2008/8/14 Vesa Jääskeläinen <[EMAIL PROTECTED]>: > Javier Martín wrote: >> Hi there everybody, >> >> I'm opening the RFC because I want to add some kind of infrastructure to >> retrieve the address of system/platform structures. I will explain >> myself: my use case is in i386-pc and for the drivemap module, in which >> a function installs a TSR int13h handler. This requires the function to >> have access to two real mode structures, namely the BIOS Data Area, >> which is based at 0040:0000h; and the Interrupt Vector Table, which >> conventionally starts at 0 but that could have been placed elsewhere by >> the use of the LIDT instruction. > > But it is designed to use linear address space for memory so no need to > worry about it. I do not see any reason why there would be paging or > non-linear memory mapping in GRUB 2 (i386-pcbios). Yes, but this is a "kernel" design decision that is specified nowhere to the modules writers. Thus, this could change tomorrow and the scheme would break down. > > Or did I miss something? > > So basically I do not see need for such services. As this does not even > need to be platform independent. > > If you need to alter IVT you can modify it on the fly. Though you have > to remember where to use only LOW mem addresses in there. Not just low mem addresses, I need to compute the real mode far pointer (seg:off). Besides, while the BDA always starts at 0040:0000, the IVT could have been relocated by either the BIOS or GRUB itself, so I need to use SIDT, which is not a privileged instruction itself but requires a privileged drop to r-mode to get the IVT address instead of the pmode IDT.
-Habbit > > > _______________________________________________ > Grub-devel mailing list > Grub-devel@gnu.org > http://lists.gnu.org/mailman/listinfo/grub-devel >
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