dmi_generic_find_entry_addr

Synopsis

#include <opendmi/backend/generic.h>

bool dmi_generic_find_entry_addr(
        dmi_context_t *context,
        const char    *device,
        uint64_t      *paddr);

bool dmi_generic_find_anchor(
        dmi_context_t *context,
        dmi_data_t    *buffer,
        uint64_t       base_addr,
        size_t         area_size,
        const char    *anchor,
        uint64_t      *paddr);

Description

The functions find the SMBIOS entry point the way legacy firmware lets it be found, without the help of the system: by scanning the memory between 0xF0000 and 0xFFFFF for the anchor string of the entry point, on 16-byte boundaries. The backends fall back on them when the system does not tell the address, e.g. on legacy firmware with no EFI configuration tables.

The dmi_generic_find_entry_addr function reads the memory area through device, see dmi_memory_load, and looks for the anchors of the entry points of SMBIOS 3.0 (SM3), SMBIOS 2.1 (SM) and the legacy one (DMI), in this order, so that the newest entry point the firmware provides is found.

The dmi_generic_find_anchor function looks for a single anchor in a memory area which has been read already.

Anchor strings occur in firmware code and data as well, so a match of the anchor alone proves nothing. An entry point is taken only if its length is valid and fits in the area, and its checksum is valid, the way dmidecode checks it. The intermediate entry point of SMBIOS 2.1 must be present and valid as well. Entry points which are not are skipped, and the scan goes on past them.

Parameters

context: Context to raise errors on, and to log the progress of the scan on.
device: Path to the memory device to read the area through, e.g. /dev/mem, or nullptr in the kernel, where the memory is mapped directly.
buffer: Memory area which has been read.
base_addr: Physical address of the memory area, which is aligned on 16 bytes.
area_size: Size of the memory area, which is a multiple of 16 bytes.
anchor: Anchor string of the entry point to look for, e.g. DMI_ANCHOR_V30.
paddr: Variable to store the physical address of the entry point in. It is left as it is if no entry point is found.

Return value

Returns true if a valid entry point has been found, and false otherwise.

Errors

dmi_generic_find_entry_addr raises the errors of dmi_memory_load if the memory area cannot be read. Finding no entry point is not an error.

dmi_generic_find_anchor raises DMI_ERROR_ARGUMENT_NULL if buffer, anchor or paddr is nullptr.

Notes

The functions are available on x86 only, since other architectures have no such memory area, and the header is installed only on the systems whose backends use them, which are FreeBSD and NetBSD.