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/*
* This file is part of the coreboot project.
*
* Copyright (C) 2008 coresystems GmbH
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License as
* published by the Free Software Foundation; version 2 of
* the License.
*
* This program 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 General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 51 Franklin St, Fifth Floor, Boston,
* MA 02110-1301 USA
*/
/* NOTE: This handler assumes the SMM window goes from 0xa0000
* to 0xaffff. In fact, at least on Intel Core CPUs (i945 chipset)
* the SMM window is 128K big, covering 0xa0000 to 0xbffff.
* So there is a lot of potential for growth in here. Let's stick
* to 64k if we can though.
*/
/*
* +--------------------------------+ 0xaffff
* | Save State Map Node 0 |
* | Save State Map Node 1 |
* | Save State Map Node 2 |
* | Save State Map Node 3 |
* | ... |
* +--------------------------------+ 0xaf000
* | |
* | |
* | |
* +--------------------------------+ 0xa8400
* | SMM Entry Node 0 (+ stack) |
* +--------------------------------+ 0xa8000
* | SMM Entry Node 1 (+ stack) |
* | SMM Entry Node 2 (+ stack) |
* | SMM Entry Node 3 (+ stack) |
* | ... |
* +--------------------------------+ 0xa7400
* | |
* | SMM Handler |
* | |
* +--------------------------------+ 0xa0000
*
*/
#define LAPIC_ID 0xfee00020
/* SMM_HANDLER_OFFSET is the 16bit offset within the ASEG
* at which smm_handler_start lives. At the moment the handler
* lives right at 0xa0000, so the offset is 0.
*/
#define SMM_HANDLER_OFFSET 0x0000
/* initially SMM is some sort of real mode. Let gcc know
* how to treat the SMM handler stub
*/
.section ".handler", "a", @progbits
.code16
/**
* SMM code to enable protected mode and jump to the
* C-written function void smi_handler(u32 smm_revision)
*
* All the bad magic is not all that bad after all.
*/
smm_handler_start:
movw $(smm_gdtptr16 - smm_handler_start + SMM_HANDLER_OFFSET), %bx
data32 lgdt %cs:(%bx)
movl %cr0, %eax
andl $0x7FFAFFD1, %eax /* PG,AM,WP,NE,TS,EM,MP = 0 */
orl $0x60000001, %eax /* CD, NW, PE = 1 */
movl %eax, %cr0
/* Enable protected mode */
data32 ljmp $0x08, $1f
.code32
1:
/* Use flat data segment */
movw $0x10, %ax
movw %ax, %ds
movw %ax, %es
movw %ax, %ss
movw %ax, %fs
movw %ax, %gs
/* Get this CPU's LAPIC ID */
movl $LAPIC_ID, %esi
movl (%esi), %ecx
shr $24, %ecx
/* calculate stack offset by multiplying the APIC ID
* by 1024 (0x400), and save that offset in ebp.
*/
shl $10, %ecx
movl %ecx, %ebp
/* We put the stack for each core right above
* its SMM entry point. Core 0 starts at 0xa8000,
* we spare 0x10 bytes for the jump to be sure.
*/
movl $0xa8010, %eax
subl %ecx, %eax /* subtract offset, see above */
movl %eax, %ebx /* Save bottom of stack in ebx */
#define SMM_STACK_SIZE (0x400 - 0x10)
/* clear stack */
cld
movl %eax, %edi
movl $(SMM_STACK_SIZE >> 2), %ecx
xorl %eax, %eax
rep stosl
/* set new stack */
addl $SMM_STACK_SIZE, %ebx
movl %ebx, %esp
/* Get SMM revision */
movl $0xa8000 + 0x7efc, %ebx /* core 0 address */
subl %ebp, %ebx /* subtract core X offset */
movl (%ebx), %eax
pushl %eax
/* Call 32bit C handler */
call smi_handler
/* To return, just do rsm. It will "clean up" protected mode */
rsm
.code16
.align 4, 0xff
smm_gdtptr16:
.word smm_gdt_end - smm_gdt - 1
.long smm_gdt - smm_handler_start + 0xa0000 + SMM_HANDLER_OFFSET
.code32
smm_gdt:
/* The first GDT entry can not be used. Keep it zero */
.long 0x00000000, 0x00000000
/* gdt selector 0x08, flat code segment */
.word 0xffff, 0x0000
.byte 0x00, 0x9b, 0xcf, 0x00 /* G=1 and 0x0f, 4GB limit */
/* gdt selector 0x10, flat data segment */
.word 0xffff, 0x0000
.byte 0x00, 0x93, 0xcf, 0x00
smm_gdt_end:
.section ".jumptable", "a", @progbits
/* This is the SMM jump table. All cores use the same SMM handler
* for simplicity. But SMM Entry needs to be different due to the
* save state area. The jump table makes sure all CPUs jump into the
* real handler on SMM entry.
*/
/* This code currently supports up to 4 CPU cores. If more than 4 CPU cores
* shall be used, below table has to be updated, as well as smm.ld
*/
/* GNU AS/LD will always generate code that assumes CS is 0xa000. In reality
* CS will be set to SMM_BASE[19:4] though. Knowing that the smm handler is the
* first thing in the ASEG, we do a far jump here, to set CS to 0xa000.
*/
.code16
jumptable:
/* core 3 */
ljmp $0xa000, $SMM_HANDLER_OFFSET
.align 1024, 0x00
/* core 2 */
ljmp $0xa000, $SMM_HANDLER_OFFSET
.align 1024, 0x00
/* core 1 */
ljmp $0xa000, $SMM_HANDLER_OFFSET
.align 1024, 0x00
/* core 0 */
ljmp $0xa000, $SMM_HANDLER_OFFSET
.align 1024, 0x00
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