Commit-ID: 29dee3c03abce04cd527878ef5f9e5f91b7b83f4
Gitweb: http://git.kernel.org/tip/29dee3c03abce04cd527878ef5f9e5f91b7b83f4
Author: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
AuthorDate: Fri, 10 Feb 2017 16:27:52 +0100
Committer: Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Fri, 24 Feb 2017 09:02:10 +0100
locking/refcounts: Out-of-line everything
Linus asked to please make this real C code.
And since size then isn't an issue what so ever anymore, remove the
debug knob and make all WARN()s unconditional.
Suggested-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: dwindsor@xxxxxxxxx
Cc: elena.reshetova@xxxxxxxxx
Cc: gregkh@xxxxxxxxxxxxxxxxxxx
Cc: ishkamiel@xxxxxxxxx
Cc: keescook@xxxxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
include/linux/refcount.h | 277 ++---------------------------
lib/Kconfig.debug | 13 --
lib/Makefile | 2 +-
include/linux/refcount.h => lib/refcount.c | 87 ++++-----
4 files changed, 43 insertions(+), 336 deletions(-)
diff --git a/include/linux/refcount.h b/include/linux/refcount.h
index 600aadf..0e8cfb2 100644
--- a/include/linux/refcount.h
+++ b/include/linux/refcount.h
@@ -1,55 +1,10 @@
#ifndef _LINUX_REFCOUNT_H
#define _LINUX_REFCOUNT_H
-/*
- * Variant of atomic_t specialized for reference counts.
- *
- * The interface matches the atomic_t interface (to aid in porting) but only
- * provides the few functions one should use for reference counting.
- *
- * It differs in that the counter saturates at UINT_MAX and will not move once
- * there. This avoids wrapping the counter and causing 'spurious'
- * use-after-free issues.
- *
- * Memory ordering rules are slightly relaxed wrt regular atomic_t functions
- * and provide only what is strictly required for refcounts.
- *
- * The increments are fully relaxed; these will not provide ordering. The
- * rationale is that whatever is used to obtain the object we're increasing the
- * reference count on will provide the ordering. For locked data structures,
- * its the lock acquire, for RCU/lockless data structures its the dependent
- * load.
- *
- * Do note that inc_not_zero() provides a control dependency which will order
- * future stores against the inc, this ensures we'll never modify the object
- * if we did not in fact acquire a reference.
- *
- * The decrements will provide release order, such that all the prior loads and
- * stores will be issued before, it also provides a control dependency, which
- * will order us against the subsequent free().
- *
- * The control dependency is against the load of the cmpxchg (ll/sc) that
- * succeeded. This means the stores aren't fully ordered, but this is fine
- * because the 1->0 transition indicates no concurrency.
- *
- * Note that the allocator is responsible for ordering things between free()
- * and alloc().
- *
- */
-
#include <linux/atomic.h>
-#include <linux/bug.h>
#include <linux/mutex.h>
#include <linux/spinlock.h>
-#ifdef CONFIG_DEBUG_REFCOUNT
-#define REFCOUNT_WARN(cond, str) WARN_ON(cond)
-#define __refcount_check __must_check
-#else
-#define REFCOUNT_WARN(cond, str) (void)(cond)
-#define __refcount_check
-#endif
-
typedef struct refcount_struct {
atomic_t refs;
} refcount_t;
@@ -66,229 +21,21 @@ static inline unsigned int refcount_read(const refcount_t *r)
return atomic_read(&r->refs);
}
-static inline __refcount_check
-bool refcount_add_not_zero(unsigned int i, refcount_t *r)
-{
- unsigned int old, new, val = atomic_read(&r->refs);
-
- for (;;) {
- if (!val)
- return false;
-
- if (unlikely(val == UINT_MAX))
- return true;
-
- new = val + i;
- if (new < val)
- new = UINT_MAX;
- old = atomic_cmpxchg_relaxed(&r->refs, val, new);
- if (old == val)
- break;
-
- val = old;
- }
-
- REFCOUNT_WARN(new == UINT_MAX, "refcount_t: saturated; leaking memory.\n");
-
- return true;
-}
-
-static inline void refcount_add(unsigned int i, refcount_t *r)
-{
- REFCOUNT_WARN(!refcount_add_not_zero(i, r), "refcount_t: addition on 0; use-after-free.\n");
-}
-
-/*
- * Similar to atomic_inc_not_zero(), will saturate at UINT_MAX and WARN.
