From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pf1-f178.google.com (mail-pf1-f178.google.com [209.85.210.178]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id A59E32C9D for ; Fri, 17 Apr 2026 15:23:36 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.210.178 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776439418; cv=none; b=iA9EWdPo2PJjChqvT+JIt49AROlTs8YgunVQJ3F4qaQreX64d6gPCpaQch0BTwIBExIUCEuLXmzl2GbxRa0mgxyKvmW6XBq23YqBXp5H1R+bKtbq7n4sIC/PKJglUViKbXFxvSyMIXMUwURHgo658QX1xqxmwpM1NuqNVR1huzQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776439418; c=relaxed/simple; bh=5FTPUPuJVsTLpqcjhVFxeZpAV4lxrHWidC31zn6JrrU=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=pj9UKqv3nDyhfz+ESYWvwvxIl7TG9pQBP3OwGcTUBkaf+a9ovnqZkHABricOp1UrZ2ijWSRwFCMDuNXi2wqYO5jM+Wh3AAtpObJtBnWKlUEYtdAobO2ilPZ+WGCGyTynsDKkigN8aXhy/xE6/9WLgzBJMNiaOZfT0Q56Fvf6WMc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=IgmAB3ge; arc=none smtp.client-ip=209.85.210.178 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="IgmAB3ge" Received: by mail-pf1-f178.google.com with SMTP id d2e1a72fcca58-827270d50d4so748444b3a.3 for ; Fri, 17 Apr 2026 08:23:36 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20251104; t=1776439416; x=1777044216; darn=lists.linux.dev; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=DwPvJVxOydbYWn8IiNW1x83FpaENNDbiz2YSZJBpMak=; b=IgmAB3gexvgemkBn3qmZ1YQetEjNU1HQGmiZ43CKjMvxOcdStTesLpFZJdvrZZNH1Y tEYeAbz7gdsoNXWQmrJiwcMx558qc1vhHR5ieUKF40PM6mzuB36q5dUyidmxvC59P7So 9zJ4qwCMmtc7DgJBppi7IBdcsl0+6b2zWQ8AFYTxIIqFz77x3wasNqYcHTtBY3l1DrqR zWSP5AwdP/utFDEgQw876dHm1A4IFVkt9tTfQPlUnYColzWl3ptYPtuH0nmNlDxP5OoG R3HNwFrlYM5EJWp9HnVDMjkntky3YOpOnqYG7yw+/RGS3zkPaQbDTOGXY5N0bfwgLPnC 202A== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1776439416; x=1777044216; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-gg:x-gm-message-state:from :to:cc:subject:date:message-id:reply-to; bh=DwPvJVxOydbYWn8IiNW1x83FpaENNDbiz2YSZJBpMak=; b=OgKSGEBFpZXgoJi/uMyHJaRBfsyQGne70SmLhHP38mmCHumeG8hgTcDddbrtxTRW0c kO9mc1wCnV655KC5STcZq1HYipHIBkcMLotrBxu0O5/dZZApk5ZqYArmFlLKLQavhy2q tf87uTU+rSfrT5dQRmBH7BzN7Km4Pk7qf3mp2G13/SF5b2L03tC+PSfeFXGyhHobP003 qnQrID8i/1bVHRMGppO4CkY980pfSCWbOMqWfVYdd+hJLM6q3iHFWOTMpaCMhDK1DvXj fBfJVu9CAv55/OovZuwc6VAM/UhtUhQ8M78mjTZCS1V+tTeWJX14cypDl1E3FkTGGPi5 hwYg== X-Forwarded-Encrypted: i=1; AFNElJ/oihpzQr4U3/eOlbZLsiwQE9GiQQtG+zIMhxCirzWKJIFnCUbP96RWBLdedYm4DD3ir52y@lists.linux.dev X-Gm-Message-State: AOJu0YzecSjywnpLss4kHOgpM0vm8M/3te/PLBOFh+xbTP/6mUYfFMFR bFbQRy+jj5NhH1y6cZ2C+VgVuRcVvoCzgctf2mylGwB/cu7VezZptz3Q X-Gm-Gg: AeBDies5apim48tAdtVotH4VTvwswubCcb83wA7BLdH2YUM2grUzBpc/0x0jvL4U2Nl qqHZE74tSOL3pKRUNy2uUR0+cchJaNIyc/mJjMojiNrY19cxQQf3OAmU8Q1n6YPBS7uhGFce23G SrQdwMwdt6Owo0y8Sdnal3cnxGuC+uC20TjRT2SUMUX6PJv6RinBVKhsTF4D1b6suStbZbBKHS4 