linux.git/tools/build, branch master

tools build: Fix rust cross compilation

2026-03-04T14:37:30+00:00

Currently no target is specified to compile rust code when needed, which
breaks cross compilation. E.g. for arm64:

      LD      /tmp/build/tests/workloads/perf-test-in.o
    aarch64-linux-gnu-ld: /tmp/build/tests/workloads/code_with_type.a(code_with_type.code_with_type.d12f4324cb53c560-cgu.0.rcgu.o): Relocations in generic ELF (EM: 62)
    aarch64-linux-gnu-ld: /tmp/build/tests/workloads/code_with_type.a(code_with_type.code_with_type.d12f4324cb53c560-cgu.0.rcgu.o): Relocations in generic ELF (EM: 62)
    [...repeated...]
    aarch64-linux-gnu-ld: /tmp/build/tests/workloads/code_with_type.a(code_with_type.code_with_type.d12f4324cb53c560-cgu.0.rcgu.o): Relocations in generic ELF (EM: 62)
    aarch64-linux-gnu-ld: /tmp/build/tests/workloads/code_with_type.a(code_with_type.code_with_type.d12f4324cb53c560-cgu.0.rcgu.o): Relocations in generic ELF (EM: 62)
    aarch64-linux-gnu-ld: /tmp/build/tests/workloads/code_with_type.a: error adding symbols: file in wrong format
    make[5]: *** [/perf/tools/build/Makefile.build:162: /tmp/build/tests/workloads/perf-test-in.o] Error 1
    make[4]: *** [/perf/tools/build/Makefile.build:156: workloads] Error 2
    make[3]: *** [/perf/tools/build/Makefile.build:156: tests] Error 2
    make[2]: *** [Makefile.perf:785: /tmp/build/perf-test-in.o] Error 2
    make[2]: *** Waiting for unfinished jobs....
    make[1]: *** [Makefile.perf:289: sub-make] Error 2
    make: *** [Makefile:76: all] Error 2

Detect required target and pass it via rust_flags to the compiler.

Note that CROSS_COMPILE might be different from what rust compiler
expects, since it may omit the target vendor value, e.g.
"aarch64-linux-gnu" instead of "aarch64-unknown-linux-gnu".

Thus explicitly map supported CROSS_COMPILE values to corresponding Rust
versions, as suggested by Miguel Ojeda.

Tested using arm64 cross-compilation example from [1].

Fixes: 2e05bb52a12d3cdb ("perf test workload: Add code_with_type test workload")
Reviewed-by: Ian Rogers 
Signed-off-by: Dmitrii Dolgov <9erthalion6@gmail.com>
Cc: Levi Zim 
Cc: Miguel Ojeda 
Cc: Namhyung Kim 
Cc: Nathan Chancellor 
Cc: Nicolas Schier 
Link: https://perfwiki.github.io/main/arm64-cross-compilation-dockerfile/ [1]
Signed-off-by: Arnaldo Carvalho de Melo

tools build: Make in-target rule robust against too long argument error

2026-03-04T14:21:48+00:00

The command length of in-target scales with the depth of the directory
times the number of objects in the Makefile.

When there are many objects, and O=[absolute_path] is set, and the
absolute_path is relatively long.

It is possible that this line "$(call if_changed,$(host)ld_multi)" will
report error: "make[4]: /bin/sh: Argument list too long"

For example, build perf tools with O=/long/output/path

Like built-in.a and *.mod rules in scripts/Makefile.build, add
$(objpredix)/ by the shell command instead of by Make's builtin
function.

Reviewed-by: Ian Rogers 
Signed-off-by: Changqing Li 
Cc: Charlie Jenkins 
Cc: James Clark 
Cc: Namhyung Kim 
Signed-off-by: Arnaldo Carvalho de Melo

tools build: Fix feature test for rust compiler

2026-02-12T20:45:22+00:00

Currently a dummy rust code is compiled to detect if the rust feature
could be enabled. It turns out that in this case rust emits a dependency
file without any external references:

    /perf/feature/test-rust.d: test-rust.rs

    /perf/feature/test-rust.bin: test-rust.rs

    test-rust.rs:

This can lead to a situation, when rustc was removed after a successful build,
but the build process still thinks it's there and the feature is enabled on
subsequent runs.

