[PATCH v12 0/5] Tracepoints and static branch in Rust

[PATCH v12 0/5] Tracepoints and static branch in Rust

[Alice Ryhl]

An important part of a production ready Linux kernel driver is
tracepoints. So to write production ready Linux kernel drivers in Rust,
we must be able to call tracepoints from Rust code. This patch series
adds support for calling tracepoints declared in C from Rust.

This series includes a patch that adds a user of tracepoints to the
rust_print sample. Please see that sample for details on what is needed
to use this feature in Rust code.

This is intended for use in the Rust Binder driver, which was originally
sent as an RFC [1]. The RFC did not include tracepoint support, but you
can see how it will be used in Rust Binder at [2]. The author has
verified that the tracepoint support works on Android devices.

This implementation implements support for static keys in Rust so that
the actual static branch happens in the Rust object file. However, the
__DO_TRACE body remains in C code. See v1 for an implementation where
__DO_TRACE is also implemented in Rust.

Based on top of commit eb887c4567d1 ("tracing: Use atomic64_inc_return()
in trace_clock_counter()") from trace/for-next, which is in turn based
on top of v6.12-rc2.

The sample added in this series is affected by [3], so be aware that
some bindgen/libclang combinations may fail to build the sample. This
isn't something that this patch series needs to fix, though.

Link: https://lore.kernel.org/rust-for-linux/20231101-rust-binder-v1-0-08ba9197f637@google.com/ [1]
Link: https://r.android.com/3119993 [2]
Link: https://lore.kernel.org/all/20241030-bindgen-libclang-warn-v1-1-3a7ba9fedcfe@google.com/ [3]
Signed-off-by: Alice Ryhl <aliceryhl@google.com>
---
Changes in v12:
- Replace `ifneq ($(CONFIG_JUMP_LABEL),)` with `ifdef CONFIG_JUMP_LABEL`.
- Expand x86 asm to 32-bit for future-compat.
- Add note to coverletter about libclang issue.
- Link to v11: https://lore.kernel.org/r/20241015-tracepoint-v11-0-cceb65820089@google.com

Changes in v11:
- Fix build failure with CONFIG_JUMP_LABEL disabled.
- Remove CONFIG_HAVE_JUMP_LABEL_HACK duplication.
- Remove explicit export of rust_helper_static_key_count.
- Add Gary's Reviewed-by to first patch.
- Link to v10: https://lore.kernel.org/r/20241011-tracepoint-v10-0-7fbde4d6b525@google.com

Changes in v10:
- Rebase on trace/for-next.
- Use static_branch_unlikely as of [PATCH] tracepoints: Use new static branch API.
- Update second patch as of [PATCH] tracing: Declare system call tracepoints with TRACE_EVENT_SYSCALL.
- Link to v9: https://lore.kernel.org/r/20241001-tracepoint-v9-0-1ad3b7d78acb@google.com

Changes in v9:
- Rebase on v6.12-rc1.
- Add some Reviewed-by tags from Boqun.
- Link to v8: https://lore.kernel.org/r/20240822-tracepoint-v8-0-f0c5899e6fd3@google.com

Changes in v8:
- Use OBJTREE instead of SRCTREE for temporary asm file.
- Adjust comments on `asm!` wrapper to be less confusing.
- Include resolution of conflict with helpers splitting.
- Link to v7: https://lore.kernel.org/r/20240816-tracepoint-v7-0-d609b916b819@google.com

Changes in v7:
- Fix spurious file included in first patch.
- Fix issue with riscv asm.
- Fix tags on fourth patch to match fifth patch.
- Add Reviewed-by/Acked-by tags where appropriate.
- Link to v6: https://lore.kernel.org/r/20240808-tracepoint-v6-0-a23f800f1189@google.com

Changes in v6:
- Add support for !CONFIG_JUMP_LABEL.
- Add tracepoint to rust_print sample.
- Deduplicate inline asm.
- Require unsafe inside `declare_trace!`.
- Fix bug on x86 due to use of intel syntax.
- Link to v5: https://lore.kernel.org/r/20240802-tracepoint-v5-0-faa164494dcb@google.com

Changes in v5:
- Update first patch regarding inline asm duplication.
- Add __rust_do_trace helper to support conditions.
- Rename DEFINE_RUST_DO_TRACE_REAL to __DEFINE_RUST_DO_TRACE.
- Get rid of glob-import in tracepoint macro.
- Address safety requirements on tracepoints in docs.
- Link to v4: https://lore.kernel.org/rust-for-linux/20240628-tracepoint-v4-0-353d523a9c15@google.com

Changes in v4:
- Move arch-specific code into rust/kernel/arch.
- Restore DEFINE_RUST_DO_TRACE at end of define_trace.h
- Link to v3: https://lore.kernel.org/r/20240621-tracepoint-v3-0-9e44eeea2b85@google.com

Changes in v3:
- Support for Rust static_key on loongarch64 and riscv64.
- Avoid failing compilation on architectures that are missing Rust
  static_key support when the archtectures does not actually use it.
- Link to v2: https://lore.kernel.org/r/20240610-tracepoint-v2-0-faebad81b355@google.com

Changes in v2:
- Call into C code for __DO_TRACE.
- Drop static_call patch, as it is no longer needed.
- Link to v1: https://lore.kernel.org/r/20240606-tracepoint-v1-0-6551627bf51b@google.com

---
Alice Ryhl (5):
      rust: add static_branch_unlikely for static_key_false
      rust: add tracepoint support
      rust: samples: add tracepoint to Rust sample
      jump_label: adjust inline asm to be consistent
      rust: add arch_static_branch

 MAINTAINERS                             |  1 +
 arch/arm/include/asm/jump_label.h       | 14 ++++---
 arch/arm64/include/asm/jump_label.h     | 20 +++++----
 arch/loongarch/include/asm/jump_label.h | 16 ++++---
 arch/riscv/include/asm/jump_label.h     | 50 ++++++++++++----------
 arch/x86/include/asm/jump_label.h       | 35 ++++++----------
 include/linux/tracepoint.h              | 28 ++++++++++++-
 include/trace/define_trace.h            | 12 ++++++
 include/trace/events/rust_sample.h      | 31 ++++++++++++++
 rust/Makefile                           |  6 +++
 rust/bindings/bindings_helper.h         |  3 ++
 rust/helpers/helpers.c                  |  1 +
 rust/helpers/jump_label.c               | 14 +++++++
 rust/kernel/.gitignore                  |  3 ++
 rust/kernel/arch_static_branch_asm.rs.S |  7 ++++
 rust/kernel/jump_label.rs               | 74 +++++++++++++++++++++++++++++++++
 rust/kernel/lib.rs                      | 37 +++++++++++++++++
 rust/kernel/tracepoint.rs               | 49 ++++++++++++++++++++++
 samples/rust/Makefile                   |  3 +-
 samples/rust/rust_print.rs              | 18 ++++++++
 samples/rust/rust_print_events.c        |  8 ++++
 scripts/Makefile.build                  |  9 +++-
 22 files changed, 374 insertions(+), 65 deletions(-)
---
base-commit: eb887c4567d1b0e7684c026fe7df44afa96589e6
change-id: 20240606-tracepoint-31e15b90e471

Best regards,
-- 
Alice Ryhl <aliceryhl@google.com>

[PATCH v12 1/5] rust: add static_branch_unlikely for static_key_false

[Alice Ryhl]

Add just enough support for static key so that we can use it from
tracepoints. Tracepoints rely on `static_branch_unlikely` with a `struct
static_key_false`, so we add the same functionality to Rust.

This patch only provides a generic implementation without code patching
(matching the one used when CONFIG_JUMP_LABEL is disabled). Later
patches add support for inline asm implementations that use runtime
patching.

When CONFIG_JUMP_LABEL is unset, `static_key_count` is a static inline
function, so a Rust helper is defined for `static_key_count` in this
case. If Rust is compiled with LTO, this call should get inlined. The
helper can be eliminated once we have the necessary inline asm to make
atomic operations from Rust.

