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Diffstat (limited to 'sysdeps/standalone/i386/start.S')
| -rw-r--r-- | sysdeps/standalone/i386/start.S | 323 |
1 files changed, 323 insertions, 0 deletions
diff --git a/sysdeps/standalone/i386/start.S b/sysdeps/standalone/i386/start.S new file mode 100644 index 0000000000..8331a331c1 --- /dev/null +++ b/sysdeps/standalone/i386/start.S @@ -0,0 +1,323 @@ +/* Copyright (C) 1994 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., 675 Mass Ave, +Cambridge, MA 02139, 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) + |