sravan/system76-edk2
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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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15
MdePkg/Library/BaseLib/X64/DisablePaging64.S
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@@ -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