, r1[r2 << 2]
cp.w r3, 0
breq page_not_present
mfsr r1, SYSREG_PTBR
st.w r1[r2 << 2], r3
rjmp pgtbl_lookup
/*
* We currently have two bytes left at this point until we
* crash into the system call handler...
*
* Don't worry, the assembler will let us know.
*/
/* --- System Call --- */
.org 0x100
system_call:
#ifdef CONFIG_PREEMPT
mask_interrupts
#endif
pushm r12 /* r12_orig */
stmts --sp, r0-lr
mfsr r0, SYSREG_RAR_SUP
mfsr r1, SYSREG_RSR_SUP
#ifdef CONFIG_PREEMPT
unmask_interrupts
#endif
zero_fp
stm --sp, r0-r1
/* check for syscall tracing */
get_thread_info r0
ld.w r1, r0[TI_flags]
bld r1, TIF_SYSCALL_TRACE
brcs syscall_trace_enter
syscall_trace_cont:
cp.w r8, NR_syscalls
brhs syscall_badsys
lddpc lr, syscall_table_addr
ld.w lr, lr[r8 << 2]
mov r8, r5 /* 5th argument (6th is pushed by stub) */
icall lr
.global syscall_return
syscall_return:
get_thread_info r0
mask_interrupts /* make sure we don't miss an interrupt
setting need_resched or sigpending
between sampling and the rets */
/* Store the return value so that the correct value is loaded below */
stdsp sp[REG_R12], r12
ld.w r1, r0[TI_flags]
andl r1, _TIF_ALLWORK_MASK, COH
brne syscall_exit_work
syscall_exit_cont:
popm r8-r9
mtsr SYSREG_RAR_SUP, r8
mtsr SYSREG_RSR_SUP, r9
ldmts sp++, r0-lr
sub sp, -4 /* r12_orig */
rets
.align 2
syscall_table_addr:
.long sys_call_table
syscall_badsys:
mov r12, -ENOSYS
rjmp syscall_return
.global ret_from_fork
ret_from_fork:
call schedule_tail
mov r12, 0
rjmp syscall_return
.global ret_from_kernel_thread
ret_from_kernel_thread:
call schedule_tail
mov r12, r0
mov lr, r2 /* syscall_return */
mov pc, r1
syscall_trace_enter:
pushm r8-r12
call syscall_trace
popm r8-r12
rjmp syscall_trace_cont
syscall_exit_work:
bld r1, TIF_SYSCALL_TRACE
brcc 1f
unmask_interrupts
call syscall_trace
mask_interrupts
ld.w r1, r0[TI_flags]
1: bld r1, TIF_NEED_RESCHED
brcc 2f
unmask_interrupts
call schedule
mask_interrupts
ld.w r1, r0[TI_flags]
rjmp 1b
2: mov r2, _TIF_SIGPENDING | _TIF_NOTIFY_RESUME
tst r1, r2
breq 3f
unmask_interrupts
mov r12, sp
mov r11, r0
call do_notify_resume
mask_interrupts
ld.w r1, r0[TI_flags]
rjmp 1b
3: bld r1, TIF_BREAKPOINT
brcc syscall_exit_cont
rjmp enter_monitor_mode
/* This function expects to find offending PC in SYSREG_RAR_EX */
.type save_full_context_ex, @function
.align 2
save_full_context_ex:
mfsr r11, SYSREG_RAR_EX
sub r9, pc, . - debug_trampoline
mfsr r8, SYSREG_RSR_EX
cp.w r9, r11
breq 3f
mov r12, r8
andh r8, (MODE_MASK >> 16), COH
brne 2f
1: pushm r11, r12 /* PC and SR */
unmask_exceptions
ret r12
2: sub r10, sp, -(FRAME_SIZE_FULL - REG_LR)
stdsp sp[4], r10 /* replace saved SP */
rjmp 1b
/*
* The debug handler set up a trampoline to make us
* automatically enter monitor mode upon return, but since
* we're saving the full context, we must assume that the
* exception handler might want to alter the return address
* and/or status register. So we need to restore the original
* context and enter monitor mode manually after the exception
* has been handled.
