sravan/system76-edk2
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Fix the bug in x64 thunk code that it cannot handle the case when GDT is loaded in above 4G table memory.

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git-svn-id: https://edk2.svn.sourceforge.net/svnroot/edk2/trunk/edk2@8390 6f19259b-4bc3-4df7-8a09-765794883524
This commit is contained in:
qhuang8
2009-05-26 11:41:12 +00:00
parent 57ee276f16
commit a148780114
2 changed files with 37 additions and 3 deletions
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19
MdePkg/Library/BaseLib/X64/Thunk16.asm
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@@ -258,7 +258,23 @@ InternalAsmThunk16 PROC USES rbp rbx rsi rdi
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)]
sgdt fword ptr [rsp + 60h] ; save GDT stack in argument space
movzx r10, word ptr [rsp + 60h] ; r10 <- GDT limit
lea r11, [rcx + (InternalAsmThunk16 - SavedCr4) + 0xf]
and r11, 0xfffffff0 ; r11 <- 16-byte aligned shadowed GDT table in real mode buffer
mov word ptr [rcx + (SavedGdt - SavedCr4)], r10w ; save the limit of shadowed GDT table
mov qword ptr [rcx + (SavedGdt - SavedCr4) + 2], r11 ; save the base address of shadowed GDT table
mov rsi, qword ptr [rsp + 62h] ; rsi <- the original GDT base address
xchg rcx, r10 ; save rcx to r10 and initialize rcx to be the limit of GDT table
inc rcx ; rcx <- the size of memory to copy
xchg rdi, r11 ; save rdi to r11 and initialize rdi to the base address of shadowed GDT table
rep movsb ; perform memory copy to shadow GDT table
mov rcx, r10 ; restore the orignal rcx before memory copy
mov rdi, r11 ; restore the original rdi before memory copy
sidt fword ptr [rsp + 50h] ; save IDT stack in argument space
mov rax, cr0
mov [rcx + (SavedCr0 - SavedCr4)], eax
@@ -281,6 +297,7 @@ InternalAsmThunk16 PROC USES rbp rbx rsi rdi
jmp fword ptr [rcx + (_EntryPoint - SavedCr4)]
@RetFromRealMode:
popfq
lgdt fword ptr [rsp + 60h] ; restore protected mode GDTR
lidt fword ptr [rsp + 50h] ; restore protected mode IDTR
lea eax, [rbp - sizeof (IA32_REGS)]
pop gs