- *
- * Provides no memory ordering, it is assumed the caller has guaranteed the
- * object memory to be stable (RCU, etc.). It does provide a control dependency
- * and thereby orders future stores. See the comment on top.
- */
-static inline __refcount_check
-bool refcount_inc_not_zero(refcount_t *r)
-{
- unsigned int old, new, val = atomic_read(&r->refs);
-
- for (;;) {
- new = val + 1;
-
- if (!val)
- return false;
-
- if (unlikely(!new))
- return true;
-
- old = atomic_cmpxchg_relaxed(&r->refs, val, new);
- if (old == val)
- break;
-
- val = old;
- }
-
- REFCOUNT_WARN(new == UINT_MAX, "refcount_t: saturated; leaking memory.\n");
-
- return true;
-}
-
-/*
- * Similar to atomic_inc(), will saturate at UINT_MAX and WARN.
- *
- * Provides no memory ordering, it is assumed the caller already has a
- * reference on the object, will WARN when this is not so.
- */
-static inline void refcount_inc(refcount_t *r)
-{
- REFCOUNT_WARN(!refcount_inc_not_zero(r), "refcount_t: increment on 0; use-after-free.\n");
-}
-
-/*
- * Similar to atomic_dec_and_test(), it will WARN on underflow and fail to
- * decrement when saturated at UINT_MAX.
- *
- * Provides release memory ordering, such that prior loads and stores are done
- * before, and provides a control dependency such that free() must come after.
- * See the comment on top.
- */
-static inline __refcount_check
-bool refcount_sub_and_test(unsigned int i, refcount_t *r)
-{
- unsigned int old, new, val = atomic_read(&r->refs);
-
- for (;;) {
- if (unlikely(val == UINT_MAX))
- return false;
-
- new = val - i;
- if (new > val) {
- REFCOUNT_WARN(new > val, "refcount_t: underflow; use-after-free.\n");
- return false;
- }
-
- old = atomic_cmpxchg_release(&r->refs, val, new);
- if (old == val)
- break;
-
- val = old;
- }
-
- return !new;
-}
-
-static inline __refcount_check
-bool refcount_dec_and_test(refcount_t *r)
-{
- return refcount_sub_and_test(1, r);
-}
+extern __must_check bool refcount_add_not_zero(unsigned int i, refcount_t *r);
+extern void refcount_add(unsigned int i, refcount_t *r);
-/*
- * Similar to atomic_dec(), it will WARN on underflow and fail to decrement
- * when saturated at UINT_MAX.
- *
- * Provides release memory ordering, such that prior loads and stores are done
- * before.
- */
-static inline
-void refcount_dec(refcount_t *r)
-{
- REFCOUNT_WARN(refcount_dec_and_test(r), "refcount_t: decrement hit 0; leaking memory.\n");
-}
-
-/*
- * No atomic_t counterpart, it attempts a 1 -> 0 transition and returns the
- * success thereof.
- *
- * Like all decrement operations, it provides release memory order and provides
- * a control dependency.
- *
- * It can be used like a try-delete operator; this explicit case is provided
- * and not cmpxchg in generic, because that would allow implementing unsafe
- * operations.
- */
-static inline __refcount_check
-bool refcount_dec_if_one(refcount_t *r)
-{
- return atomic_cmpxchg_release(&r->refs, 1, 0) == 1;
-}
-
-/*
- * No atomic_t counterpart, it decrements unless the value is 1, in which case
- * it will return false.
