From 5febf432df1cfa5b25d99b54c32103fafbdd0eb9 Mon Sep 17 00:00:00 2001 From: Miguel Ojeda Date: Sun, 16 Aug 2026 15:32:33 +0200 Subject: kbuild: rust: keep Rust objects out of Clang LTO with inline helpers 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 Cc: Boqun Feng Cc: Alice Ryhl Cc: Matthew Maurer Cc: Josh Poimboeuf Cc: Peter Zijlstra Cc: stable@vger.kernel.org Fixes: 3a2486cc1da5 ("kbuild: rust: provide an option to inline C helpers into Rust") Acked-by: Gary Guo Link: https://patch.msgid.link/20260816133233.197500-2-ojeda@kernel.org Signed-off-by: Miguel Ojeda --- arch/microblaze/lib/modsi3.S | 74 ++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 74 insertions(+) create mode 100644 arch/microblaze/lib/modsi3.S (limited to 'arch/microblaze/lib/modsi3.S') diff --git a/arch/microblaze/lib/modsi3.S b/arch/microblaze/lib/modsi3.S new file mode 100644 index 000000000..64154865c --- /dev/null +++ b/arch/microblaze/lib/modsi3.S @@ -0,0 +1,74 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#include + +/* +* modulo operation for 32 bit integers. +* Input : op1 in Reg r5 +* op2 in Reg r6 +* Output: op1 mod op2 in Reg r3 +*/ + + .text + .globl __modsi3 + .type __modsi3, @function + .ent __modsi3 + +__modsi3: + .frame r1, 0, r15 + + addik r1, r1, -16 + swi r28, r1, 0 + swi r29, r1, 4 + swi r30, r1, 8 + swi r31, r1, 12 + + beqi r6, div_by_zero /* div_by_zero division error */ + beqi r5, result_is_zero /* result is zero */ + bgeid r5, r5_pos + /* get the sign of the result [ depends only on the first arg] */ + add r28, r5, r0 + rsubi r5, r5, 0 /* make r5 positive */ +r5_pos: + bgei r6, r6_pos + rsubi r6, r6, 0 /* make r6 positive */ +r6_pos: + addik r3, r0, 0 /* clear mod */ + addik r30, r0, 0 /* clear div */ + addik r29, r0, 32 /* initialize the loop count */ +/* first part try to find the first '1' in the r5 */ +div1: + add r5, r5, r5 /* left shift logical r5 */ + bgeid r5, div1 + addik r29, r29, -1 +div2: + /* left shift logical r5 get the '1' into the carry */ + add r5, r5, r5 + addc r3, r3, r3 /* move that bit into the mod register */ + rsub r31, r6, r3 /* try to subtract (r30 a r6) */ + blti r31, mod_too_small + /* move the r31 to mod since the result was positive */ + or r3, r0, r31 + addik r30, r30, 1 +mod_too_small: + addik r29, r29, -1 + beqi r29, loop_end + add r30, r30, r30 /* shift in the '1' into div */ + bri div2 /* div2 */ +loop_end: + bgei r28, return_here + brid return_here + rsubi r3, r3, 0 /* negate the result */ +div_by_zero: +result_is_zero: + or r3, r0, r0 /* set result to 0 [both mod as well as div are 0] */ +return_here: +/* restore values of csrs and that of r3 and the divisor and the dividend */ + lwi r28, r1, 0 + lwi r29, r1, 4 + lwi r30, r1, 8 + lwi r31, r1, 12 + rtsd r15, 8 + addik r1, r1, 16 + +.size __modsi3, . - __modsi3 +.end __modsi3 -- cgit v1.3.1