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1d9e13e8ef
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 <gustavo@embeddedor.com>
84 lines
2.2 KiB
C
84 lines
2.2 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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/*
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* Compact binary representation of ihex records. Some devices need their
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* firmware loaded in strange orders rather than a single big blob, but
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* actually parsing ihex-as-text within the kernel seems silly. Thus,...
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*/
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#ifndef __LINUX_IHEX_H__
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#define __LINUX_IHEX_H__
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#include <linux/types.h>
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#include <linux/firmware.h>
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#include <linux/device.h>
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/* Intel HEX files actually limit the length to 256 bytes, but we have
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drivers which would benefit from using separate records which are
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longer than that, so we extend to 16 bits of length */
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struct ihex_binrec {
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__be32 addr;
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__be16 len;
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uint8_t data[];
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} __attribute__((packed));
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static inline uint16_t ihex_binrec_size(const struct ihex_binrec *p)
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{
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return be16_to_cpu(p->len) + sizeof(*p);
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}
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/* Find the next record, taking into account the 4-byte alignment */
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static inline const struct ihex_binrec *
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__ihex_next_binrec(const struct ihex_binrec *rec)
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{
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const void *p = rec;
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return p + ALIGN(ihex_binrec_size(rec), 4);
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}
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static inline const struct ihex_binrec *
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ihex_next_binrec(const struct ihex_binrec *rec)
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{
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rec = __ihex_next_binrec(rec);
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return be16_to_cpu(rec->len) ? rec : NULL;
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}
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/* Check that ihex_next_binrec() won't take us off the end of the image... */
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static inline int ihex_validate_fw(const struct firmware *fw)
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{
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const struct ihex_binrec *end, *rec;
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rec = (const void *)fw->data;
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end = (const void *)&fw->data[fw->size - sizeof(*end)];
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for (; rec <= end; rec = __ihex_next_binrec(rec)) {
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/* Zero length marks end of records */
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if (rec == end && !be16_to_cpu(rec->len))
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return 0;
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}
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return -EINVAL;
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}
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/* Request firmware and validate it so that we can trust we won't
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* run off the end while reading records... */
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static inline int request_ihex_firmware(const struct firmware **fw,
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const char *fw_name,
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struct device *dev)
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{
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const struct firmware *lfw;
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int ret;
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ret = request_firmware(&lfw, fw_name, dev);
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if (ret)
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return ret;
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ret = ihex_validate_fw(lfw);
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if (ret) {
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dev_err(dev, "Firmware \"%s\" not valid IHEX records\n",
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fw_name);
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release_firmware(lfw);
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return ret;
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}
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*fw = lfw;
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return 0;
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}
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#endif /* __LINUX_IHEX_H__ */
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