linux-kernel - Re: [PATCH] x86, vdso32: fix out of memory handling setup vDSO

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Message-ID: <1395315494.1127.3.camel@vger.seibold.net>
Date:	Thu, 20 Mar 2014 12:38:14 +0100
From:	Stefani Seibold <stefani@...bold.net>
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	gregkh@...uxfoundation.org, linux-kernel@...r.kernel.org,
	x86@...nel.org, mingo@...hat.com, hpa@...or.com,
	ak@...ux.intel.com, aarcange@...hat.com, john.stultz@...aro.org,
	luto@...capital.net, xemul@...allels.com, gorcunov@...nvz.org,
	andriy.shevchenko@...ux.intel.com, Martin.Runge@...de-schwarz.com,
	Andreas.Brief@...de-schwarz.com
Subject: Re: [PATCH] x86, vdso32: fix out of memory handling setup vDSO

Am Donnerstag, den 20.03.2014, 10:53 +0100 schrieb Thomas Gleixner:
> On Thu, 20 Mar 2014, Stefani Seibold wrote:
> 
> > This patch add a correct out of memory handling for setup a 32 bit vDSO.
> > 
> > The patch is against tip commit 4e40112c4ff6a577dd06d92b2a54cdf06265bf74
> > 
> > Signed-off-by: Stefani Seibold <stefani@...bold.net>
> > ---
> >  arch/x86/vdso/vdso32-setup.c | 17 ++++++++++++++++-
> >  1 file changed, 16 insertions(+), 1 deletion(-)
> > 
> > diff --git a/arch/x86/vdso/vdso32-setup.c b/arch/x86/vdso/vdso32-setup.c
> > index 0bc363a..e1171c2 100644
> > --- a/arch/x86/vdso/vdso32-setup.c
> > +++ b/arch/x86/vdso/vdso32-setup.c
> > @@ -134,8 +134,14 @@ int __init sysenter_setup(void)
> >  	}
> >  
> >  	vdso32_size = (vdso_len + PAGE_SIZE - 1) / PAGE_SIZE;
> > -	vdso32_pages = kmalloc(sizeof(*vdso32_pages) * vdso32_size, GFP_ATOMIC); 
> > +
> > +	vdso32_pages = kmalloc(sizeof(*vdso32_pages) * vdso32_size, GFP_ATOMIC);
> 
> Why is this GFP_ATOMIC and not GFP_ATOMIC ?
> 
> That code is called either from identify_boot_cpu(), where GFP_KERNEL
> is perfectly valid and from subsys_initcall(sysenter_setup) which is
> way late in the boot process where GFP_KERNEL is the RightThing.
> 
> Aside of that, why do we need to call it early for X86_32 and late for
> X86_64?
> 
> We need the vdso before we head off to user space, but not in the
> early boot process.
> 

All complains are design decisions not made by me. I will send a patch
for the GFP_ATOMIC thing. For the other one it would be the best to ask
Andy for the reason.

- Stefani



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