- *
- * Was often done like: atomic_add_unless(&var, -1, 1)
- */
-static inline __refcount_check
-bool refcount_dec_not_one(refcount_t *r)
-{
- unsigned int old, new, val = atomic_read(&r->refs);
+extern __must_check bool refcount_inc_not_zero(refcount_t *r);
+extern void refcount_inc(refcount_t *r);
- for (;;) {
- if (unlikely(val == UINT_MAX))
- return true;
+extern __must_check bool refcount_sub_and_test(unsigned int i, refcount_t *r);
+extern void refcount_sub(unsigned int i, refcount_t *r);
- if (val == 1)
- return false;
+extern __must_check bool refcount_dec_and_test(refcount_t *r);
+extern void refcount_dec(refcount_t *r);
- new = val - 1;
- if (new > val) {
- REFCOUNT_WARN(new > val, "refcount_t: underflow; use-after-free.\n");
- return true;
- }
-
- old = atomic_cmpxchg_release(&r->refs, val, new);
- if (old == val)
- break;
-
- val = old;
- }
-
- return true;
-}
-
-/*
- * Similar to atomic_dec_and_mutex_lock(), it will WARN on underflow and fail
- * to decrement when saturated at UINT_MAX.
- *
- * Provides release memory ordering, such that prior loads and stores are done
- * before, and provides a control dependency such that free() must come after.
- * See the comment on top.
- */
-static inline __refcount_check
-bool refcount_dec_and_mutex_lock(refcount_t *r, struct mutex *lock)
-{
- if (refcount_dec_not_one(r))
- return false;
-
- mutex_lock(lock);
- if (!refcount_dec_and_test(r)) {
- mutex_unlock(lock);
- return false;
- }
-
- return true;
-}
-
-/*
- * Similar to atomic_dec_and_lock(), it will WARN on underflow and fail to
- * decrement when saturated at UINT_MAX.
- *
- * Provides release memory ordering, such that prior loads and stores are done
- * before, and provides a control dependency such that free() must come after.
- * See the comment on top.
- */
-static inline __refcount_check
-bool refcount_dec_and_lock(refcount_t *r, spinlock_t *lock)
-{
- if (refcount_dec_not_one(r))
- return false;
-
- spin_lock(lock);
- if (!refcount_dec_and_test(r)) {
- spin_unlock(lock);
- return false;
- }
-
- return true;
-}
+extern __must_check bool refcount_dec_if_one(refcount_t *r);
+extern __must_check bool refcount_dec_not_one(refcount_t *r);
+extern __must_check bool refcount_dec_and_mutex_lock(refcount_t *r, struct mutex *lock);
+extern __must_check bool refcount_dec_and_lock(refcount_t *r, spinlock_t *lock);
#endif /* _LINUX_REFCOUNT_H */
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index acedbe6..0dbce99 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -716,19 +716,6 @@ source "lib/Kconfig.kmemcheck"
source "lib/Kconfig.kasan"
-config DEBUG_REFCOUNT
- bool "Verbose refcount checks"
- help
- Say Y here if you want reference counters (refcount_t and kref) to
- generate WARNs on dubious usage. Without this refcount_t will still
- be a saturating counter and avoid Use-After-Free by turning it into
- a resource leak Denial-Of-Service.
-
- Use of this option will increase kernel text size but will alert the
- admin of potential abuse.
-
- If in doubt, say "N".
-
endmenu # "Memory Debugging"
config ARCH_HAS_KCOV
diff --git a/lib/Makefile b/lib/Makefile
index 19ea761..192e4d0 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -36,7 +36,7 @@ obj-y += bcd.o div64.o sort.o parser.o debug_locks.o random32.o \
gcd.o lcm.o list_sort.o uuid.o flex_array.o iov_iter.o clz_ctz.o \
bsearch.o find_bit.o llist.o memweight.o kfifo.o \
percpu-refcount.o percpu_ida.o rhashtable.o reciprocal_div.o \
- once.o
+ once.o refcount.o
obj-y += string_helpers.o
obj-$(CONFIG_TEST_STRING_HELPERS) += test-string_helpers.o
obj-y += hexdump.o
diff --git a/include/linux/refcount.h b/lib/refcount.c
similarity index 78%
copy from include/linux/refcount.h
copy to lib/refcount.c
index 600aadf..1d33366 100644
--- a/include/linux/refcount.h
+++ b/lib/refcount.c
@@ -1,6 +1,3 @@
-#ifndef _LINUX_REFCOUNT_H
-#define _LINUX_REFCOUNT_H
-
/*
* Variant of atomic_t specialized for reference counts.
