From 70a57b247251aabadd67795c3097c0fcc616e533 Mon Sep 17 00:00:00 2001 From: Miguel Ojeda Date: Tue, 9 Apr 2024 18:25:16 +0100 Subject: RISC-V: enable building 64-bit kernels with rust support The rust modules work on 64-bit RISC-V, with no twiddling required. Select HAVE_RUST and provide the required flags to kbuild so that the modules can be used. The Makefile and Kconfig changes are lifted from work done by Miguel in the Rust-for-Linux tree, hence his authorship. Following the rabbit hole, the Makefile changes originated in a script, created based on config files originally added by Gary, hence his co-authorship. 32-bit is broken in core rust code, so support is limited to 64-bit: ld.lld: error: undefined symbol: __udivdi3 As 64-bit RISC-V is now supported, add it to the arch support table. Co-developed-by: Gary Guo Signed-off-by: Gary Guo Signed-off-by: Miguel Ojeda Co-developed-by: Conor Dooley Signed-off-by: Conor Dooley Link: https://lore.kernel.org/r/20240409-silencer-book-ce1320f06aab@spud Signed-off-by: Palmer Dabbelt --- scripts/generate_rust_target.rs | 6 ++++++ 1 file changed, 6 insertions(+) (limited to 'scripts/generate_rust_target.rs') diff --git a/scripts/generate_rust_target.rs b/scripts/generate_rust_target.rs index 54919cf48621..8f7846b9029a 100644 --- a/scripts/generate_rust_target.rs +++ b/scripts/generate_rust_target.rs @@ -150,6 +150,12 @@ fn main() { // `llvm-target`s are taken from `scripts/Makefile.clang`. if cfg.has("ARM64") { panic!("arm64 uses the builtin rustc aarch64-unknown-none target"); + } else if cfg.has("RISCV") { + if cfg.has("64BIT") { + panic!("64-bit RISC-V uses the builtin rustc riscv64-unknown-none-elf target"); + } else { + panic!("32-bit RISC-V is an unsupported architecture"); + } } else if cfg.has("X86_64") { ts.push("arch", "x86_64"); ts.push( -- cgit From 56f64b370612d8967df2c2e0cead805444d4e71a Mon Sep 17 00:00:00 2001 From: Miguel Ojeda Date: Mon, 1 Apr 2024 23:23:03 +0200 Subject: rust: upgrade to Rust 1.78.0 This is the next upgrade to the Rust toolchain, from 1.77.1 to 1.78.0 (i.e. the latest) [1]. See the upgrade policy [2] and the comments on the first upgrade in commit 3ed03f4da06e ("rust: upgrade to Rust 1.68.2"). It is much smaller than previous upgrades, since the `alloc` fork was dropped in commit 9d0441bab775 ("rust: alloc: remove our fork of the `alloc` crate") [3]. # Unstable features There have been no changes to the set of unstable features used in our own code. Therefore, the only unstable features allowed to be used outside the `kernel` crate is still `new_uninit`. However, since we finally dropped our `alloc` fork [3], all the unstable features used by `alloc` (~30 language ones, ~60 library ones) are not a concern anymore. This reduces the maintenance burden, increases the chances of new compiler versions working without changes and gets us closer to the goal of supporting several compiler versions. It also means that, ignoring non-language/library features, we are currently left with just the few language features needed to implement the kernel `Arc`, the `new_uninit` library feature, the `compiler_builtins` marker and the few `no_*` `cfg`s we pass when compiling `core`/`alloc`. Please see [4] for details. # Required changes ## LLVM's data layout Rust 1.77.0 (i.e. the previous upgrade) introduced a check for matching LLVM data layouts [5]. Then, Rust 1.78.0 upgraded LLVM's bundled major version from 17 to 18 [6], which changed the data layout in x86 [7]. Thus update the data layout in our custom target specification for x86 so that the compiler does not complain about the mismatch: error: data-layout for target `target-5559158138856098584`, `e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128`, differs from LLVM target's `x86_64-linux-gnu` default layout, `e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-i128:128-f80:128-n8:16:32:64-S128` In the future, the goal is to drop the custom target specifications. Meanwhile, if we want to support other LLVM versions used in `rustc` (e.g. for LTO), we will need to add some extra logic (e.g. conditional on LLVM's version, or extracting the data layout from an existing built-in target specification). ## `unused_imports` Rust's `unused_imports` lint covers both unused and redundant imports. Now, in 1.78.0, the lint detects more cases of redundant imports [8]. Thus one of the previous patches cleaned them up. ## Clippy's `new_without_default` Clippy now suggests to implement `Default` even when `new()` is `const`, since `Default::default()` may call `const` functions even if it is not `const` itself [9]. Thus one of the