mirror of
https://mirrors.bfsu.edu.cn/git/linux.git
synced 2024-12-05 01:54:09 +08:00
3381df0954
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]
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>
Link: https://lore.kernel.org/r/20200521185707.GA3661@embeddedor
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
70 lines
1.6 KiB
C
70 lines
1.6 KiB
C
/*
|
|
* linux/arch/m68k/tools/amiga/dmesg.c -- Retrieve the kernel messages stored
|
|
* in Chip RAM with the kernel command
|
|
* line option `debug=mem'.
|
|
*
|
|
* © Copyright 1996 by Geert Uytterhoeven <geert@linux-m68k.org>
|
|
*
|
|
*
|
|
* Usage:
|
|
*
|
|
* dmesg
|
|
* dmesg <CHIPMEM_END>
|
|
*
|
|
*
|
|
* This file is subject to the terms and conditions of the GNU General Public
|
|
* License. See the file COPYING in the main directory of the Linux
|
|
* distribution for more details.
|
|
*/
|
|
|
|
|
|
#include <stdio.h>
|
|
#include <stdlib.h>
|
|
#include <unistd.h>
|
|
|
|
|
|
#define CHIPMEM_START 0x00000000
|
|
#define CHIPMEM_END 0x00200000 /* overridden by argv[1] */
|
|
|
|
#define SAVEKMSG_MAGIC1 0x53415645 /* 'SAVE' */
|
|
#define SAVEKMSG_MAGIC2 0x4B4D5347 /* 'KMSG' */
|
|
|
|
struct savekmsg {
|
|
u_long magic1; /* SAVEKMSG_MAGIC1 */
|
|
u_long magic2; /* SAVEKMSG_MAGIC2 */
|
|
u_long magicptr; /* address of magic1 */
|
|
u_long size;
|
|
char data[];
|
|
};
|
|
|
|
|
|
int main(int argc, char *argv[])
|
|
{
|
|
u_long start = CHIPMEM_START, end = CHIPMEM_END, p;
|
|
int found = 0;
|
|
struct savekmsg *m = NULL;
|
|
|
|
if (argc >= 2)
|
|
end = strtoul(argv[1], NULL, 0);
|
|
printf("Searching for SAVEKMSG magic...\n");
|
|
for (p = start; p <= end-sizeof(struct savekmsg); p += 4) {
|
|
m = (struct savekmsg *)p;
|
|
if ((m->magic1 == SAVEKMSG_MAGIC1) && (m->magic2 == SAVEKMSG_MAGIC2) &&
|
|
(m->magicptr == p)) {
|
|
found = 1;
|
|
break;
|
|
}
|
|
}
|
|
if (!found)
|
|
printf("Not found\n");
|
|
else {
|
|
printf("Found %ld bytes at 0x%08lx\n", m->size, (u_long)&m->data);
|
|
puts(">>>>>>>>>>>>>>>>>>>>");
|
|
fflush(stdout);
|
|
write(1, &m->data, m->size);
|
|
fflush(stdout);
|
|
puts("<<<<<<<<<<<<<<<<<<<<");
|
|
}
|
|
return(0);
|
|
}
|