Re: [uml-devel] Programs in guest segfault, amd64 host and guest

[Jeff Dike <jdike@addtoit.com>]

On Wed, Oct 18, 2006 at 09:16:14PM +0200, Jan Dittmer wrote:
> This is 100% reproducible here. Perfect test case. How to debug?

You want to dig into the code and see what's wrong?  Put a breakpoint
on the force_sig_info(SIGSEGV, ...) in segv().  Then find the faulting
instruction -
	RIP is regs.skas.regs[16]
	pid = cpu_tasks[0].pid
	Look in the host's /proc/$pid/maps for the page containing RIP
	add uml_physmem to the offset in column 3 - that's the
physical page containing RIP
	add the RIP page offset to that to get the actual physical
address for RIP
	disassemble the range of memory around it - I usually do 10 -
20 bytes before it to ~10 bytes after
	see that the asm looks sane, if not, bump the start of the
disassembly by a byte in either direction until it does
	see what the instruction at RIP is - if it involves a gs:
reference, then it's very likely a NPTL problem

If you don't want to do that, tell me what to yum, and how to run
whatever it is, and I'll look at it.

				Jeff

	

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