*/
3: get_thread_info r8
ld.w r11, r8[TI_rar_saved]
ld.w r12, r8[TI_rsr_saved]
rjmp 1b
.size save_full_context_ex, . - save_full_context_ex
/* Low-level exception handlers */
handle_critical:
/*
* AT32AP700x errata:
*
* After a Java stack overflow or underflow trap, any CPU
* memory access may cause erratic behavior. This will happen
* when the four least significant bits of the JOSP system
* register contains any value between 9 and 15 (inclusive).
*
* Possible workarounds:
* - Don't use the Java Extension Module
* - Ensure that the stack overflow and underflow trap
* handlers do not do any memory access or trigger any
* exceptions before the overflow/underflow condition is
* cleared (by incrementing or decrementing the JOSP)
* - Make sure that JOSP does not contain any problematic
* value before doing any exception or interrupt
* processing.
* - Set up a critical exception handler which writes a
* known-to-be-safe value, e.g. 4, to JOSP before doing
* any further processing.
*
* We'll use the last workaround for now since we cannot
* guarantee that user space processes don't use Java mode.
* Non-well-behaving userland will be terminated with extreme
* prejudice.
*/
#ifdef CONFIG_CPU_AT32AP700X
/*
* There's a chance we can't touch memory, so temporarily
* borrow PTBR to save the stack pointer while we fix things
* up...
*/
mtsr SYSREG_PTBR, sp
mov sp, 4
mtsr SYSREG_JOSP, sp
mfsr sp, SYSREG_PTBR
sub pc, -2
/* Push most of pt_regs on stack. We'll do the rest later */
sub sp, 4
pushm r0-r12
/* PTBR mirrors current_thread_info()->task->active_mm->pgd */
get_thread_info r0
ld.w r1, r0[TI_task]
ld.w r2, r1[TSK_active_mm]
ld.w r3, r2[MM_pgd]
mtsr SYSREG_PTBR, r3
#else
sub sp, 4
pushm r0-r12
#endif
sub r0, sp, -(14 * 4)
mov r1, lr
mfsr r2, SYSREG_RAR_EX
mfsr r3, SYSREG_RSR_EX
pushm r0-r3
mfsr r12, SYSREG_ECR
mov r11, sp
call do_critical_exception
/* We should never get here... */
bad_return:
sub r12, pc, (. - 1f)
lddpc pc, 2f
.align 2
1: .asciz "Return from critical exception!"
2: .long panic
.align 1
do_bus_error_write:
sub sp, 4
stmts --sp, r0-lr
call save_full_context_ex
mov r11, 1
rjmp 1f
do_bus_error_read:
sub sp, 4
stmts --sp, r0-lr
call save_full_context_ex
mov r11, 0
1: mfsr r12, SYSREG_BEAR
mov r10, sp
call do_bus_error
rjmp ret_from_exception
.align 1
do_nmi_ll:
sub sp, 4
stmts --sp, r0-lr
mfsr r9, SYSREG_RSR_NMI
mfsr r8, SYSREG_RAR_NMI
bfextu r0, r9, MODE_SHIFT, 3
brne 2f
1: pushm r8, r9 /* PC and SR */
mfsr r12, SYSREG_ECR
mov r11, sp
call do_nmi
popm r8-r9
mtsr SYSREG_RAR_NMI, r8
tst r0, r0
mtsr SYSREG_RSR_NMI, r9
brne 3f
ldmts sp++, r0-lr
