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/* Copyright (C) 1994, 1997 Free Software Foundation, Inc.
Contributed by Joel Sherrill (jsherril@redstone-emh2.army.mil),
On-Line Applications Research Corporation.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Library General Public License as
published by the Free Software Foundation; either version 2 of the
License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Library General Public License for more details.
You should have received a copy of the GNU Library General Public
License along with the GNU C Library; see the file COPYING.LIB. If not,
write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
Boston, MA 02111-1307, USA. */
/* entry.s
*
* This file contains the entry point for the application.
* The name of this entry point is compiler dependent.
* It jumps to the BSP which is responsible for performing
* all initialization.
*
*/
.data
.global _Do_Load_IDT
.global _Do_Load_GDT
.text
.global start # GNU default entry point
.global _establish_stack
.global _bsp_start
.global _load_segments
.global __exit
start:
nop
cli # DISABLE INTERRUPTS!!!
#
# Load the segment registers
#
# NOTE: Upon return, gs will contain the segment descriptor for
# a segment which maps directly to all of physical memory.
#
jmp _load_segments # load board dependent segments
#
# Set up the stack
#
_establish_stack:
movl $stack_end,%esp # set stack pointer
movl $stack_end,%ebp # set base pointer
#
# Zero out the BSS segment
#
zero_bss:
cld # make direction flag count up
movl $_end,%ecx # find end of .bss
movl $_bss_start,%edi # edi = beginning of .bss
subl %edi,%ecx # ecx = size of .bss in bytes
shrl $2,%ecx # size of .bss in longs
xorl %eax,%eax # value to clear out memory
repne # while ecx != 0
stosl # clear a long in the bss
#
# Set the C heap information for malloc
#
movl $heap_size,___C_heap_size # set ___C_heap_size
movl $heap_memory,___C_heap_start # set ___C_heap_start
#
# Copy the Global Descriptor Table to our space
#
sgdt _Original_GDTR # save original GDT
movzwl _Original_GDTR_limit,%ecx # size of GDT in bytes; limit
# is 8192 entries * 8 bytes per
# make ds:esi point to the original GDT
movl _Original_GDTR_base,%esi
push %ds # save ds
movw %gs,%ax
movw %ax,%ds
# make es:edi point to the new (our copy) GDT
movl $_Global_descriptor_table,%edi
rep
movsb # copy the GDT (ds:esi -> es:edi)
pop %ds # restore ds
# Build and load new contents of GDTR
movw _Original_GDTR_limit,%ecx # set new limit
movw %cx,_New_GDTR_limit
push $_Global_descriptor_table
push %es
call _Logical_to_physical
addl $6,%esp
movl %eax,_New_GDTR_base # set new base
cmpb $0,_Do_Load_GDT # Should the new GDT be loaded?
je no_gdt_load # NO, then branch
lgdt _New_GDTR # load the new GDT
no_gdt_load:
#
# Copy the Interrupt Descriptor Table to our space
#
sidt _Original_IDTR # save original IDT
movzwl _Original_IDTR_limit,%ecx # size of IDT in bytes; limit
# is 256 entries * 8 bytes per
# make ds:esi point to the original IDT
movl _Original_IDTR_base,%esi
push %ds # save ds
movw %gs,%ax
movw %ax,%ds
# make es:edi point to the new (our copy) IDT
movl $_Interrupt_descriptor_table,%edi
rep
movsb # copy the IDT (ds:esi -> es:edi)
pop %ds # restore ds
# Build and load new contents of IDTR
movw _Original_IDTR_limit,%ecx # set new limit
movw %cx,_New_IDTR_limit
push $_Interrupt_descriptor_table
push %es
call _Logical_to_physical
addl $6,%esp
movl %eax,_New_IDTR_base # set new base
cmpb $0,_Do_Load_IDT # Should the new IDT be loaded?
je no_idt_load # NO, then branch
lidt _New_IDTR # load the new IDT
no_idt_load:
#
# Initialize the i387.
#
# Using the NO WAIT form of the instruction insures that if
# it is not present the board will not lock up or get an
# exception.
#
fninit # MUST USE NO-WAIT FORM
call __Board_Initialize # initialize the board
pushl $0 # envp = NULL
pushl $0 # argv = NULL
pushl $0 # argc = NULL
call ___libc_init # initialize the library and
# call main
addl $12,%esp
pushl $0 # argc = NULL
call __exit # call the Board specific exit
addl $4,%esp
#
# Clean up
#
.global _Bsp_cleanup
.global _return_to_monitor
_Bsp_cleanup:
cmpb $0,_Do_Load_IDT # Was the new IDT loaded?
