1. Added comments to ASM files
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:
@@ -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)]
|
||||
|
Reference in New Issue
Block a user