/*
 *  linux/arch/i386/entry.S
 *
 *  Copyright (C) 1991, 1992  Linus Torvalds
 */

/*
 * 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.
 *
 * I changed all the .align's to 4 (16 byte alignment), as that's faster
 * on a 486.
 *
 * Stack layout in 'ret_from_system_call':
 * 	ptrace needs to have all regs on the stack.
 *	if the order here is changed, it needs to be
 *	updated in fork.c:copy_process, signal.c:do_signal,
 *	ptrace.c and ptrace.h
 *
 *	 0(%esp) - %ebx
 *	 4(%esp) - %ecx
 *	 8(%esp) - %edx
 *       C(%esp) - %esi
 *	10(%esp) - %edi
 *	14(%esp) - %ebp
 *	18(%esp) - %eax
 *	1C(%esp) - %ds
 *	20(%esp) - %es
 *	24(%esp) - orig_eax
 *	28(%esp) - %eip
 *	2C(%esp) - %cs
 *	30(%esp) - %eflags
 *	34(%esp) - %oldesp
 *	38(%esp) - %oldss
 *
 * "current" is in register %ebx during any slow entries.
 */

#include <linux/config.h>
#include <linux/sys.h>
#include <linux/linkage.h>
#include <asm/segment.h>
#define ASSEMBLY
#include <asm/smp.h>

EBX		= 0x00
ECX		= 0x04
EDX		= 0x08
ESI		= 0x0C
EDI		= 0x10
EBP		= 0x14
EAX		= 0x18
DS		= 0x1C
ES		= 0x20
ORIG_EAX	= 0x24
EIP		= 0x28
CS		= 0x2C
EFLAGS		= 0x30
OLDESP		= 0x34
OLDSS		= 0x38

CF_MASK		= 0x00000001
IF_MASK		= 0x00000200
NT_MASK		= 0x00004000
VM_MASK		= 0x00020000

/*
 * these are offsets into the task-struct.
 */
state		=  0
flags		=  4
sigpending	=  8
addr_limit	= 12
exec_domain	= 16
need_resched	= 20
tsk_ptrace	= 24
processor	= 52

ENOSYS = 38


#define SAVE_ALL \
	cld; \
	pushl %es; \
	pushl %ds; \
	pushl %eax; \
	pushl %ebp; \
	pushl %edi; \
	pushl %esi; \
	pushl %edx; \
	pushl %ecx; \
	pushl %ebx; \
	movl $(__KERNEL_DS),%edx; \
	movl %edx,%ds; \
	movl %edx,%es;

#define RESTORE_ALL	\
	popl %ebx;	\
	popl %ecx;	\
	popl %edx;	\
	popl %esi;	\
	popl %edi;	\
	popl %ebp;	\
	popl %eax;	\
1:	popl %ds;	\
2:	popl %es;	\
	addl $4,%esp;	\
3:	iret;		\
.section .fixup,"ax";	\
4:	movl $0,(%esp);	\
	jmp 1b;		\
5:	movl $0,(%esp);	\
	jmp 2b;		\
6:	pushl %ss;	\
	popl %ds;	\
	pushl %ss;	\
	popl %es;	\
	pushl $11;	\
	call do_exit;	\
.previous;		\
.section __ex_table,"a";\
	.align 4;	\
	.long 1b,4b;	\
	.long 2b,5b;	\
	.long 3b,6b;	\
.previous

#define GET_CURRENT(reg) \
	movl $-8192, reg; \
	andl %esp, reg

ENTRY(lcall7)
	pushfl			# We get a different stack layout with call gates,
	pushl %eax		# which has to be cleaned up later..
	SAVE_ALL
	movl EIP(%esp),%eax	# due to call gates, this is eflags, not eip..
	movl CS(%esp),%edx	# this is eip..
	movl EFLAGS(%esp),%ecx	# and this is cs..
	movl %eax,EFLAGS(%esp)	#
	movl %edx,EIP(%esp)	# Now we move them to their "normal" places
	movl %ecx,CS(%esp)	#
	movl %esp,%ebx
	pushl %ebx
	andl $-8192,%ebx	# GET_CURRENT
	movl exec_domain(%ebx),%edx	# Get the execution domain
	movl 4(%edx),%edx	# Get the lcall7 handler for the domain
	pushl $0x7
	call *%edx
	addl $4, %esp
	popl %eax
	jmp ret_from_sys_call

ENTRY(lcall27)
	pushfl			# We get a different stack layout with call gates,
	pushl %eax		# which has to be cleaned up later..
	SAVE_ALL
	movl EIP(%esp),%eax	# due to call gates, this is eflags, not eip..
	movl CS(%esp),%edx	# this is eip..
	movl EFLAGS(%esp),%ecx	# and this is cs..
	movl %eax,EFLAGS(%esp)	#
	movl %edx,EIP(%esp)	# Now we move them to their "normal" places
	movl %ecx,CS(%esp)	#
	movl %esp,%ebx
	pushl %ebx
	andl $-8192,%ebx	# GET_CURRENT
	movl exec_domain(%ebx),%edx	# Get the execution domain
	movl 4(%edx),%edx	# Get the lcall7 handler for the domain
	pushl $0x27
	call *%edx
	addl $4, %esp
	popl %eax
	jmp ret_from_sys_call


