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/kernel/setup_percpu.c b/arch/x86/kernel/setup_percpu.c
index efbafbb..90b8e15 100644
--- a/arch/x86/kernel/setup_percpu.c
+++ b/arch/x86/kernel/setup_percpu.c
@@ -77,30 +77,6 @@
static inline void setup_node_to_cpumask_map(void) { }
#endif
-/*
- * Define load_pda_offset() and per-cpu __pda for x86_64.
- * load_pda_offset() is responsible for loading the offset of pda into
- * %gs.
- *
- * On SMP, pda offset also duals as percpu base address and thus it
- * should be at the start of per-cpu area. To achieve this, it's
- * preallocated in vmlinux_64.lds.S directly instead of using
- * DEFINE_PER_CPU().
- */
-#ifdef CONFIG_X86_64
-void __cpuinit load_pda_offset(int cpu)
-{
- /* Memory clobbers used to order pda/percpu accesses */
- mb();
- wrmsrl(MSR_GS_BASE, cpu_pda(cpu));
- mb();
-}
-#ifndef CONFIG_SMP
-DEFINE_PER_CPU(struct x8664_pda, __pda);
-#endif
-EXPORT_PER_CPU_SYMBOL(__pda);
-#endif /* CONFIG_SMP && CONFIG_X86_64 */
-
#ifdef CONFIG_X86_64
/* correctly size the local cpu masks */
@@ -207,15 +183,13 @@
per_cpu(cpu_number, cpu) = cpu;
#ifdef CONFIG_X86_64
per_cpu(irq_stack_ptr, cpu) =
- (char *)per_cpu(irq_stack, cpu) + IRQ_STACK_SIZE - 64;
+ per_cpu(irq_stack_union.irq_stack, cpu) + IRQ_STACK_SIZE - 64;
/*
- * CPU0 modified pda in the init data area, reload pda
- * offset for CPU0 and clear the area for others.
+ * Up to this point, CPU0 has been using .data.init
+ * area. Reload %gs offset for CPU0.
*/
if (cpu == 0)
- load_pda_offset(0);
- else
- memset(cpu_pda(cpu), 0, sizeof(*cpu_pda(cpu)));
+ load_gs_base(cpu);
#endif
DBG("PERCPU: cpu %4d %p\n", cpu, ptr);