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aha/drivers/lguest
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Matias Zabaljauregui 88df781afb lguest: fix crash on vmlinux images 
Typical message: 'lguest: unhandled trap 6 at 0x418726 (0x0)'

vmlinux guests were broken by 4cd8b5e2a1
'lguest: use KVM hypercalls', which rewrites guest text from kvm hypercalls
to trap 31.

The Launcher mmaps the kernel image.  The Guest executes and
immediately faults in the first text page (read-only).  Then it hits a
hypercall, and we rewrite that hypercall, causing a copy-on-write.
But the Guest pagetables still refer to the old page: we fault again,
but as Host we see the hypercall already rewritten, and pass the fault
back to the Guest.  The Guest hasn't set up an IDT yet, so we kill it.

This doesn't happen with bzImages: they unpack themselves and so the
text pages are already read-write.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Tested-by: Patrick McHardy <kaber@trash.net>
2009-04-19 23:14:00 +09:30
..
x86 lguest: fix crash on vmlinux images 2009-04-19 23:14:00 +09:30
core.c lguest: use bool instead of int 2009-03-30 21:55:25 +10:30
hypercalls.c lguest: comment documentation update. 2008-03-28 11:05:54 +11:00
interrupts_and_traps.c lguest: use bool instead of int 2009-03-30 21:55:25 +10:30
Kconfig x86: remove the Voyager 32-bit subarch 2009-02-23 00:54:01 +01:00
lg.h lguest: use bool instead of int 2009-03-30 21:55:25 +10:30
lguest_device.c lguest: use KVM hypercalls 2009-03-30 21:55:24 +10:30
lguest_user.c lguest: Fix a memory leak with the lg object during launcher close 2009-01-30 11:34:11 +10:30
Makefile lguest: Add puppies which where previously missing. 2008-03-28 11:05:52 +11:00
page_tables.c lguest: use bool instead of int 2009-03-30 21:55:25 +10:30
README lguest: documentation I: Preparation 2007-07-26 11:35:16 -07:00
segments.c lguest: use bool instead of int 2009-03-30 21:55:25 +10:30

README 

Welcome, friend reader, to lguest.

Lguest is an adventure, with you, the reader, as Hero.  I can't think of many
5000-line projects which offer both such capability and glimpses of future
potential; it is an exciting time to be delving into the source!

But be warned; this is an arduous journey of several hours or more!  And as we
know, all true Heroes are driven by a Noble Goal.  Thus I offer a Beer (or
equivalent) to anyone I meet who has completed this documentation.

So get comfortable and keep your wits about you (both quick and humorous).
Along your way to the Noble Goal, you will also gain masterly insight into
lguest, and hypervisors and x86 virtualization in general.

Our Quest is in seven parts: (best read with C highlighting turned on)

I) Preparation
	- In which our potential hero is flown quickly over the landscape for a
	  taste of its scope.  Suitable for the armchair coders and other such
	  persons of faint constitution.

II) Guest
	- Where we encounter the first tantalising wisps of code, and come to
	  understand the details of the life of a Guest kernel.

III) Drivers
	- Whereby the Guest finds its voice and become useful, and our
	  understanding of the Guest is completed.

IV) Launcher
	- Where we trace back to the creation of the Guest, and thus begin our
	  understanding of the Host.

V) Host
	- Where we master the Host code, through a long and tortuous journey.
	  Indeed, it is here that our hero is tested in the Bit of Despair.

VI) Switcher
	- Where our understanding of the intertwined nature of Guests and Hosts
	  is completed.

VII) Mastery
	- Where our fully fledged hero grapples with the Great Question:
	  "What next?"

make Preparation!
Rusty Russell.