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02bddf21c3
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 7649773293 ("cxgb3/l2t: Fix undefined behaviour")
Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200507185755.GA15014@embeddedor
42 lines
968 B
C
42 lines
968 B
C
/* SPDX-License-Identifier: GPL-2.0-only */
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/*
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* Copyright 2014, Michael Ellerman, IBM Corp.
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*/
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#ifndef _SELFTESTS_POWERPC_PMU_EBB_TRACE_H
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#define _SELFTESTS_POWERPC_PMU_EBB_TRACE_H
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#include "utils.h"
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#define TRACE_TYPE_REG 1
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#define TRACE_TYPE_COUNTER 2
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#define TRACE_TYPE_STRING 3
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#define TRACE_TYPE_INDENT 4
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#define TRACE_TYPE_OUTDENT 5
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struct trace_entry
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{
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u8 type;
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u8 length;
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u8 data[];
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};
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struct trace_buffer
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{
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u64 size;
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bool overflow;
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void *tail;
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u8 data[];
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};
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struct trace_buffer *trace_buffer_allocate(u64 size);
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int trace_log_reg(struct trace_buffer *tb, u64 reg, u64 value);
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int trace_log_counter(struct trace_buffer *tb, u64 value);
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int trace_log_string(struct trace_buffer *tb, char *str);
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int trace_log_indent(struct trace_buffer *tb);
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int trace_log_outdent(struct trace_buffer *tb);
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void trace_buffer_print(struct trace_buffer *tb);
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void trace_print_location(struct trace_buffer *tb);
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#endif /* _SELFTESTS_POWERPC_PMU_EBB_TRACE_H */
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