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2026-08-22Merge tag 'perf-tools-for-v7.3-2026-08-21' of ↵Linus Torvalds2-37/+56
git://git.kernel.org/pub/scm/linux/kernel/git/perf/perf-tools Pull perf tools updates from Namhyung Kim: "perf c2c: - Add 'function view' in perf c2c report TUI (switched by pressing 'TAB' in the cacheline view) to organize samples around functions rather than cachelines in 3-level hierarchy: Level 1: Read-side function (sorted by estimated Cycles %) Level 2: Contending writer functions (sorted by Store count) Level 3: Shared cacheline addresses Users can navigate the entries and fold/unfold using 'e' key. An example output would look like below: Shared Data Functions Table (19 entries, sorted on Cycles %) Cycles Store % count Function / Contending function / Cacheline ---------------------------------------------------------------------- + 35.67% 876 + [k] cpupri_set + 24.31% 424 + [k] pull_rt_task - 16.53% 555 - [k] dequeue_pushable_task 145 - [k] pull_rt_task 145 0xff2d0082809da080 139 - [k] enqueue_pushable_task 70 0xff2d00a2071f9640 69 0xff2d0082809da000 python module support: - Extend "perf" python module so that it can be fully functional. The goal is to run scripts directly, not by 'perf script' command. This would give better performance as well as more control to build standalone programs with UI. - Add LiveSession helper (perf_live.py) to enable live event collection directly from Python using perf.evlist and perf.parse_events. perf stat: - Add --hide-zero-events option to suppress zero-count events - Reject conflicting --field-separator and --json-output options - Fix duplicate event output with --for-each-cgroup perf sched latency: - Add -H/--histogram and --hist-mode (log|linear) options to show scheduler wait latency histograms - Add --time option to filter analysis by time span in 'perf sched latency' ARM CoreSight: - Synthesize callchains for instruction samples from CoreSight trace using thread stack ('--itrace=g...') - Support call indentation ('perf script -F +callindent') to display call depth hierarchy on branch samples - Decode ETE (Embedded Trace Extension) exception packets Build system: - Add 'make install-build-deps' target to install required packages - Parallelize JSON and metric pre-computation in jevents.py for faster builds Vendor event/metric updates: - Add Intel Nova Lake events and update tables for existing models - Update AMD Zen 5 and Zen 6 core events - Update Arm64 Tegra410 metrics and PowerPC hcalls Internal changes and fixes: - Harden trace-event and synthetic event parsing against corrupted data - Fix unwinding of multi-threaded processes in libdw unwinder - Fix memory leaks in various commands and python bindings - Speed up 'perf test' shell tests" * tag 'perf-tools-for-v7.3-2026-08-21' of git://git.kernel.org/pub/scm/linux/kernel/git/perf/perf-tools: (232 commits) perf vendor events arm64: Fix Tegra410 Olympus event 0x0197 perf vendor events arm64: fix swapped MetricGroup for Tegra410 L1 prefetcher metrics perf evlist: Warn when 'sleep' workload is used without system-wide (-a) option perf c2c: document function view in perf-c2c man page perf c2c: add function view browser UI and cacheline detail perf c2c: build and finalize the function view hierarchy perf c2c: add function view hierarchy entry creation perf c2c: add function view stats merge and memory management perf c2c: add HPP list parsing for function view columns perf c2c: add column rendering for function view perf c2c: add function view model skeleton perf c2c: extract shared data structures into util/c2c.h perf test sample-parsing: Validate PERF_FORMAT_GROUP values without LOST perf dso: Replace assert with runtime check in dso__read_symbol() perf dso: Guard against cache underflow on short reads in dso_cache__memcpy() perf dso: Use stored fd error instead of stale errno in file_read() and file_size() perf dso: Guard close() against invalid fd in dso__decompress_kmodule_path() perf dso: Guard against errno==0 when dso__get_filename() returns NULL perf build: install-build-deps: add RHEL family devel package mapping perf build: Remove leftover feature tests for removed cxx and clang support ...
