Re: [Freedos-kernel] Re: [Freedos-cvs] kernel/kernel intwrap.asm,NONE,1.1.2.1
Hi! 20-Ноя-2005 13:50 [EMAIL PROTECTED] (Kenneth J. Davis) wrote to freedos-kernel@lists.sourceforge.net: >>>int13iret: >>>inc sp ; clean up stack >>>inc sp >>>sti ; ensure int's are renabled >>>retf 2 ; return to caller leaving flags asis >> I don't think that this is right way, because caller may disable >> interrupts for own purposes, whereas here interrupts enabled. KJD> I'm not sure what is correct here, I suggest, only returned ZF/CF should be copied to existing value on stack. For example: int13iret: pushax lahf pushbp mov bp,sp and byte [bp+10],not 0C1h ; 10=bp+ax+...+cs:ip and ah,0C1h ; remain only SF/ZF/CF flags or byte [bp+10],ah ; pass to caller SF/ZF/CF from INT13 pop bp pop ax add sp,2 iret KJD> but I suppose it should simply leave KJD> the flag as the user had it (I think I added this after reading a note KJD> somewhere in RBIL about a bug in earlier BIOSes that failed to do this). --- This SF.Net email is sponsored by the JBoss Inc. Get Certified Today Register for a JBoss Training Course. Free Certification Exam for All Training Attendees Through End of 2005. For more info visit: http://ads.osdn.com/?ad_id=7628&alloc_id=16845&op=click ___ Freedos-kernel mailing list Freedos-kernel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/freedos-kernel
Re: [Freedos-kernel] Re: [Freedos-cvs] kernel/kernel intwrap.asm,NONE,1.1.2.1
Arkady V.Belousov wrote: Hi! 20-Ноя-2005 16:57 [EMAIL PROTECTED] (Kenneth Davis) wrote to [EMAIL PROTECTED]: --- NEW FILE: intwrap.asm --- reloc_call_int13_handler: cli ; disable other interrupts for now INT instruction already disables IFlag. stc ; force error unless BIOS clears ?! This is issue of caller to set or reset CFlag. push dx ; store BIOS drive # for error handling usage push ds ; get segment of kernel DATA mov ds, [cs:_DGROUP_] pushf ; simulate int call so returns back here (flags+cs:ip on stack) call far [ds:_UserInt13] Bug!!! Here DS register is garbaged, whereas it used by some functions (for example, INT13/42). good catch, I rewrote this section several times until I finally tracked down my problem was my usual init-time variables don't match run-time variables [address wise, though the compiler thinks they do, so the UserInt13 initialized wasn't the one used] unless special care is taken. Earlier versions had a different path for ah < 17h versus ah > 17h, which I need to re-add (as the error values returned do not make sense for most functions ah > 17h, but even if not returned, still within same error code group for those less; that or just change it to check on int13/16h ) pop ds ; restore ds jc int13err ; test if error, if not return to caller int13iret: inc sp ; clean up stack inc sp sti ; ensure int's are renabled retf 2 ; return to caller leaving flags asis I don't think that this is right way, because caller may disable interrupts for own purposes, whereas here interrupts enabled. I'm not sure what is correct here, but I suppose it should simply leave the flag as the user had it (I think I added this after reading a note somewhere in RBIL about a bug in earlier BIOSes that failed to do this). int13wrap: %IF XCPU < 186 push ax ; preserve registers, setup stack frame push bp mov bp, sp mov ax, 13h; want to push 0x13 onto stack xchg ax, [bp+2] ; so restore pushed ax value and put 0x13 on stack pop bp ; clean up stack frame (leaving just 0x13 pushed on stack) pushbp pushbp mov bp,sp mov word [bp+2],13h pop bp I like it, cleaner and removes the easy to overlook restoration of ax Thanks for reviewing these patches, Jeremy --- This SF.Net email is sponsored by the JBoss Inc. Get Certified Today Register for a JBoss Training Course. Free Certification Exam for All Training Attendees Through End of 2005. For more info visit: http://ads.osdn.com/?ad_idv28&alloc_id845&op=click ___ Freedos-kernel mailing list Freedos-kernel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/freedos-kernel
[Freedos-kernel] Re: [Freedos-cvs] kernel/kernel intwrap.asm,NONE,1.1.2.1
Hi! 20-Ноя-2005 16:57 [EMAIL PROTECTED] (Kenneth Davis) wrote to [EMAIL PROTECTED]: > --- NEW FILE: intwrap.asm --- > reloc_call_int13_handler: > cli ; disable other interrupts for now INT instruction already disables IFlag. > stc ; force error unless BIOS clears ?! This is issue of caller to set or reset CFlag. > push dx ; store BIOS drive # for error handling usage > push ds ; get segment of kernel DATA > mov ds, [cs:_DGROUP_] > pushf ; simulate int call so returns back here (flags+cs:ip on > stack) > call far [ds:_UserInt13] Bug!!! Here DS register is garbaged, whereas it used by some functions (for example, INT13/42). > pop ds ; restore ds > jc int13err ; test if error, if not return to caller > int13iret: > inc sp ; clean up stack > inc sp > sti ; ensure int's are renabled > retf 2 ; return to caller leaving flags asis I don't think that this is right way, because caller may disable interrupts for own purposes, whereas here interrupts enabled. > int13wrap: > %IF XCPU < 186 > push ax ; preserve registers, setup stack frame > push bp > mov bp, sp > mov ax, 13h; want to push 0x13 onto stack > xchg ax, [bp+2] ; so restore pushed ax value and put 0x13 on stack > pop bp ; clean up stack frame (leaving just 0x13 pushed on stack) pushbp pushbp mov bp,sp mov word [bp+2],13h pop bp --- This SF.Net email is sponsored by the JBoss Inc. Get Certified Today Register for a JBoss Training Course. Free Certification Exam for All Training Attendees Through End of 2005. For more info visit: http://ads.osdn.com/?ad_id=7628&alloc_id=16845&op=click ___ Freedos-kernel mailing list Freedos-kernel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/freedos-kernel