Reviewed-by: Boqun Feng <boqun.feng@gmail.com>
Reviewed-by: Gary Guo <gary@garyguo.net>
Signed-off-by: Alice Ryhl <aliceryhl@google.com>
---
 rust/bindings/bindings_helper.h |  1 +
 rust/helpers/helpers.c          |  1 +
 rust/helpers/jump_label.c       | 14 ++++++++++++++
 rust/kernel/jump_label.rs       | 30 ++++++++++++++++++++++++++++++
 rust/kernel/lib.rs              |  1 +
 5 files changed, 47 insertions(+)

diff --git a/rust/bindings/bindings_helper.h b/rust/bindings/bindings_helper.h
index ae82e9c941af..e0846e7e93e6 100644
--- a/rust/bindings/bindings_helper.h
+++ b/rust/bindings/bindings_helper.h
@@ -14,6 +14,7 @@
 #include <linux/ethtool.h>
 #include <linux/firmware.h>
 #include <linux/jiffies.h>
+#include <linux/jump_label.h>
 #include <linux/mdio.h>
 #include <linux/phy.h>
 #include <linux/refcount.h>
diff --git a/rust/helpers/helpers.c b/rust/helpers/helpers.c
index 30f40149f3a9..17e1b60d178f 100644
--- a/rust/helpers/helpers.c
+++ b/rust/helpers/helpers.c
@@ -12,6 +12,7 @@
 #include "build_assert.c"
 #include "build_bug.c"
 #include "err.c"
+#include "jump_label.c"
 #include "kunit.c"
 #include "mutex.c"
 #include "page.c"
diff --git a/rust/helpers/jump_label.c b/rust/helpers/jump_label.c
new file mode 100644
index 000000000000..fc1f1e0df08e
--- /dev/null
+++ b/rust/helpers/jump_label.c
@@ -0,0 +1,14 @@
+// SPDX-License-Identifier: GPL-2.0
+
+/*
+ * Copyright (C) 2024 Google LLC.
+ */
+
+#include <linux/jump_label.h>
+
+#ifndef CONFIG_JUMP_LABEL
+int rust_helper_static_key_count(struct static_key *key)
+{
+	return static_key_count(key);
+}
+#endif
diff --git a/rust/kernel/jump_label.rs b/rust/kernel/jump_label.rs
new file mode 100644
index 000000000000..4b7655b2a022
--- /dev/null
+++ b/rust/kernel/jump_label.rs
@@ -0,0 +1,30 @@
+// SPDX-License-Identifier: GPL-2.0
+
+// Copyright (C) 2024 Google LLC.
+
+//! Logic for static keys.
+//!
+//! C header: [`include/linux/jump_label.h`](srctree/include/linux/jump_label.h).
+
+/// Branch based on a static key.
+///
+/// Takes three arguments:
+///
+/// * `key` - the path to the static variable containing the `static_key`.
+/// * `keytyp` - the type of `key`.
+/// * `field` - the name of the field of `key` that contains the `static_key`.
+///
+/// # Safety
+///
+/// The macro must be used with a real static key defined by C.
+#[macro_export]
+macro_rules! static_branch_unlikely {
+    ($key:path, $keytyp:ty, $field:ident) => {{
+        let _key: *const $keytyp = ::core::ptr::addr_of!($key);
+        let _key: *const $crate::bindings::static_key_false = ::core::ptr::addr_of!((*_key).$field);
+        let _key: *const $crate::bindings::static_key = _key.cast();
+
+        $crate::bindings::static_key_count(_key.cast_mut()) > 0
+    }};
+}
+pub use static_branch_unlikely;
diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs
index b5f4b3ce6b48..708ff817ccc3 100644
--- a/rust/kernel/lib.rs
+++ b/rust/kernel/lib.rs
@@ -36,6 +36,7 @@
 pub mod firmware;
 pub mod init;
 pub mod ioctl;
+pub mod jump_label;
 #[cfg(CONFIG_KUNIT)]
 pub mod kunit;
 pub mod list;

-- 
2.47.0.163.g1226f6d8fa-goog

[PATCH v12 2/5] rust: add tracepoint support

[Alice Ryhl]

Make it possible to have Rust code call into tracepoints defined by C
code. It is still required that the tracepoint is declared in a C
header, and that this header is included in the input to bindgen.

Instead of calling __DO_TRACE directly, the exported rust_do_trace_
function calls an inline helper function. This is because the `cond`
argument does not exist at the callsite of DEFINE_RUST_DO_TRACE.

__DECLARE_TRACE always emits an inline static and an extern declaration
that is only used when CREATE_RUST_TRACE_POINTS is set. These should not
end up in the final binary so it is not a problem that they sometimes
are emitted without a user.

Reviewed-by: Carlos Llamas <cmllamas@google.com>
Reviewed-by: Gary Guo <gary@garyguo.net>
Reviewed-by: Boqun Feng <boqun.feng@gmail.com>
Signed-off-by: Alice Ryhl <aliceryhl@google.com>
---
 include/linux/tracepoint.h      | 28 ++++++++++++++++++++++-
 include/trace/define_trace.h    | 12 ++++++++++
 rust/bindings/bindings_helper.h |  1 +
 rust/kernel/lib.rs              |  1 +
 rust/kernel/tracepoint.rs       | 49 +++++++++++++++++++++++++++++++++++++++++
 5 files changed, 90 insertions(+), 1 deletion(-)

diff --git a/include/linux/tracepoint.h b/include/linux/tracepoint.h
index 0dc67fad706c..84c4924e499f 100644
--- a/include/linux/tracepoint.h
+++ b/include/linux/tracepoint.h
@@ -225,6 +225,18 @@ static inline struct tracepoint *tracepoint_ptr_deref(tracepoint_ptr_t *p)
 			preempt_enable_notrace();			\
 	} while (0)
 
+/*
+ * Declare an exported function that Rust code can call to trigger this
+ * tracepoint. This function does not include the static branch; that is done
+ * in Rust to avoid a function call when the tracepoint is disabled.
+ */
+#define DEFINE_RUST_DO_TRACE(name, proto, args)
+#define __DEFINE_RUST_DO_TRACE(name, proto, args)			\
+	notrace void rust_do_trace_##name(proto)			\
+	{								\
+		__rust_do_trace_##name(args);				\
+	}
+
 /*
  * Make sure the alignment of the structure in the __tracepoints section will
  * not add unwanted padding between the beginning of the section and the
@@ -240,6 +252,7 @@ static inline struct tracepoint *tracepoint_ptr_deref(tracepoint_ptr_t *p)
 	extern int __traceiter_##name(data_proto);			\
 	DECLARE_STATIC_CALL(tp_func_##name, __traceiter_##name);	\
 	extern struct tracepoint __tracepoint_##name;			\
+	extern void rust_do_trace_##name(proto);			\
 	static inline int						\
 	register_trace_##name(void (*probe)(data_proto), void *data)	\
 	{								\
@@ -271,6 +284,12 @@ static inline struct tracepoint *tracepoint_ptr_deref(tracepoint_ptr_t *p)
 
 #define __DECLARE_TRACE(name, proto, args, cond, data_proto)		\
 	__DECLARE_TRACE_COMMON(name, PARAMS(proto), PARAMS(args), cond, PARAMS(data_proto)) \
+	static inline void __rust_do_trace_##name(proto)		\
+	{								\
+		__DO_TRACE(name,					\
+			TP_ARGS(args),					\
+			TP_CONDITION(cond), 0);				\
+	}								\
 	static inline void trace_##name(proto)				\
 	{								\
 		if (static_branch_unlikely(&__tracepoint_##name.key))	\
@@ -285,6 +304,12 @@ static inline struct tracepoint *tracepoint_ptr_deref(tracepoint_ptr_t *p)
 
 #define __DECLARE_TRACE_SYSCALL(name, proto, args, cond, data_proto)	\
 	__DECLARE_TRACE_COMMON(name, PARAMS(proto), PARAMS(args), cond, PARAMS(data_proto)) \
+	static inline void __rust_do_trace_##name(proto)		\
+	{								\
+		__DO_TRACE(name,					\
+			TP_ARGS(args),					\
+			TP_CONDITION(cond), 1);				\
+	}								\
 	static inline void trace_##name(proto)				\
 	{								\
 		if (static_branch_unlikely(&__tracepoint_##name.key))	\
@@ -339,7 +364,8 @@ static inline struct tracepoint *tracepoint_ptr_deref(tracepoint_ptr_t *p)
 	void __probestub_##_name(void *__data, proto)			\
 	{								\
 	}								\
-	DEFINE_STATIC_CALL(tp_func_##_name, __traceiter_##_name);
+	DEFINE_STATIC_CALL(tp_func_##_name, __traceiter_##_name);	\
+	DEFINE_RUST_DO_TRACE(_name, TP_PROTO(proto), TP_ARGS(args))
 
 #define DEFINE_TRACE(name, proto, args)		\
 	DEFINE_TRACE_FN(name, NULL, NULL, PARAMS(proto), PARAMS(args));
diff --git a/include/trace/define_trace.h b/include/trace/define_trace.h
index ff5fa17a6259..0557626b6f6a 100644
--- a/include/trace/define_trace.h
+++ b/include/trace/define_trace.h
@@ -76,6 +76,13 @@
 #define DECLARE_TRACE(name, proto, args)	\
 	DEFINE_TRACE(name, PARAMS(proto), PARAMS(args))
 
+/* If requested, create helpers for calling these tracepoints from Rust. */
+#ifdef CREATE_RUST_TRACE_POINTS
+#undef DEFINE_RUST_DO_TRACE
+#define DEFINE_RUST_DO_TRACE(name, proto, args)	\
+	__DEFINE_RUST_DO_TRACE(name, PARAMS(proto), PARAMS(args))
+#endif
+
 #undef TRACE_INCLUDE
 #undef __TRACE_INCLUDE
 