je no_idt_restore # NO, then branch
lidt _Original_IDTR # restore the new IDT
no_idt_restore:
cmpb $0,_Do_Load_GDT # Was the new GDT loaded?
je no_gdt_restore # NO, then branch
lgdt _Original_GDTR # restore the new GDT
no_gdt_restore:
jmp _return_to_monitor
#
# void *Logical_to_physical(
# rtems_unsigned16 segment,
# void *address
# );
#
# Returns thirty-two bit physical address for segment:address.
#
.global _Logical_to_physical
.set SEGMENT_ARG, 4
.set ADDRESS_ARG, 8
_Logical_to_physical:
xorl %eax,%eax # clear eax
movzwl SEGMENT_ARG(%esp),%ecx # ecx = segment value
movl $_Global_descriptor_table,%edx # edx = address of our GDT
addl %ecx,%edx # edx = address of desired entry
movb 7(%edx),%ah # ah = base 31:24
movb 4(%edx),%al # al = base 23:16
shll $16,%eax # move ax into correct bits
movw 2(%edx),%ax # ax = base 0:15
movl ADDRESS_ARG(%esp),%ecx # ecx = address to convert
addl %eax,%ecx # ecx = physical address equivalent
movl %ecx,%eax # eax = ecx
ret
#
# void *Physical_to_logical(
# rtems_unsigned16 segment,
# void *address
# );
#
# Returns thirty-two bit physical address for segment:address.
#
.global _Physical_to_logical
#.set SEGMENT_ARG, 4
#.set ADDRESS_ARG, 8 -- use sets from above
_Physical_to_logical:
xorl %eax,%eax # clear eax
movzwl SEGMENT_ARG(%esp),%ecx # ecx = segment value
movl $_Global_descriptor_table,%edx # edx = address of our GDT
addl %ecx,%edx # edx = address of desired entry
movb 7(%edx),%ah # ah = base 31:24
movb 4(%edx),%al # al = base 23:16
shll $16,%eax # move ax into correct bits
movw 2(%edx),%ax # ax = base 0:15
movl ADDRESS_ARG(%esp),%ecx # ecx = address to convert
subl %eax,%ecx # ecx = logical address equivalent
movl %ecx,%eax # eax = ecx
ret
/*
* Data Declarations. Start with a macro which helps declare space.
*/
.bss
#define DECLARE_SPACE(_name,_space,_align) \
.globl _name ; \
.align _align ; \
_name##: .space _space
#define DECLARE_LABEL(_name) \
.globl _name ; \
_name##:
#define DECLARE_PTR(_name) DECLARE_SPACE(_name,4,2)
#define DECLARE_U32(_name) DECLARE_SPACE(_name,4,2)
#define DECLARE_U16(_name) DECLARE_SPACE(_name,2,1)
/*
* Require environment stuff
*/
DECLARE_LABEL(_environ)
DECLARE_PTR(environ)
DECLARE_LABEL(_errno)
DECLARE_U32(errno)
/*
* Miscellaneous Variables used to restore the CPU state.
*
* Start with a macro to declare the space for the contents of
* a Descriptor Table register.
*/
#define DECLARE_DTR_SPACE(_name) \
.global _name ; \
.align 4 ; \
_name##: ; \
_name##_limit: .space 2 ; \
_name##_base: .space 4
DECLARE_SPACE(_Interrupt_descriptor_table,256*8,4)
DECLARE_SPACE(_Global_descriptor_table,8192*8,4)
DECLARE_DTR_SPACE(_Original_IDTR)
DECLARE_DTR_SPACE(_New_IDTR)
DECLARE_DTR_SPACE(_Original_GDTR)
DECLARE_DTR_SPACE(_New_GDTR)
DECLARE_SPACE(_Physical_base_of_ds,4,4)
DECLARE_SPACE(_Physical_base_of_cs,4,4)
/*
* Stack Size and Space
*/
.set stack_size, 0x20000
DECLARE_SPACE(stack_memory,stack_size,4)
DECLARE_LABEL(stack_end)
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