diff options
| author | Alexander Potapenko <glider@google.com> | 2017-07-19 20:27:30 +0200 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2017-07-19 15:33:50 -0700 |
| commit | beaec533fc2701a28a4d667f67c9f59c6e4e0d13 (patch) | |
| tree | d865dda1b1bf9c50ada3b4a8344aba60186c42fe /include | |
| parent | e06fdaf40a5c021dd4a2ec797e8b724f07360070 (diff) | |
llist: clang: introduce member_address_is_nonnull()
Currently llist_for_each_entry() and llist_for_each_entry_safe() iterate
until &pos->member != NULL. But when building the kernel with Clang,
the compiler assumes &pos->member cannot be NULL if the member's offset
is greater than 0 (which would be equivalent to the object being
non-contiguous in memory). Therefore the loop condition is always true,
and the loops become infinite.
To work around this, introduce the member_address_is_nonnull() macro,
which casts object pointer to uintptr_t, thus letting the member pointer
to be NULL.
Signed-off-by: Alexander Potapenko <glider@google.com>
Tested-by: Sodagudi Prasad <psodagud@codeaurora.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include')
| -rw-r--r-- | include/linux/llist.h | 21 |
1 files changed, 19 insertions, 2 deletions
diff --git a/include/linux/llist.h b/include/linux/llist.h index d11738110a7a..1957635e6d5f 100644 --- a/include/linux/llist.h +++ b/include/linux/llist.h @@ -93,6 +93,23 @@ static inline void init_llist_head(struct llist_head *list) container_of(ptr, type, member) /** + * member_address_is_nonnull - check whether the member address is not NULL + * @ptr: the object pointer (struct type * that contains the llist_node) + * @member: the name of the llist_node within the struct. + * + * This macro is conceptually the same as + * &ptr->member != NULL + * but it works around the fact that compilers can decide that taking a member + * address is never a NULL pointer. + * + * Real objects that start at a high address and have a member at NULL are + * unlikely to exist, but such pointers may be returned e.g. by the + * container_of() macro. + */ +#define member_address_is_nonnull(ptr, member) \ + ((uintptr_t)(ptr) + offsetof(typeof(*(ptr)), member) != 0) + +/** * llist_for_each - iterate over some deleted entries of a lock-less list * @pos: the &struct llist_node to use as a loop cursor * @node: the first entry of deleted list entries @@ -145,7 +162,7 @@ static inline void init_llist_head(struct llist_head *list) */ #define llist_for_each_entry(pos, node, member) \ for ((pos) = llist_entry((node), typeof(*(pos)), member); \ - &(pos)->member != NULL; \ + member_address_is_nonnull(pos, member); \ (pos) = llist_entry((pos)->member.next, typeof(*(pos)), member)) /** @@ -167,7 +184,7 @@ static inline void init_llist_head(struct llist_head *list) */ #define llist_for_each_entry_safe(pos, n, node, member) \ for (pos = llist_entry((node), typeof(*pos), member); \ - &pos->member != NULL && \ + member_address_is_nonnull(pos, member) && \ (n = llist_entry(pos->member.next, typeof(*n), member), true); \ pos = n) |