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authorMatias Zabaljauregui <zabaljauregui@gmail.com>2009-04-08 17:58:39 -0300
committerRusty Russell <rusty@rustcorp.com.au>2009-04-19 23:14:00 +0930
commit88df781afb788fa588dbf2e77f205214022a8893 (patch)
treeb73e2b470a959e60fb5332737c1fca04bb629ba7
parentff54250a0ebab7f90a5f848a0ba63f999830c872 (diff)
lguest: fix crash on vmlinux images
Typical message: 'lguest: unhandled trap 6 at 0x418726 (0x0)' vmlinux guests were broken by 4cd8b5e2a159f18a1507f1187b44a1acbfa6341b '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>
-rw-r--r--drivers/lguest/x86/core.c5
1 files changed, 5 insertions, 0 deletions
diff --git a/drivers/lguest/x86/core.c b/drivers/lguest/x86/core.c
index a6b717644be..d6d7ac0982a 100644
--- a/drivers/lguest/x86/core.c
+++ b/drivers/lguest/x86/core.c
@@ -324,6 +324,11 @@ static void rewrite_hypercall(struct lg_cpu *cpu)
u8 insn[3] = {0xcd, 0x1f, 0x90};
__lgwrite(cpu, guest_pa(cpu, cpu->regs->eip), insn, sizeof(insn));
+ /* The above write might have caused a copy of that page to be made
+ * (if it was read-only). We need to make sure the Guest has
+ * up-to-date pagetables. As this doesn't happen often, we can just
+ * drop them all. */
+ guest_pagetable_clear_all(cpu);
}
static bool is_hypercall(struct lg_cpu *cpu)