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Jeff Dike | 2 Oct 2005 04:35

Re: [PATCH] Early x86_64 crash

On Fri, Sep 30, 2005 at 04:41:58PM +0200, Blaisorblade wrote:
> I assume you've been able to reproduce this crash and see this patch fix it, 
> right?

Yup.

> I've attached the addon with additional clobber, and with fixed tabs (i.e. 
> hardtabs). Not compiled it (no time to reboot right now).

Yeah, I'll fix the spacing in my copy.

				Jeff

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Al Viro | 2 Oct 2005 18:55
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Re: UML/2.6.14-rc3 doesn't work fixes

On Sun, Oct 02, 2005 at 11:51:34AM -0400, Jeff Dike wrote:
> On Sun, Oct 02, 2005 at 12:13:39PM +0200, Blaisorblade wrote:
> > The patch in Al Viro's:
> > 
> > ecba97d4aacf4e80c56eb73e39af0369cb8539a4
> > 
> > messed up UML (in particular skas0, which doesn't boot any more - or maybe it 
> > boots one out of 10 times).
> > 
> > Btw: did Al CC you on it, at least?
> > 
> > The reason is that he messed up HOST_FRAME_SIZE on i386 (by using 
> > DEFINE_LONGS). I.e. HOST_FRAME_SIZE, which was 17, became 17/sizeof(long). 
> > Uh, nice.
> 
> He did, and I found the same problem and sent him back the fix.  I guess
> he sent in the original patch.

s/original/mismerged/ (note that original had more breakage in the same
file).  AFAICS, s/DEFINE_LONGS/DEFINE/ in that place is all that got lost.

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Blaisorblade | 2 Oct 2005 17:23
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Re: [PATCH] Early x86_64 crash

On Sunday 02 October 2005 04:35, Jeff Dike wrote:
> On Fri, Sep 30, 2005 at 04:41:58PM +0200, Blaisorblade wrote:
> > I assume you've been able to reproduce this crash and see this patch fix
> > it, right?

> Yup.

> > I've attached the addon with additional clobber, and with fixed tabs
> > (i.e. hardtabs). Not compiled it (no time to reboot right now).

> Yeah, I'll fix the spacing in my copy.

I'm assuming the additional clobbers are ok, and queuing the whole in -bs3.
--

-- 
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Paolo Giarrusso, aka Blaisorblade (Skype ID "PaoloGiarrusso", ICQ 215621894)
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Al Viro | 2 Oct 2005 19:32
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Re: UML/2.6.14-rc3 doesn't work fixes

On Sun, Oct 02, 2005 at 01:50:28PM +0200, Blaisorblade wrote:
> On Sunday 02 October 2005 13:38, Al Viro wrote:
> > On Sun, Oct 02, 2005 at 12:13:39PM +0200, Blaisorblade wrote:
> > > The patch in Al Viro's:
> 
> > > ecba97d4aacf4e80c56eb73e39af0369cb8539a4
> 
> > > messed up UML (in particular skas0, which doesn't boot any more - or
> > > maybe it boots one out of 10 times).
> 
> > > Btw: did Al CC you on it, at least?
> 
> > Yes.  Moreover, that had also been done two weeks ago when original version
> > of patch had been sent for review to Jeff.  Who'd caught that one and other
> > bugs and sent the fixed variant back.   At which point I'd fscked up the
> > merge.
> 
> Ok, you're excused... now, however, I still think that this should be 
> postponed to 2.6.15, since it's a (very nice, indeed) cleanup and we're 
> nearing completion.
> 
> Al, did you receive my "[PATCH 5/5] uml: remove empty hostfs_truncate method"? 
> What about that?

What about that?  Obvious patch that got no objections from anybody and
AFAICS got in -rc3:

; git-whatchanged fs/hostfs/hostfs_kern.c|head
diff-tree daa35edc0a967d1f77c2e2c1346f57d04371487a (from bd948057357db5febfe64cf7a9ef11d7e347ffec)
Author: Paolo 'Blaisorblade' Giarrusso <blaisorblade <at> yahoo.it>
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Blaisorblade | 2 Oct 2005 19:45
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Re: UML/2.6.14-rc3 doesn't work fixes

On Sunday 02 October 2005 19:32, Al Viro wrote:
> On Sun, Oct 02, 2005 at 01:50:28PM +0200, Blaisorblade wrote:
> > On Sunday 02 October 2005 13:38, Al Viro wrote:

> > Al, did you receive my "[PATCH 5/5] uml: remove empty hostfs_truncate
> > method"? What about that?

> What about that?  Obvious patch
Ok, that's nice.
> that got no objections from anybody and 
> AFAICS got in -rc3:
Ok, sorry - overlooked and missed it.

I saw "Hey, it's not been merged yet" and just after I saw -rc3, and didn't 
notice my last batch going in between the two ones.
--

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Blaisorblade | 2 Oct 2005 20:01
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Re: UML/2.6.14-rc3 doesn't work fixes

On Sunday 02 October 2005 17:51, Jeff Dike wrote:
> On Sun, Oct 02, 2005 at 12:13:39PM +0200, Blaisorblade wrote:

> He did, and I found the same problem and sent him back the fix.  I guess
> he sent in the original patch.
Ok, he just said he sent a mismerged patch, but it's ok.
> I was planning on sending it in after 2.6.14 because of its size.
Al, is that ok for you if we follow this original plan?

