![]() ![]() If someone could explain the logic behind this division in detail would be great. Is it just to make sure that 512HW +512Linux PTE are aligned to a Page boundary ? Thus PAGE_SHIFT is set to 12), then why do we select 11-9-12 layout(i.e. Now the question is Linux does not enforce PGD/PMD/PTE size (however it enforces page size to be 4K. Additionally since Linux memory management expects various flags non native to ARM we define 512 more entries for linux page table(one for each 2nd level HW page table). Here two 4 byte entries are clubbed together and the pointed second level translation tables are laid out one after the other in memory, so that at second level instead of 256 there are 512 entries. Kernel switches page tables when switching processes. I am trying to learn a few things about the linux kernel and I have come across a kind of exercise which asks to implement two system calls on th 4.15.0+ linux kernel which aim at reading the pages from the page table of a process. use index bits of VA to find a page table entry (PTE) construct physical address using PPN from. Where L1 translation table consists of 2048 entries where each entry is 8 bytes. Linux kernel - Syscall Implentation - Page Table Walk. So according to this any virtual address has to be divided into 12-8-12 to map to above scheme.īut on 32 bit ARM linux side this division is 11-9-12. ![]() And each of second level entry translates a 4KB page in memory. At second level it has 256 entries of 4 bytes each. ![]() each entry translates a 1MB region in memory. Linux kernel ARM Translation table base (TTB0 and TTB1)ĪRM hardware has 4096 entries of 4 byte each in L1 translation table. I have read multiple articles on this topic including below but things are still hazy to me: ![]()
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