Add support for RSDP tags

src/lib.rs

@@ -10,6 +10,7 @@ pub use elf_sections::{ElfSectionsTag, ElfSection, ElfSectionIter, ElfSectionTyp
 pub use memory_map::{MemoryMapTag, MemoryArea, MemoryAreaIter};
 pub use module::{ModuleTag, ModuleIter};
 pub use command_line::CommandLineTag;
+pub use rsdp::{RsdpV1Tag, RsdpV2Tag};
 
 #[macro_use]
 extern crate bitflags;
@@ -20,6 +21,7 @@ mod elf_sections;
 mod memory_map;
 mod module;
 mod command_line;
+mod rsdp;
 
 pub unsafe fn load(address: usize) -> BootInformation {
     if !cfg!(test) {
@@ -74,6 +76,14 @@ impl BootInformation {
         self.get_tag(1).map(|tag| unsafe { &*(tag as *const Tag as *const CommandLineTag) })
     }
 
+    pub fn rsdp_v1_tag(&self) -> Option<&'static RsdpV1Tag> {
+        self.get_tag(14).map(|tag| unsafe { &*(tag as *const Tag as *const RsdpV1Tag) })
+    }
+
+    pub fn rsdp_v2_tag(&self) -> Option<&'static RsdpV2Tag> {
+        self.get_tag(15).map(|tag| unsafe { &*(tag as *const Tag as *const RsdpV2Tag) })
+    }
+
     fn get(&self) -> &BootInformationInner {
         unsafe { &*self.inner }
     }
@@ -568,6 +578,15 @@ mod tests {
         assert_eq!(0x7FE_0000, mm2.end_address());
         assert_eq!(0x7EE_0000, mm2.size());
         assert!(mm.next().is_none());
+
+        // Test the RSDP tag
+        let rsdp_old = bi.rsdp_v1_tag().unwrap();
+        assert_eq!("RSD PTR ", rsdp_old.signature().unwrap());
+        assert_eq!(89, rsdp_old.checksum());
+        assert_eq!("BOCHS ", rsdp_old.oem_id().unwrap());
+        assert_eq!(0, rsdp_old.revision());
+        assert_eq!(0x7FE18DC, rsdp_old.rsdt_address());
+
         assert!(bi.module_tags().next().is_none());
         assert_eq!("GRUB 2.02~beta3-5", bi.boot_loader_name_tag().unwrap().name());
         assert_eq!("", bi.command_line_tag().unwrap().command_line());

src/rsdp.rs

@@ -0,0 +1,85 @@
+/// The tag that the bootloader passes will depend on the ACPI version the hardware supports.
+/// For ACPI Version 1.0, a `RsdpV1Tag` will be provided, which can be accessed from
+/// `BootInformation` using the `rsdp_v1_tag` function. For subsequent versions of ACPI, a
+/// `RsdpV2Tag` will be provided, which can be accessed with `rsdp_v2_tag`.
+///
+/// Even though the bootloader should give the address of the real RSDP/XSDT, the checksum and
+/// signature should be manually verified.
+
+use core::str;
+
+#[derive(Debug)]
+#[repr(C, packed)]
+pub struct RsdpV1Tag {
+    typ: u32,
+    size: u32,
+    signature: [u8; 8],
+    checksum: u8,
+    oem_id: [u8; 6],
+    revision: u8,
+    rsdt_address: u32,  // This is the PHYSICAL address of the RSDT
+}
+
+impl RsdpV1Tag {
+    pub fn signature<'a>(&'a self) -> Option<&'a str> {
+        str::from_utf8(&self.signature).ok()
+    }
+
+    pub fn checksum(&self) -> u8 {
+        self.checksum
+    }
+
+    pub fn oem_id<'a>(&'a self) -> Option<&'a str> {
+        str::from_utf8(&self.oem_id).ok()
+    }
+
+    pub fn revision(&self) -> u8 {
+        self.revision
+    }
+
+    pub fn rsdt_address(&self) -> usize {
+        self.rsdt_address as usize
+    }
+}
+
+#[derive(Debug)]
+#[repr(C, packed)]
+pub struct RsdpV2Tag {
+    typ: u32,
+    size: u32,
+    signature: [u8; 8],
+    checksum: u8,
+    oem_id: [u8; 6],
+    revision: u8,
+    _rsdt_address: u32,
+    length: u32,
+    xsdt_address: u64,  // This is the PHYSICAL address of the XSDT
+    ext_checksum: u8,
+    _reserved: [u8; 3],
+}
+
+impl RsdpV2Tag {
+    pub fn signature<'a>(&'a self) -> Option<&'a str> {
+        str::from_utf8(&self.signature).ok()
+    }
+
+    pub fn checksum(&self) -> u8 {
+        self.checksum
+    }
+
+    pub fn oem_id<'a>(&'a self) -> Option<&'a str> {
+        str::from_utf8(&self.oem_id).ok()
+    }
+
+    pub fn revision(&self) -> u8 {
+        self.revision
+    }
+
+    pub fn xsdt_address(&self) -> usize {
+        self.xsdt_address as usize
+    }
+
+    pub fn ext_checksum(&self) -> u8 {
+        self.ext_checksum
+    }
+}