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| author | Juergen Gross <jgross@suse.com> | 2018-02-01 13:40:19 +0100 |
|---|---|---|
| committer | Ben Hutchings <ben@decadent.org.uk> | 2018-06-16 22:22:06 +0100 |
| commit | 13fae5bb375e04e917fae901ffaf133304d79662 (patch) | |
| tree | 71f231fb5df6dfe675466a0cfa51d2fefaba5b54 /arch | |
| parent | d5b66d9c52bf38470a2b145df33a63d889741d1d (diff) | |
| download | linux-stable-13fae5bb375e04e917fae901ffaf133304d79662.tar.gz linux-stable-13fae5bb375e04e917fae901ffaf133304d79662.tar.bz2 linux-stable-13fae5bb375e04e917fae901ffaf133304d79662.zip | |
x86/xen: init %gs very early to avoid page faults with stack protector
commit 4f277295e54c5b7340e48efea3fc5cc21a2872b7 upstream.
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.
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>
[bwh: Backported to 3.16: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Diffstat (limited to 'arch')
| -rw-r--r-- | arch/x86/xen/xen-head.S | 15 |
1 files changed, 15 insertions, 0 deletions
diff --git a/arch/x86/xen/xen-head.S b/arch/x86/xen/xen-head.S index 485b69585540..3c2465aa5951 100644 --- a/arch/x86/xen/xen-head.S +++ b/arch/x86/xen/xen-head.S @@ -8,7 +8,9 @@ #include <asm/boot.h> #include <asm/asm.h> +#include <asm/msr.h> #include <asm/page_types.h> +#include <asm/percpu.h> #include <xen/interface/elfnote.h> #include <xen/interface/features.h> @@ -42,7 +44,20 @@ ENTRY(startup_xen) #else mov %rsi,xen_start_info mov $init_thread_union+THREAD_SIZE,%rsp + + /* 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 __FINIT |