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[refcnt] Check reference validity on each use of ref_get() and ref_put()

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Check that the reference count is valid (i.e. non-negative) on each
call to ref_get() and ref_put(), using an assert() at the point of
use.

Signed-off-by: Michael Brown <mcb30@ipxe.org>
This commit is contained in:
Michael Brown
2010-11-05 22:24:46 +00:00
parent fc69ab94d9
commit 6e41f2cf18
2 changed files with 52 additions and 12 deletions
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26
src/core/refcnt.c
View File

@@ -31,18 +31,16 @@ FILE_LICENCE ( GPL2_OR_LATER );
* Increment reference count * Increment reference count
* *
* @v refcnt Reference counter, or NULL * @v refcnt Reference counter, or NULL
* @ret refcnt Reference counter
* *
* If @c refcnt is NULL, no action is taken. * If @c refcnt is NULL, no action is taken.
*/ */
struct refcnt * ref_get ( struct refcnt *refcnt ) { void ref_increment ( struct refcnt *refcnt ) {
if ( refcnt ) { if ( refcnt ) {
refcnt->refcnt++; refcnt->count++;
DBGC2 ( refcnt, "REFCNT %p incremented to %d\n", DBGC2 ( refcnt, "REFCNT %p incremented to %d\n",
refcnt, refcnt->refcnt ); refcnt, refcnt->count );
} }
return refcnt;
} }
/** /**
@@ -55,18 +53,28 @@ struct refcnt * ref_get ( struct refcnt *refcnt ) {
* *
* If @c refcnt is NULL, no action is taken. * If @c refcnt is NULL, no action is taken.
*/ */
void ref_put ( struct refcnt *refcnt ) { void ref_decrement ( struct refcnt *refcnt ) {
if ( ! refcnt ) if ( ! refcnt )
return; return;
refcnt->refcnt--; refcnt->count--;
DBGC2 ( refcnt, "REFCNT %p decremented to %d\n", DBGC2 ( refcnt, "REFCNT %p decremented to %d\n",
refcnt, refcnt->refcnt ); refcnt, refcnt->count );
if ( refcnt->refcnt >= 0 ) if ( refcnt->count >= 0 )
return; return;
if ( refcnt->count < -1 ) {
DBGC ( refcnt, "REFCNT %p decremented too far (%d)!\n",
refcnt, refcnt->count );
/* Avoid multiple calls to free(), which typically
* result in memory corruption that is very hard to
* track down.
*/
return;
}
if ( refcnt->free ) { if ( refcnt->free ) {
DBGC ( refcnt, "REFCNT %p being freed via method %p\n", DBGC ( refcnt, "REFCNT %p being freed via method %p\n",
refcnt, refcnt->free ); refcnt, refcnt->free );

38
src/include/ipxe/refcnt.h
View File

@@ -9,6 +9,9 @@
FILE_LICENCE ( GPL2_OR_LATER ); FILE_LICENCE ( GPL2_OR_LATER );
#include <stddef.h>
#include <assert.h>
/** /**
* A reference counter * A reference counter
* *
@@ -26,7 +29,7 @@ struct refcnt {
* When this count is decremented below zero, the free() * When this count is decremented below zero, the free()
* method will be called. * method will be called.
*/ */
int refcnt; int count;
/** Free containing object /** Free containing object
* *
* This method is called when the reference count is * This method is called when the reference count is
@@ -75,8 +78,37 @@ ref_init ( struct refcnt *refcnt,
.free = free_fn, \ .free = free_fn, \
} }
extern struct refcnt * ref_get ( struct refcnt *refcnt ); extern void ref_increment ( struct refcnt *refcnt );
extern void ref_put ( struct refcnt *refcnt ); extern void ref_decrement ( struct refcnt *refcnt );
/**
* Get additional reference to object
*
* @v refcnt Reference counter, or NULL
* @ret refcnt Reference counter
*
* If @c refcnt is NULL, no action is taken.
*/
#define ref_get( refcnt ) ( { \
if ( refcnt ) \
assert ( (refcnt)->count >= 0 ); \
ref_increment ( refcnt ); \
(refcnt); } )
/**
* Drop reference to object
*
* @v refcnt Reference counter, or NULL
* @ret refcnt Reference counter
*
* If @c refcnt is NULL, no action is taken.
*/
#define ref_put( refcnt ) do { \
if ( refcnt ) \
assert ( (refcnt)->count >= 0 ); \
ref_decrement ( refcnt ); \
} while ( 0 )
extern void ref_no_free ( struct refcnt *refcnt ); extern void ref_no_free ( struct refcnt *refcnt );
#endif /* _IPXE_REFCNT_H */ #endif /* _IPXE_REFCNT_H */