sub sp, -4 /* skip r12_orig */
rete
2: sub r10, sp, -(FRAME_SIZE_FULL - REG_LR)
stdsp sp[4], r10 /* replace saved SP */
rjmp 1b
3: popm lr
sub sp, -4 /* skip sp */
popm r0-r12
sub sp, -4 /* skip r12_orig */
rete
handle_address_fault:
sub sp, 4
stmts --sp, r0-lr
call save_full_context_ex
mfsr r12, SYSREG_ECR
mov r11, sp
call do_address_exception
rjmp ret_from_exception
handle_protection_fault:
sub sp, 4
stmts --sp, r0-lr
call save_full_context_ex
mfsr r12, SYSREG_ECR
mov r11, sp
call do_page_fault
rjmp ret_from_exception
.align 1
do_illegal_opcode_ll:
sub sp, 4
stmts --sp, r0-lr
call save_full_context_ex
mfsr r12, SYSREG_ECR
mov r11, sp
call do_illegal_opcode
rjmp ret_from_exception
do_dtlb_modified:
pushm r0-r3
mfsr r1, SYSREG_TLBEAR
mfsr r0, SYSREG_PTBR
lsr r2, r1, PGDIR_SHIFT
ld.w r0, r0[r2 << 2]
lsl r1, (32 - PGDIR_SHIFT)
lsr r1, (32 - PGDIR_SHIFT) + PAGE_SHIFT
/* Translate to virtual address in P1 */
andl r0, 0xf000
sbr r0, 31
add r2, r0, r1 << 2
ld.w r3, r2[0]
sbr r3, _PAGE_BIT_DIRTY
mov r0, r3
st.w r2[0], r3
/* The page table is up-to-date. Update the TLB entry as well */
andl r0, lo(_PAGE_FLAGS_HARDWARE_MASK)
mtsr SYSREG_TLBELO, r0
/* MMUCR[DRP] is updated automatically, so let's go... */
tlbw
popm r0-r3
rete
do_fpe_ll:
sub sp, 4
stmts --sp, r0-lr
call save_full_context_ex
unmask_interrupts
mov r12, 26
mov r11, sp
call do_fpe
rjmp ret_from_exception
ret_from_exception:
mask_interrupts
lddsp r4, sp[REG_SR]
andh r4, (MODE_MASK >> 16), COH
brne fault_resume_kernel
get_thread_info r0
ld.w r1, r0[TI_flags]
andl r1, _TIF_WORK_MASK, COH
brne fault_exit_work
fault_resume_user:
popm r8-r9
mask_exceptions
mtsr SYSREG_RAR_EX, r8
mtsr SYSREG_RSR_EX, r9
ldmts sp++, r0-lr
sub sp, -4
rete
fault_resume_kernel:
#ifdef CONFIG_PREEMPT
get_thread_info r0
ld.w r2, r0[TI_preempt_count]
cp.w r2, 0
brne 1f
ld.w r1, r0[TI_flags]
bld r1, TIF_NEED_RESCHED
brcc 1f
lddsp r4, sp[REG_SR]
bld r4, SYSREG_GM_OFFSET
brcs 1f
call preempt_schedule_irq
1:
#endif
popm r8-r9
mask_exceptions
mfsr r1, SYSREG_SR
mtsr SYSREG_RAR_EX, r8
mtsr SYSREG_RSR_EX, r9
popm lr
sub sp, -4 /* ignore SP */
popm r0-r12
sub sp, -4 /* ignore r12_orig */
rete
irq_exit_work:
/* Switch to exception mode so that we can share the same code. */
mfsr r8, SYSREG_SR
cbr r8, SYSREG_M0_OFFSET
orh r8, hi(SYSREG_BIT(M1) | SYSREG_BIT(M2))
mtsr SYSREG_SR, r8
sub pc, -2
get_thread_info r0
ld.w r1, r0[TI_flags]
fault_exit_work:
bld r1, TIF_NEED_RESCHED
brcc 1f
unmask_interrupts
call schedule
mask_interrupts
ld.w r1, r0[TI_flags]
rjmp fault_exit_work
1: mov r2, _TIF_SIGPENDING | _TIF_NOTIFY_RESUME
tst r1, r2
