locking/refcount: Remove unused refcount_*_checked() variants

The full-fat refcount implementation is exposed via a set of functions
suffixed with "_checked()", the idea being that code can choose to use
the more expensive, yet more secure implementation on a case-by-case
basis.

In reality, this hasn't happened, so with a grand total of zero users,
let's remove the checked variants for now by simply dropping the suffix
and predicating the out-of-line functions on CONFIG_REFCOUNT_FULL=y.

Signed-off-by: Will Deacon <[email protected]>
Reviewed-by: Ard Biesheuvel <[email protected]>
Reviewed-by: Kees Cook <[email protected]>
Tested-by: Hanjun Guo <[email protected]>
Cc: Ard Biesheuvel <[email protected]>
Cc: Elena Reshetova <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Ingo Molnar <[email protected]>

Author: willdeacon

include/linux/refcount.h

@@ -44,32 +44,21 @@ static inline unsigned int refcount_read(const refcount_t *r)
 	return atomic_read(&r->refs);
 }
 
-extern __must_check bool refcount_add_not_zero_checked(int i, refcount_t *r);
-extern void refcount_add_checked(int i, refcount_t *r);
-
-extern __must_check bool refcount_inc_not_zero_checked(refcount_t *r);
-extern void refcount_inc_checked(refcount_t *r);
-
-extern __must_check bool refcount_sub_and_test_checked(int i, refcount_t *r);
-
-extern __must_check bool refcount_dec_and_test_checked(refcount_t *r);
-extern void refcount_dec_checked(refcount_t *r);
-
 #ifdef CONFIG_REFCOUNT_FULL
 
 #define REFCOUNT_MAX		(UINT_MAX - 1)
 #define REFCOUNT_SATURATED	UINT_MAX
 
-#define refcount_add_not_zero	refcount_add_not_zero_checked
-#define refcount_add		refcount_add_checked
+extern __must_check bool refcount_add_not_zero(int i, refcount_t *r);
+extern void refcount_add(int i, refcount_t *r);
 
-#define refcount_inc_not_zero	refcount_inc_not_zero_checked
-#define refcount_inc		refcount_inc_checked
+extern __must_check bool refcount_inc_not_zero(refcount_t *r);
+extern void refcount_inc(refcount_t *r);
 
-#define refcount_sub_and_test	refcount_sub_and_test_checked
+extern __must_check bool refcount_sub_and_test(int i, refcount_t *r);
 
-#define refcount_dec_and_test	refcount_dec_and_test_checked
-#define refcount_dec		refcount_dec_checked
+extern __must_check bool refcount_dec_and_test(refcount_t *r);
+extern void refcount_dec(refcount_t *r);
 
 #else
 

lib/refcount.c

@@ -43,8 +43,10 @@
 #include <linux/spinlock.h>
 #include <linux/bug.h>
 
+#ifdef CONFIG_REFCOUNT_FULL
+
 /**
- * refcount_add_not_zero_checked - add a value to a refcount unless it is 0
+ * refcount_add_not_zero - add a value to a refcount unless it is 0
  * @i: the value to add to the refcount
  * @r: the refcount
  *
@@ -61,7 +63,7 @@
  *
  * Return: false if the passed refcount is 0, true otherwise
  */
-bool refcount_add_not_zero_checked(int i, refcount_t *r)
+bool refcount_add_not_zero(int i, refcount_t *r)
 {
 	unsigned int new, val = atomic_read(&r->refs);
 
@@ -83,10 +85,10 @@ bool refcount_add_not_zero_checked(int i, refcount_t *r)
 
 	return true;
 }
-EXPORT_SYMBOL(refcount_add_not_zero_checked);
+EXPORT_SYMBOL(refcount_add_not_zero);
 
 /**
- * refcount_add_checked - add a value to a refcount
+ * refcount_add - add a value to a refcount
  * @i: the value to add to the refcount
  * @r: the refcount
  *
@@ -101,14 +103,14 @@ EXPORT_SYMBOL(refcount_add_not_zero_checked);
  * cases, refcount_inc(), or one of its variants, should instead be used to
  * increment a reference count.
  */
-void refcount_add_checked(int i, refcount_t *r)
+void refcount_add(int i, refcount_t *r)
 {
-	WARN_ONCE(!refcount_add_not_zero_checked(i, r), "refcount_t: addition on 0; use-after-free.\n");
+	WARN_ONCE(!refcount_add_not_zero(i, r), "refcount_t: addition on 0; use-after-free.\n");
 }
-EXPORT_SYMBOL(refcount_add_checked);
+EXPORT_SYMBOL(refcount_add);
 
