[PATCH v2 1/2] smbios: add parsing API

[Christian Gmeiner]

ping and a short question: would it make more sense to put the parsing
code into smbios.c and unconditionally compile it?

Am Mi., 7. Okt. 2020 um 14:33 Uhr schrieb Christian Gmeiner
<christian.gmeiner at gmail.com>:
>
> Add an very simple API to be able to access SMBIOS strings
> like vendor, model and bios version.
>
> Signed-off-by: Christian Gmeiner <christian.gmeiner at gmail.com>
> ---
>  include/smbios.h    | 27 +++++++++++++
>  lib/Kconfig         |  6 +++
>  lib/Makefile        |  1 +
>  lib/smbios-parser.c | 96 +++++++++++++++++++++++++++++++++++++++++++++
>  4 files changed, 130 insertions(+)
>  create mode 100644 lib/smbios-parser.c
>
> diff --git a/include/smbios.h b/include/smbios.h
> index 97b9ddce23..ed60c00fae 100644
> --- a/include/smbios.h
> +++ b/include/smbios.h
> @@ -237,4 +237,31 @@ typedef int (*smbios_write_type)(ulong *addr, int handle);
>   */
>  ulong write_smbios_table(ulong addr);
>
> +/**
> + * smbios_entry() - Get a vaild struct smbios_entry pointer
> + *
> + * @address:   address where smbios tables is located
> + * @size:      size of smbios table
> + * @return:    NULL or a valid pointer to a struct smbios_entry
> + */
> +const struct smbios_entry *smbios_entry(u64 address, u32 size);
> +
> +/**
> + * smbios_header() - Search for SMBIOS header type
> + *
> + * @entry:     pointer to a struct smbios_entry
> + * @type:      SMBIOS type
> + * @return:    NULL or a valid pointer to a struct smbios_header
> + */
> +const struct smbios_header *smbios_header(const struct smbios_entry *entry, int type);
> +
> +/**
> + * smbios_string() - Return string from SMBIOS
> + *
> + * @header:    pointer to struct smbios_header
> + * @index:     string index
> + * @return:    NULL or a valid const char pointer
> + */
> +const char *smbios_string(const struct smbios_header *header, int index);
> +
>  #endif /* _SMBIOS_H_ */
> diff --git a/lib/Kconfig b/lib/Kconfig
> index 8efb154f73..c92131b7bc 100644
> --- a/lib/Kconfig
> +++ b/lib/Kconfig
> @@ -667,6 +667,12 @@ config OID_REGISTRY
>         help
>           Enable fast lookup object identifier registry.
>
> +config SMBIOS_PARSER
> +       bool "SMBIOS parser"
> +       default n
> +       help
> +         A simple parser for SMBIOS data.
> +
>  source lib/efi/Kconfig
>  source lib/efi_loader/Kconfig
>  source lib/optee/Kconfig
> diff --git a/lib/Makefile b/lib/Makefile
> index 0cd7bea282..0383fddf2c 100644
> --- a/lib/Makefile
> +++ b/lib/Makefile
> @@ -37,6 +37,7 @@ obj-$(CONFIG_FIT) += fdtdec_common.o
>  obj-$(CONFIG_TEST_FDTDEC) += fdtdec_test.o
>  obj-$(CONFIG_GZIP_COMPRESSED) += gzip.o
>  obj-$(CONFIG_GENERATE_SMBIOS_TABLE) += smbios.o
> +obj-$(CONFIG_SMBIOS_PARSER) += smbios-parser.o
>  obj-$(CONFIG_IMAGE_SPARSE) += image-sparse.o
>  obj-y += ldiv.o
>  obj-$(CONFIG_XXHASH) += xxhash.o
> diff --git a/lib/smbios-parser.c b/lib/smbios-parser.c
> new file mode 100644
> index 0000000000..b89f988ef9
> --- /dev/null
> +++ b/lib/smbios-parser.c
> @@ -0,0 +1,96 @@
> +// SPDX-License-Identifier: GPL-2.0+
> +/*
> + * Copyright (C) 2020, Bachmann electronic GmbH
> + */
> +
> +#include <common.h>
> +#include <smbios.h>
> +
> +static inline int verify_checksum(const struct smbios_entry *e)
> +{
> +       /*
> +        * Checksums for SMBIOS tables are calculated to have a value, so that
> +        * the sum over all bytes yields zero (using unsigned 8 bit arithmetic).
> +        */
> +       u8 *byte = (u8 *)e;
> +       u8 sum = 0;
> +
> +       for (int i = 0; i < e->length; i++)
> +               sum += byte[i];
> +
> +       return sum;
> +}
> +
> +const struct smbios_entry *smbios_entry(u64 address, u32 size)
> +{
> +       const struct smbios_entry *entry = (struct smbios_entry *)(uintptr_t)address;
> +
> +       if (!address | !size)
> +               return NULL;
> +
> +       if (memcmp(entry->anchor, "_SM_", 4))
> +               return NULL;
> +
> +       if (verify_checksum(entry))
> +               return NULL;
> +
> +       return entry;
> +}
> +
> +static const struct smbios_header *next_header(const struct smbios_header *curr)
> +{
> +       u8 *pos = ((u8 *)curr) + curr->length;
> +
> +       /* search for _double_ NULL bytes */
> +       while (!((*pos == 0) && (*(pos + 1) == 0)))
> +               pos++;
> +
> +       /* step behind the double NULL bytes */
> +       pos += 2;
> +
> +       return (struct smbios_header *)pos;
> +}
> +
> +const struct smbios_header *smbios_header(const struct smbios_entry *entry, int type)
> +{
> +       const unsigned int num_header = entry->struct_count;
> +       const struct smbios_header *header = (struct smbios_header *)entry->struct_table_address;
> +
> +       for (unsigned int i = 0; i < num_header; i++) {
> +               if (header->type == type)
> +                       return header;
> +
> +               header = next_header(header);
> +       }
> +
> +       return NULL;
> +}
> +
> +static const char *string_from_smbios_table(const struct smbios_header *header,
> +                                           int idx)
> +{
> +       unsigned int i = 1;
> +       u8 *pos;
> +
> +       if (!header)
> +               return NULL;
> +
> +       pos = ((u8 *)header) + header->length;
> +
> +       while (i < idx) {
> +               if (*pos == 0x0)
> +                       i++;
> +
> +               pos++;
> +       }
> +
> +       return (const char *)pos;
> +}
> +
> +const char *smbios_string(const struct smbios_header *header, int index)
> +{
> +       if (!header)
> +               return NULL;
> +
> +       return string_from_smbios_table(header, index);
> +}
> --
> 2.28.0
>


-- 
greets
--
Christian Gmeiner, MSc

https://christian-gmeiner.info/privacypolicy