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

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Message-ID: <20190819150723.GH5058@ziepe.ca>
Date:   Mon, 19 Aug 2019 12:07:23 -0300
From:   Jason Gunthorpe <jgg@...pe.ca>
To:     Bernard Metzler <BMT@...ich.ibm.com>
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

On Mon, Aug 19, 2019 at 02:52:13PM +0000, Bernard Metzler 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, 

We do not. Kernel addresses are consistenyly void * or dma_addr_t

Most places that consume a data address are using lkeys anyhow, which
does have a lkey & u64, but that u64 is not a application buffer
address, but the IOVA of the lkey, which is very different.

I really have no idea why siw needs to mix kernel VAs with user
pointers, particularly in wqes...

Jason