Commit 800d6acf authored by Johannes Berg's avatar Johannes Berg Committed by Paul E. McKenney
Browse files

rcu: tiny: Record kvfree_call_rcu() call stack for KASAN 



When running KASAN with Tiny RCU (e.g. under ARCH=um, where
a working KASAN patch is now available), we don't get any
information on the original kfree_rcu() (or similar) caller
when a problem is reported, as Tiny RCU doesn't record this.

Add the recording, which required pulling kvfree_call_rcu()
out of line for the KASAN case since the recording function
(kasan_record_aux_stack_noalloc) is neither exported, nor
can we include kasan.h into rcutiny.h.

without KASAN, the patch has no size impact (ARCH=um kernel):
    text       data         bss         dec        hex    filename
 6151515    4423154    33148520    43723189    29b29b5    linux
 6151515    4423154    33148520    43723189    29b29b5    linux + patch

with KASAN, the impact on my build was minimal:
    text       data         bss         dec        hex    filename
13915539    7388050    33282304    54585893    340ea25    linux
13911266    7392114    33282304    54585684    340e954    linux + patch
   -4273      +4064         +-0        -209

Acked-by: default avatarDmitry Vyukov <dvyukov@google.com>
Signed-off-by: default avatarJohannes Berg <johannes.berg@intel.com>
Signed-off-by: default avatarPaul E. McKenney <paulmck@kernel.org>
parent 9c9b26b0

include/linux/rcutiny.h

+10 −1
Original line number Diff line number Diff line
@@ -38,7 +38,7 @@ static inline void synchronize_rcu_expedited(void) 
 */

extern void kvfree(const void *addr);



static inline void kvfree_call_rcu(struct rcu_head *head, rcu_callback_t func)

static inline void __kvfree_call_rcu(struct rcu_head *head, rcu_callback_t func)

{

	if (head) {

		call_rcu(head, func);
@@ -51,6 +51,15 @@ static inline void kvfree_call_rcu(struct rcu_head *head, rcu_callback_t func) 
	kvfree((void *) func);

}



#ifdef CONFIG_KASAN_GENERIC

void kvfree_call_rcu(struct rcu_head *head, rcu_callback_t func);

#else

static inline void kvfree_call_rcu(struct rcu_head *head, rcu_callback_t func)

{

	__kvfree_call_rcu(head, func);

}

#endif



void rcu_qs(void);



static inline void rcu_softirq_qs(void)

kernel/rcu/tiny.c

+14 −0
Original line number Diff line number Diff line
@@ -217,6 +217,20 @@ bool poll_state_synchronize_rcu(unsigned long oldstate) 
}

EXPORT_SYMBOL_GPL(poll_state_synchronize_rcu);



#ifdef CONFIG_KASAN_GENERIC

void kvfree_call_rcu(struct rcu_head *head, rcu_callback_t func)

{

	if (head) {

		void *ptr = (void *) head - (unsigned long) func;



		kasan_record_aux_stack_noalloc(ptr);

	}



	__kvfree_call_rcu(head, func);

}

EXPORT_SYMBOL_GPL(kvfree_call_rcu);

#endif



void __init rcu_init(void)

{

	open_softirq(RCU_SOFTIRQ, rcu_process_callbacks);