In this case, I'll post the dropping patch and re-send the Kbuild fix of my 
last batch (conflicted with Al's patch, but now it's needed again).
--

-- 
Inform me of my mistakes, so I can keep imitating Homer Simpson's "Doh!".
Paolo Giarrusso, aka Blaisorblade (Skype ID "PaoloGiarrusso", ICQ 215621894)
http://www.user-mode-linux.org/~blaisorblade

	

	
		
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Jeff Dike | 2 Oct 2005 20:27

Re: Clearing kmalloc_ok during shutdown is broken - malloc will clear our data.

On Sun, Oct 02, 2005 at 12:31:04PM +0200, Blaisorblade wrote:
> > Yeah, it's bad.  The other way to do it is to explictly save the registers
> > in the thread struct, which is effectively the reimplementing setjmp option
> > which you mentioned.
> At least, if we save them separately from the jmpbuf_t, we can use them for 
> sysrq t, without reimplementing setjmp() and longjmp(). Not nice, wastes 24 
> bytes, but would work.

Yup.

> I have the doubt that the location of those registers is part of the ABI, 

I think they are probably not.

> Probably, however, it's just better to test on, say, a Slackware 8.1, and hope 
> for the best and go doing a fix when things change.

Yeah, I agree.  On the positive side, I think that jmp_buf has probably been
unchanged for a long time, and will remain so.

				Jeff

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Al Viro | 2 Oct 2005 20:37
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Re: UML/2.6.14-rc3 doesn't work fixes

On Sun, Oct 02, 2005 at 08:01:21PM +0200, Blaisorblade wrote:
> On Sunday 02 October 2005 17:51, Jeff Dike wrote:
> > On Sun, Oct 02, 2005 at 12:13:39PM +0200, Blaisorblade wrote:
> 
> > He did, and I found the same problem and sent him back the fix.  I guess
> > he sent in the original patch.
> Ok, he just said he sent a mismerged patch, but it's ok.
> > I was planning on sending it in after 2.6.14 because of its size.
> Al, is that ok for you if we follow this original plan?
> 
> In this case, I'll post the dropping patch and re-send the Kbuild fix of my 
> last batch (conflicted with Al's patch, but now it's needed again).

Up to Jeff; IMO it's easier to restore the variant past his review (with
incremental replacing that DEFINE_LONGS), but maintainer gets to decide;
that was the reason for Cc when patch got sent to Linus, after all...

diff -urN RC14-rc2-git6-base/arch/um/sys-i386/user-offsets.c current/arch/um/sys-i386/user-offsets.c
--- RC14-rc2-git6-base/arch/um/sys-i386/user-offsets.c	2005-09-25 23:28:27.000000000 -0400
+++ current/arch/um/sys-i386/user-offsets.c	2005-10-02 14:08:15.000000000 -0400
 <at>  <at>  -46,7 +46,7  <at>  <at> 
 	OFFSET(HOST_SC_FP_ST, _fpstate, _st);
 	OFFSET(HOST_SC_FXSR_ENV, _fpstate, _fxsr_env);

-	DEFINE_LONGS(HOST_FRAME_SIZE, FRAME_SIZE);
+	DEFINE(HOST_FRAME_SIZE, FRAME_SIZE);
 	DEFINE_LONGS(HOST_FP_SIZE, sizeof(struct user_i387_struct));
 	DEFINE_LONGS(HOST_XFP_SIZE, sizeof(struct user_fxsr_struct));

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Jeff Dike | 2 Oct 2005 20:31

Re: a question about sigsetjmp() in copy_from/to_user()

On Sun, Oct 02, 2005 at 12:23:14PM +0200, Blaisorblade wrote:
> Sorry, any reference will fault, unless it is done on a allocated present 
> page, which the UML kernel freed but the host didn't. And remember, btw, 
> you've planned to make this impossible...

You are not making any sense t me here.

> Sorry, Jeff, which page are you going to evict? It can be a dirty page. Unless 
> you mean that since that page is still accounted in the FS, Linux will leave 
> a RAM page free to allow it to be re-read, while still swapping the page.

Swapped pages are accounted in the FS all the time and there's obviously
no dedicated page left free for them when they are next pulled in.  All 
disk-based filesystems account pages that are on disk and not in memory.
tmpfs is no different, except that its disk is the swap partition.

				Jeff

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Jeff Dike | 2 Oct 2005 03:08

Re: Clearing kmalloc_ok during shutdown is broken - malloc will clear our data.

On Thu, Sep 29, 2005 at 04:14:02PM +0200, Blaisorblade wrote:
> I now even found (by chance) the original mail from Allan Graves - and the 
> changes in arch/um/include/sysdep-x86_64/ptrace.h weren't in his patch and 
> are unrelated.
> Plus, I think they're also bogus (those registers exist), but I may be wrong, 
The patch uses UPT_REG apparently for the first time.  Those registers exist,
but there are no defines for them in the x86_64 ptrace.h.  UPT_REG is never
called with any of those as its argument, so it's easy to just remove those
cases.

> On the bogus value: I'm more accustomed to 0xdeadbeef, since 0xbadbabe could 
> be valid while 0xdeadbeef not (it's in the last giga).

Yeah, that makes sense.

> The only problem I see is that we need to test it on a wide glibc range - 
> you're using an internal header detail, so glibc will break it at will.

Yeah, it's bad.  The other way to do it is to explictly save the registers
in the thread struct, which is effectively the reimplementing setjmp option
which you mentioned.

				Jeff

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Gmane