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hi

i have a simple question: ive now written some code that boots the pc, switches over to protected mode and then jumps to some other code writen in c...before jumping there i loaded the ds register with a segment descriptor pointing to b8000 so that when in my c code i do something like
the letter A is displayed in the upper left corner. but of course there are 3 more segment registers (es, fs, gs) that *could* be used for video memory instead of having main data register ds point to video memory...is there any way at all to specify in c that for this or that particular memory reference another data register be used, so i can make use of all the 4 data registers without having to refer to assembly???

thanks

martin

Well the simple answer is no. GCC assumes that all segment registers are the same and that they are all have a base of zero IIRC.

sancho1980 wrote:is there any way at all to specify in c that for this or that particular memory reference another data register be used, so i can make use of all the 4 data registers without having to refer to assembly???

C is a platform-independant language. It does not allow for paging nor for segmentation. Paging is wrt this transparent, but segmentation just isn't going to work. There is a part-hack called __thread that allows something like this but I haven't looked into what's generated and/or whether it even works. I think it's FS or GS based access to variables but I'm not quite sure how they're allocated.