sravan/system76-edk2
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1. Added comments to ASM files

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2. Fixed a bug in 64-bit AsmDisablePaging64(), which may cause a #GP exception.

git-svn-id: https://edk2.svn.sourceforge.net/svnroot/edk2/trunk/edk2@2206 6f19259b-4bc3-4df7-8a09-765794883524
This commit is contained in:
bxing
2007-01-10 06:57:04 +00:00
parent 741fb36417
commit a9a812a0ed
45 changed files with 184 additions and 77 deletions
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34
MdePkg/Library/BaseLib/X64/Thunk16.asm
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@@ -66,6 +66,14 @@ SavedGdt LABEL FWORD
; by user code. It will be shadowed to somewhere in memory below 1MB.
;------------------------------------------------------------------------------
_BackFromUserCode PROC
;
; The order of saved registers on the stack matches the order they appears
; in IA32_REGS structure. This facilitates wrapper function to extract them
; into that structure.
;
; Some instructions for manipulation of segment registers have to be written
; in opcode since 64-bit MASM prevents accesses to those registers.
;
DB 16h ; push ss
DB 0eh ; push cs
DB 66h
@@ -115,7 +123,7 @@ SavedCr4 DD ?
;
; rdi in the instruction below is indeed bx in 16-bit code
;
DB 66h, 2eh
DB 66h, 2eh ; 2eh is "cs:" segment override
lgdt fword ptr [rdi + (SavedGdt - @Base)]
DB 66h
mov ecx, 0c0000080h
@@ -129,9 +137,8 @@ SavedCr0 DD ?
@64Eip DD ?
SavedCs DW ?
@64BitCode:
DB 48h, 0b8h ; mov rax, imm64
SavedRip DQ ?
jmp rax ; return to caller
mov rsp, r8 ; restore stack
ret
_BackFromUserCode ENDP
_EntryPoint DD _ToUserCode - m16Start
@@ -160,14 +167,14 @@ _ToUserCode PROC
mov cr4, rbp
mov ss, esi ; set up 16-bit stack segment
mov sp, bx ; set up 16-bit stack pointer
DB 66h
DB 66h ; make the following call 32-bit
call @Base ; push eip
@Base:
pop bp ; ebp <- address of @Base
push [esp + sizeof (IA32_REGS) + 2]
lea eax, [rsi + (@RealMode - @Base)]
lea eax, [rsi + (@RealMode - @Base)] ; rsi is "bp" in 16-bit code
push rax
retf
retf ; execution begins at next instruction
@RealMode:
DB 66h, 2eh ; CS and operand size override
lidt fword ptr [rsi + (_16Idtr - @Base)]
@@ -178,7 +185,7 @@ _ToUserCode PROC
pop gs
popf ; popfd
lea sp, [esp + 4] ; skip high order 32 bits of EFlags
DB 66h
DB 66h ; make the following retf 32-bit
retf ; transfer control to user code
_ToUserCode ENDP
@@ -220,8 +227,8 @@ GDT_SIZE = $ - _NullSeg
; );
;------------------------------------------------------------------------------
InternalAsmThunk16 PROC USES rbp rbx rsi rdi
mov r10d, ds
mov r11d, es
mov r10d, ds ; r9 ~ r11 are not accessible in 16-bit
mov r11d, es ; so use them for saving seg registers
mov r9d, ss
push fs
push gs
@@ -238,8 +245,8 @@ InternalAsmThunk16 PROC USES rbp rbx rsi rdi
lea ecx, [rdx + (SavedCr4 - m16Start)]
mov eax, edx ; eax <- transition code address
and edx, 0fh
shl eax, 12
lea ax, [rdx + (_BackFromUserCode - m16Start)]
shl eax, 12 ; segment address in high order 16 bits
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
@@ -257,13 +264,12 @@ InternalAsmThunk16 PROC USES rbp rbx rsi rdi
pushfq
lea edx, [rdx + DATA16 - DATA32]
lea r8, @RetFromRealMode
mov [rcx + (SavedRip - SavedCr4)], r8
push r8
mov r8d, cs
mov [rcx + (SavedCs - SavedCr4)], r8w
mov r8, rsp
jmp fword ptr [rcx + (_EntryPoint - SavedCr4)]
@RetFromRealMode:
mov rsp, r8
popfq
lidt fword ptr [rsp + 38h] ; restore protected mode IDTR
lea eax, [rbp - sizeof (IA32_REGS)]