Hi Robert,
On 2024-11-19 11:49:08+0100, Roberto Sassu wrote:
From: Roberto Sassu roberto.sassu@huawei.com
Add a parser of a generic Type-Length-Value (TLV) format:
+--------------+--+---------+--------+---------+ | field1 (u16) | len1 (u32) | value1 (u8 len1) | +--------------+------------+------------------+ | ... | ... | ... | +--------------+------------+------------------+ | fieldN (u16) | lenN (u32) | valueN (u8 lenN) | +--------------+------------+------------------+
Should mention that its big endian.
Each adopter can define its own fields. The TLV parser does not need to be aware of those, but lets the adopter obtain the data and decide how to
"adopter" -> "user".
continue.
After processing a TLV entry, call the callback function also with the callback data provided by the adopter. The latter can decide how to interpret the TLV entry depending on the field ID.
Nesting TLVs is also possible, the callback function can call tlv_parse() to parse the inner structure.
Given that we already have the netlink data structures, helpers and infrastructure, what is the advantage over those?
Signed-off-by: Roberto Sassu roberto.sassu@huawei.com
MAINTAINERS | 8 +++ include/linux/tlv_parser.h | 32 ++++++++++++ include/uapi/linux/tlv_parser.h | 41 ++++++++++++++++ lib/Kconfig | 3 ++ lib/Makefile | 2 + lib/tlv_parser.c | 87 +++++++++++++++++++++++++++++++++ lib/tlv_parser.h | 18 +++++++ 7 files changed, 191 insertions(+) create mode 100644 include/linux/tlv_parser.h create mode 100644 include/uapi/linux/tlv_parser.h create mode 100644 lib/tlv_parser.c create mode 100644 lib/tlv_parser.h
diff --git a/MAINTAINERS b/MAINTAINERS index a097afd76ded..1f7ffa1c9dbd 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -23388,6 +23388,14 @@ W: http://sourceforge.net/projects/tlan/ F: Documentation/networking/device_drivers/ethernet/ti/tlan.rst F: drivers/net/ethernet/ti/tlan.* +TLV PARSER +M: Roberto Sassu roberto.sassu@huawei.com +L: linux-kernel@vger.kernel.org +S: Maintained +F: include/linux/tlv_parser.h +F: include/uapi/linux/tlv_parser.h +F: lib/tlv_parser.*
TMIO/SDHI MMC DRIVER M: Wolfram Sang wsa+renesas@sang-engineering.com L: linux-mmc@vger.kernel.org diff --git a/include/linux/tlv_parser.h b/include/linux/tlv_parser.h new file mode 100644 index 000000000000..0c72742af548 --- /dev/null +++ b/include/linux/tlv_parser.h @@ -0,0 +1,32 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +/*
- Copyright (C) 2023-2024 Huawei Technologies Duesseldorf GmbH
- Author: Roberto Sassu roberto.sassu@huawei.com
- Header file of TLV parser.
- */
+#ifndef _LINUX_TLV_PARSER_H +#define _LINUX_TLV_PARSER_H
+#include <uapi/linux/tlv_parser.h>
+/**
- typedef callback - Callback after parsing TLV entry
- @callback_data: Opaque data to supply to the callback function
- @field: Field identifier
- @field_data: Field data
- @field_len: Length of @field_data
- This callback is invoked after a TLV entry is parsed.
- Return: Zero on success, a negative value on error.
It's not explained what happens on error.
- */
+typedef int (*callback)(void *callback_data, __u16 field,
const __u8 *field_data, __u32 field_len);
No need for __underscore types in kernel-only signatures.
+int tlv_parse(callback callback, void *callback_data, const __u8 *data,
size_t data_len, const char **fields, __u32 num_fields);+#endif /* _LINUX_TLV_PARSER_H */ diff --git a/include/uapi/linux/tlv_parser.h b/include/uapi/linux/tlv_parser.h new file mode 100644 index 000000000000..171d0cfd2c4c --- /dev/null +++ b/include/uapi/linux/tlv_parser.h @@ -0,0 +1,41 @@ +/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */ +/*
- Copyright (C) 2023-2024 Huawei Technologies Duesseldorf GmbH
- Author: Roberto Sassu roberto.sassu@huawei.com
- Implement the user space interface for the TLV parser.
- */
Can you explain in the commit message where this will be exposed to userspace as binary?
+#ifndef _UAPI_LINUX_TLV_PARSER_H +#define _UAPI_LINUX_TLV_PARSER_H
+#include <linux/types.h>
+/*
- TLV format:
- +--------------+--+---------+--------+---------+
- | field1 (u16) | len1 (u32) | value1 (u8 len1) |
- +--------------+------------+------------------+
- | ... | ... | ... |
- +--------------+------------+------------------+
- | fieldN (u16) | lenN (u32) | valueN (u8 lenN) |
- +--------------+------------+------------------+
- */
+/**
- struct tlv_entry - Entry of TLV format
- @field: Field identifier
- @length: Data length
- @data: Data
- This structure represents an entry of the TLV format.
- */
+struct tlv_entry {
- __u16 field;
- __u32 length;
Use __be16 and __be32 here.