@@ -134,6 +141,11 @@
 # undef UNDEF_TRACE_INCLUDE_PATH
 #endif
 
+#ifdef CREATE_RUST_TRACE_POINTS
+# undef DEFINE_RUST_DO_TRACE
+# define DEFINE_RUST_DO_TRACE(name, proto, args)
+#endif
+
 /* We may be processing more files */
 #define CREATE_TRACE_POINTS
 
diff --git a/rust/bindings/bindings_helper.h b/rust/bindings/bindings_helper.h
index e0846e7e93e6..752572e638a6 100644
--- a/rust/bindings/bindings_helper.h
+++ b/rust/bindings/bindings_helper.h
@@ -20,6 +20,7 @@
 #include <linux/refcount.h>
 #include <linux/sched.h>
 #include <linux/slab.h>
+#include <linux/tracepoint.h>
 #include <linux/wait.h>
 #include <linux/workqueue.h>
 
diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs
index 708ff817ccc3..55f81f49024e 100644
--- a/rust/kernel/lib.rs
+++ b/rust/kernel/lib.rs
@@ -54,6 +54,7 @@
 pub mod sync;
 pub mod task;
 pub mod time;
+pub mod tracepoint;
 pub mod types;
 pub mod uaccess;
 pub mod workqueue;
diff --git a/rust/kernel/tracepoint.rs b/rust/kernel/tracepoint.rs
new file mode 100644
index 000000000000..c6e80aa99e8e
--- /dev/null
+++ b/rust/kernel/tracepoint.rs
@@ -0,0 +1,49 @@
+// SPDX-License-Identifier: GPL-2.0
+
+// Copyright (C) 2024 Google LLC.
+
+//! Logic for tracepoints.
+
+/// Declare the Rust entry point for a tracepoint.
+///
+/// This macro generates an unsafe function that calls into C, and its safety requirements will be
+/// whatever the relevant C code requires. To document these safety requirements, you may add
+/// doc-comments when invoking the macro.
+#[macro_export]
+macro_rules! declare_trace {
+    ($($(#[$attr:meta])* $pub:vis unsafe fn $name:ident($($argname:ident : $argtyp:ty),* $(,)?);)*) => {$(
+        $( #[$attr] )*
+        #[inline(always)]
+        $pub unsafe fn $name($($argname : $argtyp),*) {
+            #[cfg(CONFIG_TRACEPOINTS)]
+            {
+                // SAFETY: It's always okay to query the static key for a tracepoint.
+                let should_trace = unsafe {
+                    $crate::macros::paste! {
+                        $crate::jump_label::static_branch_unlikely!(
+                            $crate::bindings::[< __tracepoint_ $name >],
+                            $crate::bindings::tracepoint,
+                            key
+                        )
+                    }
+                };
+
+                if should_trace {
+                    $crate::macros::paste! {
+                        // SAFETY: The caller guarantees that it is okay to call this tracepoint.
+                        unsafe { $crate::bindings::[< rust_do_trace_ $name >]($($argname),*) };
+                    }
+                }
+            }
+
+            #[cfg(not(CONFIG_TRACEPOINTS))]
+            {
+                // If tracepoints are disabled, insert a trivial use of each argument
+                // to avoid unused argument warnings.
+                $( let _unused = $argname; )*
+            }
+        }
+    )*}
+}
+
+pub use declare_trace;

-- 
2.47.0.163.g1226f6d8fa-goog

[PATCH v12 3/5] rust: samples: add tracepoint to Rust sample

[Alice Ryhl]

This updates the Rust printing sample to invoke a tracepoint. This
ensures that we have a user in-tree from the get-go even though the
patch is being merged before its real user.

Reviewed-by: Boqun Feng <boqun.feng@gmail.com>
Signed-off-by: Alice Ryhl <aliceryhl@google.com>
---
 MAINTAINERS                        |  1 +
 include/trace/events/rust_sample.h | 31 +++++++++++++++++++++++++++++++
 rust/bindings/bindings_helper.h    |  1 +
 samples/rust/Makefile              |  3 ++-
 samples/rust/rust_print.rs         | 18 ++++++++++++++++++
 samples/rust/rust_print_events.c   |  8 ++++++++
 6 files changed, 61 insertions(+), 1 deletion(-)

diff --git a/MAINTAINERS b/MAINTAINERS
index a097afd76ded..a9b71411d77a 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -20223,6 +20223,7 @@ C:	zulip://rust-for-linux.zulipchat.com
 P:	https://rust-for-linux.com/contributing
 T:	git https://github.com/Rust-for-Linux/linux.git rust-next
 F:	Documentation/rust/
+F:	include/trace/events/rust_sample.h
 F:	rust/
 F:	samples/rust/
 F:	scripts/*rust*
diff --git a/include/trace/events/rust_sample.h b/include/trace/events/rust_sample.h
new file mode 100644
index 000000000000..dbc80ca2e465
--- /dev/null
+++ b/include/trace/events/rust_sample.h
@@ -0,0 +1,31 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Tracepoints for `samples/rust/rust_print.rs`.
+ *
+ * Copyright (C) 2024 Google, Inc.
+ */
+
+#undef TRACE_SYSTEM
+#define TRACE_SYSTEM rust_sample
+
+#if !defined(_RUST_SAMPLE_TRACE_H) || defined(TRACE_HEADER_MULTI_READ)
+#define _RUST_SAMPLE_TRACE_H
+
+#include <linux/tracepoint.h>
+
+TRACE_EVENT(rust_sample_loaded,
+	TP_PROTO(int magic_number),
+	TP_ARGS(magic_number),
+	TP_STRUCT__entry(
+		__field(int, magic_number)
+	),
+	TP_fast_assign(
+		__entry->magic_number = magic_number;
+	),
+	TP_printk("magic=%d", __entry->magic_number)
+);
+
+#endif /* _RUST_SAMPLE_TRACE_H */
+
+/* This part must be outside protection */
+#include <trace/define_trace.h>
diff --git a/rust/bindings/bindings_helper.h b/rust/bindings/bindings_helper.h
index 752572e638a6..b072c197ce9e 100644
--- a/rust/bindings/bindings_helper.h
+++ b/rust/bindings/bindings_helper.h
@@ -23,6 +23,7 @@
 #include <linux/tracepoint.h>
 #include <linux/wait.h>
 #include <linux/workqueue.h>
+#include <trace/events/rust_sample.h>
 
 /* `bindgen` gets confused at certain things. */
 const size_t RUST_CONST_HELPER_ARCH_SLAB_MINALIGN = ARCH_SLAB_MINALIGN;
diff --git a/samples/rust/Makefile b/samples/rust/Makefile
index 03086dabbea4..f29280ec4820 100644
--- a/samples/rust/Makefile
+++ b/samples/rust/Makefile
@@ -1,6 +1,7 @@
 # SPDX-License-Identifier: GPL-2.0
+ccflags-y += -I$(src)				# needed for trace events
 
 obj-$(CONFIG_SAMPLE_RUST_MINIMAL)		+= rust_minimal.o
-obj-$(CONFIG_SAMPLE_RUST_PRINT)			+= rust_print.o
+obj-$(CONFIG_SAMPLE_RUST_PRINT)			+= rust_print.o rust_print_events.o
 
 subdir-$(CONFIG_SAMPLE_RUST_HOSTPROGS)		+= hostprogs
diff --git a/samples/rust/rust_print.rs b/samples/rust/rust_print.rs
index 6eabb0d79ea3..6d14b08cac1c 100644
--- a/samples/rust/rust_print.rs
+++ b/samples/rust/rust_print.rs
@@ -69,6 +69,8 @@ fn init(_module: &'static ThisModule) -> Result<Self> {
 
         arc_print()?;
 
+        trace::trace_rust_sample_loaded(42);
+
         Ok(RustPrint)
     }
 }
@@ -78,3 +80,19 @@ fn drop(&mut self) {
         pr_info!("Rust printing macros sample (exit)\n");
     }
 }
+
+mod trace {
+    use core::ffi::c_int;
+
+    kernel::declare_trace! {
+        /// # Safety
+        ///
+        /// Always safe to call.
+        unsafe fn rust_sample_loaded(magic: c_int);
+    }
+
+    pub(crate) fn trace_rust_sample_loaded(magic: i32) {
+        // SAFETY: Always safe to call.
+        unsafe { rust_sample_loaded(magic as c_int) }
+    }
+}
diff --git a/samples/rust/rust_print_events.c b/samples/rust/rust_print_events.c
new file mode 100644
index 000000000000..a9169ff0edf1
--- /dev/null
+++ b/samples/rust/rust_print_events.c
@@ -0,0 +1,8 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright 2024 Google LLC
+ */
+
+#define CREATE_TRACE_POINTS
+#define CREATE_RUST_TRACE_POINTS
+#include <trace/events/rust_sample.h>

-- 
2.47.0.163.g1226f6d8fa-goog

[PATCH v12 4/5] jump_label: adjust inline asm to be consistent

[Alice Ryhl]

To avoid duplication of inline asm between C and Rust, we need to
import the inline asm from the relevant `jump_label.h` header into Rust.
To make that easier, this patch updates the header files to expose the
inline asm via a new ARCH_STATIC_BRANCH_ASM macro.

The header files are all updated to define a ARCH_STATIC_BRANCH_ASM that
takes the same arguments in a consistent order so that Rust can use the
same logic for every architecture.

