mirror of https://github.com/ipxe/ipxe.git
Add infrastructure to support access to .data16 (and .text16) variables
from protected-mode code. Set up %ds to point to .data16 in prot_to_real, so that code specified via REAL_EXEC() and friends can access variables in .data16. Move most real-mode librm variables from .text16 to .data16.pull/1/head
Michael Brown
parent
f4429533a6
commit
832807726a
|
|
@ -336,6 +336,7 @@ install_prealloc:
|
|||
call install_highmem
|
||||
|
||||
/* Continue executing in .text16 segment */
|
||||
movw %bx, %ds
|
||||
pushw %cs
|
||||
pushw $2f
|
||||
pushw %ax
|
||||
|
|
@ -344,11 +345,11 @@ install_prealloc:
|
|||
.section ".text16", "awx", @progbits
|
||||
1:
|
||||
/* Set up protected-mode GDT, call relocate(), reset GDT */
|
||||
call init_gdt
|
||||
call init_librm
|
||||
pushl $relocate
|
||||
data32 call prot_call
|
||||
addw $4, %sp
|
||||
call init_gdt
|
||||
call init_librm
|
||||
|
||||
/* Return to executing in .prefix section */
|
||||
lret
|
||||
|
|
|
|||
|
|
@ -24,7 +24,7 @@
|
|||
/****************************************************************************
|
||||
* Global descriptor table
|
||||
*
|
||||
* Call init_gdt to set up the GDT before attempting to use any
|
||||
* Call init_librm to set up the GDT before attempting to use any
|
||||
* protected-mode code.
|
||||
*
|
||||
* Define FLATTEN_REAL_MODE if you want to use so-called "flat real
|
||||
|
|
@ -45,7 +45,7 @@
|
|||
#else
|
||||
#define RM_LIMIT_16_19__AVL__SIZE__GRANULARITY 0x00
|
||||
#endif
|
||||
.section ".text16"
|
||||
.section ".data16", "aw", @progbits
|
||||
.align 16
|
||||
gdt:
|
||||
gdt_limit: .word gdt_length - 1
|
||||
|
|
@ -86,56 +86,71 @@ gdt_end:
|
|||
.equ gdt_length, gdt_end - gdt
|
||||
|
||||
/****************************************************************************
|
||||
* init_gdt (real-mode near call, 16-bit real-mode return address)
|
||||
* init_librm (real-mode near call, 16-bit real-mode return address)
|
||||
*
|
||||
* Initialise the GDT ready for transitions to protected mode.
|
||||
*
|
||||
* Parameters:
|
||||
* %edi : Physical base of protected-mode code
|
||||
* Parameters:
|
||||
* %cs : .text16 segment
|
||||
* %ds : .data16 segment
|
||||
* %edi : Physical base of protected-mode code (virt_offset)
|
||||
****************************************************************************
|
||||
*/
|
||||
.section ".text16"
|
||||
.code16
|
||||
.globl init_gdt
|
||||
init_gdt:
|
||||
.globl init_librm
|
||||
init_librm:
|
||||
/* Preserve registers */
|
||||
pushl %eax
|
||||
pushw %bx
|
||||
pushl %ebx
|
||||
|
||||
/* Record virt_offset */
|
||||
movl %edi, %cs:virt_offset_rm_copy
|
||||
|
||||
/* Set virtual_cs and virtual_ds base */
|
||||
/* Store _virt_offset and set up virtual_cs and virtual_ds segments */
|
||||
movl %edi, %eax
|
||||
movw $virtual_cs, %bx
|
||||
call set_seg_base
|
||||
movw $virtual_ds, %bx
|
||||
call set_seg_base
|
||||
movl %edi, _virt_offset
|
||||
|
||||
/* Set real_cs and real_ds base, and GDT base */
|
||||
movw $real_cs, %bx
|
||||
/* Negate virt_offset */
|
||||
