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| author | Miguel Ojeda <ojeda@kernel.org> | 2026-08-16 15:32:33 +0200 |
|---|---|---|
| committer | Miguel Ojeda <ojeda@kernel.org> | 2026-08-23 21:27:17 +0200 |
| commit | 5febf432df1cfa5b25d99b54c32103fafbdd0eb9 (patch) | |
| tree | 93a1ed1d337bc53adf1e572c2586d347703b286e /arch/microblaze/lib/mulsi3.S | |
| download | linux-stable-5febf432df1cfa5b25d99b54c32103fafbdd0eb9.tar.gz linux-stable-5febf432df1cfa5b25d99b54c32103fafbdd0eb9.zip | |
kbuild: rust: keep Rust objects out of Clang LTO with inline helpersgrafted
Under `CONFIG_LTO_CLANG` + `CONFIG_RUST_INLINE_HELPERS`, one may hit
`objtool` errors such as:
vmlinux.o: error: objtool: _R..._3Gsp4boot+0xd6a:
can't find jump dest instruction at .text._R..._3Gsp4boot+0x1dfd
The reason is that in such builds, the Clang invocation that compiles
the combined Rust plus helpers bitcode emits LLVM bitcode (again) --
the final code generation happens in the linker's LTO step, which the
`-mllvm` trap options passed to Clang do not reach.
This, in turn, means that unreachable traps are missing, and the
impossible paths do not merely fallthrough to the next symbol, but past
the end of their own section, since LTO builds place each function in
its own section.
Thus filter `CC_FLAGS_LTO` out of the Clang invocation, so that it always
emits machine code directly, with the traps in place.
Assisted-by: LLM
Cc: Gary Guo <gary@garyguo.net>
Cc: Boqun Feng <boqun@kernel.org>
Cc: Alice Ryhl <aliceryhl@google.com>
Cc: Matthew Maurer <mmaurer@google.com>
Cc: Josh Poimboeuf <jpoimboe@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: stable@vger.kernel.org
Fixes: 3a2486cc1da5 ("kbuild: rust: provide an option to inline C helpers into Rust")
Acked-by: Gary Guo <gary@garyguo.net>
Link: https://patch.msgid.link/20260816133233.197500-2-ojeda@kernel.org
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
Diffstat (limited to 'arch/microblaze/lib/mulsi3.S')
| -rw-r--r-- | arch/microblaze/lib/mulsi3.S | 47 |
1 files changed, 47 insertions, 0 deletions
diff --git a/arch/microblaze/lib/mulsi3.S b/arch/microblaze/lib/mulsi3.S new file mode 100644 index 000000000..d6703a4d9 --- /dev/null +++ b/arch/microblaze/lib/mulsi3.S @@ -0,0 +1,47 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#include <linux/linkage.h> + +/* + * Multiply operation for 32 bit integers. + * Input : Operand1 in Reg r5 + * Operand2 in Reg r6 + * Output: Result [op1 * op2] in Reg r3 + */ + .text + .globl __mulsi3 + .type __mulsi3, @function + .ent __mulsi3 + +__mulsi3: + .frame r1, 0, r15 + add r3, r0, r0 + beqi r5, result_is_zero /* multiply by zero */ + beqi r6, result_is_zero /* multiply by zero */ + bgeid r5, r5_pos + xor r4, r5, r6 /* get the sign of the result */ + rsubi r5, r5, 0 /* make r5 positive */ +r5_pos: + bgei r6, r6_pos + rsubi r6, r6, 0 /* make r6 positive */ +r6_pos: + bri l1 +l2: + add r5, r5, r5 +l1: + srl r6, r6 + addc r7, r0, r0 + beqi r7, l2 + bneid r6, l2 + add r3, r3, r5 + blti r4, negateresult + rtsd r15, 8 + nop +negateresult: + rtsd r15, 8 + rsub r3, r3, r0 +result_is_zero: + rtsd r15, 8 + addi r3, r0, 0 + +.size __mulsi3, . - __mulsi3 +.end __mulsi3 |