[PATCH 2/4] xen/lowlevel: Implement pvop call for load_idt (sidt).

From: Konrad Rzeszutek Wilk
Date: Wed Oct 17 2012 - 10:04:23 EST

In the past it used to point to 'sidt' (native_store_idt) operation
which is a non-privileged operation. This resulted in the
'struct desc_ptr' value containing the address of Xen's IDT table,
instead of the IDT table that Linux thinks its using. The end result
is that doing:


would blow up b/c xen_load_idt would try to parse the IDT contents
(desc) and de-reference a virtual address that is outside Linux's
__va (it is in Xen's virtual address).

With this patch we are providing the last written IDT address.

Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
arch/x86/xen/enlighten.c | 8 +++++++-
1 files changed, 7 insertions(+), 1 deletions(-)

diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
index e3497f2..f29d6d6 100644
--- a/arch/x86/xen/enlighten.c
+++ b/arch/x86/xen/enlighten.c
@@ -777,7 +777,13 @@ static void xen_load_idt(const struct desc_ptr *desc)

+static void xen_store_idt(struct desc_ptr *dtr)
+ const struct desc_ptr *desc = &__get_cpu_var(idt_desc);

+ dtr->address = desc->address;
+ dtr->size = desc->size;
/* Write a GDT descriptor entry. Ignore LDT descriptors, since
they're handled differently. */
static void xen_write_gdt_entry(struct desc_struct *dt, int entry,
@@ -1200,7 +1206,7 @@ static const struct pv_cpu_ops xen_cpu_ops __initconst = {
.free_ldt = xen_free_ldt,

.store_gdt = native_store_gdt,
- .store_idt = native_store_idt,
+ .store_idt = xen_store_idt,
.store_tr = xen_store_tr,

.write_ldt_entry = xen_write_ldt_entry,

To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/