negl %edi
|
||||
|
||||
/* Store rm_cs and _text16, set up real_cs segment */
|
||||
xorl %eax, %eax
|
||||
movw %cs, %ax
|
||||
movw %ax, rm_cs
|
||||
shll $4, %eax
|
||||
movw $real_cs, %bx
|
||||
call set_seg_base
|
||||
addl $gdt, %eax
|
||||
movl %eax, %cs:gdt_base
|
||||
leal (%eax, %edi), %ebx
|
||||
movl %ebx, _text16
|
||||
|
||||
/* Store rm_ds and _data16, set up real_ds segment and set GDT base */
|
||||
xorl %eax, %eax
|
||||
movw %ds, %ax
|
||||
movw %ax, %cs:rm_ds
|
||||
shll $4, %eax
|
||||
movw $real_ds, %bx
|
||||
call set_seg_base
|
||||
leal (%eax, %edi), %ebx
|
||||
movl %ebx, _data16
|
||||
addl $gdt, %eax
|
||||
movl %eax, gdt_base
|
||||
|
||||
/* Restore registers */
|
||||
popw %bx
|
||||
negl %edi
|
||||
popl %ebx
|
||||
popl %eax
|
||||
ret
|
||||
|
||||
.section ".text16"
|
||||
.code16
|
||||
set_seg_base:
|
||||
pushl %eax
|
||||
movw %ax, %cs:(0+2)(%bx)
|
||||
movw %ax, %cs:(8+2)(%bx)
|
||||
shrl $16, %eax
|
||||
movb %al, %cs:(0+4)(%bx)
|
||||
movb %al, %cs:(8+4)(%bx)
|
||||
movb %ah, %cs:(0+7)(%bx)
|
||||
movb %ah, %cs:(8+7)(%bx)
|
||||
popl %eax
|
||||
1: movw %ax, 2(%bx)
|
||||
rorl $16, %eax
|
||||
movb %al, 4(%bx)
|
||||
movb %ah, 7(%bx)
|
||||
roll $16, %eax
|
||||
ret
|
||||
|
||||
/****************************************************************************
|
||||
|
|
@ -157,19 +172,25 @@ set_seg_base:
|
|||
.section ".text16"
|
||||
.code16
|
||||
real_to_prot:
|
||||
/* Protected-mode return address => %ebx */
|
||||
popl %ebx
|
||||
|
||||
/* Real-mode %cs => %dx, %ss => %bp */
|
||||
movw %cs, %dx
|
||||
/* Make sure we have our data segment available */
|
||||
movw %cs:rm_ds, %ax
|
||||
movw %ax, %ds
|
||||
|
||||
/* Add _virt_offset, _text16 and _data16 to stack to be
|
||||
* copied, and also copy the return address.
|
||||
*/
|
||||
pushl _virt_offset
|
||||
pushl _text16
|
||||
pushl _data16
|
||||
addw $16, %cx /* %ecx must be less than 64kB anyway */
|
||||
|
||||
/* Real-mode %ss:%sp => %bp:%esi */
|
||||
movw %ss, %bp
|
||||
|
||||
/* virt_offset => %edi */
|
||||
movl %cs:virt_offset_rm_copy, %edi
|
||||
movzwl %sp, %esi
|
||||
|
||||
/* Switch to protected mode */
|
||||
cli
|
||||
data32 lgdt %cs:gdt
|
||||
data32 lgdt gdt
|
||||
movl %cr0, %eax
|
||||
orb $CR0_PE, %al
|
||||
movl %eax, %cr0
|
||||
|
|
@ -184,24 +205,24 @@ real_to_prot:
|
|||
movw %ax, %fs
|
||||
movw %ax, %gs
|
||||
|
||||
/* Record virt_offset */
|
||||
movl %edi, virt_offset
|
||||
|
||||
/* Move data from RM stack to PM stack and set up PM stack */
|
||||
movzwl %sp, %esi
|
||||
movl pm_esp, %esp
|
||||
subl %ecx, %esp
|
||||
movl %esp, %edi
|
||||
rep ss movsb
|
||||
movw %ax, %ss
|
||||
|
||||
/* Record real-mode %cs and %ss:sp */
|
||||
movw %dx, rm_cs
|
||||
/* Record real-mode %ss:sp (after removal of data) */
|
||||
movw %bp, rm_ss
|
||||
movw %si, rm_sp
|
||||
|
||||
/* Publish virt_offset, text16 and data16 for PM code to use */
|
||||
popl data16
|
||||
popl text16
|
||||
popl virt_offset
|
||||
|
||||
/* Return to virtual address */
|
||||
jmp *%ebx
|
||||
ret
|
||||
|
||||
