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/*
* This file is part of the coreboot project.
*
* Copyright (C) 2012 ChromeOS Authors
*
* 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.
*/
/*
* The stub is a generic wrapper for bootstrapping a C-based SMM handler. Its
* primary purpose is to put the CPU into protected mode with a stack and call
* into the C handler.
*
* The stub_entry_params structure needs to correspond to the C structure
* found in smm.h.
*/
.code32
.section ".module_parameters", "aw", @progbits
stub_entry_params:
stack_size:
.long 0
stack_top:
.long 0
c_handler:
.long 0
c_handler_arg:
.long 0
/* struct smm_runtime begins here. */
smm_runtime:
smbase:
.long 0
save_state_size:
.long 0
/* apic_to_cpu_num is a table mapping the default APIC id to CPU num. If the
* APIC id is found at the given index, the contiguous CPU number is index
* into the table. */
apic_to_cpu_num:
.fill CONFIG_MAX_CPUS,1,0xff
/* end struct smm_runtime */
.data
/* Provide fallback stack to use when a valid CPU number cannot be found. */
fallback_stack_bottom:
.skip 128
fallback_stack_top:
.text
.code16
.global _start
_start:
movl $(smm_relocate_gdt), %ebx
data32 lgdt (%ebx)
movl %cr0, %eax
andl $0x1FFAFFD1, %eax /* CD,NW,PG,AM,WP,NE,TS,EM,MP = 0 */
orl $0x1, %eax /* PE = 1 */
movl %eax, %cr0
/* Enable protected mode */
data32 ljmp $0x8, $smm_trampoline32
.align 4
smm_relocate_gdt:
/* The first GDT entry is used for the lgdt instruction. */
.word smm_relocate_gdt_end - smm_relocate_gdt - 1
.long smm_relocate_gdt
.word 0x0000
/* 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_relocate_gdt_end:
.align 4
.code32
.global smm_trampoline32
smm_trampoline32:
/* Use flat data segment */
movw $0x10, %ax
movw %ax, %ds
movw %ax, %es
movw %ax, %ss
movw %ax, %fs
movw %ax, %gs
/* The CPU number is calculated by reading the initial APIC id. Since
* the OS can maniuplate the APIC id use the non-changing cpuid result
* for APIC id (ebx[31:24]). A table is used to handle a discontiguous
* APIC id space. */
mov $1, %eax
cpuid
bswap %ebx /* Default APIC id in bl. */
mov $(apic_to_cpu_num), %eax
xor %ecx, %ecx
1:
cmp (%eax, %ecx, 1), %bl
je 1f
inc %ecx
cmp $CONFIG_MAX_CPUS, %ecx
jne 1b
/* This is bad. One cannot find a stack entry because a CPU num could
* not be assigned. Use the fallback stack and check this condition in
* C handler. */
movl $(fallback_stack_top), %esp
jmp 2f
1:
movl stack_size, %eax
mul %ecx
movl stack_top, %edx
subl %eax, %edx
mov %edx, %esp
2:
/* Call into the c-based SMM relocation function with the platform
* parameters. Equivalent to:
* struct arg = { c_handler_params, cpu_num, smm_runtime {;
* c_handler(&arg)
*/
push $(smm_runtime)
push %ecx
push c_handler_arg
push %esp
mov c_handler, %eax
call *%eax
/* Exit from SM mode. */
rsm
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