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/arm/lib/memset.S | 148 ++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 148 insertions(+) create mode 100644 arch/arm/lib/memset.S (limited to 'arch/arm/lib/memset.S') diff --git a/arch/arm/lib/memset.S b/arch/arm/lib/memset.S new file mode 100644 index 000000000..de75ae4d5 --- /dev/null +++ b/arch/arm/lib/memset.S @@ -0,0 +1,148 @@ +/* SPDX-License-Identifier: GPL-2.0-only */ +/* + * linux/arch/arm/lib/memset.S + * + * Copyright (C) 1995-2000 Russell King + * + * ASM optimised string functions + */ +#include +#include +#include + + .text + .align 5 + +ENTRY(__memset) +ENTRY(mmioset) +WEAK(memset) +UNWIND( .fnstart ) + and r1, r1, #255 @ cast to unsigned char + ands r3, r0, #3 @ 1 unaligned? + mov ip, r0 @ preserve r0 as return value + bne 6f @ 1 +/* + * we know that the pointer in ip is aligned to a word boundary. + */ +1: orr r1, r1, r1, lsl #8 + orr r1, r1, r1, lsl #16 + mov r3, r1 +7: cmp r2, #16 + blt 4f +UNWIND( .fnend ) + +#if ! CALGN(1)+0 + +/* + * We need 2 extra registers for this loop - use r8 and the LR + */ +UNWIND( .fnstart ) +UNWIND( .save {r8, lr} ) + stmfd sp!, {r8, lr} + mov r8, r1 + mov lr, r3 + +2: subs r2, r2, #64 + stmiage ip!, {r1, r3, r8, lr} @ 64 bytes at a time. + stmiage ip!, {r1, r3, r8, lr} + stmiage ip!, {r1, r3, r8, lr} + stmiage ip!, {r1, r3, r8, lr} + bgt 2b + ldmfdeq sp!, {r8, pc} @ Now <64 bytes to go. +/* + * No need to correct the count; we're only testing bits from now on + */ + tst r2, #32 + stmiane ip!, {r1, r3, r8, lr} + stmiane ip!, {r1, r3, r8, lr} + tst r2, #16 + stmiane ip!, {r1, r3, r8, lr} + ldmfd sp!, {r8, lr} +UNWIND( .fnend ) + +#else + +/* + * This version aligns the destination pointer in order to write + * whole cache lines at once. + */ + +UNWIND( .fnstart ) +UNWIND( .save {r4-r8, lr} ) + stmfd sp!, {r4-r8, lr} + mov r4, r1 + mov r5, r3 + mov r6, r1 + mov r7, r3 + mov r8, r1 + mov lr, r3 + + cmp r2, #96 + tstgt ip, #31 + ble 3f + + and r8, ip, #31 + rsb r8, r8, #32 + sub r2, r2, r8 + movs r8, r8, lsl #(32 - 4) + stmiacs ip!, {r4, r5, r6, r7} + stmiami ip!, {r4, r5} + tst r8, #(1 << 30) + mov r8, r1 + strne r1, [ip], #4 + +3: subs r2, r2, #64 + stmiage ip!, {r1, r3-r8, lr} + stmiage ip!, {r1, r3-r8, lr} + bgt 3b + ldmfdeq sp!, {r4-r8, pc} + + tst r2, #32 + stmiane ip!, {r1, r3-r8, lr} + tst r2, #16 + stmiane ip!, {r4-r7} + ldmfd sp!, {r4-r8, lr} +UNWIND( .fnend ) + +#endif + +UNWIND( .fnstart ) +4: tst r2, #8 + stmiane ip!, {r1, r3} + tst r2, #4 + strne r1, [ip], #4 +/* + * When we get here, we've got less than 4 bytes to set. We + * may have an unaligned pointer as well. + */ +5: tst r2, #2 + strbne r1, [ip], #1 + strbne r1, [ip], #1 + tst r2, #1 + strbne r1, [ip], #1 + ret lr + +6: subs r2, r2, #4 @ 1 do we have enough + blt 5b @ 1 bytes to align with? + cmp r3, #2 @ 1 + strblt r1, [ip], #1 @ 1 + strble r1, [ip], #1 @ 1 + strb r1, [ip], #1 @ 1 + add r2, r2, r3 @ 1 (r2 = r2 - (4 - r3)) + b 1b +UNWIND( .fnend ) +ENDPROC(memset) +ENDPROC(mmioset) +ENDPROC(__memset) + +ENTRY(__memset32) +UNWIND( .fnstart ) + mov r3, r1 @ copy r1 to r3 and fall into memset64 +UNWIND( .fnend ) +ENDPROC(__memset32) +ENTRY(__memset64) +UNWIND( .fnstart ) + mov ip, r0 @ preserve r0 as return value + b 7b @ jump into the middle of memset +UNWIND( .fnend ) +ENDPROC(__memset64) -- cgit v1.3.1