Instead simply check the compiler presence to detect the feature, as
suggested by Arnaldo.

This way no actual test-rust.bin will be created, meaning the feature
check will not be cached and always performed. That's exactly what we
want, and the overhead of doing this every time is minimal.

Tested with multiple rounds of install/remove of the rust package.

Reported-by: Arnaldo Carvalho de Melo 
Suggested-by: Arnaldo Carvalho de Melo 
Signed-off-by: Dmitrii Dolgov <9erthalion6@gmail.com>
Tested-by: Arnaldo Carvalho de Melo 
Cc: Ian Rogers 
Cc: Miguel Ojeda 
Cc: Namhyung Kim 
Signed-off-by: Arnaldo Carvalho de Melo

tools build: Emit dependencies file for test-rust.bin

2026-02-10T12:29:58+00:00

Test it first by having rust installed, then removing it and building again.

Fixes: 6a32fa5ccd33da5d ("tools build: Add a feature test for rust compiler")
Signed-off-by: Dmitry Dolgov <9erthalion6@gmail.com>
Signed-off-by: Arnaldo Carvalho de Melo

tools build: Make test-rust.bin be removed by the 'clean' target

2026-02-10T12:29:39+00:00

test-rust.bin is missing from the list of FILES, and thus is not removed by the
clean target. This could lead to a false feature detection, since the binary
stays there. Fix it.

Fixes: 6a32fa5ccd33da5d ("tools build: Add a feature test for rust compiler")
Tested-by: Arnaldo Carvalho de Melo 
Signed-off-by: Dmitrii Dolgov <9erthalion6@gmail.com>
Signed-off-by: Arnaldo Carvalho de Melo

tools build: Fix rust feature detection

2026-02-09T14:10:56+00:00

Features in FEATURE_TESTS_BASIC will be set as being available if
test-all.c builds, so since the rust test isn't included in test-all.c,
we can't have 'rust' in there, remove it from FEATURE_TESTS_BASIC and
use feature-check so that it tries to build test-rust.bin, doing the
actual feature detection.

On a system lacking a rust compiler:

  Makefile.config:1158: Rust is not found. Test workloads with rust are disabled.

  Auto-detecting system features:
  ...                                   libdw: [ on  ]
  ...                                   glibc: [ on  ]
  ...                                  libelf: [ on  ]
  ...                                 libnuma: [ on  ]
  ...                  numa_num_possible_cpus: [ on  ]
  ...                               libpython: [ on  ]
  ...                             libcapstone: [ on  ]
  ...                               llvm-perf: [ on  ]
  ...                                    zlib: [ on  ]
  ...                                    lzma: [ on  ]
  ...                                     bpf: [ on  ]
  ...                                  libaio: [ on  ]
  ...                                 libzstd: [ on  ]
  ...                              libopenssl: [ on  ]
  ...                                    rust: [ OFF ]

  $ cat /tmp/build/perf-tools-next/feature/test-rust.make.output
  /bin/sh: line 1: rustc: command not found
  $ file /tmp/build/perf-tools-next/feature/test-rust.bin
  /tmp/build/perf-tools-next/feature/test-rust.bin: cannot open `/tmp/build/perf-tools-next/feature/test-rust.bin' (No such file or directory)
  $
  $ perf -vv | grep RUST
                  rust: [ OFF ]  # HAVE_RUST_SUPPORT
  $

And after installing it:

  ...                                    rust: [ on  ]

