some question about arch/x86/kernel/head_64.S

some question about arch/x86/kernel/head_64.S

[xiaoqiang zhao]

Hello:

After kernel is decompressed, the kernel will execute startup_64 and
the first two instructions are:

    leaq    _text(%rip), %rbp
    subq    $_text - __START_KERNEL_map, %rbp

I tried to understand them but can not figure out what rbp contains
after this two instructions. Anybody give me a clear explanation?

Thanks a lot!

回复：Re: some question about arch/x86/kernel/head_64.S

[hitmoon]

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回复：Re: some question about arch/x86/kernel/head_64.S

[Mike Krinkin]

On Wed, Dec 30, 2015 at 08:04:19PM +0800, hitmoon wrote:
> Thank you mike!
> so ?after the first instruction ?rbp contains the offset of actually loaded
> address, which equals the physical address.

yes, comment above says that at that point "someone has loaded an identity
mapped page table", so it should be equal to the physical address.

> $_text - __START_KERNEL_map contains the expected physical address .
> Right ?

yes, as far as i can tell.

回复：Re: 回复：Re: some question about arch/x86/kernel/head_64.S

[hitmoon]

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