Add a crate for driver helpers.

Cargo.toml

@@ -6,6 +6,7 @@ members = [
     "alxd",
     "bgad",
     "block-io-wrapper",
+    "common",
     "e1000d",
     "ided",
     "ihdad",

common/Cargo.toml

@@ -0,0 +1,11 @@
+[package]
+name = "common"
+version = "0.1.0"
+edition = "2021"
+authors = ["4lDO2 <4lDO2@protonmail.com>"]
+license = "MIT"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+redox_syscall = "0.3"

common/src/lib.rs

@@ -0,0 +1,57 @@
+#![feature(int_roundings)]
+
+use syscall::PAGE_SIZE;
+use syscall::error::{Error, Result, EINVAL};
+use syscall::flag::{MapFlags, O_CLOEXEC, O_RDONLY, O_RDWR, O_WRONLY};
+
+#[derive(Clone, Copy, Debug)]
+pub enum MemoryType {
+    Writeback,
+    Uncacheable,
+    WriteCombining,
+}
+impl Default for MemoryType {
+    fn default() -> Self {
+        Self::Writeback
+    }
+}
+
+#[derive(Clone, Copy, Debug)]
+pub struct Prot {
+    pub read: bool,
+    pub write: bool,
+}
+impl Prot {
+    pub const RO: Self = Self { read: true, write: false };
+    pub const WO: Self = Self { read: false, write: true };
+    pub const RW: Self = Self { read: true, write: true };
+}
+
+pub unsafe fn physmap(base_phys: usize, len: usize, Prot { read, write }: Prot, ty: MemoryType) -> Result<*mut ()> {
+    // TODO: arraystring?
+    let path = format!("memory:physical@{}", match ty {
+        MemoryType::Writeback => "wb",
+        MemoryType::Uncacheable => "uc",
+        MemoryType::WriteCombining => "wc",
+    });
+    let mode = match (read, write) {
+        (true, true) => O_RDWR,
+        (true, false) => O_RDONLY,
+        (false, true) => O_WRONLY,
+        (false, false) => return Err(Error::new(EINVAL)),
+    };
+    let mut prot = MapFlags::empty();
+    prot.set(MapFlags::PROT_READ, read);
+    prot.set(MapFlags::PROT_WRITE, write);
+
+    let file = syscall::open(path, O_CLOEXEC | mode)?;
+    let base = syscall::fmap(file, &syscall::Map {
+        offset: base_phys,
+        size: len.next_multiple_of(PAGE_SIZE),
+        flags: MapFlags::MAP_SHARED | prot,
+        address: 0,
+    });
+    let _ = syscall::close(file);
+
+    Ok(base? as *mut ())
+}