ostd/arch/x86/boot/multiboot2/
mod.rs

1// SPDX-License-Identifier: MPL-2.0
2
3use core::arch::global_asm;
4
5use multiboot2::{BootInformation, BootInformationHeader, MemoryAreaType};
6
7use crate::{
8    boot::{
9        BootloaderAcpiArg, BootloaderFramebufferArg,
10        memory_region::{MemoryRegion, MemoryRegionArray, MemoryRegionType},
11    },
12    mm::{Paddr, kspace::paddr_to_vaddr},
13};
14
15global_asm!(include_str!("header.S"));
16
17fn parse_bootloader_name(mb2_info: &BootInformation) -> Option<&'static str> {
18    let name = mb2_info.boot_loader_name_tag()?.name().ok()?;
19
20    // SAFETY: The address of `name` is physical and the bootloader name will live for `'static`.
21    Some(unsafe { make_str_vaddr_static(name) })
22}
23
24fn parse_kernel_commandline(mb2_info: &BootInformation) -> Option<&'static str> {
25    let cmdline = mb2_info.command_line_tag()?.cmdline().ok()?;
26
27    // SAFETY: The address of `cmdline` is physical and the command line will live for `'static`.
28    Some(unsafe { make_str_vaddr_static(cmdline) })
29}
30
31unsafe fn make_str_vaddr_static(str: &str) -> &'static str {
32    let vaddr = paddr_to_vaddr(str.as_ptr() as Paddr);
33
34    // SAFETY: The safety is upheld by the caller.
35    let bytes = unsafe { core::slice::from_raw_parts(vaddr as *const u8, str.len()) };
36
37    core::str::from_utf8(bytes).unwrap()
38}
39
40fn parse_initramfs(mb2_info: &BootInformation) -> Option<&'static [u8]> {
41    let module_tag = mb2_info.module_tags().next()?;
42
43    let initramfs_ptr = paddr_to_vaddr(module_tag.start_address() as usize);
44    let initramfs_len = module_tag.module_size() as usize;
45    // SAFETY: The initramfs is safe to read because of the contract with the loader.
46    let initramfs =
47        unsafe { core::slice::from_raw_parts(initramfs_ptr as *const u8, initramfs_len) };
48
49    Some(initramfs)
50}
51
52fn parse_acpi_arg(mb2_info: &BootInformation) -> BootloaderAcpiArg {
53    if let Some(v2_tag) = mb2_info.rsdp_v2_tag() {
54        // Check for RSDP v2
55        BootloaderAcpiArg::Xsdt(v2_tag.xsdt_address())
56    } else if let Some(v1_tag) = mb2_info.rsdp_v1_tag() {
57        // Fall back to RSDP v1
58        BootloaderAcpiArg::Rsdt(v1_tag.rsdt_address())
59    } else if is_efi_boot(mb2_info) {
60        BootloaderAcpiArg::NotProvided
61    } else {
62        BootloaderAcpiArg::ScanBios
63    }
64}
65
66fn is_efi_boot(mb2_info: &BootInformation) -> bool {
67    mb2_info.efi_sdt32_tag().is_some()
68        || mb2_info.efi_sdt64_tag().is_some()
69        || mb2_info.efi_memory_map_tag().is_some()
70        || mb2_info.efi_bs_not_exited_tag().is_some()
71        || mb2_info.efi_ih32_tag().is_some()
72        || mb2_info.efi_ih64_tag().is_some()
73}
74
75fn parse_framebuffer_info(mb2_info: &BootInformation) -> Option<BootloaderFramebufferArg> {
76    let fb_tag = mb2_info.framebuffer_tag()?.ok()?;
77
78    Some(BootloaderFramebufferArg {
79        address: fb_tag.address() as usize,
80        width: fb_tag.width() as usize,
81        height: fb_tag.height() as usize,
82        bpp: fb_tag.bpp() as usize,
83    })
84}
85
86impl From<MemoryAreaType> for MemoryRegionType {
87    fn from(value: MemoryAreaType) -> Self {
88        match value {
89            MemoryAreaType::Available => Self::Usable,
90            MemoryAreaType::Reserved => Self::Reserved,
91            MemoryAreaType::AcpiAvailable => Self::Reclaimable,
92            MemoryAreaType::ReservedHibernate => Self::NonVolatileSleep,
93            MemoryAreaType::Defective => Self::BadMemory,
94            MemoryAreaType::Custom(_) => Self::Reserved,
95        }
96    }
97}
98
99fn parse_memory_regions(mb2_info: &BootInformation) -> MemoryRegionArray {
100    let mut regions = MemoryRegionArray::new();
101
102    // Add the regions returned by Grub.
