BIOS(9)

✨ NAME ✨

bios_sigsearch, bios32_SDlookup, bios32, bios_oem_strings — interact with PC BIOS

okay so this is the BIOS(9) page from the Kernel Developer's Manual, and it’s literally all about talking to the PC BIOS, bestie. 💖

🛠️ SYNOPSIS 🛠️

#include <sys/param.h>
#include <vm/vm.h>
#include <vm/pmap.h>
#include <machine/pc/bios.h>

uint32_t
bios_sigsearch(uint32_t start, u_char *sig, int siglen, int paralen,
    int sigofs);

int
bios32_SDlookup(struct bios32_SDentry *ent);

int
bios32(struct bios_regs *br, u_int offset, u_short segment);

BIOS_PADDRTOVADDR(addr);

BIOS_VADDRTOPADDR(addr);

extern struct bios32_SDentry PCIbios;
extern struct SMBIOS_table SMBIOStable;
extern struct DMI_table DMItable;

int
bios_oem_strings(struct bios_oem *oem, u_char *buffer, size_t maxlen);

struct bios_oem_signature {
        char * anchor;          /* search anchor string in BIOS memory */
        size_t offset;          /* offset from anchor (may be negative) */
        size_t totlen;          /* total length of BIOS string to copy */
};
struct bios_oem_range {
        u_int from;             /* shouldn't be below 0xe0000 */
        u_int to;               /* shouldn't be above 0xfffff */
};
struct bios_oem {
        struct bios_oem_range range;
        struct bios_oem_signature signature[];
};

💖 DESCRIPTION 💖

These functions give you a general-purpose interface for dealing with the BIOS functions and data you encounter on x86 PC-architecture systems. no cap, that’s the whole vibe. 💅

• bios_sigsearch() — searches the BIOS address space for a service signature, usually an uppercase ASCII sequence surrounded by underscores. The search begins at start, or at the beginning of the BIOS if start is zero. It compares siglen bytes of the BIOS image and sig at sigofs bytes offset from the current location. If no match is found, the current location is incremented by paralen bytes and the search is repeated. If the signature is found, its effective physical address is returned. If no signature is found, zero is returned. 🔎
• bios_oem_strings() — searches a given BIOS memory range for one or more strings, and composes a printable concatenation of the ones it finds. The routine expects a structure describing the BIOS address range (within 0xe0000 - 0xfffff), plus a { NULL, 0, 0 } -terminated array of bios_oem_signature structures. Those define the anchor string, an offset from the beginning of the match (which may be negative), and totlen number of bytes to be collected from BIOS memory starting at that offset. Unmatched anchors are ignored, whereas matches are copied from BIOS memory starting at their corresponding offset with unprintable characters being replaced with space, and consecutive spaces being suppressed. This composed string is stored in buffer up to the given maxlen bytes (including trailing '\0', and any trailing space suppressed). If an error is encountered, i.e. trying to read out of said BIOS range, other invalid input, or buffer overflow, a negative integer is returned, otherwise the length of the composed string is returned. In particular, a return value of 0 means that none of the given anchor strings were found in the specified BIOS memory range. 😭
• BIOS_VADDRTOPADDR() — returns the effective physical address which corresponds to the kernel virtual address addr. 🦋
• BIOS_PADDRTOVADDR() — returns the kernel virtual address which corresponds to the effective physical address addr. ✨
• SMBIOStable — if not NULL, points to a struct SMBIOS_table structure containing information read from the System Management BIOS table during system startup. 👑
• DMItable — if not NULL, points to a struct DMI_table structure containing information read from the Desktop Management Interface parameter table during system startup. 🌸

🧚 BIOS32 🧚

At system startup, the BIOS is scanned for the BIOS32 Service Directory (part of the PCI specification), and the existence of the directory is recorded. This can then be used to locate other services. periodt. 💅

• bios32_SDlookup() — attempts to locate the BIOS32 service matching the 4-byte identifier passed in the ident field of the ent argument. 🔍
• bios32() — calls a bios32 function. This presumes that the function is capable of working within the kernel segment (normally the case). The virtual address of the entrypoint is supplied in entry and the register arguments to the function are supplied in args. 🛠️
• PCIbios — if not NULL, points to a struct bios32_SDentry structure describing the PCI BIOS entrypoint which was found during system startup. 💖

source/version: Debian · date: August 9, 2005 — that’s the whole vibe, bestie, go flex your BIOS knowledge 💅✨