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BOTOKILLER



Joined: 07 Jan 2011
Posts: 154
Location: Ukraine
BOTOKILLER
Hi everyone!
I want my OS to find and read ACPI table, Osdev wiki says that I need to look somewhere near 1MB point for a descryptor, but the code I wrote didnt work. How to locate the RSDP???

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NSOS
Post 18 Jun 2011, 16:26
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egos



Joined: 10 Feb 2009
Posts: 144
egos
See ACPI Spec.: "Finding the RSDP on IA-PC Systems"
Post 18 Jun 2011, 21:53
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BOTOKILLER



Joined: 07 Jan 2011
Posts: 154
Location: Ukraine
BOTOKILLER
Its really fun, I found it manualy in debugger on 0E0000h
Also I found out why my code didnt work, it used 'loop RSDP_LOOP' and didnt scan for the first byte of segment 0E000h, That was exactly where the signature started!

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NSOS
Post 19 Jun 2011, 07:37
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Mac2004



Joined: 15 Dec 2003
Posts: 313
Mac2004
Wikipedia contains acpi information which should be helpful for you.
Acpi spec seems to be available from there.

http://en.wikipedia.org/wiki/Advanced_Configuration_and_Power_Interface

regards
Mac2004
Post 19 Jun 2011, 10:33
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sinsi



Joined: 10 Aug 2007
Posts: 707
Location: Adelaide
sinsi
Post 19 Jun 2011, 10:44
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smiddy



Joined: 31 Oct 2004
Posts: 559
smiddy
Hey BOTOKILLER,

I put this together:

Code:

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;; ACPI memory table look up.
;;
;; I have to do this in stages. 1st I need to read the RSDP to get the XSDT, to look for other
;; tables.
;;
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

RSDPSignature:  db 'RSD PTR ',0
RSDTAddress:    dd 0
XSDTAddress:    dq 0

ACPIMemoryLookUp:

   push es
   push edi
   push eax

   mov si,ACPILookUpMessage
   call PrintString

   mov ax,0E000h        ; Need to start looking for the RSDP to get the location of the XSDT
   mov es,ax            ;   the RSDP is in the E0000h to FFFFFh area, so the search is on.
   mov edi,0            ; Start at the first byte.

.LoopToLook:

   mov eax,edi
   shl eax,24
   cmp eax,0
   jg .MoveOn
   mov al,[RSDPSignature]
   cmp byte [es:edi],al
   je .CheckTheRest

.MoveOn:

   inc edi
   cmp edi,0FFF0h
   jg .CheckSegment

.CheckTheRest:

   mov al,[RSDPSignature+1]
   cmp byte [es:edi+1],al
   jne .NotTheSame
   mov al,[RSDPSignature+2]
   cmp byte [es:edi+2],al
   jne .NotTheSame
   mov al,[RSDPSignature+3]
   cmp byte [es:edi+3],al
   jne .NotTheSame
   mov al,[RSDPSignature+4]
   cmp byte [es:edi+4],al
   jne .NotTheSame
   mov al,[RSDPSignature+5]
   cmp byte [es:edi+5],al
   jne .NotTheSame
   mov al,[RSDPSignature+6]
   cmp byte [es:edi+6],al
   jne .NotTheSame
   mov al,[RSDPSignature+7]
   cmp byte [es:edi+7],al
   jne .NotTheSame
   mov eax,[es:edi+16]              ; 32 bit physical address of the RSDT.
   mov [RSDTAddress],eax            ; 32 bit physical address of the RSDT.
   mov eax,[es:edi+24]              ; 64 bit physical address of the XSDT.
   mov [XSDTAddress],eax            ; 64 bit physical address of the XSDT.
   mov eax,[es:edi+28]              ; 64 bit physical address of the XSDT.
   mov [XSDTAddress+4],eax          ; 64 bit physical address of the XSDT.
   jmp .Done

