v2p | Implementation of x86 paging translation | Model View Controller library

When dealing with paging the golden rule is "never store physical addresses in any kind of pointer". The reasons are:

a) They aren't virtual addresses and can't be dereferenced, so it's better to make bugs obvious by ensuring you get compile time errors if you try to use a physical address as a pointer.

b) In some cases physical addresses are a different size to virtual addresses (e.g. "PAE paging" in 80x86 where virtual addresses are still 32-bit but physical addresses are potentially up to 52 bits); and it's better (for portability - e.g. so that PAE support can be added to XV6 easier at some point).

With this in mind your first line of code is an obvious bug (it breaks the "golden rule"). It should either be pde_t physPgDir = V2P(p->pgdir); or pde_t * pgDir = p->pgdir;. I'll let you figure out which (as I suspect it's homework, and I'm confident that by adhering to the "golden rule" you'll solve your own problem).

You can use the set_z_index method to set the z_index property of the parallelogram to a value less than that of the arrows.

Here I have set it to a lower value than that of v1:

This answer to the question you mentioned points to: https://askubuntu.com/questions/41930/kernel-panic-not-syncing-vfs-unable-to-mount-root-fs-on-unknown-block0-0/1048477#1048477 which contains a detailed diagnosis procedure for this error.

For that and from the kernel message, we see clearly that root= kernel CLI parameter is incorrect: the default sda1 was used instead of the required sda.

On fs.py, the correct root= can be set with:

Though it looks different from the common byte address system, actually there's nothing to do between the address assignment and the bit length of data that is pointed to by the address. The data which is accessed is called a 'word'. The serial ports of the ADE7978 can work with 32-, 16-, or 8-bit words. Continuing reading the register table, you'll find different registers that have 32- or 16- or 8-bit length, and still their addresses are incremented by 1.

The register table in a programmer's model is somewhat like this: