lguest: fix 'unhandled trap 13' with CONFIG_CC_STACKPROTECTOR
We don't set up the canary; let's disable stack protector on boot.c so
we can get into lguest_init, then set it up. As a side effect,
switch_to_new_gdt() sets up %fs for us properly too.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/arch/x86/lguest/boot.c b/arch/x86/lguest/boot.c
index ca7ec44..33a93b4 100644
--- a/arch/x86/lguest/boot.c
+++ b/arch/x86/lguest/boot.c
@@ -67,6 +67,7 @@
#include <asm/mce.h>
#include <asm/io.h>
#include <asm/i387.h>
+#include <asm/stackprotector.h>
#include <asm/reboot.h> /* for struct machine_ops */
/*G:010 Welcome to the Guest!
@@ -1088,13 +1089,21 @@
* lguest_init() where the rest of the fairly chaotic boot setup
* occurs. */
+ /* The stack protector is a weird thing where gcc places a canary
+ * value on the stack and then checks it on return. This file is
+ * compiled with -fno-stack-protector it, so we got this far without
+ * problems. The value of the canary is kept at offset 20 from the
+ * %gs register, so we need to set that up before calling C functions
+ * in other files. */
+ setup_stack_canary_segment(0);
+ /* We could just call load_stack_canary_segment(), but we might as
+ * call switch_to_new_gdt() which loads the whole table and sets up
+ * the per-cpu segment descriptor register %fs as well. */
+ switch_to_new_gdt(0);
+
/* As described in head_32.S, we map the first 128M of memory. */
max_pfn_mapped = (128*1024*1024) >> PAGE_SHIFT;
- /* Load the %fs segment register (the per-cpu segment register) with
- * the normal data segment to get through booting. */
- asm volatile ("mov %0, %%fs" : : "r" (__KERNEL_DS) : "memory");
-
/* The Host<->Guest Switcher lives at the top of our address space, and
* the Host told us how big it is when we made LGUEST_INIT hypercall:
* it put the answer in lguest_data.reserve_mem */