2026-08-12tools build: Only probe the compiler at parse time when it is installedArnaldo Carvalho de Melo2-2/+14
Two parse-time probes still invoke $(CC) unconditionally: - LP64 in tools/scripts/Makefile.arch, probing with $(CC) -E -x c, pulled in twice by tools/perf/Makefile.perf; - CC_NO_CLANG in tools/scripts/Makefile.include, probing with $(CC) -dM -E -x c /dev/null. In the corner case where gcc is not yet installed, the very setup the install-build-deps target, added in the next patch of this series, is meant for, these probes make even targets that never compile parse-time spew errors like: /bin/sh: 1: gcc: not found /bin/sh: 1: gcc: not found /bin/sh: 1: gcc: not found Guard both probes with 'command -v' using the first word of CC so a missing compiler is handled silently with the same result as a failing probe (CC_NO_CLANG and LP64 unset/0), and with no behavior change when the compiler is installed. Only the first word is consulted because CC may carry arguments such as 'ccache gcc', and shell implementations differ in how 'command -v' handles multiple words (dash only checks the first, bash any of them), so validating the whole CC value would silently disable both probes on some make SHELLs. Assisted-by: opencode:deepseek-v4-flash-free Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com> Signed-off-by: Namhyung Kim <namhyung@kernel.org>
2026-07-27arch: hookup fchroot() system callChristian Brauner1-0/+1
Wire up the fchroot() system call as number 472 on (nearly) all architectures and sync the mirrored copies of the syscall tables and the asm-generic unistd.h under tools/. Link: https://patch.msgid.link/20260724-work-failfs-v2-5-485dabbae185@kernel.org Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
2026-07-25tools/build: Allow versioning LLVM readelfJames Clark1-0/+4
Documentation/kbuild/llvm.rst mentions that readelf is included in the LLVM toolchain, but it's not currently included in this block. Add it so that LLVM=... options also apply to readelf. Users in tools/ were Perf which was hardcoding it, and another was the BPF makefile. Both already include Makefile.include so convert them to use the new variables. Where readelf wasn't doing anything arch specific, use HOSTREADELF because it's more likely to be installed. Reviewed-by: Ian Rogers <irogers@google.com> Signed-off-by: James Clark <james.clark@linaro.org> Acked-by: Ihor Solodrai <ihor.solodrai@linux.dev> Acked-by: Kumar Kartikeya Dwivedi <memxor@gmail.com> Signed-off-by: Namhyung Kim <namhyung@kernel.org>
2026-07-25tools/build: Indent if else blocksJames Clark1-38/+38
These blocks are quite big and unreadable without indentation. Indent them. No functional changes intended. Signed-off-by: James Clark <james.clark@linaro.org> Reviewed-by: Ian Rogers <irogers@google.com> Acked-by: Kumar Kartikeya Dwivedi <memxor@gmail.com> Signed-off-by: Namhyung Kim <namhyung@kernel.org>
2026-07-25tools/build: Allow versioning of all LLVM tools defined in Makefile.includeJames Clark1-17/+20
The version of LLVM tools can be given on the build command with LLVM=-15, but this isn't applied to all tools. For example $(CC) gets versioned, but $(CLANG) doesn't. This causes a Perf build with LTO=1 to fail with an error about mixed clang versions: ld.lld: error: libperf/core.o: Unknown attribute kind (86) (Producer: 'LLVM18.1.8' Reader: 'LLVM 15.0.7') This file has two "ifneq ($(LLVM),)" blocks adjacent to each other, so merge these blocks making it obvious that all tools should be versioned consistently and there is nothing special about each block. This also reveals that ?= and "allow-override" are used inconsistently between the blocks. "allow-override" is technically only required for builtin variables, but isn't only used on them, and doesn't do any harm if used on a non-builtin. Make them all "allow-override" for consistency. The only functional difference this will cause is if there is a file level definition of one of the variables followed by an "#include of Makefile.include" which will now overwrite. But this isn't done and in a later commit some of the duplicate definitions will be removed for good measure. There are also some other LLVM tools that are not defined here and will be moved in a later commit. Signed-off-by: James Clark <james.clark@linaro.org> Reviewed-by: Ian Rogers <irogers@google.com> Acked-by: Kumar Kartikeya Dwivedi <memxor@gmail.com> Fixes: e9c281928c24 ("kbuild: Make $(LLVM) more flexible") Signed-off-by: Namhyung Kim <namhyung@kernel.org>
2026-04-14Merge tag 'kbuild-7.1-1' of ↵Linus Torvalds1-0/+2
git://git.kernel.org/pub/scm/linux/kernel/git/kbuild/linux Pull Kbuild/Kconfig updates from Nicolas Schier: "Kbuild: - reject unexpected values for LLVM= - uapi: remove usage of toolchain headers - switch from '-fms-extensions' to '-fms-anonymous-structs' when available (currently: clang >= 23.0.0) - reduce the number of compiler-generated suffixes for clang thin-lto build - reduce output spam ("GEN Makefile") when building out of tree - improve portability for testing headers - also test UAPI headers against C++ compilers - drop build ID architecture allow-list in vdso_install - only run checksyscalls when necessary - update the debug information notes in reproducible-builds.rst - expand inlining hints with -fdiagnostics-show-inlining-chain Kconfig: - forbid multiple entries with the same symbol in a choice - error out on duplicated kconfig inclusion" * tag 'kbuild-7.1-1' of git://git.kernel.org/pub/scm/linux/kernel/git/kbuild/linux: (35 commits) kbuild: expand inlining hints with -fdiagnostics-show-inlining-chain kconfig: forbid multiple entries with the same symbol in a choice Documentation: kbuild: Update the debug information notes in reproducible-builds.rst checksyscalls: move instance functionality into generic code checksyscalls: only run when necessary checksyscalls: fail on all intermediate errors checksyscalls: move path to reference table to a variable kbuild: vdso_install: drop build ID architecture allow-list kbuild: vdso_install: gracefully handle images without build ID kbuild: vdso_install: hide readelf warnings kbuild: vdso_install: split out the readelf invocation kbuild: uapi: also test UAPI headers against C++ compilers kbuild: uapi: provide a C++ compatible dummy definition of NULL kbuild: uapi: handle UML in architecture-specific exclusion lists kbuild: uapi: move all include path flags together kbuild: uapi: move some compiler arguments out of the command definition check-uapi: use dummy libc includes check-uapi: honor ${CROSS_COMPILE} setting check-uapi: link into shared objects kbuild: reduce output spam when building out of tree ...
2026-03-05tools headers: Update the syscall tables and unistd.h, to support the new ↵Arnaldo Carvalho de Melo1-0/+1
'rseq_slice_yield' syscall Picking up the changes from these csets: 2153b2e8917b73e9 ("sparc: Add architecture support for clone3") 99d2592023e5d0a3 ("rseq: Implement sys_rseq_slice_yield()") 4ac286c4a8d904c8 ("s390/syscalls: Switch to generic system call table generation") This makes 'perf trace' support it, now its possible, for instance, to do: # perf trace -e rseq_slice_yield --max-stack=16 Here is an example with the 'sendmmsg' syscall: root@x1:~# perf trace -e sendmmsg --max-stack 16 --max-events=1 0.000 ( 0.062 ms): dbus-broker/1012 sendmmsg(fd: 150, mmsg: 0x7ffef57cca50, vlen: 1, flags: DONTWAIT|NOSIGNAL) = 1 syscall_exit_to_user_mode_prepare ([kernel.kallsyms]) syscall_exit_to_user_mode_prepare ([kernel.kallsyms]) syscall_exit_to_user_mode ([kernel.kallsyms]) do_syscall_64 ([kernel.kallsyms]) entry_SYSCALL_64 ([kernel.kallsyms]) [0x117ce7] (/usr/lib64/libc.so.6 (deleted)) root@x1:~# To do a system wide tracing of the new 'rseq_slice_yield' syscall with a backtrace of at most 16 entries. This addresses these perf tools build warnings: Warning: Kernel ABI header differences: diff -u tools/include/uapi/asm-generic/unistd.h include/uapi/asm-generic/unistd.h diff -u tools/scripts/syscall.tbl scripts/syscall.tbl diff -u tools/perf/arch/x86/entry/syscalls/syscall_32.tbl arch/x86/entry/syscalls/syscall_32.tbl diff -u tools/perf/arch/x86/entry/syscalls/syscall_64.tbl arch/x86/entry/syscalls/syscall_64.tbl diff -u tools/perf/arch/powerpc/entry/syscalls/syscall.tbl arch/powerpc/kernel/syscalls/syscall.tbl diff -u tools/perf/arch/s390/entry/syscalls/syscall.tbl arch/s390/kernel/syscalls/syscall.tbl diff -u tools/perf/arch/mips/entry/syscalls/syscall_n64.tbl arch/mips/kernel/syscalls/syscall_n64.tbl diff -u tools/perf/arch/arm/entry/syscalls/syscall.tbl arch/arm/tools/syscall.tbl diff -u tools/perf/arch/sh/entry/syscalls/syscall.tbl arch/sh/kernel/syscalls/syscall.tbl diff -u tools/perf/arch/sparc/entry/syscalls/syscall.tbl arch/sparc/kernel/syscalls/syscall.tbl diff -u tools/perf/arch/xtensa/entry/syscalls/syscall.tbl arch/xtensa/kernel/syscalls/syscall.tbl Cc: Andreas Larsson <andreas@gaisler.com> Cc: Heiko Carstens <hca@linux.ibm.com> Cc: Ludwig Rydberg <ludwig.rydberg@gaisler.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@kernel.org> Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
2026-03-03tools/build: Reject unexpected values for LLVM=Thomas Weißschuh1-0/+2
Since commit 502678b88cb3 ("kbuild: Reject unexpected values for LLVM=") the regular kbuild rejects unexpected values of LLVM=1 instead of silently treating them as LLVM=1. Align the tools build to kbuild. Signed-off-by: Thomas Weißschuh <linux@weissschuh.net> Reviewed-by: Nicolas Schier <nsc@kernel.org> Reviewed-by: Nathan Chancellor <nathan@kernel.org> Link: https://patch.msgid.link/20260226-kbuild-llvm-followup-v1-2-201cc2a492d9@weissschuh.net Signed-off-by: Nicolas Schier <nsc@kernel.org>
2026-02-08perf test workload: Add code_with_type test workloadDmitrii Dolgov1-0/+2
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 <acme@redhat.com> Cc: Ian Rogers <irogers@google.com> Cc: Namhyung Kim <namhyung@kernel.org> Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
2025-12-24tools headers: Sync syscall table with kernel sourcesNamhyung Kim1-0/+1
To pick up changes from: b36d4b6aa88ef039 ("arch: hookup listns() system call") This should be used to beautify the syscall arguments and it addresses these tools/perf build warnings: Warning: Kernel ABI header differences: diff -u tools/include/uapi/asm-generic/unistd.h include/uapi/asm-generic/unistd.h diff -u tools/scripts/syscall.tbl scripts/syscall.tbl diff -u tools/perf/arch/x86/entry/syscalls/syscall_32.tbl arch/x86/entry/syscalls/syscall_32.tbl diff -u tools/perf/arch/x86/entry/syscalls/syscall_64.tbl arch/x86/entry/syscalls/syscall_64.tbl diff -u tools/perf/arch/powerpc/entry/syscalls/syscall.tbl arch/powerpc/kernel/syscalls/syscall.tbl diff -u tools/perf/arch/s390/entry/syscalls/syscall.tbl arch/s390/kernel/syscalls/syscall.tbl diff -u tools/perf/arch/mips/entry/syscalls/syscall_n64.tbl arch/mips/kernel/syscalls/syscall_n64.tbl diff -u tools/perf/arch/arm/entry/syscalls/syscall.tbl arch/arm/tools/syscall.tbl diff -u tools/perf/arch/sh/entry/syscalls/syscall.tbl arch/sh/kernel/syscalls/syscall.tbl diff -u tools/perf/arch/sparc/entry/syscalls/syscall.tbl arch/sparc/kernel/syscalls/syscall.tbl diff -u tools/perf/arch/xtensa/entry/syscalls/syscall.tbl arch/xtensa/kernel/syscalls/syscall.tbl Please see tools/include/uapi/README. Note that s390 syscall table is still out of sync as it switches to use the generic table. But I'd like to minimize the change in this commit. Cc: linux-arch@vger.kernel.org Signed-off-by: Namhyung Kim <namhyung@kernel.org>
