From mboxrd@z Thu Jan  1 00:00:00 1970
From: Glauber Costa <glommer@parallels.com>
Subject: Re: [patch 10/16] x86: vdso: pvclock gettime support
Date: Thu, 1 Nov 2012 18:41:46 +0400
Message-ID: <50928A2A.70104@parallels.com>
References: <20121031224656.417434866@redhat.com> <20121031224824.293748067@redhat.com>
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Cc: <kvm@vger.kernel.org>, <johnstul@us.ibm.com>, <jeremy@goop.org>,
	<zamsden@gmail.com>, <gleb@redhat.com>, <avi@redhat.com>,
	<pbonzini@redhat.com>
To: Marcelo Tosatti <mtosatti@redhat.com>
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On 11/01/2012 02:47 AM, Marcelo Tosatti wrote:
> +#ifdef CONFIG_PARAVIRT_CLOCK
> +
> +static notrace const struct pvclock_vsyscall_time_info *get_pvti(int cpu)
> +{
> +	const aligned_pvti_t *pvti_base;
> +	int idx = cpu / (PAGE_SIZE/PVTI_SIZE);
> +	int offset = cpu % (PAGE_SIZE/PVTI_SIZE);
> +
> +	BUG_ON(PVCLOCK_FIXMAP_BEGIN + idx > PVCLOCK_FIXMAP_END);
> +
> +	pvti_base = (aligned_pvti_t *)__fix_to_virt(PVCLOCK_FIXMAP_BEGIN+idx);
> +
> +	return &pvti_base[offset].info;
> +}
> +
Does BUG_ON() really do what you believe it does while in userspace
context? We're not running with the kernel descriptors, so this will
probably just kill the process without any explanation