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Commit c6e50f93 authored by Tejun Heo's avatar Tejun Heo
Browse files

x86: cleanup stack protector 



Impact: cleanup

Make the following cleanups.

* remove duplicate comment from boot_init_stack_canary() which fits
  better in the other place - cpu_idle().

* move stack_canary offset check from __switch_to() to
  boot_init_stack_canary().

Signed-off-by: default avatarTejun Heo <tj@kernel.org>
parent 7890ba8c

arch/x86/include/asm/pda.h

+0 −2
Original line number Diff line number Diff line
@@ -40,6 +40,4 @@ extern void pda_init(int); 


#endif



#define refresh_stack_canary() write_pda(stack_canary, current->stack_canary)



#endif /* _ASM_X86_PDA_H */

arch/x86/include/asm/stackprotector.h

+6 −7
Original line number Diff line number Diff line
@@ -16,13 +16,12 @@ static __always_inline void boot_init_stack_canary(void) 
	u64 tsc;



	/*

	 * If we're the non-boot CPU, nothing set the PDA stack

	 * canary up for us - and if we are the boot CPU we have

	 * a 0 stack canary. This is a good place for updating

	 * it, as we wont ever return from this function (so the

	 * invalid canaries already on the stack wont ever

	 * trigger).

	 *

	 * 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);



	/*

	 * We both use the random pool and the current TSC as a source

	 * of randomness. The TSC only matters for very early init,

	 * there it already has some randomness on most systems. Later

arch/x86/kernel/process_64.c

+0 −7
Original line number Diff line number Diff line
@@ -638,13 +638,6 @@ __switch_to(struct task_struct *prev_p, struct task_struct *next_p) 
	percpu_write(kernel_stack,

		  (unsigned long)task_stack_page(next_p) +

		  THREAD_SIZE - KERNEL_STACK_OFFSET);

#ifdef CONFIG_CC_STACKPROTECTOR

	/*

	 * 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);

#endif



	/*

	 * Now maybe reload the debug registers and handle I/O bitmaps