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

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Date:	Thu, 20 Mar 2014 10:53:45 +0100 (CET)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Stefani Seibold <stefani@...bold.net>
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

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.

Thanks,

	tglx

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