[Linux-stable-mirror] [PATCH] 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 --- arch/x86/xen/xen-head.S | 14 ++++++++++++++ 1 file changed, 14 insertions(+)
diff --git a/arch/x86/xen/xen-head.S b/arch/x86/xen/xen-head.S index 497cc55a0c16..b47d87076efb 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 +37,18 @@ ENTRY(startup_xen) mov %_ASM_SI, xen_start_info mov $init_thread_union+THREAD_SIZE, %_ASM_SP
+ /* 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 + jmp xen_start_kernel END(startup_xen) __FINIT
On 01/02/18 12:16, 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: stable@vger.kernel.org Signed-off-by: Juergen Gross jgross@suse.com
arch/x86/xen/xen-head.S | 14 ++++++++++++++ 1 file changed, 14 insertions(+)
diff --git a/arch/x86/xen/xen-head.S b/arch/x86/xen/xen-head.S index 497cc55a0c16..b47d87076efb 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 +37,18 @@ ENTRY(startup_xen) mov %_ASM_SI, xen_start_info mov $init_thread_union+THREAD_SIZE, %_ASM_SP
- /* 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
You surely want a #ifdef __x86_64__ ? This path is common to the 32bit entry as well?
~Andrew
- jmp xen_start_kernel
END(startup_xen) __FINIT
On 01/02/18 13:22, Andrew Cooper wrote:
On 01/02/18 12:16, 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: stable@vger.kernel.org Signed-off-by: Juergen Gross jgross@suse.com
arch/x86/xen/xen-head.S | 14 ++++++++++++++ 1 file changed, 14 insertions(+)
diff --git a/arch/x86/xen/xen-head.S b/arch/x86/xen/xen-head.S index 497cc55a0c16..b47d87076efb 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 +37,18 @@ ENTRY(startup_xen) mov %_ASM_SI, xen_start_info mov $init_thread_union+THREAD_SIZE, %_ASM_SP
- /* 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
You surely want a #ifdef __x86_64__ ? This path is common to the 32bit entry as well?
Oh, indeed! Thanks for noticing.
V2 coming soon...
Juergen
linux-stable-mirror@lists.linaro.org
-
Andrew Cooper -
Juergen Gross