breq 2f
unmask_interrupts
mov r12, sp
mov r11, r0
call do_notify_resume
mask_interrupts
ld.w r1, r0[TI_flags]
rjmp fault_exit_work
2: bld r1, TIF_BREAKPOINT
brcc fault_resume_user
rjmp enter_monitor_mode
.section .kprobes.text, "ax", @progbits
.type handle_debug, @function
handle_debug:
sub sp, 4 /* r12_orig */
stmts --sp, r0-lr
mfsr r8, SYSREG_RAR_DBG
mfsr r9, SYSREG_RSR_DBG
unmask_exceptions
pushm r8-r9
bfextu r9, r9, SYSREG_MODE_OFFSET, SYSREG_MODE_SIZE
brne debug_fixup_regs
.Ldebug_fixup_cont:
#ifdef CONFIG_TRACE_IRQFLAGS
call trace_hardirqs_off
#endif
mov r12, sp
call do_debug
mov sp, r12
lddsp r2, sp[REG_SR]
bfextu r3, r2, SYSREG_MODE_OFFSET, SYSREG_MODE_SIZE
brne debug_resume_kernel
get_thread_info r0
ld.w r1, r0[TI_flags]
mov r2, _TIF_DBGWORK_MASK
tst r1, r2
brne debug_exit_work
bld r1, TIF_SINGLE_STEP
brcc 1f
mfdr r4, OCD_DC
sbr r4, OCD_DC_SS_BIT
mtdr OCD_DC, r4
1: popm r10,r11
mask_exceptions
mtsr SYSREG_RSR_DBG, r11
mtsr SYSREG_RAR_DBG, r10
#ifdef CONFIG_TRACE_IRQFLAGS
call trace_hardirqs_on
1:
#endif
ldmts sp++, r0-lr
sub sp, -4
retd
.size handle_debug, . - handle_debug
/* Mode of the trapped context is in r9 */
.type debug_fixup_regs, @function
debug_fixup_regs:
mfsr r8, SYSREG_SR
mov r10, r8
bfins r8, r9, SYSREG_MODE_OFFSET, SYSREG_MODE_SIZE
mtsr SYSREG_SR, r8
sub pc, -2
stdsp sp[REG_LR], lr
mtsr SYSREG_SR, r10
sub pc, -2
sub r8, sp, -FRAME_SIZE_FULL
stdsp sp[REG_SP], r8
rjmp .Ldebug_fixup_cont
.size debug_fixup_regs, . - debug_fixup_regs
.type debug_resume_kernel, @function
debug_resume_kernel:
mask_exceptions
popm r10, r11
mtsr SYSREG_RAR_DBG, r10
mtsr SYSREG_RSR_DBG, r11
#ifdef CONFIG_TRACE_IRQFLAGS
bld r11, SYSREG_GM_OFFSET
brcc 1f
call trace_hardirqs_on
1:
#endif
mfsr r2, SYSREG_SR
mov r1, r2
bfins r2, r3, SYSREG_MODE_OFFSET, SYSREG_MODE_SIZE
mtsr SYSREG_SR, r2
sub pc, -2
popm lr
mtsr SYSREG_SR, r1
sub pc, -2
sub sp, -4 /* skip SP */
popm r0-r12
sub sp, -4
retd
.size debug_resume_kernel, . - debug_resume_kernel
.type debug_exit_work, @function
debug_exit_work:
/*
* We must return from Monitor Mode using a retd, and we must
* not schedule since that involves the D bit in SR getting
* cleared by something other than the debug hardware. This
* may cause undefined behaviour according to the Architecture
* manual.
*
* So we fix up the return address and status and return to a
* stub below in Exception mode. From there, we can follow the
* normal exception return path.
*
* The real return address and status registers are stored on
* the stack in the way the exception return path understands,
* so no need to fix anything up there.
