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android_kernel_xiaomi_sm8350/arch/sh/kernel/entry-common.S
Paul Mundt f413d0d9fa sh: Use a jump call table for debug trap handlers. 
This rips out most of the needlessly complicated sh_bios and kgdb
trap handling, and forces it all through a common fast dispatch path.
As more debug traps are inserted, it's important to keep them in sync
for all of the parts, not just SH-3/4.

As the SH-2 parts are unable to do traps in the >= 0x40 range, we
restrict the debug traps to the 0x30-0x3f range on all parts, and
also bump the kgdb breakpoint trap down in to this range (from 0xff
to 0x3c) so it's possible to use for nommu.

Optionally, this table can be padded out to catch spurious traps for
SH-3/4, but we don't do that yet..

Signed-off-by: Paul Mundt <lethal@linux-sh.org>
2007-02-13 10:54:43 +09:00

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/* $Id: entry.S,v 1.37 2004/06/11 13:02:46 doyu Exp $
*
* linux/arch/sh/entry.S
*
* Copyright (C) 1999, 2000, 2002 Niibe Yutaka
* Copyright (C) 2003 Paul Mundt
*
* This file is subject to the terms and conditions of the GNU General Public
* License. See the file "COPYING" in the main directory of this archive
* for more details.
*
*/
! NOTE:
! GNU as (as of 2.9.1) changes bf/s into bt/s and bra, when the address
! to be jumped is too far, but it causes illegal slot exception.
/*
* entry.S contains the system-call and fault low-level handling routines.
* This also contains the timer-interrupt handler, as well as all interrupts
* and faults that can result in a task-switch.
*
* NOTE: This code handles signal-recognition, which happens every time
* after a timer-interrupt and after each system call.
*
* NOTE: This code uses a convention that instructions in the delay slot
* of a transfer-control instruction are indented by an extra space, thus:
*
* jmp @k0 ! control-transfer instruction
* ldc k1, ssr ! delay slot
*
* Stack layout in 'ret_from_syscall':
* ptrace needs to have all regs on the stack.
* if the order here is changed, it needs to be
* updated in ptrace.c and ptrace.h
*
* r0
* ...
* r15 = stack pointer
* spc
* pr
* ssr
* gbr
* mach
* macl
* syscall #
*
*/
#if defined(CONFIG_PREEMPT)
# define preempt_stop() cli
#else
# define preempt_stop()
# define resume_kernel __restore_all
#endif
.align 2
ENTRY(exception_error)
!
#ifdef CONFIG_TRACE_IRQFLAGS
mov.l 2f, r0
jsr @r0
nop
#endif
sti
mov.l 1f, r0
jmp @r0
nop
.align 2
1: .long do_exception_error
#ifdef CONFIG_TRACE_IRQFLAGS
2: .long trace_hardirqs_on
#endif
.align 2
ret_from_exception:
preempt_stop()
#ifdef CONFIG_TRACE_IRQFLAGS
mov.l 4f, r0
jsr @r0
nop
#endif
ENTRY(ret_from_irq)
!
mov #OFF_SR, r0
mov.l @(r0,r15), r0 ! get status register
shll r0
shll r0 ! kernel space?
get_current_thread_info r8, r0
bt resume_kernel ! Yes, it's from kernel, go back soon
#ifdef CONFIG_PREEMPT
bra resume_userspace
nop
ENTRY(resume_kernel)
mov.l @(TI_PRE_COUNT,r8), r0 ! current_thread_info->preempt_count
tst r0, r0
bf noresched
need_resched:
mov.l @(TI_FLAGS,r8), r0 ! current_thread_info->flags
tst #_TIF_NEED_RESCHED, r0 ! need_resched set?
bt noresched
mov #OFF_SR, r0
mov.l @(r0,r15), r0 ! get status register
and #0xf0, r0 ! interrupts off (exception path)?
