Attachment #637146 for bug #721734

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Lines 55-62 Link Here

(-)a/arch/x86/include/asm/stackprotector.h (-1 / +6 lines)
55	/*	55	/*
56	* Initialize the stackprotector canary value.	56	* Initialize the stackprotector canary value.
57	*	57	*
58	* NOTE: this must only be called from functions that never return,	58	* NOTE: this must only be called from functions that never return
59	* and it must always be inlined.	59	* and it must always be inlined.
		60	*
		61	* In addition, it should be called from a compilation unit for which
		62	* stack protector is disabled. Alternatively, the caller should not end
		63	* with a function call which gets tail-call optimized as that would
		64	* lead to checking a modified canary value.
60	*/	65	*/
61	static __always_inline void boot_init_stack_canary(void)	66	static __always_inline void boot_init_stack_canary(void)
62	{	67	{

Lines 266-271 static void notrace start_secondary(void *unused) Link Here

(-)a/arch/x86/kernel/smpboot.c (+8 lines)
266		266
267	wmb();	267	wmb();
268	cpu_startup_entry(CPUHP_AP_ONLINE_IDLE);	268	cpu_startup_entry(CPUHP_AP_ONLINE_IDLE);
		269
		270	/*
		271	* Prevent tail call to cpu_startup_entry() because the stack protector
		272	* guard has been changed a couple of function calls up, in
		273	* boot_init_stack_canary() and must not be checked before tail calling
		274	* another function.
		275	*/
		276	prevent_tail_call_optimization();
269	}	277	}
270		278
271	/**	279	/**

Lines 93-98 asmlinkage __visible void cpu_bringup_and_idle(void) Link Here

(-)a/arch/x86/xen/smp_pv.c (+1 lines)
93	cpu_bringup();	93	cpu_bringup();
94	boot_init_stack_canary();	94	boot_init_stack_canary();
95	cpu_startup_entry(CPUHP_AP_ONLINE_IDLE);	95	cpu_startup_entry(CPUHP_AP_ONLINE_IDLE);
		96	prevent_tail_call_optimization();
96	}	97	}
97		98
98	void xen_smp_intr_free_pv(unsigned int cpu)	99	void xen_smp_intr_free_pv(unsigned int cpu)

Lines 356-359 static inline void offset_to_ptr(const int off) Link Here

(-)a/include/linux/compiler.h (+6 lines)
356	/* &a[0] degrades to a pointer: a different type from an array */	356	/* &a[0] degrades to a pointer: a different type from an array */
357	#define __must_be_array(a) BUILD_BUG_ON_ZERO(__same_type((a), &(a)[0]))	357	#define __must_be_array(a) BUILD_BUG_ON_ZERO(__same_type((a), &(a)[0]))
358		358
		359	/*
		360	* This is needed in functions which generate the stack canary, see
		361	* arch/x86/kernel/smpboot.c::start_secondary() for an example.
		362	*/
		363	#define prevent_tail_call_optimization() asm("")
		364
359	#endif /* __LINUX_COMPILER_H */	365	#endif /* __LINUX_COMPILER_H */

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