x86/xen: init %gs very early to avoid page faults with stack protector
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Web: https://git.kernel.org/torvalds/c/4f277295e54c5b7340e48efea3fc5cc21a2872b7 Commit: 4f277295e54c5b7340e48efea3fc5cc21a2872b7 Parent: ddb9e13af3bba3f8c36ccee0eb9563a82b425c12 Refname: refs/heads/master Author: Juergen Gross <[email protected]> AuthorDate: Thu Feb 1 13:40:19 2018 +0100 Committer: Juergen Gross <[email protected]> CommitDate: Tue Feb 6 09:37:18 2018 +0100 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: [email protected] Signed-off-by: Juergen Gross <[email protected]> Reviewed-by: Boris Ostrovsky <[email protected]> Tested-by: Chris Patterson <[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 -- To unsubscribe from this list: send the line "unsubscribe git-commits-head" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html