2025-08-18tools headers: Sync syscall tables with the kernel sourceNamhyung Kim1-0/+2
To pick up the changes in this cset: be7efb2d20d67f33 fs: introduce file_getattr and file_setattr syscalls This addresses these perf build warnings: Warning: Kernel ABI header differences: diff -u tools/include/uapi/asm-generic/unistd.h include/uapi/asm-generic/unistd.h diff -u tools/scripts/syscall.tbl scripts/syscall.tbl diff -u tools/perf/arch/x86/entry/syscalls/syscall_32.tbl arch/x86/entry/syscalls/syscall_32.tbl diff -u tools/perf/arch/x86/entry/syscalls/syscall_64.tbl arch/x86/entry/syscalls/syscall_64.tbl diff -u tools/perf/arch/powerpc/entry/syscalls/syscall.tbl arch/powerpc/kernel/syscalls/syscall.tbl diff -u tools/perf/arch/s390/entry/syscalls/syscall.tbl arch/s390/kernel/syscalls/syscall.tbl diff -u tools/perf/arch/mips/entry/syscalls/syscall_n64.tbl arch/mips/kernel/syscalls/syscall_n64.tbl diff -u tools/perf/arch/arm/entry/syscalls/syscall.tbl arch/arm/tools/syscall.tbl diff -u tools/perf/arch/sh/entry/syscalls/syscall.tbl arch/sh/kernel/syscalls/syscall.tbl diff -u tools/perf/arch/sparc/entry/syscalls/syscall.tbl arch/sparc/kernel/syscalls/syscall.tbl diff -u tools/perf/arch/xtensa/entry/syscalls/syscall.tbl arch/xtensa/kernel/syscalls/syscall.tbl Please see tools/include/uapi/README for further details. Cc: Arnd Bergmann <arnd@arndb.de> CC: linux-api@vger.kernel.org Signed-off-by: Namhyung Kim <namhyung@kernel.org>
2025-07-08tools/build: Fix s390(x) cross-compilation with clangThomas Weißschuh1-1/+3
The heuristic to derive a clang target triple from a GCC one does not work for s390. GCC uses "s390-linux" while clang expects "s390x-linux" or "powerz-linux". Add an explicit override. Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de> Link: https://lore.kernel.org/r/20250620-tools-cross-s390-v2-1-ecda886e00e5@linutronix.de Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
2025-04-10tools headers: Update the syscall table with the kernel sourcesNamhyung Kim1-0/+1
To pick up the changes in: c4a16820d9019940 fs: add open_tree_attr() 2df1ad0d25803399 x86/arch_prctl: Simplify sys_arch_prctl() e632bca07c8eef1d arm64: generate 64-bit syscall.tbl This is basically to support the new open_tree_attr syscall. But it also needs to update asm-generic unistd.h header to get the new syscall number. And arm64 unistd.h header was converted to use the generic 64-bit header. Addressing this perf tools build warning: Warning: Kernel ABI header differences: diff -u tools/scripts/syscall.tbl scripts/syscall.tbl diff -u tools/perf/arch/x86/entry/syscalls/syscall_32.tbl arch/x86/entry/syscalls/syscall_32.tbl diff -u tools/perf/arch/x86/entry/syscalls/syscall_64.tbl arch/x86/entry/syscalls/syscall_64.tbl diff -u tools/perf/arch/powerpc/entry/syscalls/syscall.tbl arch/powerpc/kernel/syscalls/syscall.tbl diff -u tools/perf/arch/s390/entry/syscalls/syscall.tbl arch/s390/kernel/syscalls/syscall.tbl diff -u tools/perf/arch/mips/entry/syscalls/syscall_n64.tbl arch/mips/kernel/syscalls/syscall_n64.tbl diff -u tools/perf/arch/arm/entry/syscalls/syscall.tbl arch/arm/tools/syscall.tbl diff -u tools/perf/arch/sh/entry/syscalls/syscall.tbl arch/sh/kernel/syscalls/syscall.tbl diff -u tools/perf/arch/sparc/entry/syscalls/syscall.tbl arch/sparc/kernel/syscalls/syscall.tbl