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/xtensa/Kconfig.debug | 48 +++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 48 insertions(+) create mode 100644 arch/xtensa/Kconfig.debug (limited to 'arch/xtensa/Kconfig.debug') diff --git a/arch/xtensa/Kconfig.debug b/arch/xtensa/Kconfig.debug new file mode 100644 index 000000000..e84172a77 --- /dev/null +++ b/arch/xtensa/Kconfig.debug @@ -0,0 +1,48 @@ +# SPDX-License-Identifier: GPL-2.0 + +config DEBUG_TLB_SANITY + bool "Debug TLB sanity" + depends on DEBUG_KERNEL && MMU + help + Enable this to turn on TLB sanity check on each entry to userspace. + This check can spot missing TLB invalidation/wrong PTE permissions/ + premature page freeing. + + If unsure, say N. + +config LD_NO_RELAX + bool "Disable linker relaxation" + default y + help + Enable this function to disable link-time optimizations. + The default linker behavior is to combine identical literal + values to reduce code size and remove unnecessary overhead from + assembler-generated 'longcall' sequences. + Enabling this option improves the link time but increases the + code size, and possibly execution time. + +config S32C1I_SELFTEST + bool "Perform S32C1I instruction self-test at boot" + default y + help + Enable this option to test S32C1I instruction behavior at boot. + Correct operation of this instruction requires some cooperation from hardware + external to the processor (such as bus bridge, bus fabric, or memory controller). + It is easy to make wrong hardware configuration, this test should catch it early. + + Say 'N' on stable hardware. + +config PRINT_STACK_DEPTH + int "Stack depth to print" if DEBUG_KERNEL + default 64 + help + This option allows you to set the stack depth that the kernel + prints in stack traces. + +config PRINT_USER_CODE_ON_UNHANDLED_EXCEPTION + bool "Dump user code around unhandled exception address" + help + Enable this option to display user code around PC of the unhandled + exception (starting at address aligned on 16 byte boundary). + This may simplify finding faulting code in the absence of other + debug facilities. -- cgit v1.3.1