Syslinux - May 2010 - [syslinux:pathbased] comboot: fix comapi_open

Op 20100514 om 10:03 schreef syslinux-bot for Sebastian
Herbszt:
> Gitweb:
http://syslinux.zytor.com/commit/7d7b2bc2cdb8d99eee9ef41c21612a60728a7713
> 
> Fix breakage introduced by commit e375515ddc712f1f69ee21337db2a3267caa5d49
> (Add 32-bit versions of open file/close file).
> 
> --- a/core/comboot.inc
> +++ b/core/comboot.inc
> @@ -517,7 +517,12 @@ comapi_textmode:
>  ; INT 22h AX=0006h	Open file
>  ;
>  comapi_open:
> +		mov es,P_ES
> +		mov si,P_SI
>  		pm_call pm_open_file
> +		mov P_EAX,eax
> +		mov P_CX,cx
> +		mov P_SI,si
>  		ret
>  
>  ;
> 
That looks like ( (    } } )

 

Stappers
expecting something like
>  ; INT 22h AX=0006h	Open file
>  ;
>  comapi_open:
> +		mov es,P_ES
> +		mov si,P_SI
* +		mov cx,P_CX
* +		mov eax,P_EAX
>  		pm_call pm_open_file
> +		mov P_EAX,eax
> +		mov P_CX,cx
> +		mov P_SI,si
* +		mov P_ES,es
>  		ret
>  
>  ;
>

Geert Stappers wrote:
> Op 20100514 om 10:03 schreef syslinux-bot for Sebastian Herbszt:
>> Gitweb:
http://syslinux.zytor.com/commit/7d7b2bc2cdb8d99eee9ef41c21612a60728a7713
>> 
>> Fix breakage introduced by commit
e375515ddc712f1f69ee21337db2a3267caa5d49
>> (Add 32-bit versions of open file/close file).
>> 
>> --- a/core/comboot.inc
>> +++ b/core/comboot.inc
>> @@ -517,7 +517,12 @@ comapi_textmode:
>>  ; INT 22h AX=0006h Open file
>>  ;
>>  comapi_open:
>> + mov es,P_ES
>> + mov si,P_SI
>>  pm_call pm_open_file
>> + mov P_EAX,eax
>> + mov P_CX,cx
>> + mov P_SI,si
>>  ret
>>  
>>  ;
>> 
> 
> That looks like ( (    } } )
> 
> 
> 
> Stappers
> expecting something like
>>  ; INT 22h AX=0006h Open file
>>  ;
>>  comapi_open:
>> + mov es,P_ES
>> + mov si,P_SI
> * + mov cx,P_CX
> * + mov eax,P_EAX
>>  pm_call pm_open_file
>> + mov P_EAX,eax
>> + mov P_CX,cx
>> + mov P_SI,si
> * + mov P_ES,es
>>  ret
>>  
>>  ;
>From doc/comboot.txt
AX=0006h [2.08] Open file

        Input:  AX      0006h
                ES:SI   null-terminated filename
        Output: SI      file handle
                EAX     length of file in bytes, or -1
                CX      file block size

My patch only cares about the output registers (EAX, CX and SI) and only ES and
SI
are used inside pm_open_file(). So there is no need to pass (correct) EAX and CX
register values to pm_open_file() nor restore ES; P_ES should still contain the
correct
input value on exit.

Sebastian

Op 20100514 om 20:07 schreef Sebastian Herbszt:
> Geert Stappers wrote:
>> expecting something like
>>>  ; INT 22h AX=0006h Open file
>>>  ;
>>>  comapi_open:
>>> + mov es,P_ES
>>> + mov si,P_SI
>>* + mov cx,P_CX
>>* + mov eax,P_EAX
>>>  pm_call pm_open_file
>>> + mov P_EAX,eax
>>> + mov P_CX,cx
>>> + mov P_SI,si
>>* + mov P_ES,es
>>>  ret
>>>   ;
>
>> From doc/comboot.txt
>
> AX=0006h [2.08] Open file
>
>        Input:  AX      0006h
>                ES:SI   null-terminated filename
>        Output: SI      file handle
>                EAX     length of file in bytes, or -1
>                CX      file block size
>
> My patch only cares about the output registers (EAX, CX and SI) and only ES
and SI
> are used inside pm_open_file(). So there is no need to pass (correct) EAX
and CX
> register values to pm_open_file() nor restore ES; P_ES should still contain
the correct
> input value on exit.
Thanks for the clarification.


Stappers