[PATCH v2] kbuild: rust: avoid creating temporary files

From: Miguel Ojeda
Date: Sun Jul 23 2023 - 10:21:54 EST


`rustc` outputs by default the temporary files (i.e. the ones saved
by `-Csave-temps`, such as `*.rcgu*` files) in the current working
directory when `-o` and `--out-dir` are not given (even if
`--emit=x=path` is given, i.e. it does not use those for temporaries).

Since out-of-tree modules are compiled from the `linux` tree,
`rustc` then tries to create them there, which may not be accessible.

Thus pass `--out-dir` explicitly, even if it is just for the temporary
files.

Similarly, do so for Rust host programs too.

Reported-by: Raphael Nestler <raphael.nestler@xxxxxxxxx>
Closes: https://github.com/Rust-for-Linux/linux/issues/1015
Reported-by: Andrea Righi <andrea.righi@xxxxxxxxxxxxx>
Tested-by: Raphael Nestler <raphael.nestler@xxxxxxxxx> # non-hostprogs
Tested-by: Andrea Righi <andrea.righi@xxxxxxxxxxxxx> # non-hostprogs
Fixes: 295d8398c67e ("kbuild: specify output names separately for each emission type from rustc")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Miguel Ojeda <ojeda@xxxxxxxxxx>
---
v2:
- Add fix for host programs too (Masahiro).

scripts/Makefile.build | 5 ++++-
scripts/Makefile.host | 6 +++++-
2 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/scripts/Makefile.build b/scripts/Makefile.build
index 6413342a03f4..82e3fb19fdaf 100644
--- a/scripts/Makefile.build
+++ b/scripts/Makefile.build
@@ -264,6 +264,9 @@ $(obj)/%.lst: $(src)/%.c FORCE

rust_allowed_features := new_uninit

+# `--out-dir` is required to avoid temporaries being created by `rustc` in the
+# current working directory, which may be not accessible in the out-of-tree
+# modules case.
rust_common_cmd = \
RUST_MODFILE=$(modfile) $(RUSTC_OR_CLIPPY) $(rust_flags) \
-Zallow-features=$(rust_allowed_features) \
@@ -272,7 +275,7 @@ rust_common_cmd = \
--extern alloc --extern kernel \
--crate-type rlib -L $(objtree)/rust/ \
--crate-name $(basename $(notdir $@)) \
- --emit=dep-info=$(depfile)
+ --out-dir $(dir $@) --emit=dep-info=$(depfile)

# `--emit=obj`, `--emit=asm` and `--emit=llvm-ir` imply a single codegen unit
# will be used. We explicitly request `-Ccodegen-units=1` in any case, and
diff --git a/scripts/Makefile.host b/scripts/Makefile.host
index 7aea9005e497..8f7f842b54f9 100644
--- a/scripts/Makefile.host
+++ b/scripts/Makefile.host
@@ -86,7 +86,11 @@ hostc_flags = -Wp,-MMD,$(depfile) \
hostcxx_flags = -Wp,-MMD,$(depfile) \
$(KBUILD_HOSTCXXFLAGS) $(HOST_EXTRACXXFLAGS) \
$(HOSTCXXFLAGS_$(target-stem).o)
-hostrust_flags = --emit=dep-info=$(depfile) \
+
+# `--out-dir` is required to avoid temporaries being created by `rustc` in the
+# current working directory, which may be not accessible in the out-of-tree
+# modules case.
+hostrust_flags = --out-dir $(dir $@) --emit=dep-info=$(depfile) \
$(KBUILD_HOSTRUSTFLAGS) $(HOST_EXTRARUSTFLAGS) \
$(HOSTRUSTFLAGS_$(target-stem))


base-commit: 06c2afb862f9da8dc5efa4b6076a0e48c3fbaaa5
--
2.41.0