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Remove assumption that the transition code for transitioning from 64-bit to 32-bit mode is 64 bytes. Instead compute the size based on the implementation in the ASM file.

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Update logic to align new 32-bit stack on a 4 byte boundary
Update logic to prevent one slot overlap between the transition code and the new stack.


git-svn-id: https://edk2.svn.sourceforge.net/svnroot/edk2/trunk/edk2@10133 6f19259b-4bc3-4df7-8a09-765794883524
This commit is contained in:
mdkinney
2010-03-01 05:35:20 +00:00
parent 3df4b6e7e9
commit be04587c86
2 changed files with 21 additions and 15 deletions
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21
MdePkg/Library/BaseLib/X64/DisablePaging64.asm
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@@ -38,20 +38,23 @@ InternalX86DisablePaging64 PROC
cli
lea rsi, @F ; rsi <- The start address of transition code
mov edi, [rsp + 28h] ; rdi <- New stack
sub edi, 64 ; rdi <- use 64 byte in stack to hold transition code
mov r10d, edi ; r10 <- The start address of transicition code below 4G
lea rax, mTransitionEnd ; rax <- end of transition code
sub rax, rsi ; rax <- The size of transition piece code
add rax, 4 ; Round RAX up to the next 4 byte boundary
and rax, 0fffffffch
sub rdi, rax ; rdi <- Use stack to hold transition code
mov r10d, edi ; r10 <- The start address of transicition code below 4G
push rcx ; save rcx to stack
mov rcx, rax ; rcx <- The size of transition piece code
rep movsb ; copy transition code to (new stack - 64byte) below 4G
rep movsb ; copy transition code to top of new stack which must be below 4GB
pop rcx ; restore rcx
mov esi, r8d
mov edi, r9d
mov eax, [rsp + 28h] ; eax <- New Stack
mov eax, r10d ; eax <- start of the transition code on the stack
sub eax, 4 ; eax <- One slot below transition code on the stack
push rcx ; push Cs to stack
push r10
push r10 ; push address of tansition code on stack
DB 48h ; prefix to composite "retq" with next "retf"
retf ; Use far return to load CS register from stack
@@ -59,10 +62,10 @@ InternalX86DisablePaging64 PROC
@@:
mov esp, eax ; set up new stack
mov rax, cr0
btr eax, 31
mov cr0, rax ; disable paging
mov rbx, rdx ; save EntryPoint to rbx, for rdmsr will overwrite rdx
btr eax, 31 ; Clear CR0.PG
mov cr0, rax ; disable paging and caches
mov ebx, edx ; save EntryPoint to rbx, for rdmsr will overwrite rdx
mov ecx, 0c0000080h
rdmsr
and ah, NOT 1 ; clear LME