1 .. SPDX-License-Identifier: GPL-2.0 1 .. SPDX-License-Identifier: GPL-2.0
2 2
3 ======================= !! 3 BMIPS DeviceTree Booting
4 Booting Linux/LoongArch !! 4 ------------------------
5 ======================= !! 5
6 !! 6 Some bootloaders only support a single entry point, at the start of the
7 :Author: Yanteng Si <siyanteng@loongson.cn> !! 7 kernel image. Other bootloaders will jump to the ELF start address.
8 :Date: 18 Nov 2022 !! 8 Both schemes are supported; CONFIG_BOOT_RAW=y and CONFIG_NO_EXCEPT_FILL=y,
9 !! 9 so the first instruction immediately jumps to kernel_entry().
10 Information passed from BootLoader to kernel !! 10
11 ============================================ !! 11 Similar to the arch/arm case (b), a DT-aware bootloader is expected to
12 !! 12 set up the following registers:
13 LoongArch supports ACPI and FDT. The informati !! 13
14 to the kernel includes the memmap, the initrd, !! 14 a0 : 0
15 the ACPI/FDT tables, and so on. !! 15
16 !! 16 a1 : 0xffffffff
17 The kernel is passed the following arguments o !! 17
18 !! 18 a2 : Physical pointer to the device tree block (defined in chapter
19 - a0 = efi_boot: `efi_boot` is a flag in !! 19 II) in RAM. The device tree can be located anywhere in the first
20 this boot environment is fully UEFI-co !! 20 512MB of the physical address space (0x00000000 - 0x1fffffff),
21 !! 21 aligned on a 64 bit boundary.
22 - a1 = cmdline: `cmdline` is a pointer t !! 22
23 !! 23 Legacy bootloaders do not use this convention, and they do not pass in a
24 - a2 = systemtable: `systemtable` points !! 24 DT block. In this case, Linux will look for a builtin DTB, selected via
25 All pointers involved at this stage ar !! 25 CONFIG_DT_*.
26 !! 26
27 Header of Linux/LoongArch kernel images !! 27 This convention is defined for 32-bit systems only, as there are not
28 ======================================= !! 28 currently any 64-bit BMIPS implementations.
29 <<
30 Linux/LoongArch kernel images are EFI images. <<
31 a 64-byte header structured like:: <<
32 <<
33 u32 MZ_MAGIC /* "MZ <<
34 u32 res0 = 0 /* Res <<
35 u64 kernel_entry /* Ker <<
36 u64 _end - _text /* Ker <<
37 u64 load_offset /* Ker <<
38 u64 res1 = 0 /* Res <<
39 u64 res2 = 0 /* Res <<
40 u64 res3 = 0 /* Res <<
41 u32 LINUX_PE_MAGIC /* Mag <<
42 u32 pe_header - _head /* Off <<
Linux® is a registered trademark of Linus Torvalds in the United States and other countries.
TOMOYO® is a registered trademark of NTT DATA CORPORATION.