Date: Sun, 29 Jan 2006 12:34:54 -0800 From: Julian Elischer <julian@elischer.org> To: Luigi Rizzo <rizzo@icir.org> Cc: current@freebsd.org Subject: Re: for review: sys/dev/md/md.c patch Message-ID: <43DD26EE.50608@elischer.org> In-Reply-To: <20060129050435.A5945@xorpc.icir.org> References: <20060129050435.A5945@xorpc.icir.org>
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Luigi Rizzo wrote:
>just discovered, trying to resurrect picobsd on -current,
>that the compiler in 6.x/7.x has become smart and, at least
>with the default compilation flags, will optimize out
>the "end_mfs_root" string from the object.
>As a consequence, any checks that the preloaded module
>does not overflow the allocated space (looking at the
>'MFS Filesystem had better STOP here' string in the patched
>object) will fail.
>
>The attached patch fixes the issue. Any objection if i commit it ?
>
>
seems fair to me. can't hurt anything unless MD_ROOT_SIZE is defined..
I LIKE PicoBSD.. and it woul dbe a shame if it was lost as a capacity.
It's a pitty everythng has grown so much.. last I tried (on 5.x)
you could JUST get a kenrel plus a shell and one small app. (in my case
ssh).
onto a floppy.. I hav eserious doubts about being able to do that now..
pitty.. I have an old laptop with no HD that was a good little VPN
endpoint using
the 5.x based picoBSD.
> cheers
> luigi
>
>Index: md.c
>===================================================================
>RCS file: /prova/home/ncvs/src/sys/dev/md/md.c,v
>retrieving revision 1.159
>diff -u -p -r1.159 md.c
>--- md.c 31 Oct 2005 15:41:19 -0000 1.159
>+++ md.c 29 Jan 2006 12:57:22 -0000
>@@ -102,8 +102,13 @@ SYSCTL_INT(_debug, OID_AUTO, mddebug, CT
>
> #if defined(MD_ROOT) && defined(MD_ROOT_SIZE)
> /* Image gets put here: */
>-static u_char mfs_root[MD_ROOT_SIZE*1024] = "MFS Filesystem goes here";
>-static u_char end_mfs_root[] __unused = "MFS Filesystem had better STOP here";
>+static struct {
>+ u_char start[MD_ROOT_SIZE*1024];
>+ u_char end[128];
>+} mfs_root = {
>+ .start = "MFS Filesystem goes here",
>+ .end = "MFS Filesystem had better STOP here",
>+};
> #endif
>
> static g_init_t g_md_init;
>@@ -1139,7 +1144,7 @@ g_md_init(struct g_class *mp __unused)
> g_topology_unlock();
> #ifdef MD_ROOT_SIZE
> sx_xlock(&md_sx);
>- md_preloaded(mfs_root, MD_ROOT_SIZE * 1024);
>+ md_preloaded(mfs_root.start, MD_ROOT_SIZE * 1024);
> sx_xunlock(&md_sx);
> #endif
> /* XXX: are preload_* static or do they need Giant ? */
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