/****************************************************************************
|
||||
* prot_to_real (protected-mode near call, 32-bit real-mode return address)
|
||||
|
|
@ -209,9 +230,9 @@ real_to_prot:
|
|||
* Switch from 32-bit protected mode with virtual addresses to 16-bit
|
||||
* real mode. The protected-mode %esp is stored in pm_esp and the
|
||||
* real-mode %ss:sp is restored from the saved rm_ss and rm_sp. All
|
||||
* real-mode data segment registers are set equal to %ss. Interrupts
|
||||
* are *not* enabled, since we want to be able to use prot_to_real in
|
||||
* an ISR. All other registers may be destroyed.
|
||||
* real-mode data segment registers are loaded from the saved rm_ds.
|
||||
* Interrupts are *not* enabled, since we want to be able to use
|
||||
* prot_to_real in an ISR. All other registers may be destroyed.
|
||||
*
|
||||
* The return address for this function should be a 32-bit (sic)
|
||||
* real-mode offset within .code16.
|
||||
|
|
@ -224,15 +245,15 @@ real_to_prot:
|
|||
.section ".text"
|
||||
.code32
|
||||
prot_to_real:
|
||||
/* Real-mode return address => %ebx */
|
||||
popl %ebx
|
||||
/* Add return address to data to be moved to RM stack */
|
||||
addl $4, %ecx
|
||||
|
||||
/* Real-mode %ss:sp => %ebp:edx */
|
||||
movzwl rm_ss, %ebp
|
||||
movzwl rm_sp, %edx
|
||||
subl %ecx, %edx
|
||||
|
||||
/* Copy data from PM stack to RM stack */
|
||||
/* Move data from PM stack to RM stack */
|
||||
movl %ebp, %eax
|
||||
shll $4, %eax
|
||||
leal (%eax,%edx), %edi
|
||||
|
|
@ -240,12 +261,9 @@ prot_to_real:
|
|||
movl %esp, %esi
|
||||
rep movsb
|
||||
|
||||
/* Record protected-mode %esp */
|
||||
/* Record protected-mode %esp (after removal of data) */
|
||||
movl %esi, pm_esp
|
||||
|
||||
/* Real-mode %cs => %di */
|
||||
movw rm_cs, %di
|
||||
|
||||
/* Load real-mode segment limits */
|
||||
movw $REAL_DS, %ax
|
||||
movw %ax, %ds
|
||||
|
|
@ -257,27 +275,40 @@ prot_to_real:
|
|||
.section ".text16"
|
||||
.code16
|
||||
1:
|
||||
/* Set up real-mode ljmp instruction */
|
||||
movw %di, %ds:(p2r_ljmp + 3)
|
||||
|
||||
/* Switch to real mode */
|
||||
movl %cr0, %eax
|
||||
andb $0!CR0_PE, %al
|
||||
movl %eax, %cr0
|
||||
ljmp *p2r_jump_vector
|
||||
p2r_jump_target:
|
||||
|
||||
p2r_ljmp:
|
||||
ljmp $0, $1f /* Segment is filled in by above code */
|
||||
1:
|
||||
/* Set up real-mode stack and data segments, and stack pointer */
|
||||
movw %bp, %ds
|
||||
movw %bp, %es
|
||||
movw %bp, %fs
|
||||
movw %bp, %gs
|
||||
/* Set up real-mode stack */
|
||||
movw %bp, %ss
|
||||
movw %dx, %sp
|
||||
|
||||
/* Set up real-mode data segments */
|
||||
movw %cs:rm_ds, %ax
|
||||
movw %ax, %ds
|
||||
movw %ax, %es
|
||||
movw %ax, %fs
|
||||
movw %ax, %gs
|
||||
|
||||
/* Return to real-mode address */
|
||||
jmp *%bx
|
||||
data32 ret
|
||||
|
||||
|
||||
/* Real-mode code and data segments. Assigned by the call to
|
||||
* init_librm. rm_cs doubles as the segment part of the jump
|
||||
* vector used by prot_to_real. rm_ds is located in .text16
|
||||
* rather than .data16 because code needs to be able to locate
|
||||
* the data segment.