*/
sub r8, pc, . - fault_exit_work
mtsr SYSREG_RAR_DBG, r8
mov r9, 0
orh r9, hi(SR_EM | SR_GM | MODE_EXCEPTION)
mtsr SYSREG_RSR_DBG, r9
sub pc, -2
retd
.size debug_exit_work, . - debug_exit_work
.set rsr_int0, SYSREG_RSR_INT0
.set rsr_int1, SYSREG_RSR_INT1
.set rsr_int2, SYSREG_RSR_INT2
.set rsr_int3, SYSREG_RSR_INT3
.set rar_int0, SYSREG_RAR_INT0
.set rar_int1, SYSREG_RAR_INT1
.set rar_int2, SYSREG_RAR_INT2
.set rar_int3, SYSREG_RAR_INT3
.macro IRQ_LEVEL level
.type irq_level\level, @function
irq_level\level:
sub sp, 4 /* r12_orig */
stmts --sp,r0-lr
mfsr r8, rar_int\level
mfsr r9, rsr_int\level
#ifdef CONFIG_PREEMPT
sub r11, pc, (. - system_call)
cp.w r11, r8
breq 4f
#endif
pushm r8-r9
mov r11, sp
mov r12, \level
call do_IRQ
lddsp r4, sp[REG_SR]
bfextu r4, r4, SYSREG_M0_OFFSET, 3
cp.w r4, MODE_SUPERVISOR >> SYSREG_M0_OFFSET
breq 2f
cp.w r4, MODE_USER >> SYSREG_M0_OFFSET
#ifdef CONFIG_PREEMPT
brne 3f
#else
brne 1f
#endif
get_thread_info r0
ld.w r1, r0[TI_flags]
andl r1, _TIF_WORK_MASK, COH
brne irq_exit_work
1:
#ifdef CONFIG_TRACE_IRQFLAGS
call trace_hardirqs_on
#endif
popm r8-r9
mtsr rar_int\level, r8
mtsr rsr_int\level, r9
ldmts sp++,r0-lr
sub sp, -4 /* ignore r12_orig */
rete
#ifdef CONFIG_PREEMPT
4: mask_interrupts
mfsr r8, rsr_int\level
sbr r8, 16
mtsr rsr_int\level, r8
ldmts sp++, r0-lr
sub sp, -4 /* ignore r12_orig */
rete
#endif
2: get_thread_info r0
ld.w r1, r0[TI_flags]
bld r1, TIF_CPU_GOING_TO_SLEEP
#ifdef CONFIG_PREEMPT
brcc 3f
#else
brcc 1b
#endif
sub r1, pc, . - cpu_idle_skip_sleep
stdsp sp[REG_PC], r1
#ifdef CONFIG_PREEMPT
3: get_thread_info r0
ld.w r2, r0[TI_preempt_count]
cp.w r2, 0
brne 1b
ld.w r1, r0[TI_flags]
bld r1, TIF_NEED_RESCHED
brcc 1b
lddsp r4, sp[REG_SR]
bld r4, SYSREG_GM_OFFSET
brcs 1b
call preempt_schedule_irq
#endif
rjmp 1b
.endm
.section .irq.text,"ax",@progbits
.global irq_level0
.global irq_level1
.global irq_level2
.global irq_level3
IRQ_LEVEL 0
IRQ_LEVEL 1
IRQ_LEVEL 2
IRQ_LEVEL 3
.section .kprobes.text, "ax", @progbits
.type enter_monitor_mode, @function
enter_monitor_mode:
/*
* We need to enter monitor mode to do a single step. The
* monitor code will alter the return address so that we
* return directly to the user instead of returning here.
*/
breakpoint
rjmp breakpoint_failed
.size enter_monitor_mode, . - enter_monitor_mode
.type debug_trampoline, @function
.global debug_trampoline
debug_trampoline:
/*
* Save the registers on the stack so that the monitor code
* can find them easily.
*/
sub sp, 4 /* r12_orig */
stmts --sp, r0-lr
get_thread_info r0
ld.w r8, r0[TI_rar_saved]
ld.w r9, r0[TI_rsr_saved]
pushm r8-r9
/*
* The monitor code will alter the return address so we don't
* return here.
*/
breakpoint
rjmp breakpoint_failed
.size debug_trampoline, . - debug_trampoline
.type breakpoint_failed, @function
breakpoint_failed:
/*
* Something went wrong. Perhaps the debug hardware isn't
* enabled?
*/
lda.w r12, msg_breakpoint_failed
mov r11, sp
mov r10, 9 /* SIGKILL */
call die
1: rjmp 1b
msg_breakpoint_failed:
.asciz "Failed to enter Debug Mode"
