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linux/arch/sh/kernel/entry-common.S
Stuart Menefy fea966f756 sh: Remove implicit sign extension from assembler immediates 
The SH instruction set has several instructions which accept an 8 bit
immediate operand. For logical instructions this operand is zero extended,
for arithmetic instructions the operand is sign extended. After adding an
option to the assembler to check this, it was found that several pieces
of assembly code were assuming this behaviour, and in one case
getting it wrong.

So this patch explicitly sign extends any immediate operands, which makes
it obvious what is happening, and fixes the one case which got it wrong.

Signed-off-by: Stuart Menefy <stuart.menefy@st.com>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>
2009-08-24 17:09:53 +09:00

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/*
* Copyright (C) 1999, 2000, 2002 Niibe Yutaka
* Copyright (C) 2003 - 2008 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 #
*
*/
#include <asm/dwarf.h>
#if defined(CONFIG_PREEMPT)
# define preempt_stop() cli ; TRACE_IRQS_OFF
#else
# define preempt_stop()
# define resume_kernel __restore_all
#endif
.align 2
ENTRY(exception_error)
!
TRACE_IRQS_ON
sti
mov.l 1f, r0
jmp @r0
nop
.align 2
1: .long do_exception_error
.align 2
ret_from_exception:
CFI_STARTPROC simple
CFI_DEF_CFA r14, 0
CFI_REL_OFFSET 17, 64
CFI_REL_OFFSET 15, 0
CFI_REL_OFFSET 14, 56
preempt_stop()
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)
cli
TRACE_IRQS_OFF
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
shlr r0
and #(0xf0>>1), r0 ! interrupts off (exception path)?
cmp/eq #(0xf0>>1), r0
bt noresched
mov.l 3f, r0
jsr @r0 ! call preempt_schedule_irq
nop
bra need_resched
nop
noresched:
bra __restore_all
nop
.align 2
1: .long PREEMPT_ACTIVE
2: .long schedule
3: .long preempt_schedule_irq
#endif
ENTRY(resume_userspace)
! r8: current_thread_info
cli
TRACE_IRQS_OfF
mov.l @(TI_FLAGS,r8), r0 ! current_thread_info->flags
tst #(_TIF_WORK_MASK & 0xff), 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:
mov.l 1f, r1
jsr @r1 ! schedule
nop
cli
TRACE_IRQS_OFF
!
mov.l @(TI_FLAGS,r8), r0 ! current_thread_info->flags
tst #(_TIF_WORK_MASK & 0xff), r0
bt __restore_all
bra work_pending
tst #_TIF_NEED_RESCHED, r0
.align 2
1: .long schedule
2: .long do_notify_resume
3: .long resume_userspace
.align 2
syscall_exit_work:
! r0: current_thread_info->flags
! r8: current_thread_info
tst #(_TIF_WORK_SYSCALL_MASK & 0xff), r0
bt/s work_pending
tst #_TIF_NEED_RESCHED, r0
TRACE_IRQS_ON
sti
mov r15, r4
mov.l 8f, r0 ! do_syscall_trace_leave
jsr @r0
nop
bra resume_userspace
nop
.align 2
syscall_trace_entry:
! Yes it is traced.
mov r15, r4
mov.l 7f, r11 ! Call do_syscall_trace_enter which notifies
jsr @r11 ! superior (will chomp R[0-7])
nop
mov.l r0, @(OFF_R0,r15) ! Save return value
! 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 #OFF_SR, r0
mov.l @(r0,r15), r0 ! get status register
shlr2 r0
and #0x3c, r0
cmp/eq #0x3c, r0
bt 1f
TRACE_IRQS_ON
bra 2f
nop
1:
TRACE_IRQS_OFF
2:
mov.l 3f, r0
jmp @r0
nop
.align 2
3: .long restore_all
.align 2
syscall_badsys: ! Bad syscall number
get_current_thread_info r8, r0
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
jsr @r8
nop
bra __restore_all
nop
CFI_ENDPROC
.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)
setup_frame_reg
#if !defined(CONFIG_CPU_SH2)
mov.l 1f, r9
mov.l @r9, r8 ! Read from TRA (Trap Address) Register
#endif
mov #OFF_TRA, r10
add r15, r10
mov.l r8, @r10 ! set TRA value to tra
/*
* Check the trap type
*/
mov #((0x20 << 2) - 1), r9
cmp/hi r9, r8
bt/s debug_trap ! it's a debug trap..
nop
TRACE_IRQS_ON
sti
!
get_current_thread_info r8, r10
mov.l @(TI_FLAGS,r8), r8
mov #(_TIF_WORK_SYSCALL_MASK & 0xff), r10
mov #(_TIF_WORK_SYSCALL_MASK >> 8), r9
tst r10, r8
shll8 r9
bf syscall_trace_entry
tst r9, 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
TRACE_IRQS_OFF
!
get_current_thread_info r8, r0
mov.l @(TI_FLAGS,r8), r0 ! current_thread_info->flags
tst #(_TIF_ALLWORK_MASK & 0xff), r0
mov #(_TIF_ALLWORK_MASK >> 8), r1
bf syscall_exit_work
shlr8 r0
tst r0, r1
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
7: .long do_syscall_trace_enter
8: .long do_syscall_trace_leave
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