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| author |   Gustavo A. R. Silva <gustavoars@kernel.org> | 2020-05-07 13:58:04 -0500 |
|---|---|---|
| committer |   Peter Zijlstra <peterz@infradead.org> | 2020-05-19 20:34:18 +0200 |
| commit | db78538c75e49c09b002a2cd96a19ae0c39be771 (patch) | |
| tree | e728d72971ab7f6bb4c0735d16475b7f80971cd3 /kernel | |
| parent | locking/rtmutex: Remove unused rt_mutex_cmpxchg_relaxed() (diff) | |
| download | wireguard-linux-db78538c75e49c09b002a2cd96a19ae0c39be771.tar.xz wireguard-linux-db78538c75e49c09b002a2cd96a19ae0c39be771.zip | |
locking/lockdep: Replace zero-length array with flexible-array
The current codebase makes use of the zero-length array language
extension to the C90 standard, but the preferred mechanism to declare
variable-length types such as these ones is a flexible array member[1][2],
introduced in C99:
struct foo {
int stuff;
struct boo array[];
};
By making use of the mechanism above, we will get a compiler warning
in case the flexible array does not occur last in the structure, which
will help us prevent some kind of undefined behavior bugs from being
inadvertently introduced[3] to the codebase from now on.
Also, notice that, dynamic memory allocations won't be affected by
this change:
"Flexible array members have incomplete type, and so the sizeof operator
may not be applied. As a quirk of the original implementation of
zero-length arrays, sizeof evaluates to zero."[1]
sizeof(flexible-array-member) triggers a warning because flexible array
members have incomplete type[1]. There are some instances of code in
which the sizeof operator is being incorrectly/erroneously applied to
zero-length arrays and the result is zero. Such instances may be hiding
some bugs. So, this work (flexible-array member conversions) will also
help to get completely rid of those sorts of issues.
This issue was found with the help of Coccinelle.
[1] https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html
[2] https://github.com/KSPP/linux/issues/21
[3] commit 76497732932f ("cxgb3/l2t: Fix undefined behaviour")
Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20200507185804.GA15036@embeddedor
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/locking/lockdep.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c index ac10db66cc63..cfdff122905b 100644 --- a/kernel/locking/lockdep.c +++ b/kernel/locking/lockdep.c @@ -489,7 +489,7 @@ struct lock_trace { struct hlist_node hash_entry; u32 hash; u32 nr_entries; - unsigned long entries[0] __aligned(sizeof(unsigned long)); + unsigned long entries[] __aligned(sizeof(unsigned long)); }; #define LOCK_TRACE_SIZE_IN_LONGS \ (sizeof(struct lock_trace) / sizeof(unsigned long)) |