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| author | Gustavo A. R. Silva <gustavoars@kernel.org> | 2020-05-11 23:12:27 +0300 |
|---|---|---|
| committer | Peter Zijlstra <peterz@infradead.org> | 2020-05-19 21:34:16 +0300 |
| commit | c50c75e9b87946499a62bffc021e95c87a1d57cd (patch) | |
| tree | 82700776a4656589d67ee2d6885869a4f6e2b7cf /kernel/events | |
| parent | 8ac7571a8cd3c11da24c3c3555f6e40e33049609 (diff) | |
| download | linux-c50c75e9b87946499a62bffc021e95c87a1d57cd.tar.xz | |
perf/core: 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/20200511201227.GA14041@embeddedor
Diffstat (limited to 'kernel/events')
| -rw-r--r-- | kernel/events/callchain.c | 2 | ||||
| -rw-r--r-- | kernel/events/internal.h | 2 |
2 files changed, 2 insertions, 2 deletions
diff --git a/kernel/events/callchain.c b/kernel/events/callchain.c index c2b41a263166..b1991043b7d8 100644 --- a/kernel/events/callchain.c +++ b/kernel/events/callchain.c @@ -16,7 +16,7 @@ struct callchain_cpus_entries { struct rcu_head rcu_head; - struct perf_callchain_entry *cpu_entries[0]; + struct perf_callchain_entry *cpu_entries[]; }; int sysctl_perf_event_max_stack __read_mostly = PERF_MAX_STACK_DEPTH; diff --git a/kernel/events/internal.h b/kernel/events/internal.h index f16f66b6b655..fcbf5616a441 100644 --- a/kernel/events/internal.h +++ b/kernel/events/internal.h @@ -55,7 +55,7 @@ struct perf_buffer { void *aux_priv; struct perf_event_mmap_page *user_page; - void *data_pages[0]; + void *data_pages[]; }; extern void rb_free(struct perf_buffer *rb); |