2. Booting Linux/LoongArch¶
- Author:
Yanteng Si <siyanteng@loongson.cn>
- Date:
18 Nov 2022
2.1. Information passed from BootLoader to kernel¶
LoongArch supports ACPI and FDT. The information that needs to be passed to the kernel includes the memmap, the initrd, the command line, optionally the ACPI/FDT tables, and so on.
The kernel is passed the following arguments on kernel_entry :
a0 = efi_boot: efi_boot is a flag indicating whether this boot environment is fully UEFI-compliant.
a1 = cmdline: cmdline is a pointer to the kernel command line.
a2 = systemtable: systemtable points to the EFI system table. All pointers involved at this stage are in physical addresses.
2.2. Header of Linux/LoongArch kernel images¶
Linux/LoongArch kernel images are EFI images. Being PE files, they have a 64-byte header structured like:
u32 MZ_MAGIC /* "MZ", MS-DOS header */
u32 res0 = 0 /* Reserved */
u64 kernel_entry /* Kernel entry point */
u64 _end - _text /* Kernel image effective size */
u64 load_offset /* Kernel image load offset from start of RAM */
u64 res1 = 0 /* Reserved */
u64 res2 = 0 /* Reserved */
u64 res3 = 0 /* Reserved */
u32 LINUX_PE_MAGIC /* Magic number */
u32 pe_header - _head /* Offset to the PE header */