os+uQjZ6PNkwdj9szUZXon9l/8J9szx3wDE/jrHli6dll+3teumh+u0CbUivfAC5Dj0iu0avyzZ m2iDAbnbMpiQlaiUDj8earzpJ8dN2XjJgI9w2MdgEZa3xW+YuGkKRG1QZFumoVxbN7WBNlIEJPr dMYjcd7ibrG/68zHmecGvgxx2NQ8240JC5IqRhpE8gGW7zoPN5dvoQqtvMC2oEvhx/tOFWy6nbG PcY72fgP9p5usOWXJqh2hRgfwuWj/zXhZ79kuiomVljIZn8HpgHBT0GZd4IX4KXfbFpBg8jNrjS f136/mvRrDzOTc= X-Received: by 2002:a05:6a00:4c86:b0:82f:7076:cf2b with SMTP id d2e1a72fcca58-82f8c90ba46mr3696324b3a.40.1776439415810; Fri, 17 Apr 2026 08:23:35 -0700 (PDT) Received: from li-1a3e774c-28e4-11b2-a85c-acc9f2883e29.ibm.com.com ([106.51.164.157]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-82f8ebb3829sm2384373b3a.31.2026.04.17.08.23.26 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 17 Apr 2026 08:23:35 -0700 (PDT) From: "Mukesh Kumar Chaurasiya (IBM)" To: maddy@linux.ibm.com, mpe@ellerman.id.au, npiggin@gmail.com, chleroy@kernel.org, peterz@infradead.org, jpoimboe@kernel.org, jbaron@akamai.com, aliceryhl@google.com, rostedt@goodmis.org, ardb@kernel.org, ojeda@kernel.org, boqun@kernel.org, gary@garyguo.net, bjorn3_gh@protonmail.com, lossin@kernel.org, a.hindborg@kernel.org, tmgross@umich.edu, dakr@kernel.org, nathan@kernel.org, nick.desaulniers+lkml@gmail.com, morbo@google.com, justinstitt@google.com, linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, rust-for-linux@vger.kernel.org, llvm@lists.linux.dev Cc: "Mukesh Kumar Chaurasiya (IBM)" Subject: [PATCH V11 1/4] rust: Fix "multiple candidates for rmeta dependency core" error Date: Fri, 17 Apr 2026 20:52:50 +0530 Message-ID: <20260417152253.2312961-2-mkchauras@gmail.com> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260417152253.2312961-1-mkchauras@gmail.com> References: <20260417152253.2312961-1-mkchauras@gmail.com> Precedence: bulk X-Mailing-List: llvm@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit When building Rust code for powerpc64le with LLVM=1 and -j1, rustc encounters an error: "multiple candidates for `rmeta` dependency `core` found", with two candidates: 1. The host's standard library from the rustup toolchain 2. The kernel's custom libcore.rmeta in the rust/ directory This occurs because the build system uses `-L$(objtree)/rust` for host library builds (proc_macro2, quote, syn), which causes rustc to search the rust/ directory. During this search, rustc finds both the kernel's custom libcore.rmeta and gains access to the host's standard library, creating a conflict. The solution is to separate host libraries into a dedicated rust/host/ subdirectory and use `-L$(objtree)/rust/host` for host builds instead of `-L$(objtree)/rust`. This ensures that: 1. Host library builds (proc_macro2, quote, syn) only search rust/host/ and never encounter the kernel's libcore.rmeta 2. Proc macro builds use `-L$(objtree)/rust/host` to find their dependencies Special handling is added for rustdoc-pin_init, which is a host build (to access the alloc crate) but depends on proc macros from the main rust/ directory. It uses explicit `--extern` paths to reference the proc macros without adding `-L$(objtree)/rust`, which would reintroduce the conflict. The rust/host/ directory is added to clean-files to ensure it's removed during `make clean`. Link: https://github.com/Rust-for-Linux/linux/issues/105 Link: https://github.com/linuxppc/issues/issues/451 Signed-off-by: Mukesh Kumar Chaurasiya (IBM) --- rust/Makefile | 38 +++++++++++++++++++++----------------- 1 file changed, 21 insertions(+), 17 deletions(-) diff --git a/rust/Makefile b/rust/Makefile index 9801af2e1e02..e234b8a39358 100644 --- a/rust/Makefile +++ b/rust/Makefile @@ -3,6 +3,9 @@ # Where to place rustdoc generated documentation rustdoc_output := $(objtree)/Documentation/output/rust/rustdoc +# Clean generated host directory +clean-files := host/ + obj-$(CONFIG_RUST) += core.o compiler_builtins.o ffi.o always-$(CONFIG_RUST) += exports_core_generated.h @@ -27,7 +30,7 @@ endif obj-$(CONFIG_RUST) += exports.o -always-$(CONFIG_RUST) += libproc_macro2.rlib libquote.rlib libsyn.rlib +always-$(CONFIG_RUST) += host/libproc_macro2.rlib host/libquote.rlib host/libsyn.rlib always-$(CONFIG_RUST_KERNEL_DOCTESTS) += doctests_kernel_generated.rs always-$(CONFIG_RUST_KERNEL_DOCTESTS) += doctests_kernel_generated_kunit.c @@ -150,7 +153,7 @@ quiet_cmd_rustdoc = RUSTDOC $(if $(rustdoc_host),H, ) $< OBJTREE=$(abspath $(objtree)) \ $(RUSTDOC) $(filter-out $(skip_flags) --remap-path-prefix=% --remap-path-scope=%, \ $(if $(rustdoc_host),$(rust_common_flags),$(rust_flags))) \ - $(rustc_target_flags) -L$(objtree)/$(obj) \ + $(rustc_target_flags) -L$(objtree)/$(obj)$(if $(rustdoc_host),/host) \ -Zunstable-options --generate-link-to-definition \ --output $(rustdoc_output) \ --crate-name $(subst rustdoc-,,$@) \ @@ -237,6 +240,7 @@ rustdoc-pin_init_internal: $(src)/pin-init/internal/src/lib.rs \ rustdoc-pin_init: private rustdoc_host = yes rustdoc-pin_init: private rustc_target_flags = $(pin_init-flags) \ + --extern pin_init_internal=$(objtree)/$(obj)/$(libpin_init_internal_name) \ --extern alloc --cfg feature=\"alloc\" rustdoc-pin_init: $(src)/pin-init/src/lib.rs rustdoc-pin_init_internal \ rustdoc-macros FORCE @@ -528,23 +532,23 @@ quiet_cmd_rustc_procmacrolibrary = $(RUSTC_OR_CLIPPY_QUIET) PL $@ $(if $(skip_clippy),$(RUSTC),$(RUSTC_OR_CLIPPY)) \ $(filter-out $(skip_flags),$(rust_common_flags) $(rustc_target_flags)) \ --emit=dep-info=$(depfile) --emit=link=$@ --crate-type rlib -O \ - --out-dir $(objtree)/$(obj) -L$(objtree)/$(obj) \ + --out-dir $(objtree)/$(obj)/host -\L$(objtree)/$(obj)/host \ --crate-name $(patsubst lib%.rlib,%,$(notdir $@)) $< -$(obj)/libproc_macro2.rlib: private skip_clippy = 1 -$(obj)/libproc_macro2.rlib: