Date: Wed, 17 Feb 2010 16:16:07 +0100 From: Bernd Walter <ticso@cicely7.cicely.de> To: Rui Paulo <rpaulo@gmail.com> Cc: freebsd-arm@freebsd.org Subject: Re: kdump on ARM Message-ID: <20100217151607.GU43625@cicely7.cicely.de> In-Reply-To: <FF73974A-6960-4F75-82E9-1DBAACCB8E0F@gmail.com> References: <4B7BFAA4.4040607@semihalf.com> <FF73974A-6960-4F75-82E9-1DBAACCB8E0F@gmail.com>
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On Wed, Feb 17, 2010 at 02:54:05PM +0000, Rui Paulo wrote:
>
> On 17 Feb 2010, at 14:18, Grzegorz Bernacki wrote:
>
> > Hi,
> >
> > I've noticed that kdump on ARM doesn't work properly, it generates bus error. The problem is that structures dumped into ktrace.out are not aligned. Processing such a structure causes Aligment Fault. One solution is to copy structure into local variable and then process it, please see patch below. But I am not sure if this is the best solution and maybe someone has a better idea.
Excellent!
> > grzesiek
> >
> >
> > diff --git a/usr.bin/kdump/kdump.c b/usr.bin/kdump/kdump.c
> > index 386221e..5a15886 100644
> > --- a/usr.bin/kdump/kdump.c
> > +++ b/usr.bin/kdump/kdump.c
> > @@ -1325,6 +1325,10 @@ ktrstat(struct stat *statp)
> > void
> > ktrstruct(char *buf, size_t buflen)
> > {
> > +#if defined(__arm__)
> > + struct stat stat;
> > + struct sockaddr sockaddr;
> > +#endif
> > char *name, *data;
> > size_t namelen, datalen;
> > int i;
> > @@ -1348,12 +1352,22 @@ ktrstruct(char *buf, size_t buflen)
> > if (strcmp(name, "stat") == 0) {
> > if (datalen != sizeof(struct stat))
> > goto invalid;
> > +#if defined(__arm__)
> > + memcpy(&stat, data, sizeof(struct stat));
> > + ktrstat(&stat);
> > +#else
> > ktrstat((struct stat *)data);
> > +#endif
> > } else if (strcmp(name, "sockaddr") == 0) {
> > if (datalen < sizeof(struct sockaddr) ||
> > datalen != ((struct sockaddr *)(data))->sa_len)
> > goto invalid;
> > +#if defined(__arm__)
> > + memcpy(&sockaddr, data, sizeof(struct sockaddr));
> > + ktrsockaddr(&sockaddr);
> > +#else
> > ktrsockaddr((struct sockaddr *)data);
> > +#endif
> > } else {
> > printf("unknown structure\n");
> > }
>
> I wonder if this can't be made non arm conditional?
Either this struct is properly aligned or not.
So why should this be made conditional?
Non strict alignment architecturs also have problems with this, but
it is usualy just speed penalties.
There is one ARM sepcific struct missalignment problem.
In this case we usually add __packed macro to structure definition.
For most structures this usually means no change on other
archtitectures and we only declare the struct to forcibly be what the
programmer already expected.
Only a few programmers are aware that they expect something from
structures, which is not garantied.
--
B.Walter <bernd@bwct.de> http://www.bwct.de
Modbus/TCP Ethernet I/O Baugruppen, ARM basierte FreeBSD Rechner uvm.
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