x86/kernel/head_32.S

[Valdis.Kletnieks at vt.edu]

On Fri, 05 Dec 2014 17:50:40 +0800, 孙建希 said:
>
> I am confused by `leal -__PAGE_OFFSET(%ecx),%esp`.
> `pa(stack_start)` have convert `stack_start` to physicall address.
> why we need `-__PAGE_OFFSET(%ecx)` instead of `%ecx`?

>From the commit message:

"This retains start_stack as a virtual address, even though a physical
address would be more convenient for 32 bits;"

In other words, pa() converted it to a physical adddress - and now we're
converting it back to a virtual address....
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