[PATCH v2] dmi: add support for SMBIOS 3.0 64-bit entry point

[Leif Lindholm]

On Wed, Oct 29, 2014 at 04:11:25PM +0100, Ard Biesheuvel wrote:
> The DMTF SMBIOS reference spec v3.0.0 defines a new 64-bit entry point,
> which enables support for SMBIOS structure tables residing at a physical
> offset over 4 GB. This is especially important for upcoming arm64
> platforms whose system RAM resides entirely above the 4 GB boundary.
> 
> For the UEFI case, this code attempts to detect the new SMBIOS 3.0
> header magic at the offset passed in the SMBIOS3_TABLE_GUID UEFI
> configuration table. If this configuration table is not provided, or
> if we fail to parse the header, we fall back to using the legacy
> SMBIOS_TABLE_GUID configuration table. This is in line with the spec,
> that allows both configuration tables to be provided, but mandates that
> they must point to the same structure table, unless the version pointed
> to by the 64-bit entry point is a superset of the 32-bit one.
> 
> For the non-UEFI case, the detection logic is modified to look for the
> SMBIOS 3.0 header magic before it looks for the legacy header magic.
> 
> Note that this patch is based on version 3.0.0d [draft] of the
> specification, which is expected not to deviate from the final version
> in ways that would affect the correctness of this implementation.
> 
> Tested-by: Suravee Suthikulpanit <suravee.suthikulpanit at amd.com>
> Acked-by: Leif Lindholm <leif.lindholm at linaro.org>

Also, for SMBIOS 2 on X64 Ovmf and FVP Base AEMv8-A (with UEFI),
Tested-by: Leif Lindholm <leif.lindholm at linaro.org>

