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Message-ID: <997ef050c13e3654dee6a862d810cffcafce249b.camel@intel.com>
Subject: Re: [PATCH v7 03/14] x86/cet/ibt: Add IBT legacy code bitmap setup
 function
From:   Yu-cheng Yu <yu-cheng.yu@intel.com>
To:     Dave Hansen <dave.hansen@intel.com>, x86@kernel.org,
        "H. Peter Anvin" <hpa@zytor.com>,
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        Balbir Singh <bsingharora@gmail.com>,
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        Dave Hansen <dave.hansen@linux.intel.com>,
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Date:   Fri, 07 Jun 2019 12:23:46 -0700
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References: <20190606200926.4029-1-yu-cheng.yu@intel.com>
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On Fri, 2019-06-07 at 12:03 -0700, Dave Hansen wrote:
> On 6/6/19 1:09 PM, Yu-cheng Yu wrote:
> > +	modify_fpu_regs_begin();
> > +	rdmsrl(MSR_IA32_U_CET, r);
> > +	r |= (MSR_IA32_CET_LEG_IW_EN | bitmap);
> > +	wrmsrl(MSR_IA32_U_CET, r);
> > +	modify_fpu_regs_end();
> 
> Isn't there a bunch of other stuff in this MSR?  It seems like the
> bitmap value would allow overwriting lots of bits in the MSR that have
> nothing to do with the bitmap... in a prctl() that's supposed to only be
> dealing with the bitmap.

Yes, the bitmap address should have been masked, although it is checked for page
alignment (which has the same effect).  I will fix it.

Yu-cheng