From: "Mukesh Kumar Chaurasiya (IBM)" <mkchauras@gmail.com>
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)" <mkchauras@gmail.com>
Subject: [PATCH V10 1/4] rust: Separate host libraries to fix rmeta dependency conflict
Date: Tue, 7 Apr 2026 01:31:46 +0530 [thread overview]
Message-ID: <20260406200149.3727922-2-mkchauras@gmail.com> (raw)
In-Reply-To: <20260406200149.3727922-1-mkchauras@gmail.com>
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$(objtree)/rust` for host
library builds (proc_macro2, quote, syn), which causes rustc to search
the rust/ directory. During this search, rustc finds both the kernel's
custom libcore.rmeta and gains access to the host's standard library,
creating a conflict.
Separate all host-side build artifacts (host libraries and proc macros)
into a dedicated rust/host/ subdirectory and use `-L$(objtree)/rust/host`
for host builds. This ensures host builds only search rust/host/ and
never encounter the kernel's libcore.rmeta.
The `--out-dir` flag is removed from cmd_rustc_procmacrolibrary because
the output directory is now created explicitly with `mkdir -p $(dir $@)`
and the output file path is specified directly with `--emit=link=$@`,
making `--out-dir` redundant.
Moving the proc macros (libmacros and libpin_init_internal) to rust/host/
eliminates the need for special handling in rustdoc-pin_init, which can
now use the pin_init-flags variable directly instead of duplicating the
flags with absolute paths.
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) <mkchauras@gmail.com>
---
rust/Makefile | 56 +++++++++++++++++++++++++++------------------------
1 file changed, 30 insertions(+), 26 deletions(-)
diff --git a/rust/Makefile b/rust/Makefile
index 9801af2e1e02..d8f34c4858b8 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
@@ -49,7 +52,7 @@ libmacros_extension := $(patsubst libmacros.%,%,$(libmacros_name))
libpin_init_internal_name := $(shell MAKEFLAGS= $(RUSTC) --print file-names --crate-name pin_init_internal --crate-type proc-macro - </dev/null)
libpin_init_internal_extension := $(patsubst libpin_init_internal.%,%,$(libpin_init_internal_name))
-always-$(CONFIG_RUST) += $(libmacros_name) $(libpin_init_internal_name)
+always-$(CONFIG_RUST) += host/$(libmacros_name) host/$(libpin_init_internal_name)
# `$(rust_flags)` is passed in case the user added `--sysroot`.
rustc_sysroot := $(shell MAKEFLAGS= $(RUSTC) $(rust_flags) --print sysroot)
@@ -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 $(subst rustdoc-,,$@) \
@@ -247,7 +250,7 @@ rustdoc-kernel: private rustc_target_flags = --extern ffi --extern pin_init \
--extern build_error --extern macros \
--extern bindings --extern uapi
rustdoc-kernel: $(src)/kernel/lib.rs rustdoc-core rustdoc-ffi rustdoc-macros \
- rustdoc-pin_init rustdoc-compiler_builtins $(obj)/$(libmacros_name) \
+ rustdoc-pin_init rustdoc-compiler_builtins $(obj)/host/$(libmacros_name) \
$(obj)/bindings.o FORCE
+$(call if_changed,rustdoc)
@@ -299,14 +302,14 @@ rusttestlib-pin_init_internal: $(src)/pin-init/internal/src/lib.rs \
rusttestlib-pin_init: private rustc_target_flags = $(pin_init-flags)
rusttestlib-pin_init: $(src)/pin-init/src/lib.rs rusttestlib-macros \
- rusttestlib-pin_init_internal $(obj)/$(libpin_init_internal_name) FORCE
+ rusttestlib-pin_init_internal $(obj)/host/$(libpin_init_internal_name) FORCE
+$(call if_changed,rustc_test_library)
rusttestlib-kernel: private rustc_target_flags = --extern ffi \
--extern build_error --extern macros --extern pin_init \
--extern bindings --extern uapi
rusttestlib-kernel: $(src)/kernel/lib.rs rusttestlib-bindings rusttestlib-uapi \