Suggested-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Co-developed-by: Miguel Ojeda <ojeda@kernel.org>
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: Palmer Dabbelt <palmer@rivosinc.com> # RISC-V
Signed-off-by: Alice Ryhl <aliceryhl@google.com>
---
 arch/arm/include/asm/jump_label.h       | 14 +++++----
 arch/arm64/include/asm/jump_label.h     | 20 ++++++++-----
 arch/loongarch/include/asm/jump_label.h | 16 +++++++----
 arch/riscv/include/asm/jump_label.h     | 50 ++++++++++++++++++---------------
 arch/x86/include/asm/jump_label.h       | 35 +++++++++--------------
 5 files changed, 73 insertions(+), 62 deletions(-)

diff --git a/arch/arm/include/asm/jump_label.h b/arch/arm/include/asm/jump_label.h
index e4eb54f6cd9f..a35aba7f548c 100644
--- a/arch/arm/include/asm/jump_label.h
+++ b/arch/arm/include/asm/jump_label.h
@@ -9,13 +9,17 @@
 
 #define JUMP_LABEL_NOP_SIZE 4
 
+/* This macro is also expanded on the Rust side. */
+#define ARCH_STATIC_BRANCH_ASM(key, label)		\
+	"1:\n\t"					\
+	WASM(nop) "\n\t"				\
+	".pushsection __jump_table,  \"aw\"\n\t"	\
+	".word 1b, " label ", " key "\n\t"		\
+	".popsection\n\t"				\
+
 static __always_inline bool arch_static_branch(struct static_key *key, bool branch)
 {
-	asm goto("1:\n\t"
-		 WASM(nop) "\n\t"
-		 ".pushsection __jump_table,  \"aw\"\n\t"
-		 ".word 1b, %l[l_yes], %c0\n\t"
-		 ".popsection\n\t"
+	asm goto(ARCH_STATIC_BRANCH_ASM("%c0", "%l[l_yes]")
 		 : :  "i" (&((char *)key)[branch]) :  : l_yes);
 
 	return false;
diff --git a/arch/arm64/include/asm/jump_label.h b/arch/arm64/include/asm/jump_label.h
index a0a5bbae7229..424ed421cd97 100644
--- a/arch/arm64/include/asm/jump_label.h
+++ b/arch/arm64/include/asm/jump_label.h
@@ -19,10 +19,14 @@
 #define JUMP_TABLE_ENTRY(key, label)			\
 	".pushsection	__jump_table, \"aw\"\n\t"	\
 	".align		3\n\t"				\
-	".long		1b - ., %l["#label"] - .\n\t"	\
-	".quad		%c0 - .\n\t"			\
-	".popsection\n\t"				\
-	:  :  "i"(key) :  : label
+	".long		1b - ., " label " - .\n\t"	\
+	".quad		" key " - .\n\t"		\
+	".popsection\n\t"
+
+/* This macro is also expanded on the Rust side. */
+#define ARCH_STATIC_BRANCH_ASM(key, label)		\
+	"1:	nop\n\t"				\
+	JUMP_TABLE_ENTRY(key, label)
 
 static __always_inline bool arch_static_branch(struct static_key * const key,
 					       const bool branch)
@@ -30,8 +34,8 @@ static __always_inline bool arch_static_branch(struct static_key * const key,
 	char *k = &((char *)key)[branch];
 
 	asm goto(
-		"1:	nop					\n\t"
-		JUMP_TABLE_ENTRY(k, l_yes)
+		ARCH_STATIC_BRANCH_ASM("%c0", "%l[l_yes]")
+		:  :  "i"(k) :  : l_yes
 		);
 
 	return false;
@@ -43,9 +47,11 @@ static __always_inline bool arch_static_branch_jump(struct static_key * const ke
 						    const bool branch)
 {
 	char *k = &((char *)key)[branch];
+
 	asm goto(
 		"1:	b		%l[l_yes]		\n\t"
-		JUMP_TABLE_ENTRY(k, l_yes)
+		JUMP_TABLE_ENTRY("%c0", "%l[l_yes]")
+		:  :  "i"(k) :  : l_yes
 		);
 	return false;
 l_yes:
diff --git a/arch/loongarch/include/asm/jump_label.h b/arch/loongarch/include/asm/jump_label.h
index 29acfe3de3fa..8a924bd69d19 100644
--- a/arch/loongarch/include/asm/jump_label.h
+++ b/arch/loongarch/include/asm/jump_label.h
@@ -13,18 +13,22 @@
 
 #define JUMP_LABEL_NOP_SIZE	4
 
-#define JUMP_TABLE_ENTRY				\
+/* This macro is also expanded on the Rust side. */
+#define JUMP_TABLE_ENTRY(key, label)			\
 	 ".pushsection	__jump_table, \"aw\"	\n\t"	\
 	 ".align	3			\n\t"	\
-	 ".long		1b - ., %l[l_yes] - .	\n\t"	\
-	 ".quad		%0 - .			\n\t"	\
+	 ".long		1b - ., " label " - .	\n\t"	\
+	 ".quad		" key " - .		\n\t"	\
 	 ".popsection				\n\t"
 
+#define ARCH_STATIC_BRANCH_ASM(key, label)		\
+	"1:	nop				\n\t"	\
+	JUMP_TABLE_ENTRY(key, label)
+
 static __always_inline bool arch_static_branch(struct static_key * const key, const bool branch)
 {
 	asm goto(
-		"1:	nop			\n\t"
-		JUMP_TABLE_ENTRY
+		ARCH_STATIC_BRANCH_ASM("%0", "%l[l_yes]")
 		:  :  "i"(&((char *)key)[branch]) :  : l_yes);
 
 	return false;
@@ -37,7 +41,7 @@ static __always_inline bool arch_static_branch_jump(struct static_key * const ke
 {
 	asm goto(
 		"1:	b	%l[l_yes]	\n\t"
-		JUMP_TABLE_ENTRY
+		JUMP_TABLE_ENTRY("%0", "%l[l_yes]")
 		:  :  "i"(&((char *)key)[branch]) :  : l_yes);
 
 	return false;
diff --git a/arch/riscv/include/asm/jump_label.h b/arch/riscv/include/asm/jump_label.h
index 1c768d02bd0c..87a71cc6d146 100644
--- a/arch/riscv/include/asm/jump_label.h
+++ b/arch/riscv/include/asm/jump_label.h
@@ -16,21 +16,28 @@
 
 #define JUMP_LABEL_NOP_SIZE 4
 
+#define JUMP_TABLE_ENTRY(key, label)			\
+	".pushsection	__jump_table, \"aw\"	\n\t"	\
+	".align		" RISCV_LGPTR "		\n\t"	\
+	".long		1b - ., " label " - .	\n\t"	\
+	"" RISCV_PTR "	" key " - .		\n\t"	\
+	".popsection				\n\t"
+
+/* This macro is also expanded on the Rust side. */
+#define ARCH_STATIC_BRANCH_ASM(key, label)		\
+	"	.align		2		\n\t"	\
+	"	.option push			\n\t"	\
+	"	.option norelax			\n\t"	\
+	"	.option norvc			\n\t"	\
+	"1:	nop				\n\t"	\
+	"	.option pop			\n\t"	\
+	JUMP_TABLE_ENTRY(key, label)
+
 static __always_inline bool arch_static_branch(struct static_key * const key,
 					       const bool branch)
 {
 	asm goto(
-		"	.align		2			\n\t"
-		"	.option push				\n\t"
-		"	.option norelax				\n\t"
-		"	.option norvc				\n\t"
-		"1:	nop					\n\t"
-		"	.option pop				\n\t"
-		"	.pushsection	__jump_table, \"aw\"	\n\t"
-		"	.align		" RISCV_LGPTR "		\n\t"
-		"	.long		1b - ., %l[label] - .	\n\t"
-		"	" RISCV_PTR "	%0 - .			\n\t"
-		"	.popsection				\n\t"
+		ARCH_STATIC_BRANCH_ASM("%0", "%l[label]")
 		:  :  "i"(&((char *)key)[branch]) :  : label);
 
 	return false;
@@ -38,21 +45,20 @@ static __always_inline bool arch_static_branch(struct static_key * const key,
 	return true;
 }
 
+#define ARCH_STATIC_BRANCH_JUMP_ASM(key, label)		\
+	"	.align		2		\n\t"	\
+	"	.option push			\n\t"	\
+	"	.option norelax			\n\t"	\
+	"	.option norvc			\n\t"	\
+	"1:	j	" label "		\n\t" \
+	"	.option pop			\n\t"	\
+	JUMP_TABLE_ENTRY(key, label)
+
 static __always_inline bool arch_static_branch_jump(struct static_key * const key,
 						    const bool branch)
 {
 	asm goto(
-		"	.align		2			\n\t"
-		"	.option push				\n\t"
-		"	.option norelax				\n\t"
-		"	.option norvc				\n\t"
-		"1:	j		%l[label]		\n\t"
-		"	.option pop				\n\t"
-		"	.pushsection	__jump_table, \"aw\"	\n\t"
-		"	.align		" RISCV_LGPTR "		\n\t"
-		"	.long		1b - ., %l[label] - .	\n\t"
-		"	" RISCV_PTR "	%0 - .			\n\t"
-		"	.popsection				\n\t"
+		ARCH_STATIC_BRANCH_JUMP_ASM("%0", "%l[label]")
 		:  :  "i"(&((char *)key)[branch]) :  : label);
 
 	return false;
diff --git a/arch/x86/include/asm/jump_label.h b/arch/x86/include/asm/jump_label.h
index cbbef32517f0..3f1c1d6c0da1 100644
--- a/arch/x86/include/asm/jump_label.h
+++ b/arch/x86/include/asm/jump_label.h
@@ -12,35 +12,28 @@
 #include <linux/stringify.h>
 #include <linux/types.h>
 