diff -u tools/perf/arch/xtensa/entry/syscalls/syscall.tbl arch/xtensa/kernel/syscalls/syscall.tbl diff -u tools/arch/arm64/include/uapi/asm/unistd.h arch/arm64/include/uapi/asm/unistd.h diff -u tools/include/uapi/asm-generic/unistd.h include/uapi/asm-generic/unistd.h Please see tools/include/uapi/README for further details. Acked-by: Ingo Molnar <mingo@kernel.org> Tested-by: Venkat Rao Bagalkote <venkat88@linux.ibm.com> Cc: linux-arch@vger.kernel.org Link: https://lore.kernel.org/r/20250410001125.391820-6-namhyung@kernel.org Signed-off-by: Namhyung Kim <namhyung@kernel.org>
2025-03-27Merge tag 'trace-tools-v6.15' of ↵Linus Torvalds1-0/+3
git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace Pull tracing tooling updates from Steven Rostedt: - Allow RTLA to collect data via BPF The current implementation of rtla uses libtracefs and libtraceevent to pull sample events generated by the timerlat tracer from the trace buffer. rtla then processes the sample by updating the histogram and summary (current, maximum, minimum, and sum values) as well as checks if tracing has been stopped due to threshold overflow. In use cases where a large number of samples is being generated, that is, with measurements running on many CPUs and with a low interval, this sample processing design causes a significant CPU load on the rtla side. Furthermore, with >100 CPUs and 100us interval, rtla was reported as not being able to keep up with the samples and dropping most of them, leading to it being unusable. Change the way the timerlat trace processes samples by attaching a BPF program to the trace event using the BPF skeleton feature of bpftool. Unlike the current implementation, the BPF implementation does not check whether tracing is stopped (in BPF mode, tracing is always off to improve performance), but waits for a write to a BPF ringbuffer instead. This allows rtla to exit immediately when a threshold is violated, without waiting for the next iteration of the while loop. If the requirements for the BPF implementation are not met, either at build time or at run time, the current implementation is used as fallback. Which implementation is being used can be seen when running rtla timerlat with "-D" option. rtla can be forced to run in non-BPF mode by setting the RTLA_NO_BPF option to 1, for debugging purposes. - Fix LD_FLAGS from being dropped in build - Refactor code to remove duplication of save_trace_to_file - Always set options and do not rely on default settings Do not rely on the default kernel settings of the tracers when starting. They could have been changed by the user which gives inconsistent results. Always set the options that rtla expects. - Add creation of ctags and TAGS for traversing code * tag 'trace-tools-v6.15' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace: rtla: Add the ability to create ctags and etags rtla/tests: Test setting default options rtla/tests: Reset osnoise options before check rtla: Always set all tracer options rtla/osnoise: Set OSNOISE_WORKLOAD to true rtla: Unify apply_config between top and hist rtla/osnoise: Unify params struct rtla: Fix segfault in save_trace_to_file call tools/build: Use SYSTEM_BPFTOOL for system bpftool rtla: Refactor save_trace_to_file tools/rv: Keep user LDFLAGS in build rtla/timerlat: Test BPF mode rtla/timerlat_top: Use BPF to collect samples rtla/timerlat_top: Move divisor to update rtla/timerlat_hist: Use BPF to collect samples rtla/timerlat: Add BPF skeleton to collect samples rtla: Add optional dependency on BPF tooling tools/build: Add bpftool-skeletons feature test rtla/timerlat: Unify params struct
2025-03-26tools/build: Use SYSTEM_BPFTOOL for system bpftoolTomas Glozar1-1/+1
