On Tue, 2 Jun 2009 05:24:44 am Johannes Stezenbach wrote:
> lguest: unhandled trap 13 at 0xc07d627a (0x0)
...
> c07d627a: 65 a1 14 00 00 00 mov %gs:0x14,%eax
Ah, CONFIG_STACK_PROTECTOR. Interesting, I never tried that...
OK, this fixes it here:
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 <ru...@rustcorp.com.au>
diff --git a/arch/x86/lguest/Makefile b/arch/x86/lguest/Makefile
--- a/arch/x86/lguest/Makefile
+++ b/arch/x86/lguest/Makefile
@@ -1,1 +1,2 @@
obj-y := i386_head.o boot.o
+CFLAGS_boot.o := $(call cc-option, -fno-stack-protector)
diff --git a/arch/x86/lguest/boot.c b/arch/x86/lguest/boot.c
--- 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 @@ __init void lguest_init(void)
* 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 */
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