 /**
- * refcount_inc_not_zero_checked - increment a refcount unless it is 0
+ * refcount_inc_not_zero - increment a refcount unless it is 0
  * @r: the refcount to increment
  *
  * Similar to atomic_inc_not_zero(), but will saturate at REFCOUNT_SATURATED
@@ -120,7 +122,7 @@ EXPORT_SYMBOL(refcount_add_checked);
  *
  * Return: true if the increment was successful, false otherwise
  */
-bool refcount_inc_not_zero_checked(refcount_t *r)
+bool refcount_inc_not_zero(refcount_t *r)
 {
 	unsigned int new, val = atomic_read(&r->refs);
 
@@ -140,10 +142,10 @@ bool refcount_inc_not_zero_checked(refcount_t *r)
 
 	return true;
 }
-EXPORT_SYMBOL(refcount_inc_not_zero_checked);
+EXPORT_SYMBOL(refcount_inc_not_zero);
 
 /**
- * refcount_inc_checked - increment a refcount
+ * refcount_inc - increment a refcount
  * @r: the refcount to increment
  *
  * Similar to atomic_inc(), but will saturate at REFCOUNT_SATURATED and WARN.
@@ -154,14 +156,14 @@ EXPORT_SYMBOL(refcount_inc_not_zero_checked);
  * Will WARN if the refcount is 0, as this represents a possible use-after-free
  * condition.
  */
-void refcount_inc_checked(refcount_t *r)
+void refcount_inc(refcount_t *r)
 {
-	WARN_ONCE(!refcount_inc_not_zero_checked(r), "refcount_t: increment on 0; use-after-free.\n");
+	WARN_ONCE(!refcount_inc_not_zero(r), "refcount_t: increment on 0; use-after-free.\n");
 }
-EXPORT_SYMBOL(refcount_inc_checked);
+EXPORT_SYMBOL(refcount_inc);
 
 /**
- * refcount_sub_and_test_checked - subtract from a refcount and test if it is 0
+ * refcount_sub_and_test - subtract from a refcount and test if it is 0
  * @i: amount to subtract from the refcount
  * @r: the refcount
  *
@@ -180,7 +182,7 @@ EXPORT_SYMBOL(refcount_inc_checked);
  *
  * Return: true if the resulting refcount is 0, false otherwise
  */
-bool refcount_sub_and_test_checked(int i, refcount_t *r)
+bool refcount_sub_and_test(int i, refcount_t *r)
 {
 	unsigned int new, val = atomic_read(&r->refs);
 
@@ -203,10 +205,10 @@ bool refcount_sub_and_test_checked(int i, refcount_t *r)
 	return false;
 
 }
-EXPORT_SYMBOL(refcount_sub_and_test_checked);
+EXPORT_SYMBOL(refcount_sub_and_test);
 
 /**
- * refcount_dec_and_test_checked - decrement a refcount and test if it is 0
+ * refcount_dec_and_test - decrement a refcount and test if it is 0
  * @r: the refcount
  *
  * Similar to atomic_dec_and_test(), it will WARN on underflow and fail to
@@ -218,14 +220,14 @@ EXPORT_SYMBOL(refcount_sub_and_test_checked);
  *
  * Return: true if the resulting refcount is 0, false otherwise
  */
-bool refcount_dec_and_test_checked(refcount_t *r)
+bool refcount_dec_and_test(refcount_t *r)
 {
-	return refcount_sub_and_test_checked(1, r);
+	return refcount_sub_and_test(1, r);
 }
-EXPORT_SYMBOL(refcount_dec_and_test_checked);
+EXPORT_SYMBOL(refcount_dec_and_test);
 
 /**
- * refcount_dec_checked - decrement a refcount
+ * refcount_dec - decrement a refcount
  * @r: the refcount
  *
  * Similar to atomic_dec(), it will WARN on underflow and fail to decrement
@@ -234,11 +236,13 @@ EXPORT_SYMBOL(refcount_dec_and_test_checked);
  * Provides release memory ordering, such that prior loads and stores are done
  * before.
  */
-void refcount_dec_checked(refcount_t *r)
+void refcount_dec(refcount_t *r)
 {
-	WARN_ONCE(refcount_dec_and_test_checked(r), "refcount_t: decrement hit 0; leaking memory.\n");
+	WARN_ONCE(refcount_dec_and_test(r), "refcount_t: decrement hit 0; leaking memory.\n");
 }
-EXPORT_SYMBOL(refcount_dec_checked);
+EXPORT_SYMBOL(refcount_dec);
+
+#endif /* CONFIG_REFCOUNT_FULL */
 
 /**
  * refcount_dec_if_one - decrement a refcount if it is 1