- rusttestlib-build_error rusttestlib-pin_init $(obj)/$(libmacros_name) \
+ rusttestlib-build_error rusttestlib-pin_init $(obj)/host/$(libmacros_name) \
$(obj)/bindings.o FORCE
+$(call if_changed,rustc_test_library)
@@ -525,26 +528,27 @@ $(obj)/exports_kernel_generated.h: $(obj)/kernel.o FORCE
quiet_cmd_rustc_procmacrolibrary = $(RUSTC_OR_CLIPPY_QUIET) PL $@
cmd_rustc_procmacrolibrary = \
+ mkdir -p $(dir $@); \
$(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) \
+ -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)/$(libmacros_name): private rustc_target_flags = \
+$(obj)/host/$(libmacros_name): private rustc_target_flags = \
--extern proc_macro2 --extern quote --extern syn
-$(obj)/$(libmacros_name): $(src)/macros/lib.rs $(obj)/libproc_macro2.rlib \
- $(obj)/libquote.rlib $(obj)/libsyn.rlib FORCE
+$(obj)/host/$(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/$(libpin_init_internal_name): private rustc_target_flags = $(pin_init_internal-flags)
+$(obj)/host/$(libpin_init_internal_name): $(src)/pin-init/internal/src/lib.rs \
+ $(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
@@ -665,7 +669,7 @@ $(obj)/compiler_builtins.o: $(src)/compiler_builtins.rs $(obj)/core.o FORCE
$(obj)/pin_init.o: private skip_gendwarfksyms = 1
$(obj)/pin_init.o: private rustc_target_flags = $(pin_init-flags)
$(obj)/pin_init.o: $(src)/pin-init/src/lib.rs $(obj)/compiler_builtins.o \
- $(obj)/$(libpin_init_internal_name) $(obj)/$(libmacros_name) FORCE
+ $(obj)/host/$(libpin_init_internal_name) $(obj)/host/$(libmacros_name) FORCE
+$(call if_changed_rule,rustc_library)
# Even if normally `build_error` is not a kernel object, it should still be
@@ -699,7 +703,7 @@ $(obj)/uapi.o: $(src)/uapi/lib.rs \
$(obj)/kernel.o: private rustc_target_flags = --extern ffi --extern pin_init \
--extern build_error --extern macros --extern bindings --extern uapi
$(obj)/kernel.o: $(src)/kernel/lib.rs $(obj)/build_error.o $(obj)/pin_init.o \
- $(obj)/$(libmacros_name) $(obj)/bindings.o $(obj)/uapi.o FORCE
+ $(obj)/host/$(libmacros_name) $(obj)/bindings.o $(obj)/uapi.o FORCE
+$(call if_changed_rule,rustc_library)
ifdef CONFIG_JUMP_LABEL
--
2.53.0
next prev parent reply other threads:[~2026-04-06 20:02 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-04-06 20:01 [PATCH V10 0/4] Rust support for powerpc Mukesh Kumar Chaurasiya (IBM)
2026-04-06 20:01 ` Mukesh Kumar Chaurasiya (IBM) [this message]
2026-04-06 20:01 ` [PATCH V10 2/4] powerpc/jump_label: adjust inline asm to be consistent Mukesh Kumar Chaurasiya (IBM)
2026-04-06 20:01 ` [PATCH V10 3/4] rust: Add PowerPC support Mukesh Kumar Chaurasiya (IBM)
2026-04-06 20:01 ` [PATCH V10 4/4] powerpc: Enable Rust for ppc64le Mukesh Kumar Chaurasiya (IBM)
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20260406200149.3727922-2-mkchauras@gmail.com \
--to=mkchauras@gmail.com \
--cc=a.hindborg@kernel.org \
--cc=aliceryhl@google.com \
--cc=ardb@kernel.org \
--cc=bjorn3_gh@protonmail.com \
--cc=boqun@kernel.org \
--cc=chleroy@kernel.org \
--cc=dakr@kernel.org \
--cc=gary@garyguo.net \
--cc=jbaron@akamai.com \
--cc=jpoimboe@kernel.org \
--cc=justinstitt@google.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linuxppc-dev@lists.ozlabs.org \
--cc=llvm@lists.linux.dev \
--cc=lossin@kernel.org \
--cc=maddy@linux.ibm.com \
--cc=morbo@google.com \
--cc=mpe@ellerman.id.au \
--cc=nathan@kernel.org \
--cc=nick.desaulniers+lkml@gmail.com \
--cc=npiggin@gmail.com \
--cc=ojeda@kernel.org \
--cc=peterz@infradead.org \
--cc=rostedt@goodmis.org \
--cc=rust-for-linux@vger.kernel.org \
--cc=tmgross@umich.edu \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox