Messages in this thread | | | Date | Mon, 16 Jul 2007 02:15:00 -0700 | From | "H. Peter Anvin" <> | Subject | Re: RE : Re: RE : Re: x86 setup code rewrite in C - revised |
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Etienne Lorrain wrote:
> BUGS: some implementations (including the original IBM PC) have a bug which > destroys BP > the Trident TVGA8900CL (BIOS dated 1992/9/8) clears DS to 0000h when > scrolling in an SVGA mode (800x600 or higher)
"When scrolling in an SVGA mode", sounds to me like a bug when using BIOS for text output in graphics mode. We don't do that.
>>>>>> Also, I do not know if "m" is right in here: >>>>>> static inline u8 rdfs8(addr_t addr) >>>>>> { >>>>>> u8 v; >>>>>> asm("movb %%fs:%1,%0" : "=r" (v) : "m" (*(u8 *)addr)); >>>>>> return v; >>>>>> } >>>> The "m" is correct right there. >>> strange, "g" would mean anything can go there - and this assembly instruction >>> should accept every access modes. >> Not with an %fs: prefix. It would also allow the compiler to do a move >> into a register "on its own", which would be disastrous, since it would >> lack the prefix. So "m" is correct. > > "mov %fs:(%ebx,%eax,4),%ecx" works for me.
That's an example on what "m" can generate.
"g" could produce stuff like:
mov %fs:$1234,%ecx mov %fs:%eax,%ecx
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