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Diffstat (limited to 'arch/x86/kernel/cpu/common.c')
-rw-r--r--arch/x86/kernel/cpu/common.c59
1 files changed, 53 insertions, 6 deletions
diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index 58094a1f9e9d..8ee32119144d 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -448,19 +448,60 @@ void load_percpu_segment(int cpu)
load_stack_canary_segment();
}
+/* Setup the fixmap mapping only once per-processor */
+static inline void setup_fixmap_gdt(int cpu)
+{
+#ifdef CONFIG_X86_64
+ /* On 64-bit systems, we use a read-only fixmap GDT. */
+ pgprot_t prot = PAGE_KERNEL_RO;
+#else
+ /*
+ * On native 32-bit systems, the GDT cannot be read-only because
+ * our double fault handler uses a task gate, and entering through
+ * a task gate needs to change an available TSS to busy. If the GDT
+ * is read-only, that will triple fault.
+ *
+ * On Xen PV, the GDT must be read-only because the hypervisor requires
+ * it.
+ */
+ pgprot_t prot = boot_cpu_has(X86_FEATURE_XENPV) ?
+ PAGE_KERNEL_RO : PAGE_KERNEL;
+#endif
+
+ __set_fixmap(get_cpu_gdt_ro_index(cpu), get_cpu_gdt_paddr(cpu), prot);
+}
+
+/* Load the original GDT from the per-cpu structure */
+void load_direct_gdt(int cpu)
+{
+ struct desc_ptr gdt_descr;
+
+ gdt_descr.address = (long)get_cpu_gdt_rw(cpu);
+ gdt_descr.size = GDT_SIZE - 1;
+ load_gdt(&gdt_descr);
+}
+EXPORT_SYMBOL_GPL(load_direct_gdt);
+
+/* Load a fixmap remapping of the per-cpu GDT */
+void load_fixmap_gdt(int cpu)
+{
+ struct desc_ptr gdt_descr;
+
+ gdt_descr.address = (long)get_cpu_gdt_ro(cpu);
+ gdt_descr.size = GDT_SIZE - 1;
+ load_gdt(&gdt_descr);
+}
+EXPORT_SYMBOL_GPL(load_fixmap_gdt);
+
/*
* Current gdt points %fs at the "master" per-cpu area: after this,
* it's on the real one.
*/
void switch_to_new_gdt(int cpu)
{
- struct desc_ptr gdt_descr;
-
- gdt_descr.address = (long)get_cpu_gdt_table(cpu);
- gdt_descr.size = GDT_SIZE - 1;
- load_gdt(&gdt_descr);
+ /* Load the original GDT */
+ load_direct_gdt(cpu);
/* Reload the per-cpu base */
-
load_percpu_segment(cpu);
}
@@ -1526,6 +1567,9 @@ void cpu_init(void)
if (is_uv_system())
uv_cpu_init();
+
+ setup_fixmap_gdt(cpu);
+ load_fixmap_gdt(cpu);
}
#else
@@ -1581,6 +1625,9 @@ void cpu_init(void)
dbg_restore_debug_regs();
fpu__init_cpu();
+
+ setup_fixmap_gdt(cpu);
+ load_fixmap_gdt(cpu);
}
#endif