cmp/eq #0xf0, r0
bt noresched
mov.l 1f, r0
mov.l r0, @(TI_PRE_COUNT,r8)
#ifdef CONFIG_TRACE_IRQFLAGS
mov.l 3f, r0
jsr @r0
nop
#endif
sti
mov.l 2f, r0
jsr @r0
nop
mov #0, r0
mov.l r0, @(TI_PRE_COUNT,r8)
cli
#ifdef CONFIG_TRACE_IRQFLAGS
mov.l 4f, r0
jsr @r0
nop
#endif
bra need_resched
nop
noresched:
bra __restore_all
nop
.align 2
1: .long PREEMPT_ACTIVE
2: .long schedule
#ifdef CONFIG_TRACE_IRQFLAGS
3: .long trace_hardirqs_on
4: .long trace_hardirqs_off
#endif
#endif
ENTRY(resume_userspace)
! r8: current_thread_info
cli
#ifdef CONFIG_TRACE_IRQFLAGS
mov.l 5f, r0
jsr @r0
nop
#endif
mov.l @(TI_FLAGS,r8), r0 ! current_thread_info->flags
tst #_TIF_WORK_MASK, r0
bt/s __restore_all
tst #_TIF_NEED_RESCHED, r0
.align 2
work_pending:
! r0: current_thread_info->flags
! r8: current_thread_info
! t: result of "tst #_TIF_NEED_RESCHED, r0"
bf/s work_resched
tst #(_TIF_SIGPENDING | _TIF_RESTORE_SIGMASK), r0
work_notifysig:
bt/s __restore_all
mov r15, r4
mov r12, r5 ! set arg1(save_r0)
mov r0, r6
mov.l 2f, r1
mov.l 3f, r0
jmp @r1
lds r0, pr
work_resched:
#ifndef CONFIG_PREEMPT
! gUSA handling
mov.l @(OFF_SP,r15), r0 ! get user space stack pointer
mov r0, r1
shll r0
bf/s 1f
shll r0
bf/s 1f
mov #OFF_PC, r0
! SP >= 0xc0000000 : gUSA mark
mov.l @(r0,r15), r2 ! get user space PC (program counter)
mov.l @(OFF_R0,r15), r3 ! end point
cmp/hs r3, r2 ! r2 >= r3?
bt 1f
add r3, r1 ! rewind point #2
mov.l r1, @(r0,r15) ! reset PC to rewind point #2
!
1:
#endif
mov.l 1f, r1
jsr @r1 ! schedule
nop
cli
#ifdef CONFIG_TRACE_IRQFLAGS
mov.l 5f, r0
jsr @r0
nop
#endif
!
mov.l @(TI_FLAGS,r8), r0 ! current_thread_info->flags
tst #_TIF_WORK_MASK, r0
bt __restore_all
bra work_pending
tst #_TIF_NEED_RESCHED, r0
.align 2
1: .long schedule
2: .long do_notify_resume
3: .long restore_all
#ifdef CONFIG_TRACE_IRQFLAGS
4: .long trace_hardirqs_on
5: .long trace_hardirqs_off
#endif
.align 2
syscall_exit_work:
! r0: current_thread_info->flags
! r8: current_thread_info
tst #_TIF_SYSCALL_TRACE, r0
bt/s work_pending
tst #_TIF_NEED_RESCHED, r0
#ifdef CONFIG_TRACE_IRQFLAGS
mov.l 5f, r0
jsr @r0
nop
#endif
sti
! XXX setup arguments...
mov.l 4f, r0 ! do_syscall_trace
jsr @r0
nop
bra resume_userspace
nop
.align 2
syscall_trace_entry:
! Yes it is traced.
! XXX setup arguments...
mov.l 4f, r11 ! Call do_syscall_trace which notifies
jsr @r11 ! superior (will chomp R[0-7])
nop
! Reload R0-R4 from kernel stack, where the
! parent may have modified them using
! ptrace(POKEUSR). (Note that R0-R2 are
! used by the system call handler directly
! from the kernel stack anyway, so don't need
! to be reloaded here.) This allows the parent
! to rewrite system calls and args on the fly.
mov.l @(OFF_R4,r15), r4 ! arg0
mov.l @(OFF_R5,r15), r5
mov.l @(OFF_R6,r15), r6
mov.l @(OFF_R7,r15), r7 ! arg3
mov.l @(OFF_R3,r15), r3 ! syscall_nr
!
mov.l 2f, r10 ! Number of syscalls
cmp/hs r10, r3
bf syscall_call
mov #-ENOSYS, r0
bra syscall_exit
mov.l r0, @(OFF_R0,r15) ! Return value
__restore_all:
mov.l 1f, r0
jmp @r0
nop
.align 2
1: .long restore_all
.align 2
syscall_badsys: ! Bad syscall number
mov #-ENOSYS, r0
bra resume_userspace
mov.l r0, @(OFF_R0,r15) ! Return value
/*
* The main debug trap handler.
