Robert P. J. Day wrote:
On Fri, 25 Apr 2008, Peter Teoh wrote:
In general, user cannot see kernel memory, but kernel can see user
memory. To enforce this, all memory are not to be shared. And this
is also enforce at the x86 hardware level - no OS feature is needed
(ie, windows/l
Correct me if wrong, according to my aging memory, the Intel x86
architecture actually have individual stack for each ring. So
ring0,1,2,3 everyone have one ring. Normal OS only uses 0 and 3,
but VMWare uses an additional ring1, and XEN HVM uses ring "-1", for
its hypervisor implementation.
On Don, 2008-04-24 at 18:52 +0200, Michael Blizek wrote:
> On 17:49 Thu 24 Apr , Bernd Petrovitsch wrote:
> > On Don, 2008-04-24 at 17:08 +0200, Michael Blizek wrote:
> > > It is not just cleaning the stack up. You have to make sure that no other
> > > thread in the userspace accesses it. This
On Fri, 25 Apr 2008, Peter Teoh wrote:
> In general, user cannot see kernel memory, but kernel can see user
> memory. To enforce this, all memory are not to be shared. And this
> is also enforce at the x86 hardware level - no OS feature is needed
> (ie, windows/linux all worked in the same way).
On Fri, 2008-04-25 at 00:54 +0800, Peter Teoh wrote:
> this violate the first principle mentioned above.the current CPU
> may be processing in kernel mode, but another CPU may be processing in
> userspace mode, same process, and as all the userspace memory are
> visible to him, he can view the
On 17:49 Thu 24 Apr , Bernd Petrovitsch wrote:
> On Don, 2008-04-24 at 17:08 +0200, Michael Blizek wrote:
> > It is not just cleaning the stack up. You have to make sure that no other
> > thread in the userspace accesses it. This means you have to unmap it first.
>
> Uuugh, that looks like a q
On Thu, 2008-04-24 at 21:09 +0530, sahlot arvind wrote:
> I feel there are two stacks for security reasons but I dont know what
> they are precisely.
there are both read and write security questions.. on the read side
you're concerned about data you leave behind (or the cost of zeroing it)
- reme
In general, user cannot see kernel memory, but kernel can see user
memory. To enforce this, all memory are not to be shared. And this
is also enforce at the x86 hardware level - no OS feature is needed
(ie, windows/linux all worked in the same way)the keyword to
search is called "stack swit
On Don, 2008-04-24 at 17:08 +0200, Michael Blizek wrote:
> Hi!
>
> On 14:41 Thu 24 Apr , sahlot arvind wrote:
> > Why do we have two stacks per process i.e. one user mode and other kernel
> > mode?
> > As soon as process enters into kernel mode it starts using kernel mode
> > stack, but as soo
>pre-process "thread_info" structure at the bottom of the >kernel stack.
>in short, that per-process stack has to exist the whole time >the
>process does, since it's actually keeping track of some >process
>information. you couldn't do that if you just used the >user-space stack.
Why could not we
On Thu, 2008-04-24 at 09:35 -0400, Robert P. J. Day wrote:
> On Thu, 24 Apr 2008, sahlot arvind wrote:
>
> > Yes. I agree with Robert. There are two stacks per process. But why
> > cannot we just use one stack as I said earlier?
>
> while there may be other reasons, there's one obvious one -- as
Hi!
On 14:41 Thu 24 Apr , sahlot arvind wrote:
> Why do we have two stacks per process i.e. one user mode and other kernel
> mode?
> As soon as process enters into kernel mode it starts using kernel mode
> stack, but as soon as it comes out of kernel mode stack there is nothing in
> the kernel
On Thu, 24 Apr 2008, sahlot arvind wrote:
> Yes. I agree with Robert. There are two stacks per process. But why
> cannot we just use one stack as I said earlier?
while there may be other reasons, there's one obvious one -- as i
mentioned in my earlier email, the kernel likes to store a small,
pre
Yes. I agree with Robert. There are two stacks per process. But why cannot
we just use one stack as I said earlier?
- A
On 4/24/08, Robert P. J. Day <[EMAIL PROTECTED]> wrote:
>
> On Thu, 24 Apr 2008, dinesh bansal wrote:
>
> > AFAIK there is only one kernel stack and all the processes share
> >
On Thu, 24 Apr 2008, dinesh bansal wrote:
> AFAIK there is only one kernel stack and all the processes share
> that space.
this is incorrect -- each process has its own personal kernel stack
area.
rday
Robert P. J. Day
Lin
On Thu, Apr 24, 2008 at 2:41 PM, sahlot arvind <[EMAIL PROTECTED]> wrote:
> Why do we have two stacks per process i.e. one user mode and other kernel
> mode?
> As soon as process enters into kernel mode it starts using kernel mode
> stack, but as soon as it comes out of kernel mode stack there is
Why do we have two stacks per process i.e. one user mode and other kernel
mode?
As soon as process enters into kernel mode it starts using kernel mode
stack, but as soon as it comes out of kernel mode stack there is nothing in
the kernel mode stack. So cannot we simply have a single stack i.e. just
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