Re: [PATCH [repost]] block/blkio: Don't assume size_t is 64 bit

[Richard W.M. Jones]

On Tue, Jan 30, 2024 at 09:51:59AM +0100, Kevin Wolf wrote:
> Am 29.01.2024 um 19:53 hat Richard W.M. Jones geschrieben:
> > With GCC 14 the code failed to compile on i686 (and was wrong for any
> > version of GCC):
> > 
> > ../block/blkio.c: In function ‘blkio_file_open’:
> > ../block/blkio.c:857:28: error: passing argument 3 of ‘blkio_get_uint64’ 
> > from incompatible pointer type [-Wincompatible-pointer-types]
> >   857 |                            &s->mem_region_alignment);
> >       |                            ^~~~~~~~~~~~~~~~~~~~~~~~
> >       |                            |
> >       |                            size_t * {aka unsigned int *}
> > In file included from ../block/blkio.c:12:
> > /usr/include/blkio.h:49:67: note: expected ‘uint64_t *’ {aka ‘long long 
> > unsigned int *’} but argument is of type ‘size_t *’ {aka ‘unsigned int *’}
> >    49 | int blkio_get_uint64(struct blkio *b, const char *name, uint64_t 
> > *value);
> >       |                                                         
> > ~~~~~~~~~~^~~~~
> > 
> > Signed-off-by: Richard W.M. Jones <rjones@redhat.com>
> 
> Why not simply make BDRVBlkioState.mem_region_alignment a uint64_t
> instead of keeping it size_t and doing an additional conversion with
> a check that requires an #if (probably to avoid a warning on 64 bit
> hosts because the condition is never true)?

The smaller change (attached) does work on i686, but this worries me a
little (although it doesn't give any error or warning):

    if (((uintptr_t)host | size) % s->mem_region_alignment) {
    error_setg(errp, "unaligned buf %p with size %zu", host, size);
        return BMRR_FAIL;
    }

Rich.

> Kevin
> 
> >  block/blkio.c | 12 +++++++++++-
> >  1 file changed, 11 insertions(+), 1 deletion(-)
> > 
> > diff --git a/block/blkio.c b/block/blkio.c
> > index 0a0a6c0f5fd..52d78935147 100644
> > --- a/block/blkio.c
> > +++ b/block/blkio.c
> > @@ -794,6 +794,7 @@ static int blkio_file_open(BlockDriverState *bs, QDict 
> > *options, int flags,
> >      const char *blkio_driver = bs->drv->protocol_name;
> >      BDRVBlkioState *s = bs->opaque;
> >      int ret;
> > +    uint64_t val;
> >  
> >      ret = blkio_create(blkio_driver, &s->blkio);
> >      if (ret < 0) {
> > @@ -854,7 +855,7 @@ static int blkio_file_open(BlockDriverState *bs, QDict 
> > *options, int flags,
> >  
> >      ret = blkio_get_uint64(s->blkio,
> >                             "mem-region-alignment",
> > -                           &s->mem_region_alignment);
> > +                           &val);
> >      if (ret < 0) {
> >          error_setg_errno(errp, -ret,
> >                           "failed to get mem-region-alignment: %s",
> > @@ -862,6 +863,15 @@ static int blkio_file_open(BlockDriverState *bs, QDict 
> > *options, int flags,
> >          blkio_destroy(&s->blkio);
> >          return ret;
> >      }
> > +#if HOST_LONG_BITS == 32
> > +    if (val > SIZE_MAX) {
> > +        error_setg_errno(errp, ERANGE,
> > +                         "mem-region-alignment too large for size_t");
> > +        blkio_destroy(&s->blkio);
> > +        return -ERANGE;
> > +    }
> > +#endif
> > +    s->mem_region_alignment = (size_t)val;
> >  
> >      ret = blkio_get_bool(s->blkio,
> >                           "may-pin-mem-regions",
> > -- 
> > 2.43.0
> > 

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
Read my programming and virtualization blog: http://rwmj.wordpress.com
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0001-block-blkio-Make-s-mem_region_alignment-be-64-bits.patch
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