103    let memory_regions_tag = mb2_info
104        .memory_map_tag()
105        .expect("No memory regions are found in the Multiboot2 header!");
106    for region in memory_regions_tag.memory_areas() {
107        let start = region.start_address();
108        let end = region.end_address();
109        let area_typ: MemoryRegionType = MemoryAreaType::from(region.typ()).into();
110        let region = MemoryRegion::new(
111            start.try_into().unwrap(),
112            (end - start).try_into().unwrap(),
113            area_typ,
114        );
115        regions.push(region).unwrap();
116    }
117
118    // Add the framebuffer region since Grub does not specify it.
119    if let Some(fb) = parse_framebuffer_info(mb2_info) {
120        regions.push(MemoryRegion::framebuffer(&fb)).unwrap();
121    }
122
123    // Add the kernel region since Grub does not specify it.
124    regions.push(MemoryRegion::kernel()).unwrap();
125
126    // Add the initramfs region.
127    if let Some(initramfs) = parse_initramfs(mb2_info) {
128        regions.push(MemoryRegion::module(initramfs)).unwrap();
129    }
130
131    // Add the AP boot code region that will be copied into by the BSP.
132    regions
133        .push(super::smp::reclaimable_memory_region())
134        .unwrap();
135
136    // Add the kernel cmdline and boot loader name region since Grub does not specify it.
137    if let Some(kcmdline) = parse_kernel_commandline(mb2_info) {
138        regions
139            .push(MemoryRegion::module(kcmdline.as_bytes()))
140            .unwrap();
141    }
142    if let Some(bootloader_name) = parse_bootloader_name(mb2_info) {
143        regions
144            .push(MemoryRegion::module(bootloader_name.as_bytes()))
145            .unwrap();
146    }
147
148    regions.into_non_overlapping()
149}
150
151/// The entry point of the Rust code portion of Asterinas (with multiboot2 parameters).
152///
153/// # Safety
154///
155/// - This function must be called only once at a proper timing in the BSP's boot assembly code.
156/// - The caller must follow C calling conventions and put the right arguments in registers.
157/// - If this function is called, entry points of other boot protocols must never be called.
158// SAFETY: The name does not collide with other symbols.
159#[unsafe(no_mangle)]
160unsafe extern "sysv64" fn __multiboot2_entry(boot_magic: u32, boot_params: u64) -> ! {
161    assert_eq!(boot_magic, multiboot2::MAGIC);
162    let mb2_info =
163        unsafe { BootInformation::load(boot_params as *const BootInformationHeader).unwrap() };
164
165    use crate::boot::{EARLY_INFO, EarlyBootInfo, start_kernel};
166
167    EARLY_INFO.call_once(|| EarlyBootInfo {
168        bootloader_name: parse_bootloader_name(&mb2_info).unwrap_or("Unknown Multiboot2 Loader"),
169        kernel_cmdline: parse_kernel_commandline(&mb2_info).unwrap_or(""),
170        initramfs: parse_initramfs(&mb2_info),
171        acpi_arg: parse_acpi_arg(&mb2_info),
172        framebuffer_arg: parse_framebuffer_info(&mb2_info),
173        memory_regions: parse_memory_regions(&mb2_info),
174    });
175
176    // SAFETY: The safety is guaranteed by the safety preconditions and the fact that we call it
177    // once after setting up necessary resources.
178    unsafe { start_kernel() };
179}
ostd/arch/x86/boot/multiboot2/mod.rs

ostd/arch/x86/boot/multiboot2/
mod.rs