-#define JUMP_TABLE_ENTRY				\
+#define JUMP_TABLE_ENTRY(key, label)			\
 	".pushsection __jump_table,  \"aw\" \n\t"	\
 	_ASM_ALIGN "\n\t"				\
 	".long 1b - . \n\t"				\
-	".long %l[l_yes] - . \n\t"			\
-	_ASM_PTR "%c0 + %c1 - .\n\t"			\
+	".long " label " - . \n\t"			\
+	_ASM_PTR " " key " - . \n\t"			\
 	".popsection \n\t"
 
+/* This macro is also expanded on the Rust side. */
 #ifdef CONFIG_HAVE_JUMP_LABEL_HACK
-
-static __always_inline bool arch_static_branch(struct static_key *key, bool branch)
-{
-	asm goto("1:"
-		"jmp %l[l_yes] # objtool NOPs this \n\t"
-		JUMP_TABLE_ENTRY
-		: :  "i" (key), "i" (2 | branch) : : l_yes);
-
-	return false;
-l_yes:
-	return true;
-}
-
+#define ARCH_STATIC_BRANCH_ASM(key, label)		\
+	"1: jmp " label " # objtool NOPs this \n\t"	\
+	JUMP_TABLE_ENTRY(key " + 2", label)
 #else /* !CONFIG_HAVE_JUMP_LABEL_HACK */
+#define ARCH_STATIC_BRANCH_ASM(key, label)		\
+	"1: .byte " __stringify(BYTES_NOP5) "\n\t"	\
+	JUMP_TABLE_ENTRY(key, label)
+#endif /* CONFIG_HAVE_JUMP_LABEL_HACK */
 
 static __always_inline bool arch_static_branch(struct static_key * const key, const bool branch)
 {
-	asm goto("1:"
-		".byte " __stringify(BYTES_NOP5) "\n\t"
-		JUMP_TABLE_ENTRY
+	asm goto(ARCH_STATIC_BRANCH_ASM("%c0 + %c1", "%l[l_yes]")
 		: :  "i" (key), "i" (branch) : : l_yes);
 
 	return false;
@@ -48,13 +41,11 @@ static __always_inline bool arch_static_branch(struct static_key * const key, co
 	return true;
 }
 
-#endif /* CONFIG_HAVE_JUMP_LABEL_HACK */
-
 static __always_inline bool arch_static_branch_jump(struct static_key * const key, const bool branch)
 {
 	asm goto("1:"
 		"jmp %l[l_yes]\n\t"
-		JUMP_TABLE_ENTRY
+		JUMP_TABLE_ENTRY("%c0 + %c1", "%l[l_yes]")
 		: :  "i" (key), "i" (branch) : : l_yes);
 
 	return false;

-- 
2.47.0.163.g1226f6d8fa-goog

[PATCH v12 5/5] rust: add arch_static_branch

[Alice Ryhl]

To allow the Rust implementation of static_key_false to use runtime code
patching instead of the generic implementation, pull in the relevant
inline assembly from the jump_label.h header by running the C
preprocessor on a .rs.S file. Build rules are added for .rs.S files.

Since the relevant inline asm has been adjusted to export the inline asm
via the ARCH_STATIC_BRANCH_ASM macro in a consistent way, the Rust side
does not need architecture specific code to pull in the asm.

It is not possible to use the existing C implementation of
arch_static_branch via a Rust helper because it passes the argument
`key` to inline assembly as an 'i' parameter. Any attempt to add a C
helper for this function will fail to compile because the value of `key`
must be known at compile-time.

Suggested-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Co-developed-by: Miguel Ojeda <ojeda@kernel.org>
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
Reviewed-by: Boqun Feng <boqun.feng@gmail.com>
Signed-off-by: Alice Ryhl <aliceryhl@google.com>
---
 rust/Makefile                           |  6 +++++
 rust/kernel/.gitignore                  |  3 +++
 rust/kernel/arch_static_branch_asm.rs.S |  7 +++++
 rust/kernel/jump_label.rs               | 46 ++++++++++++++++++++++++++++++++-
 rust/kernel/lib.rs                      | 35 +++++++++++++++++++++++++
 scripts/Makefile.build                  |  9 ++++++-
 6 files changed, 104 insertions(+), 2 deletions(-)

diff --git a/rust/Makefile b/rust/Makefile
index b5e0a73b78f3..bc2a9071dd29 100644
--- a/rust/Makefile
+++ b/rust/Makefile
@@ -36,6 +36,8 @@ always-$(CONFIG_RUST_KERNEL_DOCTESTS) += doctests_kernel_generated_kunit.c
 obj-$(CONFIG_RUST_KERNEL_DOCTESTS) += doctests_kernel_generated.o
 obj-$(CONFIG_RUST_KERNEL_DOCTESTS) += doctests_kernel_generated_kunit.o
 
+always-$(subst y,$(CONFIG_RUST),$(CONFIG_JUMP_LABEL)) += kernel/arch_static_branch_asm.rs
+
 # Avoids running `$(RUSTC)` for the sysroot when it may not be available.
 ifdef CONFIG_RUST
 
@@ -424,4 +426,8 @@ $(obj)/kernel.o: $(src)/kernel/lib.rs $(obj)/alloc.o $(obj)/build_error.o \
     $(obj)/libmacros.so $(obj)/bindings.o $(obj)/uapi.o FORCE
 	+$(call if_changed_rule,rustc_library)
 
+ifdef CONFIG_JUMP_LABEL
+$(obj)/kernel.o: $(obj)/kernel/arch_static_branch_asm.rs
+endif
+
 endif # CONFIG_RUST
diff --git a/rust/kernel/.gitignore b/rust/kernel/.gitignore
new file mode 100644
index 000000000000..d082731007c6
--- /dev/null
+++ b/rust/kernel/.gitignore
@@ -0,0 +1,3 @@
+# SPDX-License-Identifier: GPL-2.0
+
+/arch_static_branch_asm.rs
diff --git a/rust/kernel/arch_static_branch_asm.rs.S b/rust/kernel/arch_static_branch_asm.rs.S
new file mode 100644
index 000000000000..2afb638708db
--- /dev/null
+++ b/rust/kernel/arch_static_branch_asm.rs.S
@@ -0,0 +1,7 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+#include <linux/jump_label.h>
+
+// Cut here.
+
+::kernel::concat_literals!(ARCH_STATIC_BRANCH_ASM("{symb} + {off} + {branch}", "{l_yes}"))
diff --git a/rust/kernel/jump_label.rs b/rust/kernel/jump_label.rs
index 4b7655b2a022..2f2df03a3275 100644
--- a/rust/kernel/jump_label.rs
+++ b/rust/kernel/jump_label.rs
@@ -24,7 +24,51 @@ macro_rules! static_branch_unlikely {
         let _key: *const $crate::bindings::static_key_false = ::core::ptr::addr_of!((*_key).$field);
         let _key: *const $crate::bindings::static_key = _key.cast();
 
