[v3,06/13] rust: init: make initializer values inaccessible after initializing
Commit Message
Previously the init macros would create a local variable with the name
and hygiene of the field that is being initialized to store the value of
the field. This would override any user defined variables. For example:
```
struct Foo {
a: usize,
b: usize,
}
let a = 10;
let foo = init!(Foo{
a: a + 1, // This creates a local variable named `a`.
b: a, // This refers to that variable!
});
let foo = Box::init!(foo)?;
assert_eq!(foo.a, 11);
assert_eq!(foo.b, 11);
```
This patch changes this behavior, so the above code would panic at the
last assertion, since `b` would have value 10.
Reviewed-by: Martin Rodriguez Reboredo <yakoyoku@gmail.com>
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Signed-off-by: Benno Lossin <benno.lossin@proton.me>
---
v2 -> v3:
- added Reviewed-by's from Martin and Alice.
rust/kernel/init/macros.rs | 20 +++++++++++---------
1 file changed, 11 insertions(+), 9 deletions(-)
Comments
On Sat, 29 Jul 2023 09:09:53 +0000
Benno Lossin <benno.lossin@proton.me> wrote:
> Previously the init macros would create a local variable with the name
> and hygiene of the field that is being initialized to store the value of
> the field. This would override any user defined variables. For example:
> ```
> struct Foo {
> a: usize,
> b: usize,
> }
> let a = 10;
> let foo = init!(Foo{
> a: a + 1, // This creates a local variable named `a`.
> b: a, // This refers to that variable!
> });
> let foo = Box::init!(foo)?;
> assert_eq!(foo.a, 11);
> assert_eq!(foo.b, 11);
> ```
>
> This patch changes this behavior, so the above code would panic at the
> last assertion, since `b` would have value 10.
>
> Reviewed-by: Martin Rodriguez Reboredo <yakoyoku@gmail.com>
> Reviewed-by: Alice Ryhl <aliceryhl@google.com>
> Signed-off-by: Benno Lossin <benno.lossin@proton.me>
Reviewed-by: Gary Guo <gary@garyguo.net>
> ---
> v2 -> v3:
> - added Reviewed-by's from Martin and Alice.
>
> rust/kernel/init/macros.rs | 20 +++++++++++---------
> 1 file changed, 11 insertions(+), 9 deletions(-)
>
> diff --git a/rust/kernel/init/macros.rs b/rust/kernel/init/macros.rs
> index 2bad086cda0a..cfeacc4b3f7d 100644
> --- a/rust/kernel/init/macros.rs
> +++ b/rust/kernel/init/macros.rs
> @@ -1075,13 +1075,13 @@ macro_rules! __init_internal {
> // In-place initialization syntax.
> @munch_fields($field:ident <- $val:expr, $($rest:tt)*),
> ) => {
> - let $field = $val;
> + let init = $val;
> // Call the initializer.
> //
> // SAFETY: `slot` is valid, because we are inside of an initializer closure, we
> // return when an error/panic occurs.
> // We also use the `data` to require the correct trait (`Init` or `PinInit`) for `$field`.
> - unsafe { $data.$field(::core::ptr::addr_of_mut!((*$slot).$field), $field)? };
> + unsafe { $data.$field(::core::ptr::addr_of_mut!((*$slot).$field), init)? };
> // Create the drop guard:
> //
> // We rely on macro hygiene to make it impossible for users to access this local variable.
> @@ -1107,12 +1107,12 @@ macro_rules! __init_internal {
> // In-place initialization syntax.
> @munch_fields($field:ident <- $val:expr, $($rest:tt)*),
> ) => {
> - let $field = $val;
> + let init = $val;
> // Call the initializer.
> //
> // SAFETY: `slot` is valid, because we are inside of an initializer closure, we
> // return when an error/panic occurs.
> - unsafe { $crate::init::Init::__init($field, ::core::ptr::addr_of_mut!((*$slot).$field))? };
> + unsafe { $crate::init::Init::__init(init, ::core::ptr::addr_of_mut!((*$slot).$field))? };
> // Create the drop guard:
> //
> // We rely on macro hygiene to make it impossible for users to access this local variable.
> @@ -1138,11 +1138,13 @@ macro_rules! __init_internal {
> // Init by-value.
> @munch_fields($field:ident $(: $val:expr)?, $($rest:tt)*),
> ) => {
> - $(let $field = $val;)?
> - // Initialize the field.
> - //
> - // SAFETY: The memory at `slot` is uninitialized.
> - unsafe { ::core::ptr::write(::core::ptr::addr_of_mut!((*$slot).$field), $field) };
> + {
> + $(let $field = $val;)?
> + // Initialize the field.
> + //
> + // SAFETY: The memory at `slot` is uninitialized.
> + unsafe { ::core::ptr::write(::core::ptr::addr_of_mut!((*$slot).$field), $field) };
> + }
> // Create the drop guard:
> //
> // We rely on macro hygiene to make it impossible for users to access this local variable.
@@ -1075,13 +1075,13 @@ macro_rules! __init_internal {
// In-place initialization syntax.
@munch_fields($field:ident <- $val:expr, $($rest:tt)*),
) => {
- let $field = $val;
+ let init = $val;
// Call the initializer.
//
// SAFETY: `slot` is valid, because we are inside of an initializer closure, we
// return when an error/panic occurs.
// We also use the `data` to require the correct trait (`Init` or `PinInit`) for `$field`.
- unsafe { $data.$field(::core::ptr::addr_of_mut!((*$slot).$field), $field)? };
+ unsafe { $data.$field(::core::ptr::addr_of_mut!((*$slot).$field), init)? };
// Create the drop guard:
//
// We rely on macro hygiene to make it impossible for users to access this local variable.
@@ -1107,12 +1107,12 @@ macro_rules! __init_internal {
// In-place initialization syntax.
@munch_fields($field:ident <- $val:expr, $($rest:tt)*),
) => {
- let $field = $val;
+ let init = $val;
// Call the initializer.
//
// SAFETY: `slot` is valid, because we are inside of an initializer closure, we
// return when an error/panic occurs.
- unsafe { $crate::init::Init::__init($field, ::core::ptr::addr_of_mut!((*$slot).$field))? };
+ unsafe { $crate::init::Init::__init(init, ::core::ptr::addr_of_mut!((*$slot).$field))? };
// Create the drop guard:
//
// We rely on macro hygiene to make it impossible for users to access this local variable.
@@ -1138,11 +1138,13 @@ macro_rules! __init_internal {
// Init by-value.
@munch_fields($field:ident $(: $val:expr)?, $($rest:tt)*),
) => {
- $(let $field = $val;)?
- // Initialize the field.
- //
- // SAFETY: The memory at `slot` is uninitialized.
- unsafe { ::core::ptr::write(::core::ptr::addr_of_mut!((*$slot).$field), $field) };
+ {
+ $(let $field = $val;)?
+ // Initialize the field.
+ //
+ // SAFETY: The memory at `slot` is uninitialized.
+ unsafe { ::core::ptr::write(::core::ptr::addr_of_mut!((*$slot).$field), $field) };
+ }
// Create the drop guard:
//
// We rely on macro hygiene to make it impossible for users to access this local variable.