Save segment registers on stack in case the thunk code assembly calls CF9 soft reset and the x64 registers get cleared.

git-svn-id: https://edk2.svn.sourceforge.net/svnroot/edk2/trunk/edk2@8123 6f19259b-4bc3-4df7-8a09-765794883524

2 files changed, 42 insertions, 22 deletions

diff --git a/MdePkg/Library/BaseLib/X64/Thunk16.S b/MdePkg/Library/BaseLib/X64/Thunk16.S
index b829685b43..f9770b258c 100644
--- a/MdePkg/Library/BaseLib/X64/Thunk16.S
+++ b/MdePkg/Library/BaseLib/X64/Thunk16.S
@@ -136,10 +136,13 @@ SavedCr4:   .space  4
 SavedCr0:    .space      4

     movq    %rax, %cr0

     .byte 0x66,0xea                     # jmp far cs:L_64Bit

-L_64Eip:      .space      4

+L_64Eip:     .space      4

 SavedCs:     .space      2

 L_64BitCode: 

-    movq     %r8, %rsp

+    .byte   0x90

+    .byte   0x67,0xbc                  # mov esp, imm32

+SavedSp:    .space 4                   # restore stack

+    nop

     ret

 

 _EntryPoint: .long      ASM_PFX(ToUserCode) - ASM_PFX(m16Start)

@@ -227,7 +230,6 @@ ASM_PFX(_32Data):
 #   IN OUT  VOID                      *Transition

 #   );

 #------------------------------------------------------------------------------

-# MISMATCH: "InternalAsmThunk16  PROC    USES    rbp rbx rsi rdi"

 

 .globl ASM_PFX(InternalAsmThunk16)

 ASM_PFX(InternalAsmThunk16):

@@ -236,9 +238,13 @@ ASM_PFX(InternalAsmThunk16):
     pushq   %rsi

     pushq   %rdi

     

-    movl    %ds, %r10d                  # r9 ~ r11 are not accessible in 16-bit

-    movl    %es, %r11d                  # so use them for saving seg registers

-    movl    %ss, %r9d

+    movq    %ds, %rbx

+    pushq   %rbx      # Save ds segment register on the stack

+    movq    %es, %rbx

+    pushq   %rbx      # Save es segment register on the stack

+    movq    %ss, %rbx

+    pushq   %rbx      # Save ss segment register on the stack

+

     .byte   0x0f, 0xa0                  #push   fs

     .byte   0x0f, 0xa8                  #push   gs

     movq    %rcx, %rsi

@@ -259,7 +265,7 @@ ASM_PFX(InternalAsmThunk16):
     lea     (_BackFromUserCode - ASM_PFX(m16Start))(%rdx), %ax

     stosl                               # [edi] <- return address of user code

     sgdt    (SavedGdt - SavedCr4)(%rcx) 

-    sidt    0x38(%rsp)

+    sidt    0x50(%rsp)

     movq    %cr0, %rax

     movl    %eax, (SavedCr0 - SavedCr4)(%rcx)

     andl    $0x7ffffffe,%eax            # clear PE, PG bits

@@ -277,18 +283,22 @@ ASM_PFX(InternalAsmThunk16):
     pushq   %r8

     movl    %cs, %r8d

     movw    %r8w, (SavedCs - SavedCr4)(%rcx)

-    movq     %rsp, %r8

+    movl    %esp, (SavedSp - SavedCr4)(%rcx)

     .byte   0xff, 0x69                  #  jmp (_EntryPoint - SavedCr4)(%rcx)

     .byte   _EntryPoint - SavedCr4

 L_RetFromRealMode: 

     popfq

-    lidt    0x38(%rsp)

+    lidt    0x50(%rsp)

     lea     -IA32_REGS_SIZE(%rbp), %eax

     .byte 0x0f, 0xa9                    # pop gs

     .byte 0x0f, 0xa1                    # pop fs

-    movl    %r9d, %ss

-    movl    %r11d, %es

-    movl    %r10d, %ds

+    

+    popq     %rbx
+    movq     %rbx, %ss
+    popq     %rbx
+    movq     %rbx, %es
+    popq     %rbx
+    movq     %rbx, %ds
     

     popq    %rdi

     popq    %rsi

diff --git a/MdePkg/Library/BaseLib/X64/Thunk16.asm b/MdePkg/Library/BaseLib/X64/Thunk16.asm
index d93af44597..cef63d98e1 100644
--- a/MdePkg/Library/BaseLib/X64/Thunk16.asm
+++ b/MdePkg/Library/BaseLib/X64/Thunk16.asm
@@ -140,7 +140,10 @@ SavedCr0    DD      ?
 @64Eip      DD      ?

 SavedCs     DW      ?

 @64BitCode:

-    mov     rsp, r8                     ; restore stack

+    db      090h 

+    db      067h, 0bch                 ; mov esp, imm32

+SavedSp     DD   ?                     ; restore stack

+    nop

     ret

 _BackFromUserCode   ENDP

 

@@ -230,9 +233,13 @@ GDT_SIZE = $ - _NullSeg
 ;   );

 ;------------------------------------------------------------------------------

 InternalAsmThunk16  PROC    USES    rbp rbx rsi rdi

-    mov     r10d, ds                    ; r9 ~ r11 are not accessible in 16-bit

-    mov     r11d, es                    ; so use them for saving seg registers

-    mov     r9d, ss

+    mov     rbx, ds

+    push    rbx          ; Save ds segment register on the stack

+    mov     rbx, es

+    push    rbx          ; Save es segment register on the stack

+    mov     rbx, ss

+    push    rbx          ; Save ss segment register on the stack

+    

     push    fs

     push    gs

     mov     rsi, rcx

@@ -252,7 +259,7 @@ InternalAsmThunk16  PROC    USES    rbp rbx rsi rdi
     lea     ax, [rdx + (_BackFromUserCode - m16Start)]  ; offset address

     stosd                               ; [edi] <- return address of user code

     sgdt    fword ptr [rcx + (SavedGdt - SavedCr4)]

-    sidt    fword ptr [rsp + 38h]       ; save IDT stack in argument space

+    sidt    fword ptr [rsp + 50h]       ; save IDT stack in argument space

     mov     rax, cr0

     mov     [rcx + (SavedCr0 - SavedCr4)], eax

     and     eax, 7ffffffeh              ; clear PE, PG bits

@@ -270,17 +277,20 @@ InternalAsmThunk16  PROC    USES    rbp rbx rsi rdi
     push    r8

     mov     r8d, cs

     mov     [rcx + (SavedCs - SavedCr4)], r8w

-    mov     r8, rsp

+    mov     [rcx + (SavedSp - SavedCr4)], esp

     jmp     fword ptr [rcx + (_EntryPoint - SavedCr4)]

 @RetFromRealMode:

     popfq

-    lidt    fword ptr [rsp + 38h]       ; restore protected mode IDTR

+    lidt    fword ptr [rsp + 50h]       ; restore protected mode IDTR

     lea     eax, [rbp - sizeof (IA32_REGS)]

     pop     gs

     pop     fs

-    mov     ss, r9d

-    mov     es, r11d

-    mov     ds, r10d

+    pop     rbx

+    mov     ss, rbx

+    pop     rbx

+    mov     es, rbx

+    pop     rbx

+    mov     ds, rbx

     ret

 InternalAsmThunk16  ENDP