I/O memory is typically either mapped through direct calls to ioremap()
or subsystem / bus specific ones such as pci_iomap().
Even though subsystem / bus specific functions to map I/O memory are
based on ioremap() / iounmap() it is not desirable to re-implement them
in Rust.
Instead, implement a base type for I/O mapped memory, which generically
provides the corresponding accessors, such as `Io::readb` or
`Io:try_readb`.
`Io` supports an optional const generic, such that a driver can indicate
the minimal expected and required size of the mapping at compile time.
Correspondingly, calls to the 'non-try' accessors, support compile time
checks of the I/O memory offset to read / write, while the 'try'
accessors, provide boundary checks on runtime.
`Io` is meant to be embedded into a structure (e.g. pci::Bar or
io::IoMem) which creates the actual I/O memory mapping and initializes
`Io` accordingly.
To ensure that I/O mapped memory can't out-live the device it may be
bound to, subsystems should embedd the corresponding I/O memory type
(e.g. pci::Bar) into a `Devres` container, such that it gets revoked
once the device is unbound.
Co-developed-by: Philipp Stanner <pstanner@xxxxxxxxxx>
Signed-off-by: Philipp Stanner <pstanner@xxxxxxxxxx>
Signed-off-by: Danilo Krummrich <dakr@xxxxxxxxxx>
---
rust/helpers.c | 106 ++++++++++++++++++++++
rust/kernel/io.rs | 219 +++++++++++++++++++++++++++++++++++++++++++++
rust/kernel/lib.rs | 1 +
3 files changed, 326 insertions(+)
create mode 100644 rust/kernel/io.rs
diff --git a/rust/helpers.c b/rust/helpers.c
index 0ce40ccb978b..824b7c0b98dc 100644
--- a/rust/helpers.c
+++ b/rust/helpers.c
@@ -26,6 +26,7 @@
#include <linux/device.h>
#include <linux/err.h>
#include <linux/errname.h>
+#include <linux/io.h>
#include <linux/mutex.h>
#include <linux/rcupdate.h>
#include <linux/refcount.h>
@@ -181,6 +182,111 @@ void rust_helper_rcu_read_unlock(void)
EXPORT_SYMBOL_GPL(rust_helper_rcu_read_unlock);
/* end rcu */
+/* io.h */
+u8 rust_helper_readb(const volatile void __iomem *addr)
+{
+ return readb(addr);
+}
+EXPORT_SYMBOL_GPL(rust_helper_readb);
+
+u16 rust_helper_readw(const volatile void __iomem *addr)
+{
+ return readw(addr);
+}
+EXPORT_SYMBOL_GPL(rust_helper_readw);
+
+u32 rust_helper_readl(const volatile void __iomem *addr)
+{
+ return readl(addr);
+}
+EXPORT_SYMBOL_GPL(rust_helper_readl);
+
+#ifdef CONFIG_64BIT
+u64 rust_helper_readq(const volatile void __iomem *addr)
+{
+ return readq(addr);
+}
+EXPORT_SYMBOL_GPL(rust_helper_readq);
+#endif
+
+void rust_helper_writeb(u8 value, volatile void __iomem *addr)
+{
+ writeb(value, addr);
+}
+EXPORT_SYMBOL_GPL(rust_helper_writeb);
+
+void rust_helper_writew(u16 value, volatile void __iomem *addr)
+{
+ writew(value, addr);
+}
+EXPORT_SYMBOL_GPL(rust_helper_writew);
+
+void rust_helper_writel(u32 value, volatile void __iomem *addr)
+{
+ writel(value, addr);
+}
+EXPORT_SYMBOL_GPL(rust_helper_writel);
+
+#ifdef CONFIG_64BIT
+void rust_helper_writeq(u64 value, volatile void __iomem *addr)
+{
+ writeq(value, addr);
+}
+EXPORT_SYMBOL_GPL(rust_helper_writeq);
+#endif
+
+u8 rust_helper_readb_relaxed(const volatile void __iomem *addr)
+{
+ return readb_relaxed(addr);
+}
+EXPORT_SYMBOL_GPL(rust_helper_readb_relaxed);
+
+u16 rust_helper_readw_relaxed(const volatile void __iomem *addr)
+{
+ return readw_relaxed(addr);
+}
+EXPORT_SYMBOL_GPL(rust_helper_readw_relaxed);
+
+u32 rust_helper_readl_relaxed(const volatile void __iomem *addr)
+{
+ return readl_relaxed(addr);
+}
+EXPORT_SYMBOL_GPL(rust_helper_readl_relaxed);
+
+#ifdef CONFIG_64BIT
+u64 rust_helper_readq_relaxed(const volatile void __iomem *addr)
+{
+ return readq_relaxed(addr);
+}
+EXPORT_SYMBOL_GPL(rust_helper_readq_relaxed);
+#endif
+
+void rust_helper_writeb_relaxed(u8 value, volatile void __iomem *addr)
+{
+ writeb_relaxed(value, addr);
+}
+EXPORT_SYMBOL_GPL(rust_helper_writeb_relaxed);
+
+void rust_helper_writew_relaxed(u16 value, volatile void __iomem *addr)
+{
+ writew_relaxed(value, addr);
+}
+EXPORT_SYMBOL_GPL(rust_helper_writew_relaxed);
+
+void rust_helper_writel_relaxed(u32 value, volatile void __iomem *addr)
+{
+ writel_relaxed(value, addr);
+}
+EXPORT_SYMBOL_GPL(rust_helper_writel_relaxed);
+
+#ifdef CONFIG_64BIT
+void rust_helper_writeq_relaxed(u64 value, volatile void __iomem *addr)
+{
+ writeq_relaxed(value, addr);
+}
+EXPORT_SYMBOL_GPL(rust_helper_writeq_relaxed);
+#endif
+
/*
* `bindgen` binds the C `size_t` type as the Rust `usize` type, so we can
* use it in contexts where Rust expects a `usize` like slice (array) indices.