*
@@ -37,36 +34,9 @@
*
*/
-#include <linux/atomic.h>
+#include <linux/refcount.h>
#include <linux/bug.h>
-#include <linux/mutex.h>
-#include <linux/spinlock.h>
-
-#ifdef CONFIG_DEBUG_REFCOUNT
-#define REFCOUNT_WARN(cond, str) WARN_ON(cond)
-#define __refcount_check __must_check
-#else
-#define REFCOUNT_WARN(cond, str) (void)(cond)
-#define __refcount_check
-#endif
-
-typedef struct refcount_struct {
- atomic_t refs;
-} refcount_t;
-
-#define REFCOUNT_INIT(n) { .refs = ATOMIC_INIT(n), }
-
-static inline void refcount_set(refcount_t *r, unsigned int n)
-{
- atomic_set(&r->refs, n);
-}
-static inline unsigned int refcount_read(const refcount_t *r)
-{
- return atomic_read(&r->refs);
-}
-
-static inline __refcount_check
bool refcount_add_not_zero(unsigned int i, refcount_t *r)
{
unsigned int old, new, val = atomic_read(&r->refs);
@@ -88,15 +58,17 @@ bool refcount_add_not_zero(unsigned int i, refcount_t *r)
val = old;
}
- REFCOUNT_WARN(new == UINT_MAX, "refcount_t: saturated; leaking memory.\n");
+ WARN(new == UINT_MAX, "refcount_t: saturated; leaking memory.\n");
return true;
}
+EXPORT_SYMBOL_GPL(refcount_add_not_zero);
-static inline void refcount_add(unsigned int i, refcount_t *r)
+void refcount_add(unsigned int i, refcount_t *r)
{
- REFCOUNT_WARN(!refcount_add_not_zero(i, r), "refcount_t: addition on 0; use-after-free.\n");
+ WARN(!refcount_add_not_zero(i, r), "refcount_t: addition on 0; use-after-free.\n");
}
+EXPORT_SYMBOL_GPL(refcount_add);
/*
* Similar to atomic_inc_not_zero(), will saturate at UINT_MAX and WARN.
@@ -105,7 +77,6 @@ static inline void refcount_add(unsigned int i, refcount_t *r)
* object memory to be stable (RCU, etc.). It does provide a control dependency
* and thereby orders future stores. See the comment on top.
*/
-static inline __refcount_check
bool refcount_inc_not_zero(refcount_t *r)
{
unsigned int old, new, val = atomic_read(&r->refs);
@@ -126,10 +97,11 @@ bool refcount_inc_not_zero(refcount_t *r)
val = old;
}
- REFCOUNT_WARN(new == UINT_MAX, "refcount_t: saturated; leaking memory.\n");
+ WARN(new == UINT_MAX, "refcount_t: saturated; leaking memory.\n");
return true;
}
+EXPORT_SYMBOL_GPL(refcount_inc_not_zero);
/*
* Similar to atomic_inc(), will saturate at UINT_MAX and WARN.
@@ -137,20 +109,12 @@ bool refcount_inc_not_zero(refcount_t *r)
* Provides no memory ordering, it is assumed the caller already has a
* reference on the object, will WARN when this is not so.
*/
-static inline void refcount_inc(refcount_t *r)
+void refcount_inc(refcount_t *r)
{
- REFCOUNT_WARN(!refcount_inc_not_zero(r), "refcount_t: increment on 0; use-after-free.\n");
+ WARN(!refcount_inc_not_zero(r), "refcount_t: increment on 0; use-after-free.\n");
}
+EXPORT_SYMBOL_GPL(refcount_inc);
-/*
- * Similar to atomic_dec_and_test(), it will WARN on underflow and fail to
- * decrement when saturated at UINT_MAX.
- *
- * Provides release memory ordering, such that prior loads and stores are done
- * before, and provides a control dependency such that free() must come after.
- * See the comment on top.
- */
-static inline __refcount_check
bool refcount_sub_and_test(unsigned int i, refcount_t *r)
{
unsigned int old, new, val = atomic_read(&r->refs);
@@ -161,7 +125,7 @@ bool refcount_sub_and_test(unsigned int i, refcount_t *r)
new = val - i;
if (new > val) {
- REFCOUNT_WARN(new > val, "refcount_t: underflow; use-after-free.\n");
+ WARN(new > val, "refcount_t: underflow; use-after-free.\n");
return false;
}
@@ -174,12 +138,21 @@ bool refcount_sub_and_test(unsigned int i, refcount_t *r)
return !new;
}
+EXPORT_SYMBOL_GPL(refcount_sub_and_test);
-static inline __refcount_check
+/*
+ * Similar to atomic_dec_and_test(), it will WARN on underflow and fail to
+ * decrement when saturated at UINT_MAX.
