[PATCH v2 3/6] smbios: Use SMBIOS 3.0 to support an address above 4GB

[Simon Glass]

Hi Heinrich,

On Mon, 20 Nov 2023 at 19:11, Heinrich Schuchardt <xypron.glpk at gmx.de> wrote:
>
> On 10/15/23 04:45, Simon Glass wrote:
> > When the SMBIOS table is written to an address above 4GB a 32-bit table
> > address is not large enough.
> >
> > Use an SMBIOS3 table in that case.
> >
> > Note that we cannot use efi_allocate_pages() since this function has
> > nothing to do with EFI. There is no equivalent function to allocate
> > memory below 4GB in U-Boot. One solution would be to create a separate
> > malloc() pool, or just always put the malloc() pool below 4GB.
> >
> > Signed-off-by: Simon Glass <sjg at chromium.org>
> > ---
> >
> > Changes in v2:
> > - Check the end of the table rather than the start.
> >
> >   include/smbios.h | 22 +++++++++++++++++++++-
> >   lib/smbios.c     | 24 +++++++++++++++++++-----
> >   2 files changed, 40 insertions(+), 6 deletions(-)
> >
> > diff --git a/include/smbios.h b/include/smbios.h
> > index c9df2706f5a6..ddabb558299e 100644
> > --- a/include/smbios.h
> > +++ b/include/smbios.h
> > @@ -12,7 +12,8 @@
> >
> >   /* SMBIOS spec version implemented */
> >   #define SMBIOS_MAJOR_VER    3
> > -#define SMBIOS_MINOR_VER     0
> > +#define SMBIOS_MINOR_VER     7
> > +
> >
> >   enum {
> >       SMBIOS_STR_MAX  = 64,   /* Maximum length allowed for a string */
> > @@ -54,6 +55,25 @@ struct __packed smbios_entry {
> >       u8 bcd_rev;
> >   };
> >
> > +struct __packed smbios3_entry {
> > +     u8 anchor[5];
> > +     u8 checksum;
> > +     u8 length;
> > +     u8 major_ver;
> > +
> > +     u8 minor_ver;
> > +     u8 docrev;
> > +     u8 entry_point_rev;
> > +     u8 reserved;
> > +     u32 max_struct_size;
> > +
> > +     u64 struct_table_address;
> > +};
> > +
> > +/* These two structures should use the same amount of 16-byte-aligned space */
> > +static_assert(ALIGN(16, sizeof(struct smbios_entry)) ==
> > +           ALIGN(16, sizeof(struct smbios3_entry)));
> > +
> >   /* BIOS characteristics */
> >   #define BIOS_CHARACTERISTICS_PCI_SUPPORTED  (1 << 7)
> >   #define BIOS_CHARACTERISTICS_UPGRADEABLE    (1 << 11)
> > diff --git a/lib/smbios.c b/lib/smbios.c
> > index c7a557bc9b7b..92e98388084f 100644
> > --- a/lib/smbios.c
> > +++ b/lib/smbios.c
> > @@ -487,7 +487,11 @@ ulong write_smbios_table(ulong addr)
> >       addr = ALIGN(addr, 16);
> >       start_addr = addr;
> >
> > -     addr += sizeof(struct smbios_entry);
> > +     /*
> > +      * So far we don't know which struct will be used, but they both end
> > +      * up using the same amount of 16-bit-aligned space
> > +      */
> > +     addr += max(sizeof(struct smbios_entry), sizeof(struct smbios3_entry));
> >       addr = ALIGN(addr, 16);
> >       tables = addr;
> >
> > @@ -512,14 +516,24 @@ ulong write_smbios_table(ulong addr)
> >        * sandbox's DRAM buffer.
> >        */
> >       table_addr = (ulong)map_sysmem(tables, 0);
> > -     if (sizeof(table_addr) > sizeof(u32) && table_addr > (ulong)UINT_MAX) {
> > +     if (sizeof(table_addr) > sizeof(u32) && addr >= (ulong)UINT_MAX) {
>
> You have to check the end of the the last SMBIOS structure not the start
> of the first SMBIOS structure against UINT_MAX.
>
> > +             struct smbios3_entry *se;
> >               /*
> >                * We need to put this >32-bit pointer into the table but the
> >                * field is only 32 bits wide.
> >                */
> > -             printf("WARNING: SMBIOS table_address overflow %llx\n",
> > -                    (unsigned long long)table_addr);
> > -             addr = 0;
> > +             printf("WARNING: Using SMBIOS3.0 due to table-address overflow %lx\n",
> > +                    table_addr);
>
> This should be log_debug().
>
> > +             se = map_sysmem(start_addr, sizeof(struct smbios_entry));
> > +             memset(se, '\0', sizeof(struct smbios_entry));
> > +             memcpy(se->anchor, "_SM3_", 5);
> > +             se->length = sizeof(struct smbios3_entry);
> > +             se->major_ver = SMBIOS_MAJOR_VER;
> > +             se->minor_ver = SMBIOS_MINOR_VER;
> > +             se->docrev = 0;
> > +             se->entry_point_rev = 1;
> > +             se->max_struct_size = len;
> > +             se->struct_table_address = table_addr;
>
> You must fill the checksum:
>
> se->checksum = table_compute_checksum(se, sizeof(struct smbios3_entry));
>
> With the checksum filled I can use dmidecode in Linux based on the
> SMBIOS3 table:
>
> ubuntu at ubuntu:~$ sudo dmidecode
> # dmidecode 3.5
> # SMBIOS3 entry point at 0x27ef53000
> Found SMBIOS entry point in EFI, reading table from /dev/mem.
> SMBIOS 3.7.0 present.
> # SMBIOS implementations newer than version 3.5.0 are not
> # fully supported by this version of dmidecode.
> Table at 0x27EF53020.
>
> Handle 0x0000, DMI type 0, 24 bytes
> BIOS Information
>          Vendor: U-Boot

OK, great, thank you for figuring this out. Do you think this might be
a reasonable solution for -next ?

Regards,
Simon