diff --git a/rust/kernel/io.rs b/rust/kernel/io.rs
new file mode 100644
index 000000000000..a19a1226181d
--- /dev/null
+++ b/rust/kernel/io.rs
@@ -0,0 +1,219 @@
+// SPDX-License-Identifier: GPL-2.0
+
+//! Memory-mapped IO.
+//!
+//! C header: [`include/asm-generic/io.h`](srctree/include/asm-generic/io.h)
+
+use crate::error::{code::EINVAL, Result};
+use crate::{bindings, build_assert};
+
+/// IO-mapped memory, starting at the base address @addr and spanning @maxlen bytes.
+///
+/// The creator (usually a subsystem such as PCI) is responsible for creating the
+/// mapping, performing an additional region request etc.
+///
+/// # Invariant
+///
+/// `addr` is the start and `maxsize` the length of valid I/O remapped memory region.
+///
+/// # Examples
+///
+/// ```
+/// # use kernel::{bindings, io::Io};
+/// # use core::ops::Deref;
+///
+/// // See also [`pci::Bar`] for a real example.
+/// struct IoMem<const SIZE: usize>(Io<SIZE>);
+///
+/// impl<const SIZE: usize> IoMem<SIZE> {
+/// fn new(paddr: usize) -> Result<Self>{
+///
+/// // SAFETY: assert safety for this example
+/// let addr = unsafe { bindings::ioremap(paddr as _, SIZE.try_into().unwrap()) };
+/// if addr.is_null() {
+/// return Err(ENOMEM);
+/// }
+///
+/// // SAFETY: `addr` is guaranteed to be the start of a valid I/O mapped memory region of
+/// // size `SIZE`.
+/// let io = unsafe { Io::new(addr as _, SIZE)? };
+///
+/// Ok(IoMem(io))
+/// }
+/// }
+///
+/// impl<const SIZE: usize> Drop for IoMem<SIZE> {
+/// fn drop(&mut self) {
+/// // SAFETY: Safe as by the invariant of `Io`.
+/// unsafe { bindings::iounmap(self.0.base_addr() as _); };
+/// }
+/// }
+///
+/// impl<const SIZE: usize> Deref for IoMem<SIZE> {
+/// type Target = Io<SIZE>;
+///
+/// fn deref(&self) -> &Self::Target {
+/// &self.0
+/// }
+/// }
+///
+/// let iomem = IoMem::<{ core::mem::size_of::<u32>() }>::new(0xBAAAAAAD).unwrap();
+/// iomem.writel(0x42, 0x0);
+/// assert!(iomem.try_writel(0x42, 0x0).is_ok());
+/// assert!(iomem.try_writel(0x42, 0x4).is_err());
+/// ```
+pub struct Io<const SIZE: usize = 0> {
+ addr: usize,
+ maxsize: usize,
+}
+
+macro_rules! define_read {
+ ($(#[$attr:meta])* $name:ident, $try_name:ident, $type_name:ty) => {
+ /// Read IO data from a given offset known at compile time.
+ ///
+ /// Bound checks are performed on compile time, hence if the offset is not known at compile
+ /// time, the build will fail.
+ $(#[$attr])*
+ #[inline]
+ pub fn $name(&self, offset: usize) -> $type_name {
+ let addr = self.io_addr_assert::<$type_name>(offset);
+
+ unsafe { bindings::$name(addr as _) }
+ }
+
+ /// Read IO data from a given offset.
+ ///
+ /// Bound checks are performed on runtime, it fails if the offset (plus the type size) is
+ /// out of bounds.
