Date: Tue, 17 Feb 2009 22:26:08 -0800 From: Marcel Moolenaar <xcllnt@mac.com> To: "M. Warner Losh" <imp@bsdimp.com> Cc: mips@FreeBSD.org, tinderbox@FreeBSD.org, current@FreeBSD.org Subject: Re: [head tinderbox] failure on mips/mips Message-ID: <4CB77F1D-4235-47D8-B654-1C4F29B6C649@mac.com> In-Reply-To: <20090217.222152.-109416210.imp@bsdimp.com> References: <20090218023328.227617302F@freebsd-current.sentex.ca> <20090217.203647.-1518647466.imp@bsdimp.com> <20090217.222152.-109416210.imp@bsdimp.com>
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On Feb 17, 2009, at 9:21 PM, M. Warner Losh wrote: > In message: <20090217.203647.-1518647466.imp@bsdimp.com> > "M. Warner Losh" <imp@bsdimp.com> writes: > : In message: <20090218023328.227617302F@freebsd-current.sentex.ca> > : FreeBSD Tinderbox <tinderbox@freebsd.org> writes: > : : /src/usr.sbin/bsnmpd/modules/snmp_mibII/../../../../contrib/ > bsnmp/snmp_mibII/mibII.c:1016: warning: cast increases required > alignment of target type > : > : there's still 3 or 4 of these in the tree that I'm trying to track > : back to root cause. A simple (void *) fixes the problem, but I want > : to understand the issues before I slap that bad-boy in there... > > The first one is: > > case RTM_IFINFO: > ifm = (struct if_msghdr *)rtm; > mib_extract_addrs(ifm->ifm_addrs, (u_char *)(ifm + 1), addrs); > if ((ifp = mib_find_if_sys(ifm->ifm_index)) == NULL) > break; > > rtm is of type struct rt_msghdr. This has an alignment requirement of > 4 on mips, at least on 32-bit mips (the biggest data element is a > u_long). struct if_msghdr has an alignment requirement of 8, because > time_t is int64_t on MIPS, which is 8-bytes in size. Normally on 32-bit architectures, 64-bit data types have a 32-bit alignment requirement by virtue of needing 2 32-bit loads/stores to read/write them. Does 32-bit MIPS use 64-bit wide registers? > One way to fix this is to add __aligned(8) to struct rt_msghdr to > compensate for this. Otherwise, if the time_t element is referenced > in ifm_data we'll core dump. A safer approach is to mark ifi_epoch as packed or put differently, define time_t as a 64-bit integral with 32-bit alignment. This can avoid a lot of unexpected internal padding as well (e.g. struct timeval). Just a thought. -- Marcel Moolenaar xcllnt@mac.com
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