xen: rearrange things to fix stackprotector

Make sure the stack-protector segment registers are properly set up
before calling any functions which may have stack-protection compiled
into them.

[ Impact: prevent Xen early-boot crash when stack-protector is enabled ]
Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>

2 files changed, 14 insertions, 12 deletions

diff --git a/arch/x86/xen/Makefile b/arch/x86/xen/Makefile
index 3b767d03fd6..a5b9288b7da 100644
--- a/arch/x86/xen/Makefile
+++ b/arch/x86/xen/Makefile
@@ -5,6 +5,10 @@ CFLAGS_REMOVE_time.o = -pg
 CFLAGS_REMOVE_irq.o = -pg
 endif
 
+# Make sure early boot has no stackprotector
+nostackp := $(call cc-option, -fno-stack-protector)
+CFLAGS_enlighten.o              := $(nostackp)
+
 obj-y           := enlighten.o setup.o multicalls.o mmu.o irq.o \
                         time.o xen-asm.o xen-asm_$(BITS).o \
                         grant-table.o suspend.o
diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
index f09e8c36ee8..edcf72a3c29 100644
--- a/arch/x86/xen/enlighten.c
+++ b/arch/x86/xen/enlighten.c
@@ -925,10 +925,6 @@ asmlinkage void __init xen_start_kernel(void)
 
         xen_domain_type = XEN_PV_DOMAIN;
 
-        BUG_ON(memcmp(xen_start_info->magic, "xen-3", 5) != 0);
-
-        xen_setup_features();
-
         /* Install Xen paravirt ops */
         pv_info = xen_info;
         pv_init_ops = xen_init_ops;
@@ -937,8 +933,15 @@ asmlinkage void __init xen_start_kernel(void)
         pv_apic_ops = xen_apic_ops;
         pv_mmu_ops = xen_mmu_ops;
 
-        xen_init_irq_ops();
+#ifdef CONFIG_X86_64
+        /*
+         * Setup percpu state.  We only need to do this for 64-bit
+         * because 32-bit already has %fs set properly.
+         */
+        load_percpu_segment(0);
+#endif
 
+        xen_init_irq_ops();
         xen_init_cpuid_mask();
 
 #ifdef CONFIG_X86_LOCAL_APIC
@@ -948,6 +951,8 @@ asmlinkage void __init xen_start_kernel(void)
         set_xen_basic_apic_ops();
 #endif
 
+        xen_setup_features();
+
         if (xen_feature(XENFEAT_mmu_pt_update_preserve_ad)) {
                 pv_mmu_ops.ptep_modify_prot_start = xen_ptep_modify_prot_start;
                 pv_mmu_ops.ptep_modify_prot_commit = xen_ptep_modify_prot_commit;
@@ -955,13 +960,6 @@ asmlinkage void __init xen_start_kernel(void)
 
         machine_ops = xen_machine_ops;
 
-#ifdef CONFIG_X86_64
-        /*
-         * Setup percpu state.  We only need to do this for 64-bit
-         * because 32-bit already has %fs set properly.
-         */
-        load_percpu_segment(0);
-#endif
         /*
          * The only reliable way to retain the initial address of the
          * percpu gdt_page is to remember it here, so we can go and