|
||||
*/
|
||||
.section ".data16"
|
||||
p2r_jump_vector:
|
||||
.word p2r_jump_target
|
||||
rm_cs: .word 0
|
||||
.section ".text16"
|
||||
rm_ds: .word 0
|
||||
|
||||
/****************************************************************************
|
||||
* prot_call (real-mode near call, 32-bit real-mode return address)
|
||||
|
|
@ -406,11 +437,12 @@ real_call:
|
|||
/* Construct call to real-mode function */
|
||||
movw %sp, %bp
|
||||
movw RC_OFFSET_FUNCTION(%bp), %ax
|
||||
movw %ax, %cs:rc_function
|
||||
movw %ax, rc_function
|
||||
|
||||
/* Call real-mode function */
|
||||
popal
|
||||
call *%cs:rc_function
|
||||
call *RC_OFFSET_FUNCTION(%esp)
|
||||
call *rc_function
|
||||
pushal
|
||||
|
||||
/* Switch to protected mode and move register dump back to PM stack */
|
||||
|
|
@ -427,7 +459,9 @@ real_call:
|
|||
popal
|
||||
ret
|
||||
|
||||
.section ".text16"
|
||||
|
||||
/* Function vector, used because */
|
||||
.section ".data16"
|
||||
rc_function: .word 0
|
||||
|
||||
/****************************************************************************
|
||||
|
|
@ -464,19 +498,33 @@ rc_function: .word 0
|
|||
* to us.
|
||||
****************************************************************************
|
||||
*/
|
||||
|
||||
.section ".data"
|
||||
.globl rm_sp
|
||||
rm_sp: .word 0
|
||||
.globl rm_ss
|
||||
rm_ss: .word 0
|
||||
.globl rm_cs
|
||||
rm_cs: .word 0
|
||||
.globl pm_esp
|
||||
pm_esp: .long _estack
|
||||
|
||||
.section ".text16"
|
||||
virt_offset_rm_copy: .long 0
|
||||
/****************************************************************************
|
||||
* Virtual address offsets
|
||||
*
|
||||
* These are used by the protected-mode code to map between virtual
|
||||
* and physical addresses, and to access variables in the .text16 or
|
||||
* .data16 segments.
|
||||
****************************************************************************
|
||||
*/
|
||||
/* Internal copies, created by init_librm (which runs in real mode) */
|
||||
.section ".data16"
|
||||
_virt_offset: .long 0
|
||||
_text16: .long 0
|
||||
_data16: .long 0
|
||||
|
||||
/* Externally-visible copies, created by real_to_prot */
|
||||
.section ".data"
|
||||
.globl virt_offset
|
||||
virt_offset: .long 0
|
||||
virt_offset: .long 0
|
||||
.globl text16
|
||||
text16: .long 0
|
||||
.globl data16
|
||||
data16: .long 0
|
||||
|
|
|
|||
Loading…
Reference in New Issue