.NotTheSame:

   inc edi
   jmp .LoopToLook

.CheckSegment:

   mov ax,es
   cmp ax,0F000h
   je .FailedToLocateRSDP
   mov ax,0F000h
   mov es,ax
   mov edi,0
   jmp .LoopToLook

.FailedToLocateRSDP:

   mov si,FailedMessage
   call PrintString

.Done:

   mov si,ESMessage
   call PrintString

   mov eax,es
   mov cl,10h
   call ToHex
   mov si,HexBuffer
   call PrintString
   mov si,TheHexAfter
   call PrintString

   mov si,EDIMessage
   call PrintString

   mov eax,edi
   mov cl,20h
   call ToHex
   mov si,HexBuffer
   call PrintString
   mov si,TheHexAfter
   call PrintString
   mov si,TheEndOfLine
   call PrintString

   cmp dword [RSDTAddress],0
   je .CheckXSDTAddress
   mov si,RSDTAddressMessage
   call PrintString
   mov eax,[RSDTAddress]
   mov cl,20h
   call ToHex
   mov si,HexBuffer
   call PrintString
   mov si,TheHexAfter
   call PrintString
   mov si,TheEndOfLine
   call PrintString

.CheckXSDTAddress:

   cmp dword [XSDTAddress],0
   je .DoTheEndOfTheLine
   mov si,XSDTAddressMessage
   call PrintString
   mov eax,[XSDTAddress+4]
   mov cl,20h
   call ToHex
   mov si,HexBuffer
   call PrintString
   mov eax,[XSDTAddress]
   mov cl,20h
   call ToHex
   mov si,HexBuffer
   call PrintString
   mov si,TheHexAfter
   call PrintString
   mov si,TheEndOfLine
   call PrintString

.DoTheEndOfTheLine:

   mov si,TheEndOfLine
   call PrintString

   pop eax
   pop edi
   pop es

   ret
    


This finds both the RSDT and XSDT addresses. However, and this is not fully tested (yet), when I look at the length of the RSDT and XSDT from their respective locations, I get weird results from Virtual PC and Virtualbox.

Did you get very far in your endeavor?
Post 16 May 2012, 23:25
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cod3b453



Joined: 25 Aug 2004
Posts: 619
cod3b453
For reference, VirtualBox locations are:

RSDP 000E0000
FACP 3FFF00F0
APIC 3FFF0240
DSDT 3FFF0480

(those are the ones I've parsed so far; there are plenty more) and reports ACPI v2.

----

One thing to be careful of is one VM (and theoretically some BIOS') have the signature in more than one place in the EBDA so it's probably a good idea to perform the checksum.
Post 17 May 2012, 20:20
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smiddy



Joined: 31 Oct 2004
Posts: 559
smiddy
cod3b453 wrote:
For reference, VirtualBox locations are:

RSDP 000E0000
FACP 3FFF00F0
APIC 3FFF0240
DSDT 3FFF0480

(those are the ones I've parsed so far; there are plenty more) and reports ACPI v2.

----

One thing to be careful of is one VM (and theoretically some BIOS') have the signature in more than one place in the EBDA so it's probably a good idea to perform the checksum.

Well, I figured this, that it is all over the place. RSDT tends to be reasonable in size, but I get F000FF53h for the XSDT, which in reality is off target since the numbers are even, so I must be doing something wrong.

Thanks for the addresses. I'll try to verify them. I'm working to get the memory allocation information (outside of E820) and if the data spec is 2.0 versus 5.0 perhaps I need to revert some of my texts and adjust accordingly. (?)
Post 18 May 2012, 01:20
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smiddy



Joined: 31 Oct 2004
Posts: 559
smiddy
Ok, I was hosing up my addressing for the XSDT, however, it seems the RSDP at E0000h has a bad addess information for the XSDT. I will have to check elsewhere in Virtualbox, VirtualPC seems to work nicely.
Post 19 May 2012, 01:01
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