About signal stack

[Xianglong Huang]

Hi there,

Now I am implementing sigaltstack() system call in a simulator. What
confused me is that I thought the signal stack is pointed by the register
sp. I mean, while the signal handler is running, it will use the address
of signal stack as its stack pointer and run the function on this stack.
But I found by GDB that it is not the case. After I use sigaltstack() in
the program and invoked the signal handler, the sp is not changed by the
value I gave to signal stack by sigaltstack().

My question is: What is the signal stack used for if it is not to replace
the stack pointer? How can I check the value of signal stack by GDB?
Thanks a lot!

Regards,
Long

ps: Please cc the answer to my email address because I am not on the
list. Thanks