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authorJuergen Gross <jgross@suse.com>2018-02-01 13:40:19 +0100
committerJuergen Gross <jgross@suse.com>2018-02-06 09:37:18 +0100
commit4f277295e54c5b7340e48efea3fc5cc21a2872b7 (patch)
treec0afd5986abcc7183cf4253a578e7a732753f7d8 /arch/x86/xen/xen-head.S
parentddb9e13af3bba3f8c36ccee0eb9563a82b425c12 (diff)
downloadlinux-4f277295e54c5b7340e48efea3fc5cc21a2872b7.tar.bz2
x86/xen: init %gs very early to avoid page faults with stack protector
When running as Xen pv guest %gs is initialized some time after C code is started. Depending on stack protector usage this might be too late, resulting in page faults. So setup %gs and MSR_GS_BASE in assembly code already. Cc: stable@vger.kernel.org Signed-off-by: Juergen Gross <jgross@suse.com> Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com> Tested-by: Chris Patterson <cjp256@gmail.com> Signed-off-by: Juergen Gross <jgross@suse.com>
Diffstat (limited to 'arch/x86/xen/xen-head.S')
-rw-r--r--arch/x86/xen/xen-head.S16
1 files changed, 16 insertions, 0 deletions
diff --git a/arch/x86/xen/xen-head.S b/arch/x86/xen/xen-head.S
index 497cc55a0c16..96f26e026783 100644
--- a/arch/x86/xen/xen-head.S
+++ b/arch/x86/xen/xen-head.S
@@ -9,7 +9,9 @@
#include <asm/boot.h>
#include <asm/asm.h>
+#include <asm/msr.h>
#include <asm/page_types.h>
+#include <asm/percpu.h>
#include <asm/unwind_hints.h>
#include <xen/interface/elfnote.h>
@@ -35,6 +37,20 @@ ENTRY(startup_xen)
mov %_ASM_SI, xen_start_info
mov $init_thread_union+THREAD_SIZE, %_ASM_SP
+#ifdef CONFIG_X86_64
+ /* Set up %gs.
+ *
+ * The base of %gs always points to the bottom of the irqstack
+ * union. If the stack protector canary is enabled, it is
+ * located at %gs:40. Note that, on SMP, the boot cpu uses
+ * init data section till per cpu areas are set up.
+ */
+ movl $MSR_GS_BASE,%ecx
+ movq $INIT_PER_CPU_VAR(irq_stack_union),%rax
+ cdq
+ wrmsr
+#endif
+
jmp xen_start_kernel
END(startup_xen)
__FINIT