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authorGustavo A. R. Silva <gustavoars@kernel.org>2020-05-11 15:12:27 -0500
committerPeter Zijlstra <peterz@infradead.org>2020-05-19 20:34:16 +0200
commitc50c75e9b87946499a62bffc021e95c87a1d57cd (patch)
tree82700776a4656589d67ee2d6885869a4f6e2b7cf /kernel/events
parentperf/x86: Replace zero-length array with flexible-array (diff)
downloadlinux-dev-c50c75e9b87946499a62bffc021e95c87a1d57cd.tar.xz
linux-dev-c50c75e9b87946499a62bffc021e95c87a1d57cd.zip
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.c2
-rw-r--r--kernel/events/internal.h2
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);