*
* r8=TRA (not the trap number!)
*
* Note: This assumes that the trapa value is left in its original
* form (without the shlr2 shift) so the calculation for the jump
* call table offset remains a simple in place mask.
*/
debug_trap:
mov r8, r0
and #(0xf << 2), r0
mov.l 1f, r8
add r0, r8
mov.l @r8, r8
jmp @r8
nop
.align 2
1: .long debug_trap_table
/*
* Syscall interface:
*
* Syscall #: R3
* Arguments #0 to #3: R4--R7
* Arguments #4 to #6: R0, R1, R2
* TRA: (number of arguments + ABI revision) x 4
*
* This code also handles delegating other traps to the BIOS/gdb stub
* according to:
*
* Trap number
* (TRA>>2) Purpose
* -------- -------
* 0x00-0x0f original SH-3/4 syscall ABI (not in general use).
* 0x10-0x1f general SH-3/4 syscall ABI.
* 0x20-0x2f syscall ABI for SH-2 parts.
* 0x30-0x3f debug traps used by the kernel.
* 0x40-0xff Not supported by all parts, so left unhandled.
*
* Note: When we're first called, the TRA value must be shifted
* right 2 bits in order to get the value that was used as the "trapa"
* argument.
*/
.align 2
.globl ret_from_fork
ret_from_fork:
mov.l 1f, r8
jsr @r8
mov r0, r4
bra syscall_exit
nop
.align 2
1: .long schedule_tail
/*
* The poorly named main trapa decode and dispatch routine, for
* system calls and debug traps through their respective jump tables.
*/
ENTRY(system_call)
#if !defined(CONFIG_CPU_SH2)
mov.l 1f, r9
mov.l @r9, r8 ! Read from TRA (Trap Address) Register
#endif
/*
* Check the trap type
*/
mov #((0x20 << 2) - 1), r9
cmp/hi r9, r8
bt/s debug_trap ! it's a debug trap..
mov #OFF_TRA, r9
add r15, r9
mov.l r8, @r9 ! set TRA value to tra
#ifdef CONFIG_TRACE_IRQFLAGS
mov.l 5f, r10
jsr @r10
nop
#endif
sti
!
get_current_thread_info r8, r10
mov.l @(TI_FLAGS,r8), r8
mov #_TIF_SYSCALL_TRACE, r10
tst r10, r8
bf syscall_trace_entry
!
mov.l 2f, r8 ! Number of syscalls
cmp/hs r8, r3
bt syscall_badsys
!
syscall_call:
shll2 r3 ! x4
mov.l 3f, r8 ! Load the address of sys_call_table
add r8, r3
mov.l @r3, r8
jsr @r8 ! jump to specific syscall handler
nop
mov.l @(OFF_R0,r15), r12 ! save r0
mov.l r0, @(OFF_R0,r15) ! save the return value
!
syscall_exit:
cli
#ifdef CONFIG_TRACE_IRQFLAGS
mov.l 6f, r0
jsr @r0
nop
#endif
!
get_current_thread_info r8, r0
mov.l @(TI_FLAGS,r8), r0 ! current_thread_info->flags
tst #_TIF_ALLWORK_MASK, r0
bf syscall_exit_work
bra __restore_all
nop
.align 2
#if !defined(CONFIG_CPU_SH2)
1: .long TRA
#endif
2: .long NR_syscalls
3: .long sys_call_table
4: .long do_syscall_trace
#ifdef CONFIG_TRACE_IRQFLAGS
5: .long trace_hardirqs_on
6: .long trace_hardirqs_off
#endif
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