Re: [uml-devel] [PATCH] Ok, I build x86-64 -skas0, and it still segfaults.

[Blaisorblade <blaisorblade@yahoo.it>]

On Sunday 13 November 2005 20:32, Jeff Dike wrote:
> On Sat, Nov 12, 2005 at 07:36:41PM -0600, Rob Landley wrote:
> > Stub registers -
> >         0 - 9090909090909090
> >         1 - 9090909090909090
> >         2 - 9090909090909090
> >         3 - 9090909090909090
> >         4 - 9090909090909090
> >         5 - 9090909090909090
> >         6 - 9090909090909090
> >         7 - 9090909090909090
> >         8 - 9090909090909090
> >         9 - 9090909090909090
> >         10 - 0
> >         11 - 9090909090909090
> >         12 - 9090909090909090
> >         13 - 9090909090909090
> >         14 - 9090909090909090
> >         15 - ffffffffffffffff
> >         16 - 9090909090909090
> >         17 - 33
> >         18 - 292
> >         19 - 9090909090909090
> >         20 - 2b
>
> I remain baffled by this.  There is nothing valid there.  At the very least
> RSP and RIP should be reasonable, and they're not.

Jeff, given the current state, I think that we need a look at the disassembly 
- or better:
*) build a 2.6.15-rc1 binary with Rob's config.
*) test that it works
*) send him and see if it works for him
*) finally, conclude GCC is misassembling stuff and take measures for this 
case.

Meanwhile, Rob, can you provide the disassembly? We need to look at 
disassembled arch/um/sys-x86_64/stub_segv.c arch/um/kernel/skas/clone.c, i.e. 
stub_segv_handler() and stub_clone_handler().

* Also, about the miscompilation bug you described:
is it caused by GCC saving the "from" value (UML_CONFIG_STUB_DATA) on the 
stack and re-loading it?


* Ah, Jeff, while giving a casual look: should I remove x86_64 "syscall_stub" 
label from stub.S, since it should be unused (replaced by 
batch_syscall_stub), doesn't exist for 386 and the content is bogus?

-- 
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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