ENTRY(ret_from_fork)
	pushl %ebx
	call SYMBOL_NAME(schedule_tail)
	addl $4, %esp
	GET_CURRENT(%ebx)
	testb $0x02,tsk_ptrace(%ebx)	# PT_TRACESYS
	jne tracesys_exit
	jmp	ret_from_sys_call

/*
 * Return to user mode is not as complex as all this looks,
 * but we want the default path for a system call return to
 * go as quickly as possible which is why some of this is
 * less clear than it otherwise should be.
 */

ENTRY(system_call)
	pushl %eax			# save orig_eax
	SAVE_ALL
	GET_CURRENT(%ebx)
	cmpl $(NR_syscalls),%eax
	jae badsys
	testb $0x02,tsk_ptrace(%ebx)	# PT_TRACESYS
	jne tracesys
	call *SYMBOL_NAME(sys_call_table)(,%eax,4)
	movl %eax,EAX(%esp)		# save the return value
ENTRY(ret_from_sys_call)
#ifdef CONFIG_SMP
	movl processor(%ebx),%eax
	shll $CONFIG_X86_L1_CACHE_SHIFT,%eax
	movl SYMBOL_NAME(irq_stat)(,%eax),%ecx		# softirq_active
	testl SYMBOL_NAME(irq_stat)+4(,%eax),%ecx	# softirq_mask
#else
	movl SYMBOL_NAME(irq_stat),%ecx		# softirq_active
	testl SYMBOL_NAME(irq_stat)+4,%ecx	# softirq_mask
#endif
	jne   handle_softirq
	
ret_with_reschedule:
	cmpl $0,need_resched(%ebx)
	jne reschedule
	cmpl $0,sigpending(%ebx)
	jne signal_return
restore_all:
	RESTORE_ALL

	ALIGN
signal_return:
	sti				# we can get here from an interrupt handler
	testl $(VM_MASK),EFLAGS(%esp)
	movl %esp,%eax
	jne v86_signal_return
	xorl %edx,%edx
	call SYMBOL_NAME(do_signal)
	jmp restore_all

	ALIGN
v86_signal_return:
	call SYMBOL_NAME(save_v86_state)
	movl %eax,%esp
	xorl %edx,%edx
	call SYMBOL_NAME(do_signal)
	jmp restore_all

	ALIGN
tracesys:
	movl $-ENOSYS,EAX(%esp)
	call SYMBOL_NAME(syscall_trace)
	movl ORIG_EAX(%esp),%eax
	cmpl $(NR_syscalls),%eax
	jae tracesys_exit
	call *SYMBOL_NAME(sys_call_table)(,%eax,4)
	movl %eax,EAX(%esp)		# save the return value
tracesys_exit:
	call SYMBOL_NAME(syscall_trace)
	jmp ret_from_sys_call
badsys:
	movl $-ENOSYS,EAX(%esp)
	jmp ret_from_sys_call

	ALIGN
ret_from_exception:
#ifdef CONFIG_SMP
	GET_CURRENT(%ebx)
	movl processor(%ebx),%eax
	shll $CONFIG_X86_L1_CACHE_SHIFT,%eax
	movl SYMBOL_NAME(irq_stat)(,%eax),%ecx		# softirq_active
	testl SYMBOL_NAME(irq_stat)+4(,%eax),%ecx	# softirq_mask
#else
	movl SYMBOL_NAME(irq_stat),%ecx		# softirq_active
	testl SYMBOL_NAME(irq_stat)+4,%ecx	# softirq_mask
#endif
	jne   handle_softirq

ENTRY(ret_from_intr)
	GET_CURRENT(%ebx)
	movl EFLAGS(%esp),%eax		# mix EFLAGS and CS
	movb CS(%esp),%al
	testl $(VM_MASK | 3),%eax	# return to VM86 mode or non-supervisor?
	jne ret_with_reschedule
	jmp restore_all

	ALIGN
handle_softirq:
	call SYMBOL_NAME(do_softirq)
	jmp ret_from_intr
	
	ALIGN
reschedule:
	call SYMBOL_NAME(schedule)    # test
	jmp ret_from_sys_call

ENTRY(divide_error)
	pushl $0		# no error code
	pushl $ SYMBOL_NAME(do_divide_error)
	ALIGN
error_code:
	pushl %ds
	pushl %eax
	xorl %eax,%eax
	pushl %ebp
	pushl %edi
	pushl %esi
	pushl %edx
	decl %eax			# eax = -1
	pushl %ecx
	pushl %ebx
	cld
	movl %es,%ecx
	movl ORIG_EAX(%esp), %esi	# get the error code
	movl ES(%esp), %edi		# get the function address
	movl %eax, ORIG_EAX(%esp)
	movl %ecx, ES(%esp)
	movl %esp,%edx
	pushl %esi			# push the error code
	pushl %edx			# push the pt_regs pointer
	movl $(__KERNEL_DS),%edx
	movl %edx,%ds
	movl %edx,%es
	GET_CURRENT(%ebx)
	call *%edi
	addl $8,%esp
	jmp ret_from_exception

ENTRY(coprocessor_error)
	pushl $0
	pushl $ SYMBOL_NAME(do_coprocessor_error)
	jmp error_code

ENTRY(simd_coprocessor_error)
	pushl $0
	pushl $ SYMBOL_NAME(do_simd_coprocessor_error)