  $ cat /tmp/build/perf-tools-next/feature/test-rust.make.output
  $ file /tmp/build/perf-tools-next/feature/test-rust.bin
/tmp/build/perf-tools-next/feature/test-rust.bin: ELF 64-bit LSB pie executable, x86-64, version 1 (SYSV), dynamically linked, interpreter /lib64/ld-linux-x86-64.so.2, BuildID[sha1]=9c416edf673ee3705b97bae893a99a6fcf1ee258, for GNU/Linux 3.2.0, with debug_info, not stripped
  $
  $ perf -vv | grep RUST
                  rust: [ on  ]  # HAVE_RUST_SUPPORT
  $

Fixes: 6a32fa5ccd33da5d ("tools build: Add a feature test for rust compiler")
Cc: Dmitrii Dolgov <9erthalion6@gmail.com>
Signed-off-by: Arnaldo Carvalho de Melo

perf test workload: Add code_with_type test workload

2026-02-08T22:16:24+00:00

The purpose of the workload is to gather samples of rust runtime. To
achieve that it has a dummy rust library linked with it.

Per recommendations for such scenarios [1], the rust library is
statically linked.

An example:

$ perf record perf test -w code_with_type
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 0.160 MB perf.data (4074 samples) ]

$ perf report --stdio --dso perf -s srcfile,srcline
    45.16%  ub_checks.rs       ub_checks.rs:72
     6.72%  code_with_type.rs  code_with_type.rs:15
     6.64%  range.rs           range.rs:767
     4.26%  code_with_type.rs  code_with_type.rs:21
     4.23%  range.rs           range.rs:0
     3.99%  code_with_type.rs  code_with_type.rs:16
    [...]

[1]: https://doc.rust-lang.org/reference/linkage.html#mixed-rust-and-foreign-codebases

Signed-off-by: Dmitrii Dolgov <9erthalion6@gmail.com>
Tested-by: Arnaldo Carvalho de Melo 
Cc: Ian Rogers 
Cc: Namhyung Kim 
Signed-off-by: Arnaldo Carvalho de Melo

tools build: Add a feature test for rust compiler

2026-02-08T14:30:45+00:00

Add a feature test to identify if the rust compiler is available, so
that perf could build rust based worloads based on that.

Signed-off-by: Dmitrii Dolgov <9erthalion6@gmail.com>
Cc: Ian Rogers 
Cc: Namhyung Kim 
Signed-off-by: Arnaldo Carvalho de Melo

perf build: Feature test for libbfd thread safety API

2026-01-06T22:14:46+00:00

The non-distro build requires libbfd 2.42 since commit b72b8132d8fd
("perf libbfd: Ensure libbfd is initialized prior to use"). Add a
feature test so that it's obvious why the build fails if this criteria
isn't met.

Signed-off-by: James Clark 
Cc: Adrian Hunter 
Cc: Alexander Shishkin 
Cc: Bill Wendling 
Cc: Ian Rogers 
Cc: Ingo Molnar 
Cc: Jiri Olsa 
Cc: Justin Stitt 
Cc: Leo Yan 
Cc: Mark Rutland 
Cc: Namhyung Kim 
Cc: Nathan Chancellor 
Cc: Nick Desaulniers 
Cc: Peter Zijlstra 
Signed-off-by: Arnaldo Carvalho de Melo

perf build: Remove unused libbfd-buildid feature test

2026-01-06T22:14:00+00:00

HAVE_LIBBFD_BUILDID_SUPPORT isn't used in the codebase so remove the
feature test that sets it.

Signed-off-by: James Clark 
Cc: Adrian Hunter 
Cc: Alexander Shishkin 
Cc: Bill Wendling 
Cc: Ian Rogers 
Cc: Ingo Molnar 
Cc: Jiri Olsa 
Cc: Justin Stitt 
Cc: Leo Yan 
Cc: Mark Rutland 
Cc: Namhyung Kim 
Cc: Nathan Chancellor 
Cc: Nick Desaulniers 
Cc: Peter Zijlstra 
Signed-off-by: Arnaldo Carvalho de Melo