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Emulate moving cr0, cr2, cr3, or cr4 into any i386 general register

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rather than just emulating mov cr0, eax.  This fixes some Compaq/HP BIOS
with DMA (as the BIOS tried to read cr3 so it could translate addresses
if paging was enabled).

MFC after:	1 week
This commit is contained in:
jhb 2006-09-27 19:32:26 +00:00
parent 28bd6c8699
commit f6b387ce53
1 changed files with 18 additions and 6 deletions
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24
sys/boot/i386/btx/btx/btx.S
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@ -493,9 +493,7 @@ v86mon.3: cmpb $0xf,%al # Prefixed instruction?
je v86wrmsr # Yes
cmpb $0x32,(%esi) # Is it a RDMSR?
je v86rdmsr # Yes
cmpb $0x20,(%esi) # Is this a
jne v86mon.4 # MOV EAX,CR0
cmpb $0xc0,0x1(%esi) # instruction?
cmpb $0x20,(%esi) # Is this a MOV reg,CRx?
je v86mov # Yes
v86mon.4: cmpb $0xfa,%al # CLI?
je v86cli # Yes
@ -527,10 +525,24 @@ v86mon.7: subl %edi,%esi # From linear
leal 0x8(%esp,1),%esp # Discard int no, error
iret # To V86 mode
/*
* Emulate MOV EAX,CR0.
* Emulate MOV reg,CRx.
*/
v86mov: movl %cr0,%eax # CR0 to
movl %eax,0x1c(%ebp) # saved EAX
v86mov: movb 0x1(%esi),%bl # Fetch Mod R/M byte
testb $0x10,%bl # Read CR2 or CR3?
jnz v86mov.1 # Yes
movl %cr0,%eax # Read CR0
testb $0x20,%bl # Read CR4 instead?
jz v86mov.2 # No
movl %cr4,%eax # Read CR4
jmp v86mov.2
v86mov.1: movl %cr2,%eax # Read CR2
testb $0x08,%bl # Read CR3 instead?
jz v86mov.2 # No
movl %cr3,%eax # Read CR3
v86mov.2: andl $0x7,%ebx # Compute offset in
shl $2,%ebx # frame of destination
neg %ebx # register
movl %eax,0x1c(%ebp,%ebx,1) # Store CR to reg
incl %esi # Adjust IP
/*
* Return from emulating a 0x0f prefixed instruction