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>

1 files changed, 3 insertions, 3 deletions

diff --git a/arch/x86/include/asm/stackprotector.h b/arch/x86/include/asm/stackprotector.h
index 2383e5bb475c..36a700acaf2b 100644
--- a/arch/x86/include/asm/stackprotector.h
+++ b/arch/x86/include/asm/stackprotector.h
@@ -2,7 +2,7 @@
 #define _ASM_STACKPROTECTOR_H 1
 
 #include <asm/tsc.h>
-#include <asm/pda.h>
+#include <asm/processor.h>
 
 /*
  * Initialize the stackprotector canary value.
@@ -19,7 +19,7 @@ static __always_inline void boot_init_stack_canary(void)
          * Build time only check to make sure the stack_canary is at
          * offset 40 in the pda; this is a gcc ABI requirement
          */
-        BUILD_BUG_ON(offsetof(struct x8664_pda, stack_canary) != 40);
+        BUILD_BUG_ON(offsetof(union irq_stack_union, stack_canary) != 40);
 
         /*
          * We both use the random pool and the current TSC as a source
@@ -32,7 +32,7 @@ static __always_inline void boot_init_stack_canary(void)
         canary += tsc + (tsc << 32UL);
 
         current->stack_canary = canary;
-        write_pda(stack_canary, canary);
+        percpu_write(irq_stack_union.stack_canary, canary);
 }
 
 #endif