Add MCFG parsing for PCIe.

pcid/src/main.rs

@@ -21,6 +21,7 @@ use crate::pci::cap::Capability as PciCapability;
 mod config;
 mod driver_interface;
 mod pci;
+mod pcie;
 
 pub struct DriverHandler {
     config: config::DriverConfig,

pcid/src/pcie/mod.rs

@@ -0,0 +1,91 @@
+use std::{fs, io, mem, slice};
+use smallvec::SmallVec;
+
+pub const MCFG_NAME: [u8; 4] = *b"MCFG";
+
+#[repr(packed)]
+#[derive(Clone, Copy, Debug)]
+pub struct Mcfg {
+    // base sdt fields
+    name: [u8; 4],
+    length: u32,
+    revision: u8,
+    checksum: u8,
+    oem_id: [u8; 6],
+    oem_table_id: [u8; 8],
+    oem_revision: u32,
+    creator_id: [u8; 4],
+    _rsvd: [u8; 8],
+
+    base_addrs: [PcieAlloc; 0],
+}
+unsafe impl plain::Plain for Mcfg {}
+
+/// The "Memory Mapped Enhanced Configuration Space Base Address Allocation Structure" (yes, it's
+/// called that).
+
+#[repr(packed)]
+#[derive(Clone, Copy, Debug)]
+pub struct PcieAlloc {
+    pub base_addr: u64,
+    pub seg_group_num: u16,
+    pub start_bus: u8,
+    pub end_bus: u8,
+    _rsvd: [u8; 4],
+}
+unsafe impl plain::Plain for PcieAlloc {}
+
+impl Mcfg {
+    pub fn base_addr_structs(&self) -> &[PcieAlloc] {
+        let total_length = mem::size_of::<Self>();
+        let len = total_length - 44;
+        // safe because the length cannot be changed arbitrarily
+        unsafe { slice::from_raw_parts(&self.base_addrs as *const PcieAlloc, len / mem::size_of::<PcieAlloc>()) }
+    }
+}
+
+pub struct Mcfgs {
+    tables: SmallVec<[Vec<u8>; 2]>,
+}
+impl Mcfgs {
+    pub fn tables<'a>(&'a self) -> impl Iterator<Item = &'a Mcfg> + 'a {
+        self.tables.iter().filter_map(|bytes| {
+            let mcfg = plain::from_bytes::<Mcfg>(bytes).ok()?;
+            if mcfg.length as usize > bytes.len() {
+                return None;
+            }
+            Some(mcfg)
+        })
+    }
+
+    pub fn fetch() -> io::Result<Self> {
+        let table_dir = fs::read_dir("acpi:tables")?;
+
+        let tables = table_dir.map(|table_direntry| -> io::Result<Option<_>> {
+            let table_direntry = table_direntry?;
+            let table_path = table_direntry.path();
+
+            let table_filename = match table_path.file_name() {
+                Some(n) => n.to_str().ok_or(io::Error::new(io::ErrorKind::InvalidData, "Non-UTF-8 ACPI table filename"))?,
+                None => return Ok(None),
+            };
+
+            if table_filename.starts_with("MCFG") {
+                Ok(Some(fs::read(table_path)?))
+            } else {
+                Ok(None)
+            }
+        }).filter_map(|result_option| result_option.transpose()).collect::<Result<SmallVec<_>, _>>()?;
+
+        Ok(Self {
+            tables,
+        })
+    }
+    pub fn at_bus(&self, bus: u8) -> Option<(&Mcfg, &PcieAlloc)> {
+        self.tables().find_map(|table| {
+            Some((table, table.base_addr_structs().iter().find(|addr_struct| {
+                (addr_struct.start_bus..addr_struct.end_bus).contains(&bus)
+            })?))
+        })
+    }
+}