private rustc_target_flags = $(proc_macro2-flags) -$(obj)/libproc_macro2.rlib: $(src)/proc-macro2/lib.rs FORCE +$(obj)/host/libproc_macro2.rlib: private skip_clippy = 1 +$(obj)/host/libproc_macro2.rlib: private rustc_target_flags = $(proc_macro2-flags) +$(obj)/host/libproc_macro2.rlib: $(src)/proc-macro2/lib.rs FORCE +$(call if_changed_dep,rustc_procmacrolibrary) -$(obj)/libquote.rlib: private skip_clippy = 1 -$(obj)/libquote.rlib: private skip_flags = $(quote-skip_flags) -$(obj)/libquote.rlib: private rustc_target_flags = $(quote-flags) -$(obj)/libquote.rlib: $(src)/quote/lib.rs $(obj)/libproc_macro2.rlib FORCE +$(obj)/host/libquote.rlib: private skip_clippy = 1 +$(obj)/host/libquote.rlib: private skip_flags = $(quote-skip_flags) +$(obj)/host/libquote.rlib: private rustc_target_flags = $(quote-flags) +$(obj)/host/libquote.rlib: $(src)/quote/lib.rs $(obj)/host/libproc_macro2.rlib FORCE +$(call if_changed_dep,rustc_procmacrolibrary) -$(obj)/libsyn.rlib: private skip_clippy = 1 -$(obj)/libsyn.rlib: private rustc_target_flags = $(syn-flags) -$(obj)/libsyn.rlib: $(src)/syn/lib.rs $(obj)/libquote.rlib FORCE +$(obj)/host/libsyn.rlib: private skip_clippy = 1 +$(obj)/host/libsyn.rlib: private rustc_target_flags = $(syn-flags) +$(obj)/host/libsyn.rlib: $(src)/syn/lib.rs $(obj)/host/libquote.rlib FORCE +$(call if_changed_dep,rustc_procmacrolibrary) quiet_cmd_rustc_procmacro = $(RUSTC_OR_CLIPPY_QUIET) P $@ @@ -553,20 +557,20 @@ quiet_cmd_rustc_procmacro = $(RUSTC_OR_CLIPPY_QUIET) P $@ -Clinker-flavor=gcc -Clinker=$(HOSTCC) \ -Clink-args='$(call escsq,$(KBUILD_PROCMACROLDFLAGS))' \ --emit=dep-info=$(depfile) --emit=link=$@ --extern proc_macro \ - --crate-type proc-macro -L$(objtree)/$(obj) \ + --crate-type proc-macro -L$(objtree)/$(obj)/host \ --crate-name $(patsubst lib%.$(libmacros_extension),%,$(notdir $@)) \ @$(objtree)/include/generated/rustc_cfg $< # Procedural macros can only be used with the `rustc` that compiled it. $(obj)/$(libmacros_name): private rustc_target_flags = \ --extern proc_macro2 --extern quote --extern syn -$(obj)/$(libmacros_name): $(src)/macros/lib.rs $(obj)/libproc_macro2.rlib \ - $(obj)/libquote.rlib $(obj)/libsyn.rlib FORCE +$(obj)/$(libmacros_name): $(src)/macros/lib.rs $(obj)/host/libproc_macro2.rlib \ + $(obj)/host/libquote.rlib $(obj)/host/libsyn.rlib FORCE +$(call if_changed_dep,rustc_procmacro) $(obj)/$(libpin_init_internal_name): private rustc_target_flags = $(pin_init_internal-flags) $(obj)/$(libpin_init_internal_name): $(src)/pin-init/internal/src/lib.rs \ - $(obj)/libproc_macro2.rlib $(obj)/libquote.rlib $(obj)/libsyn.rlib FORCE + $(obj)/host/libproc_macro2.rlib $(obj)/host/libquote.rlib $(obj)/host/libsyn.rlib FORCE +$(call if_changed_dep,rustc_procmacro) # `rustc` requires `-Zunstable-options` to use custom target specifications -- 2.53.0