Hi,
On 4/10/07, h h <harsh512@xxxxxxxxx> wrote:
Hi,
I am trying to understand how does the stack pointer (for kernel itself) get
setup in head.S. I am specifically looking at MIPS CPU. Here's the code
fragment from arch/mips/kernel/head.S :
PTR_LA $28, init_thread_union
PTR_ADDIU sp, $28, _THREAD_SIZE - 32
The init_thread_union and init_task are statically defined structures
that represent the init task (PID=0). They are defined in
arch/mips/kernel/init_task.c. The thread_union structure represents
the (thread_info + kernel stack).
So the above code is first loading the address of thread_info of init
task into $28. Then it is adding THREAD_SIZE-32 (generaly 8192-32) to
arrive at the kernel stack pointer of init task.
set_saved_sp sp, t0, t1
PTR_SUBU sp, 4 * SZREG # init stack pointer
Ummm ... I'm not sure about this jugglery.
Thanks,
Rajat
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