pvh: Add Structures for PVH Boot Protocol

These are simply translated from the C structs in:
    xen/include/public/arch-x86/hvm/start_info.h

Note that unlike the Linux Boot Protocol structures, these structures
don't need to be `#[repr(packed)]` as they are garunteed to have the
proper alignment.

Signed-off-by: Joe Richey <joerichey@google.com>

Author: josephlr

src/main.rs

@@ -44,6 +44,7 @@ mod paging;
 mod part;
 mod pci;
 mod pe;
+mod pvh;
 mod virtio;
 
 #[cfg(all(not(test), feature = "log-panic"))]

src/pvh.rs

@@ -0,0 +1,55 @@
+use crate::{
+    boot::{E820Entry, Info},
+    common,
+};
+
+// Structures from xen/include/public/arch-x86/hvm/start_info.h
+#[derive(Debug)]
+#[repr(C)]
+pub struct StartInfo {
+    magic: [u8; 4],
+    version: u32,
+    flags: u32,
+    nr_modules: u32,
+    modlist_paddr: u64,
+    cmdline_paddr: u64,
+    rsdp_paddr: u64,
+    memmap_paddr: u64,
+    memmap_entries: u32,
+    _pad: u32,
+}
+
+#[derive(Clone, Copy, Debug)]
+#[repr(C)]
+struct MemMapEntry {
+    addr: u64,
+    size: u64,
+    entry_type: u32,
+    _pad: u32,
+}
+
+impl Info for StartInfo {
+    fn rsdp_addr(&self) -> u64 {
+        self.rsdp_paddr
+    }
+    fn cmdline(&self) -> &[u8] {
+        unsafe { common::from_cstring(self.cmdline_paddr) }
+    }
+    fn num_entries(&self) -> u8 {
+        // memmap_paddr and memmap_entries only exist in version 1 or later
+        if self.version < 1 || self.memmap_paddr == 0 {
+            return 0;
+        }
+        self.memmap_entries as u8
+    }
+    fn entry(&self, idx: u8) -> E820Entry {
+        assert!(idx < self.num_entries());
+        let ptr = self.memmap_paddr as *const MemMapEntry;
+        let entry = unsafe { *ptr.offset(idx as isize) };
+        E820Entry {
+            addr: entry.addr,
+            size: entry.size,
+            entry_type: entry.entry_type,
+        }
+    }
+}