+ *
+ * Provides release memory ordering, such that prior loads and stores are done
+ * before, and provides a control dependency such that free() must come after.
+ * See the comment on top.
+ */
bool refcount_dec_and_test(refcount_t *r)
{
return refcount_sub_and_test(1, r);
}
+EXPORT_SYMBOL_GPL(refcount_dec_and_test);
/*
* Similar to atomic_dec(), it will WARN on underflow and fail to decrement
@@ -188,11 +161,12 @@ bool refcount_dec_and_test(refcount_t *r)
* Provides release memory ordering, such that prior loads and stores are done
* before.
*/
-static inline
+
void refcount_dec(refcount_t *r)
{
- REFCOUNT_WARN(refcount_dec_and_test(r), "refcount_t: decrement hit 0; leaking memory.\n");
+ WARN(refcount_dec_and_test(r), "refcount_t: decrement hit 0; leaking memory.\n");
}
+EXPORT_SYMBOL_GPL(refcount_dec);
/*
* No atomic_t counterpart, it attempts a 1 -> 0 transition and returns the
@@ -205,11 +179,11 @@ void refcount_dec(refcount_t *r)
* and not cmpxchg in generic, because that would allow implementing unsafe
* operations.
*/
-static inline __refcount_check
bool refcount_dec_if_one(refcount_t *r)
{
return atomic_cmpxchg_release(&r->refs, 1, 0) == 1;
}
+EXPORT_SYMBOL_GPL(refcount_dec_if_one);
/*
* No atomic_t counterpart, it decrements unless the value is 1, in which case
@@ -217,7 +191,6 @@ bool refcount_dec_if_one(refcount_t *r)
*
* Was often done like: atomic_add_unless(&var, -1, 1)
*/
-static inline __refcount_check
bool refcount_dec_not_one(refcount_t *r)
{
unsigned int old, new, val = atomic_read(&r->refs);
@@ -231,7 +204,7 @@ bool refcount_dec_not_one(refcount_t *r)
new = val - 1;
if (new > val) {
- REFCOUNT_WARN(new > val, "refcount_t: underflow; use-after-free.\n");
+ WARN(new > val, "refcount_t: underflow; use-after-free.\n");
return true;
}
@@ -244,6 +217,7 @@ bool refcount_dec_not_one(refcount_t *r)
return true;
}
+EXPORT_SYMBOL_GPL(refcount_dec_not_one);
/*
* Similar to atomic_dec_and_mutex_lock(), it will WARN on underflow and fail
@@ -253,7 +227,6 @@ bool refcount_dec_not_one(refcount_t *r)
* before, and provides a control dependency such that free() must come after.
* See the comment on top.
*/
-static inline __refcount_check
bool refcount_dec_and_mutex_lock(refcount_t *r, struct mutex *lock)
{
if (refcount_dec_not_one(r))
@@ -267,6 +240,7 @@ bool refcount_dec_and_mutex_lock(refcount_t *r, struct mutex *lock)
return true;
}
+EXPORT_SYMBOL_GPL(refcount_dec_and_mutex_lock);
/*
* Similar to atomic_dec_and_lock(), it will WARN on underflow and fail to
@@ -276,7 +250,6 @@ bool refcount_dec_and_mutex_lock(refcount_t *r, struct mutex *lock)
* before, and provides a control dependency such that free() must come after.
* See the comment on top.
*/
-static inline __refcount_check
bool refcount_dec_and_lock(refcount_t *r, spinlock_t *lock)
{
if (refcount_dec_not_one(r))
@@ -290,5 +263,5 @@ bool refcount_dec_and_lock(refcount_t *r, spinlock_t *lock)
return true;
}
+EXPORT_SYMBOL_GPL(refcount_dec_and_lock);
-#endif /* _LINUX_REFCOUNT_H */
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