matrix reloaded (matrix_reloaded18@xxxxxxxxxxxxxx) wrote: > If it's so, then what is the significance of __pa and __va ? > Could you please throw some light on this ... > > Thanks. > Sumit. Hi, kernel memory is placed before PAGE_OFFSET 0xC0000000. So __pa() and __va() translate virtual adress to real and real to virtual. But a read of code would be better ;-) http://lxr.linux.no/source/include/asm-i386/page.h?v=2.4.26 http://kos.enix.org/pub/intelvol1.pdf.gz http://kos.enix.org/pub/intelvol2.pdf.gz http://kos.enix.org/pub/intelvol3.pdf.gz The three lastest are pointer to ia32 book. Hope this help. > On Mon, 09 Aug 2004 Ed L Cashin wrote : > >"matrix reloaded" <matrix_reloaded18@xxxxxxxxxxxxxx> writes: > > > > > Hi, > > > Sorry if this kinda request has already been logged in this mailing list. I would > > > like to know how the interpretation of Kernel Address and User Address is > made. I > > > mean to say that how does mmu know that it needs to call __pa(x) or __va(x) > for > > > Kernel Adderss and others for user address ? Could you also tell me where this > > > code is exactly present ? > > > >It doesn't. On x86, it has a pointer to the base of the page tables > >in control register three. When it's translating a virtual address it > >uses the page tables found there to resolve any translation that isn't > >already in the TLB. It's the same whether the CPU is running in ring > >0 (kernel) or ring 3 (userland). -- Amicalement/Regards Christophe ----------------------------------------------------------------- Christophe Lucas <c.lucas@xxxxxxxxxxx> developer/sysadmin Registered User #271267 http://odie.mcom.fr/~clucas/ RotomaLUG member (http://www.rotomalug.org) gpg dsa: 0x1E87C874 ----------------------------------------------------------------- Se tromper est humain ; Vraiment foutre la merde necessite le mot de passe de root.
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