linux-kernel - RE: Re: Re: [PATCH] RDMA/siw: Fix compiler warnings on 32-bit due to u64/pointer abuse

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Date:   Mon, 19 Aug 2019 14:52:13 +0000
From:   "Bernard Metzler" <BMT@...ich.ibm.com>
To:     "Jason Gunthorpe" <jgg@...pe.ca>
Cc:     "Geert Uytterhoeven" <geert@...ux-m68k.org>,
        "Doug Ledford" <dledford@...hat.com>, linux-rdma@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: RE: Re: Re: [PATCH] RDMA/siw: Fix compiler warnings on 32-bit due to
 u64/pointer abuse

-----"Jason Gunthorpe" <jgg@...pe.ca> wrote: -----

>To: "Bernard Metzler" <BMT@...ich.ibm.com>
>From: "Jason Gunthorpe" <jgg@...pe.ca>
>Date: 08/19/2019 04:19PM
>Cc: "Geert Uytterhoeven" <geert@...ux-m68k.org>, "Doug Ledford"
><dledford@...hat.com>, linux-rdma@...r.kernel.org,
>linux-kernel@...r.kernel.org
>Subject: [EXTERNAL] Re: Re: Re: [PATCH] RDMA/siw: Fix compiler
>warnings on 32-bit due to u64/pointer abuse
>
>On Mon, Aug 19, 2019 at 02:15:36PM +0000, Bernard Metzler wrote:
>> 
>> >To: "Bernard Metzler" <BMT@...ich.ibm.com>
>> >From: "Jason Gunthorpe" <jgg@...pe.ca>
>> >Date: 08/19/2019 03:52PM
>> >Cc: "Geert Uytterhoeven" <geert@...ux-m68k.org>, "Doug Ledford"
>> ><dledford@...hat.com>, linux-rdma@...r.kernel.org,
>> >linux-kernel@...r.kernel.org
>> >Subject: [EXTERNAL] Re: Re: [PATCH] RDMA/siw: Fix compiler
>warnings
>> >on 32-bit due to u64/pointer abuse
>> >
>> >On Mon, Aug 19, 2019 at 01:36:11PM +0000, Bernard Metzler wrote:
>> >> >If the value is really a kernel pointer, then it ought to be
>> >printed
>> >> >with %p. We have been getting demanding on this point lately in
>> >RDMA
>> >> >to enforce the ability to keep kernel pointers secret.
>> >> >
>> >> >> -			wqe->sqe.sge[0].laddr = (u64)&wqe->sqe.sge[1];
>> >> >> +			wqe->sqe.sge[0].laddr = (uintptr_t)&wqe->sqe.sge[1];
>> >> >
>> >> >[..]
>> >> >
>> >> >>  			rv = siw_rx_kva(srx,
>> >> >> -					(void *)(sge->laddr + frx->sge_off),
>> >> >> +					(void *)(uintptr_t)(sge->laddr + frx->sge_off),
>> >> >>  					sge_bytes);
>> >> >
>> >> >Bernard, this is nonsense, what is going on here with
>sge->laddr
>> >that
>> >> >it can't be a void *?
>> >> >
>> >> siw_sge is defined in siw-abi.h. We make the address u64 to keep
>> >the ABI
>> >> arch independent.
>> >
>> >Eh? How does the siw-abi.h store a kernel pointer? Sounds like
>kernel
>> >and user types are being mixed.
>> >
>> 
>> siw-abi.h defines the work queue elements of a siw send queue.
>> For user land, the send queue is mmapped. Kernel or user land
>> clients write to its send queue when posting work
>> (SGE: buffer address, length, local key). 
>
>Should have different types.. Don't want to accidently mix a laddr
>under user control with one under kernel control.
>
Well we have an unsigned 64bit for both user and kernel
application buffer addresses throughout the rdma stack, and
we have it on the wire for all transports as well. Why do
we want to have it differently for the siw driver? 

Thanks and best regards
Bernard.