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Date: Thu, 27 Aug 2020 07:54:23 -0000
From: "tip-bot2 for Peter Zijlstra" <tip-bot2@...utronix.de>
To: linux-tip-commits@...r.kernel.org
Cc: "Peter Zijlstra (Intel)" <peterz@...radead.org>,
Kees Cook <keescook@...omium.org>, x86 <x86@...nel.org>,
LKML <linux-kernel@...r.kernel.org>
Subject: [tip: locking/core] locking/refcount: Provide __refcount API to
obtain the old value
The following commit has been merged into the locking/core branch of tip:
Commit-ID: a435b9a14356587cf512ea6473368a579373c74c
Gitweb: https://git.kernel.org/tip/a435b9a14356587cf512ea6473368a579373c74c
Author: Peter Zijlstra <peterz@...radead.org>
AuthorDate: Wed, 29 Jul 2020 13:00:57 +02:00
Committer: Peter Zijlstra <peterz@...radead.org>
CommitterDate: Wed, 26 Aug 2020 12:42:02 +02:00
locking/refcount: Provide __refcount API to obtain the old value
David requested means to obtain the old/previous value from the
refcount API for tracing purposes.
Duplicate (most of) the API as __refcount*() with an additional
'int *' argument into which, if !NULL, the old value will be stored.
Requested-by: David Howells <dhowells@...hat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Reviewed-by: Kees Cook <keescook@...omium.org>
Link: https://lkml.kernel.org/r/20200729111120.GA2638@hirez.programming.kicks-ass.net
---
include/linux/refcount.h | 65 ++++++++++++++++++++++++++++++++++-----
1 file changed, 57 insertions(+), 8 deletions(-)
diff --git a/include/linux/refcount.h b/include/linux/refcount.h
index 0e3ee25..7fabb1a 100644
--- a/include/linux/refcount.h
+++ b/include/linux/refcount.h
@@ -165,7 +165,7 @@ static inline unsigned int refcount_read(const refcount_t *r)
*
* Return: false if the passed refcount is 0, true otherwise
*/
-static inline __must_check bool refcount_add_not_zero(int i, refcount_t *r)
+static inline __must_check bool __refcount_add_not_zero(int i, refcount_t *r, int *oldp)
{
int old = refcount_read(r);
@@ -174,12 +174,20 @@ static inline __must_check bool refcount_add_not_zero(int i, refcount_t *r)
break;
} while (!atomic_try_cmpxchg_relaxed(&r->refs, &old, old + i));
+ if (oldp)
+ *oldp = old;
+
if (unlikely(old < 0 || old + i < 0))
refcount_warn_saturate(r, REFCOUNT_ADD_NOT_ZERO_OVF);
return old;
}
+static inline __must_check bool refcount_add_not_zero(int i, refcount_t *r)
+{
+ return __refcount_add_not_zero(i, r, NULL);
+}
+
/**
* refcount_add - add a value to a refcount
* @i: the value to add to the refcount
@@ -196,16 +204,24 @@ static inline __must_check bool refcount_add_not_zero(int i, refcount_t *r)
* cases, refcount_inc(), or one of its variants, should instead be used to
* increment a reference count.
*/
-static inline void refcount_add(int i, refcount_t *r)
+static inline void __refcount_add(int i, refcount_t *r, int *oldp)
{
int old = atomic_fetch_add_relaxed(i, &r->refs);
+ if (oldp)
+ *oldp = old;
+
if (unlikely(!old))
refcount_warn_saturate(r, REFCOUNT_ADD_UAF);
else if (unlikely(old < 0 || old + i < 0))
refcount_warn_saturate(r, REFCOUNT_ADD_OVF);
}
+static inline void refcount_add(int i, refcount_t *r)
+{
+ __refcount_add(i, r, NULL);
+}
+
/**
* refcount_inc_not_zero - increment a refcount unless it is 0
* @r: the refcount to increment
@@ -219,9 +235,14 @@ static inline void refcount_add(int i, refcount_t *r)
*
* Return: true if the increment was successful, false otherwise
*/
+static inline __must_check bool __refcount_inc_not_zero(refcount_t *r, int *oldp)
+{
+ return __refcount_add_not_zero(1, r, oldp);
+}
+
static inline __must_check bool refcount_inc_not_zero(refcount_t *r)
{
- return refcount_add_not_zero(1, r);
+ return __refcount_inc_not_zero(r, NULL);
}
/**
@@ -236,9 +257,14 @@ static inline __must_check bool refcount_inc_not_zero(refcount_t *r)
* Will WARN if the refcount is 0, as this represents a possible use-after-free
* condition.
*/
+static inline void __refcount_inc(refcount_t *r, int *oldp)
+{
+ __refcount_add(1, r, oldp);
+}
+
static inline void refcount_inc(refcount_t *r)
{
- refcount_add(1, r);
+ __refcount_inc(r, NULL);
}
/**
@@ -261,10 +287,13 @@ static inline void refcount_inc(refcount_t *r)
*
* Return: true if the resulting refcount is 0, false otherwise
*/
-static inline __must_check bool refcount_sub_and_test(int i, refcount_t *r)
+static inline __must_check bool __refcount_sub_and_test(int i, refcount_t *r, int *oldp)
{
int old = atomic_fetch_sub_release(i, &r->refs);
+ if (oldp)
+ *oldp = old;
+
if (old == i) {
smp_acquire__after_ctrl_dep();
return true;
@@ -276,6 +305,11 @@ static inline __must_check bool refcount_sub_and_test(int i, refcount_t *r)
return false;
}
+static inline __must_check bool refcount_sub_and_test(int i, refcount_t *r)
+{
+ return __refcount_sub_and_test(i, r, NULL);
+}
+
/**
* refcount_dec_and_test - decrement a refcount and test if it is 0
* @r: the refcount
@@ -289,9 +323,14 @@ static inline __must_check bool refcount_sub_and_test(int i, refcount_t *r)
*
* Return: true if the resulting refcount is 0, false otherwise
*/
+static inline __must_check bool __refcount_dec_and_test(refcount_t *r, int *oldp)
+{
+ return __refcount_sub_and_test(1, r, oldp);
+}
+
static inline __must_check bool refcount_dec_and_test(refcount_t *r)
{
- return refcount_sub_and_test(1, r);
+ return __refcount_dec_and_test(r, NULL);
}
/**
@@ -304,12 +343,22 @@ static inline __must_check 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)
+static inline void __refcount_dec(refcount_t *r, int *oldp)
{
- if (unlikely(atomic_fetch_sub_release(1, &r->refs) <= 1))
+ int old = atomic_fetch_sub_release(1, &r->refs);
+
+ if (oldp)
+ *oldp = old;
+
+ if (unlikely(old <= 1))
refcount_warn_saturate(r, REFCOUNT_DEC_LEAK);
}
+static inline void refcount_dec(refcount_t *r)
+{
+ __refcount_dec(r, NULL);
+}
+
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);
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