- __u8 data[];
__counted_by()? Not sure how this interacts with __be.
+} __attribute__((packed));
+#endif /* _UAPI_LINUX_TLV_PARSER_H */ diff --git a/lib/Kconfig b/lib/Kconfig index b38849af6f13..9141dcfc1704 100644 --- a/lib/Kconfig +++ b/lib/Kconfig @@ -777,3 +777,6 @@ config POLYNOMIAL config FIRMWARE_TABLE bool
+config TLV_PARSER
- bool
diff --git a/lib/Makefile b/lib/Makefile index 773adf88af41..630de494eab5 100644 --- a/lib/Makefile +++ b/lib/Makefile @@ -393,5 +393,7 @@ obj-$(CONFIG_USERCOPY_KUNIT_TEST) += usercopy_kunit.o obj-$(CONFIG_GENERIC_LIB_DEVMEM_IS_ALLOWED) += devmem_is_allowed.o obj-$(CONFIG_FIRMWARE_TABLE) += fw_table.o +obj-$(CONFIG_TLV_PARSER) += tlv_parser.o +CFLAGS_tlv_parser.o += -I lib
Does this work with out of tree builds?
subdir-$(CONFIG_FORTIFY_SOURCE) += test_fortify diff --git a/lib/tlv_parser.c b/lib/tlv_parser.c new file mode 100644 index 000000000000..dbbe08018b4d --- /dev/null +++ b/lib/tlv_parser.c @@ -0,0 +1,87 @@ +// SPDX-License-Identifier: GPL-2.0 +/*
- Copyright (C) 2023-2024 Huawei Technologies Duesseldorf GmbH
- Author: Roberto Sassu roberto.sassu@huawei.com
- Implement the TLV parser.
- */
+#define pr_fmt(fmt) "tlv_parser: "fmt +#include <tlv_parser.h>
This should be "tlv_parser.h", but the header files looks unnecessary in the first place.
+/**
- tlv_parse - Parse TLV data
- @callback: Callback function to call to parse the entries
- @callback_data: Opaque data to supply to the callback function
- @data: Data to parse
- @data_len: Length of @data
- @fields: Array of field strings
- @num_fields: Number of elements of @fields
- Parse the TLV data format and call the supplied callback function for each
- entry, passing also the opaque data pointer.
- The callback function decides how to process data depending on the field.
Mention that a callback return an error will abort the whole parsing.
- Return: Zero on success, a negative value on error.
- */
+int tlv_parse(callback callback, void *callback_data, const __u8 *data,
size_t data_len, const char **fields, __u32 num_fields)
No need for __underscore types in kernel-only functions.
"num_fields" and "fields" are accessed without checking for validity.
"fields" is only every used for debug logging, so can be removed. "num_fields" probably, too.
+{
- const __u8 *data_ptr = data;
- struct tlv_entry *entry;
This comes from the input data, should also be const.
- __u16 parsed_field;
- __u32 len;
field_len
- int ret;
- if (data_len > U32_MAX) {
pr_debug("Data too big, size: %zd\n", data_len);return -E2BIG;- }
- while (data_len) {
if (data_len < sizeof(*entry))return -EBADMSG;entry = (struct tlv_entry *)data_ptr;data_ptr += sizeof(*entry);data_len -= sizeof(*entry);parsed_field = __be16_to_cpu(entry->field);
This doesn't seem to handle invalid alignment, some architectures will trap unaligned accesses. Depending on the size and usage patterns it may make sense to document some alignment recommendations/requirements. (Not sure how big of a performance difference it would make)
if (parsed_field >= num_fields) {pr_debug("Invalid field %u, max: %u\n",parsed_field, num_fields - 1);return -EBADMSG;}len = __be32_to_cpu(entry->length);if (data_len < len)return -EBADMSG;pr_debug("Data: field: %s, len: %u\n", fields[parsed_field],len);if (!len)continue;
Empty fields are discarded silently, is this intentional? It should be documented. Those fields could be useful for flag data.
ret = callback(callback_data, parsed_field, data_ptr, len);if (ret < 0) {pr_debug("Parsing of field %s failed, ret: %d\n",fields[parsed_field], ret);return ret;}data_ptr += len;data_len -= len;- }
- if (data_len) {
Can this ever happen? The check at the beginning of the loop should have caught it already.
pr_debug("Excess data: %zu bytes\n", data_len);return -EBADMSG;- }
- return 0;
+} +EXPORT_SYMBOL_GPL(tlv_parse);
Some kunit tests would be great.
diff --git a/lib/tlv_parser.h b/lib/tlv_parser.h new file mode 100644 index 000000000000..e663966deac5 --- /dev/null +++ b/lib/tlv_parser.h @@ -0,0 +1,18 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +/*
- Copyright (C) 2023-2024 Huawei Technologies Duesseldorf GmbH
- Author: Roberto Sassu roberto.sassu@huawei.com
- Header file of TLV parser.
- */
+#ifndef _LIB_TLV_PARSER_H +#define _LIB_TLV_PARSER_H
+#include <linux/kernel.h> +#include <linux/err.h> +#include <linux/limits.h> +#include <linux/tlv_parser.h>
The #includes should move to the .c file and the header be removed.
+#endif /* _LIB_TLV_PARSER_H */
2.47.0.118.gfd3785337b