linux-kernel - Re: [PATCH] ioatdma: silence GCC warnings

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Message-ID: <20130715094016.GP16653@intel.com>
Date:	Mon, 15 Jul 2013 15:10:16 +0530
From:	Vinod Koul <vinod.koul@...el.com>
To:	Paul Bolle <pebolle@...cali.nl>
Cc:	Dan Williams <djbw@...com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ioatdma: silence GCC warnings

On Mon, Jul 15, 2013 at 11:50:07AM +0200, Paul Bolle wrote:
> On Mon, 2013-06-17 at 12:35 +0200, Paul Bolle wrote:
> > Building dma_v3.o triggers two GCC warnings:
> >     drivers/dma/ioat/dma_v3.c: In function ‘__ioat3_prep_pq16_lock’:
> >     drivers/dma/ioat/dma_v3.c:264:11: warning: array subscript is below array bounds [-Warray-bounds]
> >     drivers/dma/ioat/dma_v3.c:264:11: warning: array subscript is below array bounds [-Warray-bounds]
> > 
> > These warnings are caused by pq16_set_src(). It uses "int idx" as an
> > index to an eight element array. Changing "idx" to unsigned int silences
> > these warnings. Apparently GCC can then determine that "idx" will never
> > be negative.
> > 
> > Signed-off-by: Paul Bolle <pebolle@...cali.nl>
> 
> Identical warnings can still be seen in v3.11-rc1. Did anyone had a
> chance to look at this patch?
Looks okay to me. Dan do you want this to go thru my tree with you Ack of
course...

~Vinod
> 
> 
> Paul Bolle
> > ---
> > 0) Compile tested only.
> > 
> > 1) These warning were introduced in v3.10-rc1. That must have been
> > through commit 7727eaa449 ("ioatdma: Adding support for 16 src PQ ops
> > and super extended descriptors").
> > 
> >  drivers/dma/ioat/dma_v3.c | 5 +++--
> >  1 file changed, 3 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/dma/ioat/dma_v3.c b/drivers/dma/ioat/dma_v3.c
> > index ca6ea9b..b5102da 100644
> > --- a/drivers/dma/ioat/dma_v3.c
> > +++ b/drivers/dma/ioat/dma_v3.c
> > @@ -251,7 +251,7 @@ static bool is_bwd_noraid(struct pci_dev *pdev)
> >  }
> >  
> >  static void pq16_set_src(struct ioat_raw_descriptor *desc[3],
> > -			dma_addr_t addr, u32 offset, u8 coef, int idx)
> > +			dma_addr_t addr, u32 offset, u8 coef, unsigned int idx)
> >  {
> >  	struct ioat_pq_descriptor *pq = (struct ioat_pq_descriptor *)desc[0];
> >  	struct ioat_pq16a_descriptor *pq16 =
> > @@ -1180,7 +1180,7 @@ __ioat3_prep_pq16_lock(struct dma_chan *c, enum sum_check_flags *result,
> >  	struct ioat_pq_descriptor *pq;
> >  	u32 offset = 0;
> >  	u8 op;
> > -	int i, s, idx, num_descs;
> > +	int i, idx, num_descs;
> >  
> >  	/* this function only handles src_cnt 9 - 16 */
> >  	BUG_ON(src_cnt < 9);
> > @@ -1206,6 +1206,7 @@ __ioat3_prep_pq16_lock(struct dma_chan *c, enum sum_check_flags *result,
> >  	do {
> >  		struct ioat_raw_descriptor *descs[4];
> >  		size_t xfer_size = min_t(size_t, len, 1 << ioat->xfercap_log);
> > +		unsigned int s;
> >  
> >  		desc = ioat2_get_ring_ent(ioat, idx + i);
> >  		pq = desc->pq;
> 

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