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

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