lkml.org 
[lkml]   [2016]   [Oct]   [18]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [PATCH 25/28] s390: pci: don't print uninitialized data for debugging
    On Tue, 18 Oct 2016, Martin Schwidefsky wrote:
    > On Tue, 18 Oct 2016 00:16:13 +0200
    > Arnd Bergmann <arnd@arndb.de> wrote:
    >
    > > gcc correctly warns about an incorrect use of the 'pa' variable
    > > in case we pass an empty scatterlist to __s390_dma_map_sg:
    > >
    > > arch/s390/pci/pci_dma.c: In function '__s390_dma_map_sg':
    > > arch/s390/pci/pci_dma.c:309:13: warning: 'pa' may be used uninitialized in this function [-Wmaybe-uninitialized]
    > >
    > > This adds a bogus initialization to the function to sanitize
    > > the debug output. I would have preferred a solution without
    > > the initialization, but I only got the report from the
    > > kbuild bot after turning on the warning again, and didn't
    > > manage to reproduce it myself.
    > >
    > > Signed-off-by: Arnd Bergmann <arnd@arndb.de>
    > > ---
    > > arch/s390/pci/pci_dma.c | 2 +-
    > > 1 file changed, 1 insertion(+), 1 deletion(-)
    > >
    > > diff --git a/arch/s390/pci/pci_dma.c b/arch/s390/pci/pci_dma.c
    > > index 7350c8b..6b2f72f 100644
    > > --- a/arch/s390/pci/pci_dma.c
    > > +++ b/arch/s390/pci/pci_dma.c
    > > @@ -423,7 +423,7 @@ static int __s390_dma_map_sg(struct device *dev, struct scatterlist *sg,
    > > dma_addr_t dma_addr_base, dma_addr;
    > > int flags = ZPCI_PTE_VALID;
    > > struct scatterlist *s;
    > > - unsigned long pa;
    > > + unsigned long pa = 0;
    > > int ret;
    > >
    > > size = PAGE_ALIGN(size);
    >
    > The compiler is right. pa is set in the for-loop. If "dma_addr < dma_addr_base + size"
    > is never true and __dma_purge_tlb() returns with an error, pa *is* uninitialized.
    > The fix seems sensible to me.

    Although that could only happen if map_sg is called with zero length sg
    list entries I'm in favor getting rid of that warning.

    Acked-by: Sebastian Ott <sebott@linux.vnet.ibm.com>

    Regards,
    Sebastian

    \
     
     \ /
      Last update: 2016-10-18 10:54    [W:4.218 / U:0.120 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site