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dea1bf3814
Running `make rusttest` with `ARCH=` set to an architecture other than
the host's may fail in the future, e.g. `ARCH=arm64` on an x86_64 host:
error: alignment must be a power of 2
--> rust/kernel/jump_label.rs:51:13
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51 | include!(concat!(env!("OBJTREE"), "/rust/kernel/generated_arch_static_branch_asm.rs"));
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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note: instantiated into assembly here
--> <inline asm>:3:10
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3 | .align 3
| ^
The reason is that `rusttest` builds the kernel crate as a host
library: it passes the `CONFIG_*` cfgs of the configured architecture,
but not `--target`, so code generation happens for the
host. `arch_static_branch!` then selects the arch-specific inline asm
arm based on CONFIG_*, and the host assembler rejects it.
This does not happen with the current master because
`arch_static_branch!` has no user inside the kernel crate itself yet,
but fix it now to avoid surprises later.
Signed-off-by: FUJITA Tomonori <fujita.tomonori@gmail.com>
Link: https://patch.msgid.link/20260809134858.1219036-1-tomo@flapping.org
[ Reworded slightly to clarify it "may fail in the future". - Miguel ]
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
87 lines
2.5 KiB
Rust
87 lines
2.5 KiB
Rust
// SPDX-License-Identifier: GPL-2.0
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// Copyright (C) 2024 Google LLC.
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//! Logic for static keys.
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//!
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//! C header: [`include/linux/jump_label.h`](srctree/include/linux/jump_label.h).
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/// Branch based on a static key.
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///
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/// Takes three arguments:
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///
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/// * `key` - the path to the static variable containing the `static_key`.
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/// * `keytyp` - the type of `key`.
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/// * `field` - the name of the field of `key` that contains the `static_key`.
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///
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/// # Safety
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///
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/// The macro must be used with a real static key defined by C.
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#[macro_export]
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macro_rules! static_branch_unlikely {
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($key:path, $keytyp:ty, $field:ident) => {{
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let _key: *const $keytyp = ::core::ptr::addr_of!($key);
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let _key: *const $crate::bindings::static_key_false = ::core::ptr::addr_of!((*_key).$field);
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let _key: *const $crate::bindings::static_key = _key.cast();
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#[cfg(not(CONFIG_JUMP_LABEL))]
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{
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$crate::bindings::static_key_count(_key.cast_mut()) > 0
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}
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#[cfg(CONFIG_JUMP_LABEL)]
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$crate::jump_label::arch_static_branch! { $key, $keytyp, $field, false }
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}};
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}
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pub use static_branch_unlikely;
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/// Assert that the assembly block evaluates to a string literal.
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#[cfg(CONFIG_JUMP_LABEL)]
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const _: &str = include!(concat!(
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env!("OBJTREE"),
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"/rust/kernel/generated_arch_static_branch_asm.rs"
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));
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#[macro_export]
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#[doc(hidden)]
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#[cfg(not(testlib))]
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#[cfg(CONFIG_JUMP_LABEL)]
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macro_rules! arch_static_branch {
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($key:path, $keytyp:ty, $field:ident, $branch:expr) => {'my_label: {
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$crate::asm!(
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include!(concat!(env!("OBJTREE"), "/rust/kernel/generated_arch_static_branch_asm.rs"));
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l_yes = label {
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break 'my_label true;
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},
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symb = sym $key,
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off = const ::core::mem::offset_of!($keytyp, $field),
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branch = const $crate::jump_label::bool_to_int($branch),
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);
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break 'my_label false;
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}};
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}
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#[macro_export]
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#[doc(hidden)]
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#[cfg(testlib)]
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#[cfg(CONFIG_JUMP_LABEL)]
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macro_rules! arch_static_branch {
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($key:path, $keytyp:ty, $field:ident, $branch:expr) => {
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// The asm falls through until patched, which never happens on the host.
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false
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};
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}
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#[cfg(CONFIG_JUMP_LABEL)]
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pub use arch_static_branch;
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/// A helper used by inline assembly to pass a boolean to as a `const` parameter.
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///
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/// Using this function instead of a cast lets you assert that the input is a boolean, and not some
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/// other type that can also be cast to an integer.
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#[doc(hidden)]
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pub const fn bool_to_int(b: bool) -> i32 {
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b as i32
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}
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