+ $(#[$attr])*
+ pub fn $try_name(&self, offset: usize) -> Result<$type_name> {
+ let addr = self.io_addr::<$type_name>(offset)?;
+
+ Ok(unsafe { bindings::$name(addr as _) })
+ }
+ };
+}
+
+macro_rules! define_write {
+ ($(#[$attr:meta])* $name:ident, $try_name:ident, $type_name:ty) => {
+ /// Write IO data from a given offset known at compile time.
+ ///
+ /// Bound checks are performed on compile time, hence if the offset is not known at compile
+ /// time, the build will fail.
+ $(#[$attr])*
+ #[inline]
+ pub fn $name(&self, value: $type_name, offset: usize) {
+ let addr = self.io_addr_assert::<$type_name>(offset);
+
+ unsafe { bindings::$name(value, addr as _, ) }
+ }
+
+ /// Write IO data from a given offset.
+ ///
+ /// Bound checks are performed on runtime, it fails if the offset (plus the type size) is
+ /// out of bounds.
+ $(#[$attr])*
+ pub fn $try_name(&self, value: $type_name, offset: usize) -> Result {
+ let addr = self.io_addr::<$type_name>(offset)?;
+
+ unsafe { bindings::$name(value, addr as _) }
+ Ok(())
+ }
+ };
+}
+
+impl<const SIZE: usize> Io<SIZE> {
+ ///
+ ///
+ /// # Safety
+ ///
+ /// Callers must ensure that `addr` is the start of a valid I/O mapped memory region of size
+ /// `maxsize`.
+ pub unsafe fn new(addr: usize, maxsize: usize) -> Result<Self> {
+ if maxsize < SIZE {
+ return Err(EINVAL);
+ }
+
+ Ok(Self { addr, maxsize })
+ }
+
+ /// Returns the base address of this mapping.
+ #[inline]
+ pub fn base_addr(&self) -> usize {
+ self.addr
+ }
+
+ /// Returns the size of this mapping.
+ #[inline]
+ pub fn maxsize(&self) -> usize {
+ self.maxsize
+ }
+
+ #[inline]
+ const fn offset_valid<U>(offset: usize, size: usize) -> bool {
+ let type_size = core::mem::size_of::<U>();
+ if let Some(end) = offset.checked_add(type_size) {
+ end <= size && offset % type_size == 0
+ } else {
+ false
+ }
+ }
+
+ #[inline]
+ fn io_addr<U>(&self, offset: usize) -> Result<usize> {
+ if !Self::offset_valid::<U>(offset, self.maxsize()) {
+ return Err(EINVAL);
+ }
+
+ // Probably no need to check, since the safety requirements of `Self::new` guarantee that
+ // this can't overflow.
+ self.base_addr().checked_add(offset).ok_or(EINVAL)
+ }
+
+ #[inline]
+ fn io_addr_assert<U>(&self, offset: usize) -> usize {
+ build_assert!(Self::offset_valid::<U>(offset, SIZE));
+
+ self.base_addr() + offset
+ }
+
+ define_read!(readb, try_readb, u8);
+ define_read!(readw, try_readw, u16);
+ define_read!(readl, try_readl, u32);
+ define_read!(
+ #[cfg(CONFIG_64BIT)]
+ readq,
+ try_readq,
+ u64
+ );
+
+ define_read!(readb_relaxed, try_readb_relaxed, u8);
+ define_read!(readw_relaxed, try_readw_relaxed, u16);
+ define_read!(readl_relaxed, try_readl_relaxed, u32);
+ define_read!(
+ #[cfg(CONFIG_64BIT)]
+ readq_relaxed,
+ try_readq_relaxed,
+ u64
+ );
+
+ define_write!(writeb, try_writeb, u8);
+ define_write!(writew, try_writew, u16);
+ define_write!(writel, try_writel, u32);
+ define_write!(
+ #[cfg(CONFIG_64BIT)]
+ writeq,
+ try_writeq,
+ u64
+ );
+
+ define_write!(writeb_relaxed, try_writeb_relaxed, u8);
+ define_write!(writew_relaxed, try_writew_relaxed, u16);
+ define_write!(writel_relaxed, try_writel_relaxed, u32);
+ define_write!(
+ #[cfg(CONFIG_64BIT)]
+ writeq_relaxed,
+ try_writeq_relaxed,
+ u64
+ );
+}
diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs
index 601c3d3c9d54..f4dd11014a65 100644
--- a/rust/kernel/lib.rs
+++ b/rust/kernel/lib.rs
@@ -56,6 +56,7 @@
#[doc(hidden)]
pub use bindings;
+pub mod io;
pub use macros;
pub use uapi;
--
2.45.1