-        $crate::bindings::static_key_count(_key.cast_mut()) > 0
+        #[cfg(not(CONFIG_JUMP_LABEL))]
+        {
+            $crate::bindings::static_key_count(_key) > 0
+        }
+
+        #[cfg(CONFIG_JUMP_LABEL)]
+        $crate::jump_label::arch_static_branch! { $key, $keytyp, $field, false }
     }};
 }
 pub use static_branch_unlikely;
+
+/// Assert that the assembly block evaluates to a string literal.
+#[cfg(CONFIG_JUMP_LABEL)]
+const _: &str = include!(concat!(
+    env!("OBJTREE"),
+    "/rust/kernel/arch_static_branch_asm.rs"
+));
+
+#[macro_export]
+#[doc(hidden)]
+#[cfg(CONFIG_JUMP_LABEL)]
+macro_rules! arch_static_branch {
+    ($key:path, $keytyp:ty, $field:ident, $branch:expr) => {'my_label: {
+        $crate::asm!(
+            include!(concat!(env!("OBJTREE"), "/rust/kernel/arch_static_branch_asm.rs"));
+            l_yes = label {
+                break 'my_label true;
+            },
+            symb = sym $key,
+            off = const ::core::mem::offset_of!($keytyp, $field),
+            branch = const $crate::jump_label::bool_to_int($branch),
+        );
+
+        break 'my_label false;
+    }};
+}
+
+#[cfg(CONFIG_JUMP_LABEL)]
+pub use arch_static_branch;
+
+/// A helper used by inline assembly to pass a boolean to as a `const` parameter.
+///
+/// Using this function instead of a cast lets you assert that the input is a boolean, and not some
+/// other type that can also be cast to an integer.
+#[doc(hidden)]
+pub const fn bool_to_int(b: bool) -> i32 {
+    b as i32
+}
diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs
index 55f81f49024e..97286b99270e 100644
--- a/rust/kernel/lib.rs
+++ b/rust/kernel/lib.rs
@@ -148,3 +148,38 @@ macro_rules! container_of {
         ptr.sub(offset) as *const $type
     }}
 }
+
+/// Helper for `.rs.S` files.
+#[doc(hidden)]
+#[macro_export]
+macro_rules! concat_literals {
+    ($( $asm:literal )* ) => {
+        ::core::concat!($($asm),*)
+    };
+}
+
+/// Wrapper around `asm!` configured for use in the kernel.
+///
+/// Uses a semicolon to avoid parsing ambiguities, even though this does not match native `asm!`
+/// syntax.
+// For x86, `asm!` uses intel syntax by default, but we want to use at&t syntax in the kernel.
+#[cfg(any(target_arch = "x86", target_arch = "x86_64"))]
+#[macro_export]
+macro_rules! asm {
+    ($($asm:expr),* ; $($rest:tt)*) => {
+        ::core::arch::asm!( $($asm)*, options(att_syntax), $($rest)* )
+    };
+}
+
+/// Wrapper around `asm!` configured for use in the kernel.
+///
+/// Uses a semicolon to avoid parsing ambiguities, even though this does not match native `asm!`
+/// syntax.
+// For non-x86 arches we just pass through to `asm!`.
+#[cfg(not(any(target_arch = "x86", target_arch = "x86_64")))]
+#[macro_export]
+macro_rules! asm {
+    ($($asm:expr),* ; $($rest:tt)*) => {
+        ::core::arch::asm!( $($asm)*, $($rest)* )
+    };
+}
diff --git a/scripts/Makefile.build b/scripts/Makefile.build
index 8f423a1faf50..03ee558fcd4d 100644
--- a/scripts/Makefile.build
+++ b/scripts/Makefile.build
@@ -248,12 +248,13 @@ $(obj)/%.lst: $(obj)/%.c FORCE
 # Compile Rust sources (.rs)
 # ---------------------------------------------------------------------------
 
-rust_allowed_features := new_uninit
+rust_allowed_features := asm_const,asm_goto,new_uninit
 
 # `--out-dir` is required to avoid temporaries being created by `rustc` in the
 # current working directory, which may be not accessible in the out-of-tree
 # modules case.
 rust_common_cmd = \
+	OBJTREE=$(abspath $(objtree)) \
 	RUST_MODFILE=$(modfile) $(RUSTC_OR_CLIPPY) $(rust_flags) \
 	-Zallow-features=$(rust_allowed_features) \
 	-Zcrate-attr=no_std \
@@ -303,6 +304,12 @@ quiet_cmd_rustc_ll_rs = $(RUSTC_OR_CLIPPY_QUIET) $(quiet_modtag) $@
 $(obj)/%.ll: $(obj)/%.rs FORCE
 	+$(call if_changed_dep,rustc_ll_rs)
 
+quiet_cmd_rustc_rs_rs_S = RSCPP $(quiet_modtag) $@
+      cmd_rustc_rs_rs_S = $(CPP) $(c_flags) -xc -C -P $< | sed '1,/^\/\/ Cut here.$$/d' >$@
+
+$(obj)/%.rs: $(obj)/%.rs.S FORCE
+	+$(call if_changed_dep,rustc_rs_rs_S)
+
 # Compile assembler sources (.S)
 # ---------------------------------------------------------------------------
 

-- 
2.47.0.163.g1226f6d8fa-goog

Re: [PATCH v12 4/5] jump_label: adjust inline asm to be consistent

[Steven Rostedt]

On Wed, 30 Oct 2024 16:04:27 +0000
Alice Ryhl <aliceryhl@google.com> wrote:

> To avoid duplication of inline asm between C and Rust, we need to
> import the inline asm from the relevant `jump_label.h` header into Rust.
> To make that easier, this patch updates the header files to expose the
> inline asm via a new ARCH_STATIC_BRANCH_ASM macro.
> 
> The header files are all updated to define a ARCH_STATIC_BRANCH_ASM that
> takes the same arguments in a consistent order so that Rust can use the
> same logic for every architecture.
> 
> Suggested-by: Peter Zijlstra (Intel) <peterz@infradead.org>
> Co-developed-by: Miguel Ojeda <ojeda@kernel.org>
> Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
> Acked-by: Catalin Marinas <catalin.marinas@arm.com>
> Acked-by: Palmer Dabbelt <palmer@rivosinc.com> # RISC-V

Still missing an ack from the ARM maintainer (32 bit, just added) and loongarch.

I'll wait till Monday, if I don't hear anything against these patches
I'll pull them in.

