2018-02-17 17:49:59 +01:00
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From cd0c80aa02dbfe649c743fa98fcc0d9f427e0827 Mon Sep 17 00:00:00 2001
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Message-Id: <cd0c80aa02dbfe649c743fa98fcc0d9f427e0827.1518828081.git.jan.steffens@gmail.com>
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In-Reply-To: <05a43fb8b36cdaf6a3580f46cab334f2c2796544.1518828081.git.jan.steffens@gmail.com>
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References: <05a43fb8b36cdaf6a3580f46cab334f2c2796544.1518828081.git.jan.steffens@gmail.com>
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2018-02-15 02:28:36 +01:00
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From: Juergen Gross <jgross@suse.com>
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Date: Thu, 1 Feb 2018 13:40:19 +0100
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2018-02-17 17:49:59 +01:00
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Subject: [PATCH 3/3] x86/xen: init %gs very early to avoid page faults with
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2018-02-15 02:28:36 +01:00
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stack protector
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When running as Xen pv guest %gs is initialized some time after
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C code is started. Depending on stack protector usage this might be
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too late, resulting in page faults.
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So setup %gs and MSR_GS_BASE in assembly code already.
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Cc: stable@vger.kernel.org
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Signed-off-by: Juergen Gross <jgross@suse.com>
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Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
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Tested-by: Chris Patterson <cjp256@gmail.com>
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Signed-off-by: Juergen Gross <jgross@suse.com>
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---
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arch/x86/xen/xen-head.S | 16 ++++++++++++++++
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1 file changed, 16 insertions(+)
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diff --git a/arch/x86/xen/xen-head.S b/arch/x86/xen/xen-head.S
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index 497cc55a0c16..96f26e026783 100644
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--- a/arch/x86/xen/xen-head.S
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+++ b/arch/x86/xen/xen-head.S
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@@ -9,32 +9,48 @@
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#include <asm/boot.h>
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#include <asm/asm.h>
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+#include <asm/msr.h>
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#include <asm/page_types.h>
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+#include <asm/percpu.h>
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#include <asm/unwind_hints.h>
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#include <xen/interface/elfnote.h>
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#include <xen/interface/features.h>
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#include <xen/interface/xen.h>
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#include <xen/interface/xen-mca.h>
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#include <asm/xen/interface.h>
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#ifdef CONFIG_XEN_PV
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__INIT
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ENTRY(startup_xen)
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UNWIND_HINT_EMPTY
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cld
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/* Clear .bss */
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xor %eax,%eax
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mov $__bss_start, %_ASM_DI
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mov $__bss_stop, %_ASM_CX
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sub %_ASM_DI, %_ASM_CX
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shr $__ASM_SEL(2, 3), %_ASM_CX
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rep __ASM_SIZE(stos)
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mov %_ASM_SI, xen_start_info
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mov $init_thread_union+THREAD_SIZE, %_ASM_SP
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+#ifdef CONFIG_X86_64
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+ /* Set up %gs.
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+ *
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+ * The base of %gs always points to the bottom of the irqstack
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+ * union. If the stack protector canary is enabled, it is
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+ * located at %gs:40. Note that, on SMP, the boot cpu uses
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+ * init data section till per cpu areas are set up.
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+ */
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+ movl $MSR_GS_BASE,%ecx
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+ movq $INIT_PER_CPU_VAR(irq_stack_union),%rax
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+ cdq
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+ wrmsr
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+#endif
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+
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jmp xen_start_kernel
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END(startup_xen)
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__FINIT
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--
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2.16.1
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