[patch V3 12/32] x86/cpu_entry_area: Prepare for IST guard pages

Thomas Gleixner
2019-04-14T16:04:30Z

To allow guard pages between the IST stacks each stack needs to be mapped
individually.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
arch/x86/mm/cpu_entry_area.c | 37 ++++++++++++++++++++++++++++++-------
1 file changed, 30 insertions(+), 7 deletions(-)

--- a/arch/x86/mm/cpu_entry_area.c
+++ b/arch/x86/mm/cpu_entry_area.c
@@ -77,6 +77,34 @@ static void __init percpu_setup_debug_st
#endif
}

+#ifdef CONFIG_X86_64
+
+#define cea_map_stack(name) do { \
+ npages = sizeof(estacks->name## _stack) / PAGE_SIZE; \
+ cea_map_percpu_pages(cea->estacks.name## _stack, \
+ estacks->name## _stack, npages, PAGE_KERNEL); \
+ } while (0)
+
+static void __init percpu_setup_exception_stacks(unsigned int cpu)
+{
+ struct exception_stacks *estacks = per_cpu_ptr(&exception_stacks, cpu);
+ struct cpu_entry_area *cea = get_cpu_entry_area(cpu);
+ unsigned int npages;
+
+ BUILD_BUG_ON(sizeof(exception_stacks) % PAGE_SIZE != 0);
+ /*
+ * The exceptions stack mappings in the per cpu area are protected
+ * by guard pages so each stack must be mapped separately.
+ */
+ cea_map_stack(DF);
+ cea_map_stack(NMI);
+ cea_map_stack(DB);
+ cea_map_stack(MCE);
+}
+#else
+static inline void percpu_setup_exception_stacks(unsigned int cpu) {}
+#endif
+
/* Setup the fixmap mappings only once per-processor */
static void __init setup_cpu_entry_area(unsigned int cpu)
{
@@ -134,13 +162,8 @@ static void __init setup_cpu_entry_area(
per_cpu(cpu_entry_area, cpu) = cea;
#endif

-#ifdef CONFIG_X86_64
- BUILD_BUG_ON(sizeof(exception_stacks) % PAGE_SIZE != 0);
- BUILD_BUG_ON(sizeof(exception_stacks) !=
- sizeof(((struct cpu_entry_area *)0)->estacks));
- cea_map_percpu_pages(&cea->estacks, &per_cpu(exception_stacks, cpu),
- sizeof(exception_stacks) / PAGE_SIZE, PAGE_KERNEL);
-#endif
+ percpu_setup_exception_stacks(cpu);
+
percpu_setup_debug_store(cpu);
}