diff options
Diffstat (limited to 'arch/i386/cpu/start.S')
| -rw-r--r-- | arch/i386/cpu/start.S | 96 |
1 files changed, 0 insertions, 96 deletions
diff --git a/arch/i386/cpu/start.S b/arch/i386/cpu/start.S index 7def8de..3cea04b 100644 --- a/arch/i386/cpu/start.S +++ b/arch/i386/cpu/start.S @@ -100,53 +100,6 @@ mem_init_ret: jmp get_mem_size get_mem_size_ret: - /* - * We are now in 'Flat Protected Mode' and we know how much memory - * the board has. The (temporary) Global Descriptor Table is not - * in a 'Safe' place (it is either in Flash which can be erased or - * reprogrammed or in a fail-safe boot-strap image which could be - * over-written). - * - * Move the final gdt to a safe place (top of RAM) and load it. - * This is not a trivial excercise - the lgdt instruction does not - * have a register operand (memory only) and we may well be - * running from Flash, so self modifying code will not work here. - * To overcome this, we copy a stub into upper memory along with - * the GDT. - */ - - /* Reduce upper memory limit by (Stub + GDT Pointer + GDT) */ - subl $(end_gdt_setup - start_gdt_setup), %eax - - /* Copy the GDT and Stub */ - movl $start_gdt_setup, %esi - movl %eax, %edi - movl $(end_gdt_setup - start_gdt_setup), %ecx - shrl $2, %ecx - cld - rep movsl - - /* write the lgdt 'parameter' */ - subl $(jmp_instr - start_gdt_setup - 4), %ebp - addl %eax, %ebp - movl $(gdt_ptr - start_gdt_setup), %ebx - addl %eax, %ebx - movl %ebx, (%ebp) - - /* write the gdt address into the pointer */ - movl $(gdt_addr - start_gdt_setup), %ebp - addl %eax, %ebp - movl $(gdt - start_gdt_setup), %ebx - addl %eax, %ebx - movl %ebx, (%ebp) - - /* Save the return address */ - movl $load_gdt_ret, %ebp - - /* Load the new (safe) Global Descriptor Table */ - jmp *%eax - -load_gdt_ret: /* Check we have enough memory for stack */ movl $CONFIG_SYS_STACK_SIZE, %ecx cmpl %ecx, %eax @@ -221,52 +174,3 @@ die: hlt blank_idt_ptr: .word 0 /* limit */ .long 0 /* base */ - -.align 4 -start_gdt_setup: - lgdt gdt_ptr -jmp_instr: - jmp *%ebp - -.align 4 -gdt_ptr: - .word 0x30 /* limit (48 bytes = 6 GDT entries) */ -gdt_addr: - .long gdt /* base */ - - /* The GDT table ... - * - * Selector Type - * 0x00 NULL - * 0x08 Unused - * 0x10 32bit code - * 0x18 32bit data/stack - * 0x20 16bit code - * 0x28 16bit data/stack - */ - -.align 4 -gdt: - .word 0, 0, 0, 0 /* NULL */ - .word 0, 0, 0, 0 /* unused */ - - .word 0xFFFF /* 4Gb - (0x100000*0x1000 = 4Gb) */ - .word 0 /* base address = 0 */ - .word 0x9B00 /* code read/exec */ - .word 0x00CF /* granularity = 4096, 386 (+5th nibble of limit) */ - - .word 0xFFFF /* 4Gb - (0x100000*0x1000 = 4Gb) */ - .word 0x0 /* base address = 0 */ - .word 0x9300 /* data read/write */ - .word 0x00CF /* granularity = 4096, 386 (+5th nibble of limit) */ - - .word 0xFFFF /* 64kb */ - .word 0 /* base address = 0 */ - .word 0x9b00 /* data read/write */ - .word 0x0010 /* granularity = 1 (+5th nibble of limit) */ - - .word 0xFFFF /* 64kb */ - .word 0 /* base address = 0 */ - .word 0x9300 /* data read/write */ - .word 0x0010 /* granularity = 1 (+5th nibble of limit) */ -end_gdt_setup: |