> Cc: Andrew Morton <akpm at linux-foundation.org>
> Cc: Tony Luck <tony.luck at intel.com>
> Signed-off-by: Ard Biesheuvel <ard.biesheuvel at linaro.org>
> ---
> v2: since dmi_base is now a phys_addr_t, prevent surprises caused by GCC's type
>     promotion rules by replacing the open coded shifts/ORs with
>     get_unaligned_leXX()
> ---
>  drivers/firmware/dmi_scan.c | 79 +++++++++++++++++++++++++++++++++++++++++----
>  1 file changed, 72 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/firmware/dmi_scan.c b/drivers/firmware/dmi_scan.c
> index 17afc51f3054..f617badc2698 100644
> --- a/drivers/firmware/dmi_scan.c
> +++ b/drivers/firmware/dmi_scan.c
> @@ -93,6 +93,12 @@ static void dmi_table(u8 *buf, int len, int num,
>  		const struct dmi_header *dm = (const struct dmi_header *)data;
>  
>  		/*
> +		 * 7.45 End-of-Table (Type 127) [SMBIOS reference spec v3.0.0]
> +		 */
> +		if (dm->type == 127)
> +			break;
> +
> +		/*
>  		 *  We want to know the total length (formatted area and
>  		 *  strings) before decoding to make sure we won't run off the
>  		 *  table in dmi_decode or dmi_string
> @@ -107,7 +113,7 @@ static void dmi_table(u8 *buf, int len, int num,
>  	}
>  }
>  
> -static u32 dmi_base;
> +static phys_addr_t dmi_base;
>  static u16 dmi_len;
>  static u16 dmi_num;
>  
> @@ -467,7 +473,7 @@ static int __init dmi_present(const u8 *buf)
>  
>  	if (memcmp(buf, "_SM_", 4) == 0 &&
>  	    buf[5] < 32 && dmi_checksum(buf, buf[5])) {
> -		smbios_ver = (buf[6] << 8) + buf[7];
> +		smbios_ver = get_unaligned_be16(buf + 6);
>  
>  		/* Some BIOS report weird SMBIOS version, fix that up */
>  		switch (smbios_ver) {
> @@ -489,10 +495,9 @@ static int __init dmi_present(const u8 *buf)
>  	buf += 16;
>  
>  	if (memcmp(buf, "_DMI_", 5) == 0 && dmi_checksum(buf, 15)) {
> -		dmi_num = (buf[13] << 8) | buf[12];
> -		dmi_len = (buf[7] << 8) | buf[6];
> -		dmi_base = (buf[11] << 24) | (buf[10] << 16) |
> -			(buf[9] << 8) | buf[8];
> +		dmi_num = get_unaligned_le16(buf + 12);
> +		dmi_len = get_unaligned_le16(buf + 6);
> +		dmi_base = get_unaligned_le32(buf + 8);
>  
>  		if (dmi_walk_early(dmi_decode) == 0) {
>  			if (smbios_ver) {
> @@ -514,12 +519,72 @@ static int __init dmi_present(const u8 *buf)
>  	return 1;
>  }
>  
> +/*
> + * Check for the SMBIOS 3.0 64-bit entry point signature. Unlike the legacy
> + * 32-bit entry point, there is no embedded DMI header (_DMI_) in here.
> + */
> +static int __init dmi_smbios3_present(const u8 *buf)
> +{
> +	if (memcmp(buf, "_SM3_", 5) == 0 &&
> +	    buf[6] < 32 && dmi_checksum(buf, buf[6])) {
> +		dmi_ver = get_unaligned_be16(buf + 7);
> +		dmi_len = get_unaligned_le32(buf + 12);
> +		dmi_base = get_unaligned_le64(buf + 16);
> +
> +		/*
> +		 * The 64-bit SMBIOS 3.0 entry point no longer has a field
> +		 * containing the number of structures present in the table.
> +		 * Instead, it defines the table size as a maximum size, and
> +		 * relies on the end-of-table structure type (#127) to be used
> +		 * to signal the end of the table.
> +		 * So let's define dmi_num as an upper bound as well: each
> +		 * structure has a 4 byte header, so dmi_len / 4 is an upper
> +		 * bound for the number of structures in the table.
> +		 */
> +		dmi_num = dmi_len / 4;
> +
> +		if (dmi_walk_early(dmi_decode) == 0) {
> +			pr_info("SMBIOS %d.%d present.\n",
> +				dmi_ver >> 8, dmi_ver & 0xFF);
> +			dmi_format_ids(dmi_ids_string, sizeof(dmi_ids_string));
> +			pr_debug("DMI: %s\n", dmi_ids_string);
> +			return 0;
> +		}
> +	}
> +	return 1;
> +}
> +
>  void __init dmi_scan_machine(void)
>  {
>  	char __iomem *p, *q;
>  	char buf[32];
>  
>  	if (efi_enabled(EFI_CONFIG_TABLES)) {
> +		/*
> +		 * According to the DMTF SMBIOS reference spec v3.0.0, it is
> +		 * allowed to define both the 64-bit entry point (smbios3) and
> +		 * the 32-bit entry point (smbios), in which case they should
> +		 * either both point to the same SMBIOS structure table, or the
> +		 * table pointed to by the 64-bit entry point should contain a
> +		 * superset of the table contents pointed to by the 32-bit entry
> +		 * point (section 5.2)
> +		 * This implies that the 64-bit entry point should have
> +		 * precedence if it is defined and supported by the OS. If we
> +		 * have the 64-bit entry point, but fail to decode it, fall
> +		 * back to the legacy one (if available)
> +		 */
> +		if (efi.smbios3 != EFI_INVALID_TABLE_ADDR) {
> +			p = dmi_early_remap(efi.smbios3, 32);
> +			if (p == NULL)
> +				goto error;
> +			memcpy_fromio(buf, p, 32);
> +			dmi_early_unmap(p, 32);
> +
> +			if (!dmi_smbios3_present(buf)) {
> +				dmi_available = 1;
> +				goto out;
> +			}
> +		}
>  		if (efi.smbios == EFI_INVALID_TABLE_ADDR)
>  			goto error;
>  
> @@ -552,7 +617,7 @@ void __init dmi_scan_machine(void)
>  		memset(buf, 0, 16);
>  		for (q = p; q < p + 0x10000; q += 16) {
>  			memcpy_fromio(buf + 16, q, 16);
> -			if (!dmi_present(buf)) {
> +			if (!dmi_smbios3_present(buf) || !dmi_present(buf)) {
>  				dmi_available = 1;
>  				dmi_early_unmap(p, 0x10000);
>  				goto out;
> -- 
> 1.8.3.2
>