Merge tag 'rust-6.11' of https://github.com/Rust-for-Linux/linux

Pull Rust updates from Miguel Ojeda:
 "The highlight is the establishment of a minimum version for the Rust
  toolchain, including 'rustc' (and bundled tools) and 'bindgen'.

  The initial minimum will be the pinned version we currently have, i.e.
  we are just widening the allowed versions. That covers three stable
  Rust releases: 1.78.0, 1.79.0, 1.80.0 (getting released tomorrow),
  plus beta, plus nightly.

  This should already be enough for kernel developers in distributions
  that provide recent Rust compiler versions routinely, such as Arch
  Linux, Debian Unstable (outside the freeze period), Fedora Linux,
  Gentoo Linux (especially the testing channel), Nix (unstable) and
  openSUSE Slowroll and Tumbleweed.

  In addition, the kernel is now being built-tested by Rust's pre-merge
  CI. That is, every change that is attempting to land into the Rust
  compiler is tested against the kernel, and it is merged only if it
  passes. Similarly, the bindgen tool has agreed to build the kernel in
  their CI too.

  Thus, with the pre-merge CI in place, both projects hope to avoid
  unintentional changes to Rust that break the kernel. This means that,
  in general, apart from intentional changes on their side (that we will
  need to workaround conditionally on our side), the upcoming Rust
  compiler versions should generally work.

  In addition, the Rust project has proposed getting the kernel into
  stable Rust (at least solving the main blockers) as one of its three
  flagship goals for 2024H2 [1].

  I would like to thank Niko, Sid, Emilio et al. for their help
  promoting the collaboration between Rust and the kernel.

  Toolchain and infrastructure:

   - Support several Rust toolchain versions.

   - Support several bindgen versions.

   - Remove 'cargo' requirement and simplify 'rusttest', thanks to
     'alloc' having been dropped last cycle.

   - Provide proper error reporting for the 'rust-analyzer' target.

  'kernel' crate:

   - Add 'uaccess' module with a safe userspace pointers abstraction.

   - Add 'page' module with a 'struct page' abstraction.

   - Support more complex generics in workqueue's 'impl_has_work!'
     macro.

  'macros' crate:

   - Add 'firmware' field support to the 'module!' macro.

   - Improve 'module!' macro documentation.

  Documentation:

   - Provide instructions on what packages should be installed to build
     the kernel in some popular Linux distributions.

   - Introduce the new kernel.org LLVM+Rust toolchains.

   - Explain '#[no_std]'.

  And a few other small bits"

Link: https://rust-lang.github.io/rust-project-goals/2024h2/index.html#flagship-goals [1]

* tag 'rust-6.11' of https://github.com/Rust-for-Linux/linux: (26 commits)
  docs: rust: quick-start: add section on Linux distributions
  rust: warn about `bindgen` versions 0.66.0 and 0.66.1
  rust: start supporting several `bindgen` versions
  rust: work around `bindgen` 0.69.0 issue
  rust: avoid assuming a particular `bindgen` build
  rust: start supporting several compiler versions
  rust: simplify Clippy warning flags set
  rust: relax most deny-level lints to warnings
  rust: allow `dead_code` for never constructed bindings
  rust: init: simplify from `map_err` to `inspect_err`
  rust: macros: indent list item in `paste!`'s docs
  rust: add abstraction for `struct page`
  rust: uaccess: add typed accessors for userspace pointers
  uaccess: always export _copy_[from|to]_user with CONFIG_RUST
  rust: uaccess: add userspace pointers
  kbuild: rust-analyzer: improve comment documentation
  kbuild: rust-analyzer: better error handling
  docs: rust: no_std is used
  rust: alloc: add __GFP_HIGHMEM flag
  rust: alloc: fix typo in docs for GFP_NOWAIT
  ...

1 files changed, 32 insertions, 14 deletions

diff --git a/include/linux/uaccess.h b/include/linux/uaccess.h
index 3064314f4832..d8e4105a2f21 100644
--- a/include/linux/uaccess.h
+++ b/include/linux/uaccess.h
@@ -5,6 +5,7 @@
 #include <linux/fault-inject-usercopy.h>
 #include <linux/instrumented.h>
 #include <linux/minmax.h>
+#include <linux/nospec.h>
 #include <linux/sched.h>
 #include <linux/thread_info.h>
 
@@ -138,13 +139,26 @@ __copy_to_user(void __user *to, const void *from, unsigned long n)
 	return raw_copy_to_user(to, from, n);
 }
 
-#ifdef INLINE_COPY_FROM_USER
+/*
+ * Architectures that #define INLINE_COPY_TO_USER use this function
+ * directly in the normal copy_to/from_user(), the other ones go
+ * through an extern _copy_to/from_user(), which expands the same code
+ * here.
+ *
+ * Rust code always uses the extern definition.
+ */
 static inline __must_check unsigned long
-_copy_from_user(void *to, const void __user *from, unsigned long n)
+_inline_copy_from_user(void *to, const void __user *from, unsigned long n)
 {
 	unsigned long res = n;
 	might_fault();
 	if (!should_fail_usercopy() && likely(access_ok(from, n))) {
+		/*
+		 * Ensure that bad access_ok() speculation will not
+		 * lead to nasty side effects *after* the copy is
+		 * finished:
+		 */
+		barrier_nospec();
 		instrument_copy_from_user_before(to, from, n);
 		res = raw_copy_from_user(to, from, n);
 		instrument_copy_from_user_after(to, from, n, res);
@@ -153,14 +167,11 @@ _copy_from_user(void *to, const void __user *from, unsigned long n)
 		memset(to + (n - res), 0, res);
 	return res;
 }
-#else
 extern __must_check unsigned long
 _copy_from_user(void *, const void __user *, unsigned long);
-#endif
 
-#ifdef INLINE_COPY_TO_USER
 static inline __must_check unsigned long
-_copy_to_user(void __user *to, const void *from, unsigned long n)
+_inline_copy_to_user(void __user *to, const void *from, unsigned long n)
 {
 	might_fault();
 	if (should_fail_usercopy())
@@ -171,25 +182,32 @@ _copy_to_user(void __user *to, const void *from, unsigned long n)
 	}
 	return n;
 }
-#else
 extern __must_check unsigned long
 _copy_to_user(void __user *, const void *, unsigned long);
-#endif
 
 static __always_inline unsigned long __must_check
 copy_from_user(void *to, const void __user *from, unsigned long n)
 {
-	if (check_copy_size(to, n, false))
-		n = _copy_from_user(to, from, n);
-	return n;
+	if (!check_copy_size(to, n, false))
+		return n;
+#ifdef INLINE_COPY_FROM_USER
+	return _inline_copy_from_user(to, from, n);
+#else
+	return _copy_from_user(to, from, n);
+#endif
 }
 
 static __always_inline unsigned long __must_check
 copy_to_user(void __user *to, const void *from, unsigned long n)
 {
-	if (check_copy_size(from, n, true))
-		n = _copy_to_user(to, from, n);
-	return n;
+	if (!check_copy_size(from, n, true))
+		return n;
+
+#ifdef INLINE_COPY_TO_USER
+	return _inline_copy_to_user(to, from, n);
+#else
+	return _copy_to_user(to, from, n);
+#endif
 }
 
 #ifndef copy_mc_to_kernel