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x86: Tidy up global descriptor table setup 

This code is a little muddled, so tidy it up. Make sure that we put the
GDT in the right place and set it up properly.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
This commit is contained in:
Simon Glass 2014-11-06 13:20:04 -07:00
parent 3c00695ee1
commit 76f90f3020
1 changed files with 16 additions and 3 deletions
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19
arch/x86/cpu/start.S
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@ -74,6 +74,16 @@ car_init_ret:
* We now have CONFIG_SYS_CAR_SIZE bytes of Cache-As-RAM (or SRAM,
* or fully initialised SDRAM - we really don't care which)
* starting at CONFIG_SYS_CAR_ADDR to be used as a temporary stack
* and early malloc area.
*
* Stack grows down from top of CAR. We have:
*
* top-> CONFIG_SYS_CAR_ADDR + CONFIG_SYS_CAR_SIZE
* global_data
* x86 global descriptor table
* early malloc area
* stack
* bottom-> CONFIG_SYS_CAR_ADDR
*/
/* Stack grows down from top of CAR */
@ -91,12 +101,16 @@ car_init_ret:
movl %esp, %edi
rep stosb
/* Setup first parameter to setup_gdt */
/* Setup first parameter to setup_gdt, pointer to global_data */
movl %esp, %eax
/* Reserve space for global descriptor table */
subl $X86_GDT_SIZE, %esp
/* Align temporary global descriptor table to 16-byte boundary */
andl $0xfffffff0, %esp
movl %esp, %ecx
#if defined(CONFIG_SYS_MALLOC_F_LEN)
subl $CONFIG_SYS_MALLOC_F_LEN, %esp
movl %eax, %edx
@ -108,14 +122,13 @@ car_init_ret:
andl $0xfffffff0, %esp
/* Set second parameter to setup_gdt */
movl %esp, %edx
movl %ecx, %edx
/* Setup global descriptor table so gd->xyz works */
call setup_gdt
/* Set parameter to board_init_f() to boot flags */
xorl %eax, %eax
movw %bx, %ax
/* Enter, U-boot! */
call board_init_f