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Message-ID: <7f245da80806050302m6b449e6m1f84dc7ef7efff46@mail.gmail.com>
Date:	Thu, 5 Jun 2008 15:32:42 +0530
From:	"Chetan Nanda" <chetannanda@gmail.com>
To:	linux-mips@linux-mips.org
Subject: understanding head.S
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Hi All,
I was reading the boot code for MIPS.
in head.S file before jumping to 'start_kernel' it calculate the stack
pointer address as follow:

"
	PTR_LA		$28, init_thread_union
	PTR_ADDIU	sp, $28, _THREAD_SIZE - 32
	set_saved_sp	sp, t0, t1
	PTR_SUBU	sp, 4 * SZREG		# init stack pointer
"

Can anyone please explains me this 4 lines of code?
Why ' _THREAD_SIZE - 32' is added in 'sp' ?
What 'set_saved_sp' will do ?
and then why we subtract '4 * SZREG' from 'sp' ?

Please hep me to understand this code better.

Thanks,
Chetan Nanda