x86: move stack_canary into irq_stack
Impact: x86_64 percpu area layout change, irq_stack now at the beginning
Now that the PDA is empty except for the stack canary, it can be removed.
The irqstack is moved to the start of the per-cpu section. If the stack
protector is enabled, the canary overlaps the bottom 48 bytes of the irqstack.
tj: * updated subject
* dropped asm relocation of irq_stack_ptr
* updated comments a bit
* rebased on top of stack canary changes
Signed-off-by: Brian Gerst <brgerst@gmail.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
index f511246..48676b9 100644
--- a/arch/x86/include/asm/processor.h
+++ b/arch/x86/include/asm/processor.h
@@ -379,8 +379,29 @@
#ifdef CONFIG_X86_64
DECLARE_PER_CPU(struct orig_ist, orig_ist);
-DECLARE_PER_CPU(char[IRQ_STACK_SIZE], irq_stack);
+union irq_stack_union {
+ char irq_stack[IRQ_STACK_SIZE];
+ /*
+ * GCC hardcodes the stack canary as %gs:40. Since the
+ * irq_stack is the object at %gs:0, we reserve the bottom
+ * 48 bytes of the irq stack for the canary.
+ */
+ struct {
+ char gs_base[40];
+ unsigned long stack_canary;
+ };
+};
+
+DECLARE_PER_CPU(union irq_stack_union, irq_stack_union);
DECLARE_PER_CPU(char *, irq_stack_ptr);
+
+static inline void load_gs_base(int cpu)
+{
+ /* Memory clobbers used to order pda/percpu accesses */
+ mb();
+ wrmsrl(MSR_GS_BASE, (unsigned long)per_cpu(irq_stack_union.gs_base, cpu));
+ mb();
+}
#endif
extern void print_cpu_info(struct cpuinfo_x86 *);