-- Steve


> Signed-off-by: Alice Ryhl <aliceryhl@google.com>
> ---
>  arch/arm/include/asm/jump_label.h       | 14 +++++----
>  arch/arm64/include/asm/jump_label.h     | 20 ++++++++-----
>  arch/loongarch/include/asm/jump_label.h | 16 +++++++----
>  arch/riscv/include/asm/jump_label.h     | 50 ++++++++++++++++++---------------
>  arch/x86/include/asm/jump_label.h       | 35 +++++++++--------------
>  5 files changed, 73 insertions(+), 62 deletions(-)
> 
> diff --git a/arch/arm/include/asm/jump_label.h b/arch/arm/include/asm/jump_label.h
> index e4eb54f6cd9f..a35aba7f548c 100644
> --- a/arch/arm/include/asm/jump_label.h
> +++ b/arch/arm/include/asm/jump_label.h
> @@ -9,13 +9,17 @@
>  
>  #define JUMP_LABEL_NOP_SIZE 4
>  
> +/* This macro is also expanded on the Rust side. */
> +#define ARCH_STATIC_BRANCH_ASM(key, label)		\
> +	"1:\n\t"					\
> +	WASM(nop) "\n\t"				\
> +	".pushsection __jump_table,  \"aw\"\n\t"	\
> +	".word 1b, " label ", " key "\n\t"		\
> +	".popsection\n\t"				\
> +
>  static __always_inline bool arch_static_branch(struct static_key *key, bool branch)
>  {
> -	asm goto("1:\n\t"
> -		 WASM(nop) "\n\t"
> -		 ".pushsection __jump_table,  \"aw\"\n\t"
> -		 ".word 1b, %l[l_yes], %c0\n\t"
> -		 ".popsection\n\t"
> +	asm goto(ARCH_STATIC_BRANCH_ASM("%c0", "%l[l_yes]")
>  		 : :  "i" (&((char *)key)[branch]) :  : l_yes);
>  
>  	return false;
> diff --git a/arch/arm64/include/asm/jump_label.h b/arch/arm64/include/asm/jump_label.h
> index a0a5bbae7229..424ed421cd97 100644
> --- a/arch/arm64/include/asm/jump_label.h
> +++ b/arch/arm64/include/asm/jump_label.h
> @@ -19,10 +19,14 @@
>  #define JUMP_TABLE_ENTRY(key, label)			\
>  	".pushsection	__jump_table, \"aw\"\n\t"	\
>  	".align		3\n\t"				\
> -	".long		1b - ., %l["#label"] - .\n\t"	\
> -	".quad		%c0 - .\n\t"			\
> -	".popsection\n\t"				\
> -	:  :  "i"(key) :  : label
> +	".long		1b - ., " label " - .\n\t"	\
> +	".quad		" key " - .\n\t"		\
> +	".popsection\n\t"
> +
> +/* This macro is also expanded on the Rust side. */
> +#define ARCH_STATIC_BRANCH_ASM(key, label)		\
> +	"1:	nop\n\t"				\
> +	JUMP_TABLE_ENTRY(key, label)
>  
>  static __always_inline bool arch_static_branch(struct static_key * const key,
>  					       const bool branch)
> @@ -30,8 +34,8 @@ static __always_inline bool arch_static_branch(struct static_key * const key,
>  	char *k = &((char *)key)[branch];
>  
>  	asm goto(
> -		"1:	nop					\n\t"
> -		JUMP_TABLE_ENTRY(k, l_yes)
> +		ARCH_STATIC_BRANCH_ASM("%c0", "%l[l_yes]")
> +		:  :  "i"(k) :  : l_yes
>  		);
>  
>  	return false;
> @@ -43,9 +47,11 @@ static __always_inline bool arch_static_branch_jump(struct static_key * const ke
>  						    const bool branch)
>  {
>  	char *k = &((char *)key)[branch];
> +
>  	asm goto(
>  		"1:	b		%l[l_yes]		\n\t"
> -		JUMP_TABLE_ENTRY(k, l_yes)
> +		JUMP_TABLE_ENTRY("%c0", "%l[l_yes]")
> +		:  :  "i"(k) :  : l_yes
>  		);
>  	return false;
>  l_yes:
> diff --git a/arch/loongarch/include/asm/jump_label.h b/arch/loongarch/include/asm/jump_label.h
> index 29acfe3de3fa..8a924bd69d19 100644
> --- a/arch/loongarch/include/asm/jump_label.h
> +++ b/arch/loongarch/include/asm/jump_label.h
> @@ -13,18 +13,22 @@
>  
>  #define JUMP_LABEL_NOP_SIZE	4
>  
> -#define JUMP_TABLE_ENTRY				\
> +/* This macro is also expanded on the Rust side. */
> +#define JUMP_TABLE_ENTRY(key, label)			\
>  	 ".pushsection	__jump_table, \"aw\"	\n\t"	\
>  	 ".align	3			\n\t"	\
> -	 ".long		1b - ., %l[l_yes] - .	\n\t"	\
> -	 ".quad		%0 - .			\n\t"	\
> +	 ".long		1b - ., " label " - .	\n\t"	\
> +	 ".quad		" key " - .		\n\t"	\
>  	 ".popsection				\n\t"
>  
> +#define ARCH_STATIC_BRANCH_ASM(key, label)		\
> +	"1:	nop				\n\t"	\
> +	JUMP_TABLE_ENTRY(key, label)
> +
>  static __always_inline bool arch_static_branch(struct static_key * const key, const bool branch)
>  {
>  	asm goto(
> -		"1:	nop			\n\t"
> -		JUMP_TABLE_ENTRY
> +		ARCH_STATIC_BRANCH_ASM("%0", "%l[l_yes]")
>  		:  :  "i"(&((char *)key)[branch]) :  : l_yes);
>  
>  	return false;
> @@ -37,7 +41,7 @@ static __always_inline bool arch_static_branch_jump(struct static_key * const ke
>  {
>  	asm goto(
>  		"1:	b	%l[l_yes]	\n\t"
> -		JUMP_TABLE_ENTRY
> +		JUMP_TABLE_ENTRY("%0", "%l[l_yes]")
>  		:  :  "i"(&((char *)key)[branch]) :  : l_yes);
>  
>  	return false;
> diff --git a/arch/riscv/include/asm/jump_label.h b/arch/riscv/include/asm/jump_label.h
> index 1c768d02bd0c..87a71cc6d146 100644
> --- a/arch/riscv/include/asm/jump_label.h
> +++ b/arch/riscv/include/asm/jump_label.h
> @@ -16,21 +16,28 @@
>  
>  #define JUMP_LABEL_NOP_SIZE 4
>  
> +#define JUMP_TABLE_ENTRY(key, label)			\
> +	".pushsection	__jump_table, \"aw\"	\n\t"	\
> +	".align		" RISCV_LGPTR "		\n\t"	\
> +	".long		1b - ., " label " - .	\n\t"	\
> +	"" RISCV_PTR "	" key " - .		\n\t"	\
> +	".popsection				\n\t"
> +
> +/* This macro is also expanded on the Rust side. */
> +#define ARCH_STATIC_BRANCH_ASM(key, label)		\
> +	"	.align		2		\n\t"	\
> +	"	.option push			\n\t"	\
> +	"	.option norelax			\n\t"	\
> +	"	.option norvc			\n\t"	\
> +	"1:	nop				\n\t"	\
> +	"	.option pop			\n\t"	\
> +	JUMP_TABLE_ENTRY(key, label)
> +
>  static __always_inline bool arch_static_branch(struct static_key * const key,
>  					       const bool branch)
>  {
>  	asm goto(
> -		"	.align		2			\n\t"
> -		"	.option push				\n\t"
> -		"	.option norelax				\n\t"
> -		"	.option norvc				\n\t"
> -		"1:	nop					\n\t"
> -		"	.option pop				\n\t"
> -		"	.pushsection	__jump_table, \"aw\"	\n\t"
> -		"	.align		" RISCV_LGPTR "		\n\t"
> -		"	.long		1b - ., %l[label] - .	\n\t"
> -		"	" RISCV_PTR "	%0 - .			\n\t"
> -		"	.popsection				\n\t"
> +		ARCH_STATIC_BRANCH_ASM("%0", "%l[label]")
>  		:  :  "i"(&((char *)key)[branch]) :  : label);
>  
>  	return false;
> @@ -38,21 +45,20 @@ static __always_inline bool arch_static_branch(struct static_key * const key,
>  	return true;
>  }
>  
> +#define ARCH_STATIC_BRANCH_JUMP_ASM(key, label)		\
> +	"	.align		2		\n\t"	\
> +	"	.option push			\n\t"	\
> +	"	.option norelax			\n\t"	\
> +	"	.option norvc			\n\t"	\
> +	"1:	j	" label "		\n\t" \
> +	"	.option pop			\n\t"	\
> +	JUMP_TABLE_ENTRY(key, label)
> +
>  static __always_inline bool arch_static_branch_jump(struct static_key * const key,
>  						    const bool branch)
>  {
>  	asm goto(
> -		"	.align		2			\n\t"
> -		"	.option push				\n\t"
> -		"	.option norelax				\n\t"
> -		"	.option norvc				\n\t"
> -		"1:	j		%l[label]		\n\t"
> -		"	.option pop				\n\t"
> -		"	.pushsection	__jump_table, \"aw\"	\n\t"
> -		"	.align		" RISCV_LGPTR "		\n\t"
> -		"	.long		1b - ., %l[label] - .	\n\t"
> -		"	" RISCV_PTR "	%0 - .			\n\t"
> -		"	.popsection				\n\t"
> +		ARCH_STATIC_BRANCH_JUMP_ASM("%0", "%l[label]")
>  		:  :  "i"(&((char *)key)[branch]) :  : label);
>  
>  	return false;
> diff --git a/arch/x86/include/asm/jump_label.h b/arch/x86/include/asm/jump_label.h
> index cbbef32517f0..3f1c1d6c0da1 100644
> --- a/arch/x86/include/asm/jump_label.h
> +++ b/arch/x86/include/asm/jump_label.h
> @@ -12,35 +12,28 @@
>  #include <linux/stringify.h>
>  #include <linux/types.h>
>  
> -#define JUMP_TABLE_ENTRY				\
> +#define JUMP_TABLE_ENTRY(key, label)			\
>  	".pushsection __jump_table,  \"aw\" \n\t"	\
>  	_ASM_ALIGN "\n\t"				\
>  	".long 1b - . \n\t"				\
> -	".long %l[l_yes] - . \n\t"			\
> -	_ASM_PTR "%c0 + %c1 - .\n\t"			\
> +	".long " label " - . \n\t"			\
> +	_ASM_PTR " " key " - . \n\t"			\
>  	".popsection \n\t"
>  
> +/* This macro is also expanded on the Rust side. */
>  #ifdef CONFIG_HAVE_JUMP_LABEL_HACK
> -
> -static __always_inline bool arch_static_branch(struct static_key *key, bool branch)
> -{
> -	asm goto("1:"
> -		"jmp %l[l_yes] # objtool NOPs this \n\t"
> -		JUMP_TABLE_ENTRY
> -		: :  "i" (key), "i" (2 | branch) : : l_yes);
> -
> -	return false;
> -l_yes:
> -	return true;
> -}
> -
> +#define ARCH_STATIC_BRANCH_ASM(key, label)		\
> +	"1: jmp " label " # objtool NOPs this \n\t"	\
> +	JUMP_TABLE_ENTRY(key " + 2", label)
>  #else /* !CONFIG_HAVE_JUMP_LABEL_HACK */
> +#define ARCH_STATIC_BRANCH_ASM(key, label)		\
> +	"1: .byte " __stringify(BYTES_NOP5) "\n\t"	\
> +	JUMP_TABLE_ENTRY(key, label)
> +#endif /* CONFIG_HAVE_JUMP_LABEL_HACK */
>  
>  static __always_inline bool arch_static_branch(struct static_key * const key, const bool branch)
>  {
> -	asm goto("1:"
> -		".byte " __stringify(BYTES_NOP5) "\n\t"
> -		JUMP_TABLE_ENTRY
> +	asm goto(ARCH_STATIC_BRANCH_ASM("%c0 + %c1", "%l[l_yes]")
>  		: :  "i" (key), "i" (branch) : : l_yes);
>  
>  	return false;
> @@ -48,13 +41,11 @@ static __always_inline bool arch_static_branch(struct static_key * const key, co
>  	return true;
>  }
>  
> -#endif /* CONFIG_HAVE_JUMP_LABEL_HACK */
> -
>  static __always_inline bool arch_static_branch_jump(struct static_key * const key, const bool branch)
>  {
>  	asm goto("1:"
>  		"jmp %l[l_yes]\n\t"
> -		JUMP_TABLE_ENTRY
> +		JUMP_TABLE_ENTRY("%c0 + %c1", "%l[l_yes]")
>  		: :  "i" (key), "i" (branch) : : l_yes);
>  
>  	return false;
> 

Re: [PATCH v12 4/5] jump_label: adjust inline asm to be consistent

[Russell King (Oracle)]

On Wed, Oct 30, 2024 at 07:13:16PM -0400, Steven Rostedt wrote:
> On Wed, 30 Oct 2024 16:04:27 +0000
> Alice Ryhl <aliceryhl@google.com> wrote:
> 
> > To avoid duplication of inline asm between C and Rust, we need to
> > import the inline asm from the relevant `jump_label.h` header into Rust.
> > To make that easier, this patch updates the header files to expose the
> > inline asm via a new ARCH_STATIC_BRANCH_ASM macro.
> > 
> > The header files are all updated to define a ARCH_STATIC_BRANCH_ASM that
> > takes the same arguments in a consistent order so that Rust can use the
> > same logic for every architecture.
> > 
> > Suggested-by: Peter Zijlstra (Intel) <peterz@infradead.org>
> > Co-developed-by: Miguel Ojeda <ojeda@kernel.org>
> > Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
> > Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
> > Acked-by: Catalin Marinas <catalin.marinas@arm.com>
> > Acked-by: Palmer Dabbelt <palmer@rivosinc.com> # RISC-V
> 
> Still missing an ack from the ARM maintainer (32 bit, just added) and loongarch.
> 
> I'll wait till Monday, if I don't hear anything against these patches
> I'll pull them in.

