// SPDX-License-Identifier: Apache-2.0
#pragma once
#ifndef SCHBOOT_H
#define SCHBOOT_H

// The loader/kernel hand-off, in one place.
//
// Included by kernel/arch/x86_64/entry.S and by boot/uefi/main.c, so the two
// cannot disagree about the magic or the layout. Defining it twice is exactly
// how a loader ends up scanning for bytes the kernel never wrote — the first
// attempt here searched for "SCH6" while the assembler had stored 0x53434836,
// which lands in the file as "6HCS".
//
// Keep this header assembler-safe: no typedefs, no structs outside the C
// guard, nothing entry.S cannot preprocess.

// Scanned for in the first 16 KB of the kernel image, 8-byte aligned, exactly
// as the BIOS loader scans for the multiboot magic. Followed by a little-endian
// 64-bit physical address: the kernel's 64-bit entry point.
//
// The values spell "SCH6" "4BOO" when stored little-endian, which is what
// makes them findable by eye in a hex dump of the image.
#define SCH64_MAGIC0 0x36484353   /* "SCH6" */
#define SCH64_MAGIC1 0x4f4f4234   /* "4BOO" */

// Where the loader leaves the ACPI RSDP, as a little-endian 64-bit physical
// address. Zero means "not provided, go and look for it yourself".
//
// The kernel's own search scans the EBDA and 0xE0000-0x100000, which is a BIOS
// convention. UEFI publishes the RSDP in its configuration table instead and is
// under no obligation to leave a copy anywhere in particular; OVMF does not.
// Without it the kernel finds no MADT, so no IOAPIC, so no interrupt routing --
// the machine boots to a prompt on polled serial output and then ignores every
// key, which looks like a broken console rather than a missing table.
//
// 0x30000 is the same low-memory hand-off block the BIOS loader uses:
// +0x100 verbose flag, +0x200 e820 count, +0x208 the e820 map (32 entries of
// 24 bytes, ending at 0x508). 0x600 is clear of all of it.
#define SCHBOOT_RSDP_ADDR (0x30000 + 0x600)

#ifndef __ASSEMBLER__

struct sch64_header {
    unsigned int       magic0;    // SCH64_MAGIC0
    unsigned int       magic1;    // SCH64_MAGIC1
    unsigned long long entry;     // physical address, entered in long mode
};

#endif /* !__ASSEMBLER__ */

#endif /* SCHBOOT_H */