diff options
| author | Gustavo A. R. Silva | 2020-05-11 15:09:11 -0500 |
|---|---|---|
| committer | Peter Zijlstra | 2020-05-19 20:34:16 +0200 |
| commit | 8ac7571a8cd3c11da24c3c3555f6e40e33049609 (patch) | |
| tree | 1d6b86b8a6f4aed651964bd0a88b3140d80a9f30 | |
| parent | 0813c40556fce1eeefb996e020cc5339e0b84137 (diff) | |
perf/x86: 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/20200511200911.GA13149@embeddedor
| -rw-r--r-- | arch/x86/events/intel/bts.c | 2 | ||||
| -rw-r--r-- | arch/x86/events/intel/uncore.h | 2 |
2 files changed, 2 insertions, 2 deletions
diff --git a/arch/x86/events/intel/bts.c b/arch/x86/events/intel/bts.c index 6a3b599ee0fe..731dd8d0dbb1 100644 --- a/arch/x86/events/intel/bts.c +++ b/arch/x86/events/intel/bts.c @@ -58,7 +58,7 @@ struct bts_buffer { local_t head; unsigned long end; void **data_pages; - struct bts_phys buf[0]; + struct bts_phys buf[]; }; static struct pmu bts_pmu; diff --git a/arch/x86/events/intel/uncore.h b/arch/x86/events/intel/uncore.h index 0da4a4605536..b469ddd45515 100644 --- a/arch/x86/events/intel/uncore.h +++ b/arch/x86/events/intel/uncore.h @@ -130,7 +130,7 @@ struct intel_uncore_box { struct list_head list; struct list_head active_list; void __iomem *io_addr; - struct intel_uncore_extra_reg shared_regs[0]; + struct intel_uncore_extra_reg shared_regs[]; }; /* CFL uncore 8th cbox MSRs */ |