previous patches implemented it. # Other changes in Rust Rust 1.78.0 introduced `feature(asm_goto)` [10] [11]. This feature was discussed in the past [12]. Rust 1.78.0 introduced `feature(const_refs_to_static)` [13] to allow referencing statics in constants and extended `feature(const_mut_refs)` to allow raw mutable pointers in constants. Together, this should cover the kernel's `VTABLE` use case. In fact, the implementation [14] in upstream Rust added a test case for it [15]. Rust 1.78.0 with debug assertions enabled (i.e. `-Cdebug-assertions=y`, kernel's `CONFIG_RUST_DEBUG_ASSERTIONS=y`) now always checks all unsafe preconditions, though without a way to opt-out for particular cases [16]. It would be ideal to have a way to selectively disable certain checks per-call site for this one (i.e. not just per check but for particular instances of a check), even if the vast majority of the checks remain in place [17]. Rust 1.78.0 also improved a couple issues we reported when giving feedback for the new `--check-cfg` feature [18] [19]. # `alloc` upgrade and reviewing As mentioned above, compiler upgrades will not update `alloc` anymore, since we dropped our `alloc` fork [3]. Link: https://github.com/rust-lang/rust/blob/stable/RELEASES.md#version-1780-2024-05-02 [1] Link: https://rust-for-linux.com/rust-version-policy [2] Link: https://lore.kernel.org/rust-for-linux/20240328013603.206764-1-wedsonaf@gmail.com/ [3] Link: https://github.com/Rust-for-Linux/linux/issues/2 [4] Link: https://github.com/rust-lang/rust/pull/120062 [5] Link: https://github.com/rust-lang/rust/pull/120055 [6] Link: https://reviews.llvm.org/D86310 [7] Link: https://github.com/rust-lang/rust/pull/117772 [8] Link: https://github.com/rust-lang/rust-clippy/pull/10903 [9] Link: https://github.com/rust-lang/rust/pull/119365 [10] Link: https://github.com/rust-lang/rust/issues/119364 [11] Link: https://lore.kernel.org/rust-for-linux/ZWipTZysC2YL7qsq@Boquns-Mac-mini.home/ [12] Link: https://github.com/rust-lang/rust/issues/119618 [13] Link: https://github.com/rust-lang/rust/pull/120932 [14] Link: https://github.com/rust-lang/rust/pull/120932/files#diff-e6fc1622c46054cd46b1d225c5386c5554564b3b0fa8a03c2dc2d8627a1079d9 [15] Link: https://github.com/rust-lang/rust/issues/120969 [16] Link: https://github.com/Rust-for-Linux/linux/issues/354 [17] Link: https://github.com/rust-lang/rust/pull/121202 [18] Link: https://github.com/rust-lang/rust/pull/121237 [19] Reviewed-by: Alice Ryhl Link: https://lore.kernel.org/r/20240401212303.537355-4-ojeda@kernel.org [ Added a few more details and links I mentioned in the list. - Miguel ] Signed-off-by: Miguel Ojeda --- scripts/generate_rust_target.rs | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'scripts/generate_rust_target.rs') diff --git a/scripts/generate_rust_target.rs b/scripts/generate_rust_target.rs index 54919cf48621..3fcbc3737b2e 100644 --- a/scripts/generate_rust_target.rs +++ b/scripts/generate_rust_target.rs @@ -154,7 +154,7 @@ fn main() { ts.push("arch", "x86_64"); ts.push( "data-layout", - "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128", + "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-i128:128-f80:128-n8:16:32:64-S128", ); let mut features = "-3dnow,-3dnowa,-mmx,+soft-float".to_string(); if cfg.has("MITIGATION_RETPOLINE") { -- cgit From 8f8d74ee110c02137f5b78ca0a2bd6c10331f267 Mon Sep 17 00:00:00 2001 From: WANG Rui Date: Tue, 14 May 2024 12:24:18 +0800 Subject: LoongArch: rust: Switch to use built-in rustc target This commit switches to use the LoongArch's built-in rustc target 'loongarch64-unknown-none-softfloat'. The Rust samples have been tested. Acked-by: Miguel Ojeda Tested-by: Miguel Ojeda Signed-off-by: WANG Rui Signed-off-by: Huacai Chen --- scripts/generate_rust_target.rs | 7 +------ 1 file changed, 1 insertion(+), 6 deletions(-) (limited to 'scripts/generate_rust_target.rs') diff --git a/scripts/generate_rust_target.rs b/scripts/generate_rust_target.rs index 54919cf48621..acd3b1acef83 100644 --- a/scripts/generate_rust_target.rs +++ b/scripts/generate_rust_target.rs @@ -164,12 +164,7 @@ fn main() { ts.push("llvm-target", "x86_64-linux-gnu"); ts.push("target-pointer-width", "64"); } else if cfg.has("LOONGARCH") { - ts.push("arch", "loongarch64"); - ts.push("data-layout", "e-m:e-p:64:64-i64:64-i128:128-n64-S128"); - ts.push("features", "-f,-d"); - ts.push("llvm-target", "loongarch64-linux-gnusf"); - ts.push("llvm-abiname", "lp64s"); - ts.push("target-pointer-width", "64"); + panic!("loongarch uses the builtin rustc loongarch64-unknown-none-softfloat target"); } else { panic!("Unsupported architecture"); } -- cgit