Re: [uml-devel] Clearing kmalloc_ok during shutdown is broken - malloc will clear our data.

[Blaisorblade <blaisorblade@yahoo.it>]

On Sunday 02 October 2005 03:08, Jeff Dike wrote:
> 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.
Ah, ok.

> > 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.
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.

I have the doubt that the location of those registers is part of the ABI, 
(pending: find an example where I can be statically linked to glibc and 
dynamically linked to a library dynamically linked to glibc, and must pass 
jmpbuf_t between the two implementations)
even if the C names aren't part of the API, so we could copy the structure.

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.
-- 
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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