[PATCH] proc: fix ->stack_start in compat mode

[PATCH] proc: fix ->stack_start in compat mode

[Alexey Dobriyan]

Assign tsk->stack_start even when doing compat execve(2).

As side effect, fix segfault inside boehm-gc library.
http://bugzilla.kernel.org/show_bug.cgi?id=14478

Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
---

 Michael, please, confirm.

 Stefani, I get "Stack usage: 0 kB", you may want to look at it.

 fs/compat.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/fs/compat.c
+++ b/fs/compat.c
@@ -1532,6 +1532,8 @@ int compat_do_execve(char * filename,
 	if (retval < 0)
 		goto out;
 
+	current->stack_start = current->mm->start_stack;
+
 	/* execve succeeded */
 	current->fs->in_exec = 0;
 	current->in_execve = 0;

Re: [PATCH] proc: fix ->stack_start in compat mode

[Stefani Seibold]

Am Mittwoch, den 28.10.2009, 14:56 +0300 schrieb Alexey Dobriyan:
> Assign tsk->stack_start even when doing compat execve(2).
> 
> As side effect, fix segfault inside boehm-gc library.
> http://bugzilla.kernel.org/show_bug.cgi?id=14478
> 
> Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
> ---
> 
>  Michael, please, confirm.
> 
>  Stefani, I get "Stack usage: 0 kB", you may want to look at it.
> 

Under which circumstance do you get 0 kb reported? What is your system
(mmu/nommu, 32bit/64bit, architecture and so on).

Stefani

Re: [PATCH] proc: fix ->stack_start in compat mode

[Alexey Dobriyan]

On Sun, Nov 01, 2009 at 10:54:05AM +0100, Stefani Seibold wrote:
> Am Mittwoch, den 28.10.2009, 14:56 +0300 schrieb Alexey Dobriyan:
> > Assign tsk->stack_start even when doing compat execve(2).
> > 
> > As side effect, fix segfault inside boehm-gc library.
> > http://bugzilla.kernel.org/show_bug.cgi?id=14478
> > 
> > Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
> > ---
> > 
> >  Michael, please, confirm.
> > 
> >  Stefani, I get "Stack usage: 0 kB", you may want to look at it.
> > 
> 
> Under which circumstance do you get 0 kb reported? What is your system
> (mmu/nommu, 32bit/64bit, architecture and so on).

i386 userpace, x86_64 kernel

Re: [PATCH] proc: fix ->stack_start in compat mode

[Alexey Dobriyan]

On Sun, Nov 01, 2009 at 10:54:05AM +0100, Stefani Seibold wrote:
> Am Mittwoch, den 28.10.2009, 14:56 +0300 schrieb Alexey Dobriyan:
> > Assign tsk->stack_start even when doing compat execve(2).
> > 
> > As side effect, fix segfault inside boehm-gc library.
> > http://bugzilla.kernel.org/show_bug.cgi?id=14478
> > 
> > Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
> > ---
> > 
> >  Michael, please, confirm.
> > 
> >  Stefani, I get "Stack usage: 0 kB", you may want to look at it.
> > 
> 
> Under which circumstance do you get 0 kb reported? What is your system
> (mmu/nommu, 32bit/64bit, architecture and so on).

Well, no wonder it doesn't work:

	#define KSTK_ESP(tsk)           -1 /* sorry. doesn't work for syscall. */

How does it supposed to work on live task?

Re: [PATCH] proc: fix ->stack_start in compat mode

[Stefani Seibold]

Am Sonntag, den 01.11.2009, 15:43 +0300 schrieb Alexey Dobriyan:
> On Sun, Nov 01, 2009 at 10:54:05AM +0100, Stefani Seibold wrote:
> > Am Mittwoch, den 28.10.2009, 14:56 +0300 schrieb Alexey Dobriyan:
> > > Assign tsk->stack_start even when doing compat execve(2).
> > > 
> > > As side effect, fix segfault inside boehm-gc library.
> > > http://bugzilla.kernel.org/show_bug.cgi?id=14478
> > > 
> > > Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
> > > ---
> > > 
> > >  Michael, please, confirm.
> > > 
> > >  Stefani, I get "Stack usage: 0 kB", you may want to look at it.
> > > 
> > 
> > Under which circumstance do you get 0 kb reported? What is your system
> > (mmu/nommu, 32bit/64bit, architecture and so on).
> 
> Well, no wonder it doesn't work:
> 
> 	#define KSTK_ESP(tsk)           -1 /* sorry. doesn't work for syscall. */
> 
> How does it supposed to work on live task?

Can you write it in a full sentence? Where did you located this define?

Re: [PATCH] proc: fix ->stack_start in compat mode

[Stefani Seibold]

Am Sonntag, den 01.11.2009, 15:43 +0300 schrieb Alexey Dobriyan:
> > >  Stefani, I get "Stack usage: 0 kB", you may want to look at it.
> > > 
> > 
> > Under which circumstance do you get 0 kb reported? What is your system
> > (mmu/nommu, 32bit/64bit, architecture and so on).
> 
> Well, no wonder it doesn't work:
> 
> 	#define KSTK_ESP(tsk)           -1 /* sorry. doesn't work for syscall. */
> 
> How does it supposed to work on live task?

Okay, you are right. That's really strange. I just build a 64 bit kernel
i will try to fix this odd behavior. This is a break in the kernel API.
KSTP_ESP should return the value of the kernel stack and not a -1. Sh..