From mboxrd@z Thu Jan  1 00:00:00 1970
Message-ID: <81344dc3bb1137ca2e54684d0f5d55ef@quanstro.net>
From: erik quanstrom <quanstro@quanstro.net>
Date: Tue,  1 Sep 2009 13:47:22 -0400
To: 9fans@9fans.net
In-Reply-To: <73d734eff7a63db5f42b7fe5210f93fc@quanstro.net>
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Subject: Re: [9fans] lowest valid stack address
Topicbox-Message-UUID: 5ded6ac6-ead5-11e9-9d60-3106f5b1d025

On Tue Sep  1 12:56:41 EDT 2009, quanstro@quanstro.net wrote:
> On Tue Sep  1 12:54:06 EDT 2009, cinap_lenrek@gmx.de wrote:
>
> > read /proc/$pid/segment
>
> how do i know how low the stack segment can go?

i should have been more explicit.  it's not that useful to know
what the current stack allocation is.  it's more useful to know
what the lowest possible stack address could be.
knowing the exact minimum address of my process
doesn't tell me anything about other process' stacks
with which i share memory space.  the address in
question might be on another proc's stack.

i'm also worried that it would not be cheep enough to do
a system call ~50x per mailbox message to check the
sbrk or look at /proc/$pid/segment.  this would mean
500000-1m extra system calls just to open a mailbox.

i suppose that a function like malloctopaddr() would
do that without locking returns the last sbrk.

but i'd settle for the lowest stack address.

- erik