As of what has recently happened, I am not participating in technical
activities until such time that I'm told what is now acceptable. So
far, that has not been forthcoming, and thus I believe it is unwise to
engage in technical discussion.

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
FTTP is here! 80Mbps down 10Mbps up. Decent connectivity at last!

Re: [PATCH v12 4/5] jump_label: adjust inline asm to be consistent

[Steven Rostedt]

On Thu, 31 Oct 2024 00:10:50 +0000
"Russell King (Oracle)" <linux@armlinux.org.uk> wrote:

> > Still missing an ack from the ARM maintainer (32 bit, just added) and loongarch.
> > 
> > I'll wait till Monday, if I don't hear anything against these patches
> > I'll pull them in.  
> 
> As of what has recently happened, I am not participating in technical
> activities until such time that I'm told what is now acceptable. So
> far, that has not been forthcoming, and thus I believe it is unwise to
> engage in technical discussion.

Oh, OK. Thanks for letting me know.

-- Steve

Re: [PATCH v12 3/5] rust: samples: add tracepoint to Rust sample

[kernel test robot]

Hi Alice,

kernel test robot noticed the following build errors:

[auto build test ERROR on eb887c4567d1b0e7684c026fe7df44afa96589e6]

url:    https://github.com/intel-lab-lkp/linux/commits/Alice-Ryhl/rust-add-static_branch_unlikely-for-static_key_false/20241031-000709
base:   eb887c4567d1b0e7684c026fe7df44afa96589e6
patch link:    https://lore.kernel.org/r/20241030-tracepoint-v12-3-eec7f0f8ad22%40google.com
patch subject: [PATCH v12 3/5] rust: samples: add tracepoint to Rust sample
config: x86_64-randconfig-103-20241101 (https://download.01.org/0day-ci/archive/20241102/202411021421.jZ0FSDq6-lkp@intel.com/config)
compiler: clang version 19.1.3 (https://github.com/llvm/llvm-project ab51eccf88f5321e7c60591c5546b254b6afab99)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20241102/202411021421.jZ0FSDq6-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202411021421.jZ0FSDq6-lkp@intel.com/

All errors (new ones prefixed by >>):

>> error[E0425]: cannot find value `__tracepoint_rust_sample_loaded` in crate `$crate::bindings`
   --> samples/rust/rust_print.rs:87:5
   |
   87 | /     kernel::declare_trace! {
   88 | |         /// # Safety
   89 | |         ///
   90 | |         /// Always safe to call.
   91 | |         unsafe fn rust_sample_loaded(magic: c_int);
   92 | |     }
   | |_____^ not found in `$crate::bindings`
   |
   = note: this error originates in the macro `kernel::declare_trace` (in Nightly builds, run with -Z macro-backtrace for more info)
--
>> error[E0425]: cannot find function `rust_do_trace_rust_sample_loaded` in crate `$crate::bindings`
   --> samples/rust/rust_print.rs:87:5
   |
   87 | /     kernel::declare_trace! {
   88 | |         /// # Safety
   89 | |         ///
   90 | |         /// Always safe to call.
   91 | |         unsafe fn rust_sample_loaded(magic: c_int);
   92 | |     }
   | |_____^ not found in `$crate::bindings`
   |
   = note: this error originates in the macro `kernel::declare_trace` (in Nightly builds, run with -Z macro-backtrace for more info)

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki

Re: [PATCH v12 3/5] rust: samples: add tracepoint to Rust sample

[Alice Ryhl]

On Sat, Nov 2, 2024 at 8:08 AM kernel test robot <lkp@intel.com> wrote:
>
> Hi Alice,
>
> kernel test robot noticed the following build errors:
>
> [auto build test ERROR on eb887c4567d1b0e7684c026fe7df44afa96589e6]
>
> url:    https://github.com/intel-lab-lkp/linux/commits/Alice-Ryhl/rust-add-static_branch_unlikely-for-static_key_false/20241031-000709
> base:   eb887c4567d1b0e7684c026fe7df44afa96589e6
> patch link:    https://lore.kernel.org/r/20241030-tracepoint-v12-3-eec7f0f8ad22%40google.com
> patch subject: [PATCH v12 3/5] rust: samples: add tracepoint to Rust sample
> config: x86_64-randconfig-103-20241101 (https://download.01.org/0day-ci/archive/20241102/202411021421.jZ0FSDq6-lkp@intel.com/config)
> compiler: clang version 19.1.3 (https://github.com/llvm/llvm-project ab51eccf88f5321e7c60591c5546b254b6afab99)
> reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20241102/202411021421.jZ0FSDq6-lkp@intel.com/reproduce)
>
> If you fix the issue in a separate patch/commit (i.e. not just a new version of
> the same patch/commit), kindly add following tags
> | Reported-by: kernel test robot <lkp@intel.com>
> | Closes: https://lore.kernel.org/oe-kbuild-all/202411021421.jZ0FSDq6-lkp@intel.com/
>
> All errors (new ones prefixed by >>):
>
> >> error[E0425]: cannot find value `__tracepoint_rust_sample_loaded` in crate `$crate::bindings`
>    --> samples/rust/rust_print.rs:87:5
>    |
>    87 | /     kernel::declare_trace! {
>    88 | |         /// # Safety
>    89 | |         ///
>    90 | |         /// Always safe to call.
>    91 | |         unsafe fn rust_sample_loaded(magic: c_int);
>    92 | |     }
>    | |_____^ not found in `$crate::bindings`
>    |
>    = note: this error originates in the macro `kernel::declare_trace` (in Nightly builds, run with -Z macro-backtrace for more info)
> --
> >> error[E0425]: cannot find function `rust_do_trace_rust_sample_loaded` in crate `$crate::bindings`
>    --> samples/rust/rust_print.rs:87:5
>    |
>    87 | /     kernel::declare_trace! {
>    88 | |         /// # Safety
>    89 | |         ///
>    90 | |         /// Always safe to call.
>    91 | |         unsafe fn rust_sample_loaded(magic: c_int);
>    92 | |     }
>    | |_____^ not found in `$crate::bindings`
>    |
>    = note: this error originates in the macro `kernel::declare_trace` (in Nightly builds, run with -Z macro-backtrace for more info)

This bot is using a buggy bindgen. Please see
https://lore.kernel.org/all/20241030-bindgen-libclang-warn-v1-1-3a7ba9fedcfe@google.com/
which was also mentioned in the cover letter.

Alice

Re: [PATCH v12 0/5] Tracepoints and static branch in Rust

[patchwork-bot+linux-riscv]

Hello:

This series was applied to riscv/linux.git (fixes)
by Steven Rostedt (Google) <rostedt@goodmis.org>:

On Wed, 30 Oct 2024 16:04:23 +0000 you wrote:
> An important part of a production ready Linux kernel driver is
> tracepoints. So to write production ready Linux kernel drivers in Rust,
> we must be able to call tracepoints from Rust code. This patch series
> adds support for calling tracepoints declared in C from Rust.
> 
> This series includes a patch that adds a user of tracepoints to the
> rust_print sample. Please see that sample for details on what is needed
> to use this feature in Rust code.
> 
> [...]

Here is the summary with links:
  - [v12,1/5] rust: add static_branch_unlikely for static_key_false
    https://git.kernel.org/riscv/c/6e59bcc9c8ad
  - [v12,2/5] rust: add tracepoint support
    https://git.kernel.org/riscv/c/ad37bcd965fd
  - [v12,3/5] rust: samples: add tracepoint to Rust sample
    https://git.kernel.org/riscv/c/91d39024e1b0
  - [v12,4/5] jump_label: adjust inline asm to be consistent
    https://git.kernel.org/riscv/c/aecaf181651c
  - [v12,5/5] rust: add arch_static_branch
    https://git.kernel.org/riscv/c/169484ab6677

You are awesome, thank you!
-- 
Deet-doot-dot, I am a bot.
https://korg.docs.kernel.org/patchwork/pwbot.html

Re: [PATCH v12 0/5] Tracepoints and static branch in Rust

[Miguel Ojeda]

On Wed, Dec 11, 2024 at 11:32 PM <patchwork-bot+linux-riscv@kernel.org> wrote:
>
> This series was applied to riscv/linux.git (fixes)
> by Steven Rostedt (Google) <rostedt@goodmis.org>:

Hmm... This is already in mainline, and I don't see it in
riscv/linux.git (fixes) -- I guess it was a mistake?

Cheers,
Miguel