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: [email protected]
Signed-off-by: Juergen Gross <[email protected]>
---
arch/x86/xen/xen-head.S | 16 ++++++++++++++++
1 file changed, 16 insertions(+)
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
--
2.13.6
On 02/01/2018 07:40 AM, Juergen Gross wrote:
> 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: [email protected]
> Signed-off-by: Juergen Gross <[email protected]>
Reviewed-by: Boris Ostrovsky <[email protected]>
Works great, tested it and it fixes booting Linux v4.15 kernel for me :)
Cheers!
On Thu, Feb 1, 2018 at 3:17 PM, Boris Ostrovsky
<[email protected]> wrote:
> On 02/01/2018 07:40 AM, Juergen Gross wrote:
>> 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: [email protected]
>> Signed-off-by: Juergen Gross <[email protected]>
>
> Reviewed-by: Boris Ostrovsky <[email protected]>
>
>
>
> _______________________________________________
> Xen-devel mailing list
> [email protected]
> https://lists.xenproject.org/mailman/listinfo/xen-devel
On 02/02/18 01:36, Chris Patterson wrote:
> Works great, tested it and it fixes booting Linux v4.15 kernel for me :)
Can I add your "Tested-by:" to the patch when committing it?
Juergen
>
> Cheers!
>
> On Thu, Feb 1, 2018 at 3:17 PM, Boris Ostrovsky
> <[email protected]> wrote:
>> On 02/01/2018 07:40 AM, Juergen Gross wrote:
>>> 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: [email protected]
>>> Signed-off-by: Juergen Gross <[email protected]>
>>
>> Reviewed-by: Boris Ostrovsky <[email protected]>
>>
>>
>>
>> _______________________________________________
>> Xen-devel mailing list
>> [email protected]
>> https://lists.xenproject.org/mailman/listinfo/xen-devel
>
On Fri, Feb 2, 2018 at 12:56 AM, Juergen Gross <[email protected]> wrote:
> On 02/02/18 01:36, Chris Patterson wrote:
>> Works great, tested it and it fixes booting Linux v4.15 kernel for me :)
>
> Can I add your "Tested-by:" to the patch when committing it?
>
>
Sure thing, have a great day.