From be04587c86ad728413586feeb648a5fd586adb24 Mon Sep 17 00:00:00 2001 From: mdkinney Date: Mon, 1 Mar 2010 05:35:20 +0000 Subject: [PATCH] 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. 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 --- MdePkg/Library/BaseLib/X64/DisablePaging64.S | 15 +++++++------ .../Library/BaseLib/X64/DisablePaging64.asm | 21 +++++++++++-------- 2 files changed, 21 insertions(+), 15 deletions(-) diff --git a/MdePkg/Library/BaseLib/X64/DisablePaging64.S b/MdePkg/Library/BaseLib/X64/DisablePaging64.S index 017d6ce945..a467fea260 100644 --- a/MdePkg/Library/BaseLib/X64/DisablePaging64.S +++ b/MdePkg/Library/BaseLib/X64/DisablePaging64.S @@ -40,10 +40,12 @@ ASM_PFX(InternalX86DisablePaging64): cli lea L1(%rip), %rsi # rsi <- The start address of transition code mov 0x28(%rsp), %edi # rdi <- New stack - sub $64, %edi # rdi <- use 64 byte in stack to hold transition code - mov %edi, %r10d # r10 <- The start address of transicition code below 4G lea _mTransitionEnd(%rip), %rax # rax <- end of transition code sub %rsi, %rax # rax <- The size of transition piece code + add $4, %rax # round rax up to the next 4 byte boundary + and $0x0fffffffc, %rax + sub %rax, %rdi # rdi <- use stack to hold transition code + mov %edi, %r10d # r10 <- The start address of transicition code below 4G push %rcx # save rcx to stack mov %rax, %rcx # rcx <- The size of transition piece code rep @@ -52,18 +54,19 @@ ASM_PFX(InternalX86DisablePaging64): mov %r8d, %esi mov %r9d, %edi - mov 0x28(%rsp), %eax # eax <- New Stack + mov %r10d, %eax + sub $4, %eax push %rcx # push Cs to stack - push %r10 + push %r10 # push address of transition code on stack .byte 0x48, 0xcb # retq: Use far return to load CS register from stack # (Use raw byte code since some GNU assemblers generates incorrect code for "retq") L1: mov %eax,%esp # set up new stack mov %cr0,%rax - btr $0x1f,%eax + btr $0x1f,%eax # clear CR0.PG mov %rax,%cr0 # disable paging - mov %rdx,%rbx # save EntryPoint to rbx, for rdmsr will overwrite rdx + mov %edx,%ebx # save EntryPoint to ebx, for rdmsr will overwrite edx mov $0xc0000080,%ecx rdmsr and $0xfe,%ah # clear LME diff --git a/MdePkg/Library/BaseLib/X64/DisablePaging64.asm b/MdePkg/Library/BaseLib/X64/DisablePaging64.asm index a2995daa33..5f556a4ca6 100644 --- a/MdePkg/Library/BaseLib/X64/DisablePaging64.asm +++ b/MdePkg/Library/BaseLib/X64/DisablePaging64.asm @@ -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 -- 2.39.2