Re: [Qemu-devel] [PATCH] hw/smbios: handle both file formats regardless of machine type

[Bruce Rogers]

>>> On 4/11/2019 at 11:51 AM, Bruce Rogers <address@hidden> wrote:
> It's easy enough to handle either per‑spec or legacy smbios structures
> in the smbios file input without regard to the machine type used, by
> simply applying the basic smbios formatting rules. then depending on
> what is detected. terminal numm bytes are added or removed for machine
> type specific processing.
> 
> Signed‑off‑by: Bruce Rogers <address@hidden>
> ‑‑‑
>  hw/smbios/smbios.c | 43 +++++++++++++++++++++++++++++++++++++++‑‑‑‑
>  1 file changed, 39 insertions(+), 4 deletions(‑)
> 
> diff ‑‑git a/hw/smbios/smbios.c b/hw/smbios/smbios.c
> index 47be9071fa..d4b95ebc84 100644
> ‑‑‑ a/hw/smbios/smbios.c
> +++ b/hw/smbios/smbios.c
> @@ ‑960,6 +960,7 @@ void smbios_entry_add(QemuOpts *opts, Error **errp)
>          struct smbios_structure_header *header;
>          int size;
>          struct smbios_table *table; /* legacy mode only */
> +        uint8_t *dbl_nulls, *orig_end;
>  
>          qemu_opts_validate(opts, qemu_smbios_file_opts, &err);
>          if (err) {
> @@ ‑974,11 +975,21 @@ void smbios_entry_add(QemuOpts *opts, Error **errp)
>          }
>  
>          /*
> ‑         * NOTE: standard double '\0' terminator expected, per smbios spec.
> ‑         * (except in legacy mode, where the second '\0' is implicit and
> ‑         *  will be inserted by the BIOS).
> +         * NOTE: standard double '\0' terminator expected, per smbios spec,
> +         * unless the data is formatted for legacy mode, which is used by
> +         * pc‑i440fx‑2.0 and earlier machine types. Legacy mode structures
> +         * without strings have no '\0' terminators, and those with strings
> +         * also don't have an additional '\0' terminator at the end of the
> +         * final string '\0' terminator. The BIOS will add the '\0' 
> terminators
> +         * to comply with the smbios spec.
> +         * For greater compatibility, regardless of the machine type used,
> +         * either format is accepted.
>           */
> ‑        smbios_tables = g_realloc(smbios_tables, smbios_tables_len + size);
> +        smbios_tables = g_realloc(smbios_tables, smbios_tables_len + size + 
> 2);
> +        orig_end = smbios_tables + smbios_tables_len + size;
> +        /* add extra null bytes to end in case of legacy file data */
> +        *orig_end = '\0';
> +        *(orig_end + 1) = '\0';
>          header = (struct smbios_structure_header *)(smbios_tables +
>                                                      smbios_tables_len);
>  
> @@ ‑993,6 +1004,19 @@ void smbios_entry_add(QemuOpts *opts, Error **errp)
>                         header‑>type);
>              return;
>          }
> +        for (dbl_nulls = smbios_tables + smbios_tables_len + header‑>length;
> +             dbl_nulls + 2 <= orig_end; dbl_nulls++) {
> +            if (*dbl_nulls == '\0' && *(dbl_nulls + 1) == '\0') {
> +                break;
> +            }
> +        }
> +        if (dbl_nulls + 2  < orig_end) {
> +            error_setg(errp, "SMBIOS file data malformed");
> +            return;
> +        }
> +        /* increase size by how many extra nulls were actually needed */
> +        size += dbl_nulls + 2 ‑ orig_end;
> +        smbios_tables = g_realloc(smbios_tables, smbios_tables_len + size);
>          set_bit(header‑>type, have_binfile_bitmap);
>  
>          if (header‑>type == 4) {
> @@ ‑1013,6 +1037,17 @@ void smbios_entry_add(QemuOpts *opts, Error **errp)
>           *       delete the one we don't need from smbios_set_defaults(),
>           *       once we know which machine version has been requested.
>           */
> +        if (dbl_nulls + 2 == orig_end) {
> +            /* chop off nulls to get legacy format */
> +            if (header‑>length + 2 == size) {
> +                size ‑= 2;
> +            } else {
> +                size ‑= 1;
> +
    }
> +        } else {
> +            /* undo conversion from legacy format to per‑spec format */
> +            size ‑= dbl_nulls + 2 ‑ orig_end;
> +        }
>          if (!smbios_entries) {
>              smbios_entries_len = sizeof(uint16_t);
>              smbios_entries = g_malloc0(smbios_entries_len);
> ‑‑ 
> 2.21.0

ping

- Bruce