On Fri, Feb 04, 2022 at 07:32:52PM +1000, David Gwynne wrote:
> as discussed in "m_pullup alingment crash armv7 sparc64", at worst it
> doesnt hurt to have m_pullup maintain the data alignment of payloads,
> and at best it will encourage aligned loads even if the arch allows
> unaligned accesses. aligned loads are faster than unaligned.
>
> ok?
adj is unsigned int, so assigning a mtod(m0, unsigned long) looks
strange. Of course the higher bits are cut off anyway, but an
explicit & is clearer than a assingment with different types.
Please use
adj = mtod(m, unsigned long) & (sizeof(long) - 1);
adj = mtod(m0, unsigned long) & (sizeof(long) - 1);
otherwise OK bluhm@
> Index: uipc_mbuf.c
> ===================================================================
> RCS file: /cvs/src/sys/kern/uipc_mbuf.c,v
> retrieving revision 1.280
> diff -u -p -r1.280 uipc_mbuf.c
> --- uipc_mbuf.c 18 Jan 2022 12:38:21 -0000 1.280
> +++ uipc_mbuf.c 4 Feb 2022 09:30:02 -0000
> @@ -945,9 +945,11 @@ m_pullup(struct mbuf *m0, int len)
> goto freem0;
> }
>
> - adj = mtod(m, unsigned long) & ALIGNBYTES;
> + adj = mtod(m, unsigned long);
> } else
> - adj = mtod(m0, unsigned long) & ALIGNBYTES;
> + adj = mtod(m0, unsigned long);
> +
> + adj &= sizeof(long) - 1;
>
> tail = head + M_SIZE(m0);
> head += adj;