The feature test for system bpftool uses BPFTOOL as the variable to set its path, defaulting to just "bpftool" if not set by the user. This conflicts with selftests and a few other utilities, which expect BPFTOOL to be set to the in-tree bpftool path by default. For example, bpftool selftests fail to build: $ make -C tools/testing/selftests/bpf/ make: Entering directory '/home/tglozar/dev/linux/tools/testing/selftests/bpf' make: *** No rule to make target 'bpftool', needed by '/home/tglozar/dev/linux/tools/testing/selftests/bpf/tools/include/vmlinux.h'. Stop. make: Leaving directory '/home/tglozar/dev/linux/tools/testing/selftests/bpf' Fix the problem by renaming the variable used for system bpftool from BPFTOOL to SYSTEM_BPFTOOL, so that the new usage does not conflict with the existing one of BPFTOOL. Cc: John Kacur <jkacur@redhat.com> Cc: Luis Goncalves <lgoncalv@redhat.com> Link: https://lore.kernel.org/20250326004018.248357-1-tglozar@redhat.com Fixes: 8a635c3856dd ("tools/build: Add bpftool-skeletons feature test") Closes: https://lore.kernel.org/linux-kernel/5df6968a-2e5f-468e-b457-fc201535dd4c@linux.ibm.com/ Reported-by: Venkat Rao Bagalkote <venkat88@linux.ibm.com> Tested-by: Venkat Rao Bagalkote <venkat88@linux.ibm.com> Suggested-by: Quentin Monnet <qmo@kernel.org> Acked-by: Quentin Monnet <qmo@kernel.org> Signed-off-by: Tomas Glozar <tglozar@redhat.com> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
2025-03-04tools/build: Add bpftool-skeletons feature testTomas Glozar1-0/+3
Add bpftool-skeletons feature test, testing the presence of a bpftool capable of generating skeletons. This is to be used for tools that do not require building their own bootstrap bpftool from the kernel source tree. Cc: John Kacur <jkacur@redhat.com> Cc: Luis Goncalves <lgoncalv@redhat.com> Cc: Gabriele Monaco <gmonaco@redhat.com> Cc: Clark Williams <williams@redhat.com> Link: https://lore.kernel.org/20250218145859.27762-3-tglozar@redhat.com Signed-off-by: Tomas Glozar <tglozar@redhat.com> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
2025-02-18tools: Unify top-level quiet infrastructureCharlie Jenkins1-0/+30
Commit f2868b1a66d4f40f ("perf tools: Expose quiet/verbose variables in Makefile.perf") moved the quiet infrastructure out of tools/build/Makefile.build and into the top-level Makefile.perf file so that the quiet infrastructure could be used throughout perf and not just in Makefile.build. Extract out the quiet infrastructure into Makefile.include so that it can be leveraged outside of perf. Fixes: f2868b1a66d4f40f ("perf tools: Expose quiet/verbose variables in Makefile.perf") Reviewed-by: Jiri Olsa <jolsa@kernel.org> Signed-off-by: Charlie Jenkins <charlie@rivosinc.com> Acked-by: Andrii Nakryiko <andrii@kernel.org> Cc: Adrian Hunter <adrian.hunter@intel.com> Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com> Cc: Alexei Starovoitov <ast@kernel.org> Cc: Benjamin Tissoires <bentiss@kernel.org> Cc: Daniel Borkmann <daniel@iogearbox.net> Cc: Daniel Lezcano <daniel.lezcano@linaro.org> Cc: Eduard Zingerman <eddyz87@gmail.com> Cc: Hao Luo <haoluo@google.com> Cc: Ian Rogers <irogers@google.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: Jiri Kosina <jikos@kernel.org> Cc: John Fastabend <john.fastabend@gmail.com> Cc: Josh Poimboeuf <jpoimboe@kernel.org> Cc: KP Singh <kpsingh@kernel.org> Cc: Lukasz Luba <lukasz.luba@arm.com> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Martin KaFai Lau <martin.lau@linux.dev> Cc: Mykola Lysenko <mykolal@fb.com> Cc: Namhyung Kim <namhyung@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Quentin Monnet <qmo@kernel.org> Cc: Rafael J. Wysocki <rafael@kernel.org> Cc: Shuah Khan <shuah@kernel.org> Cc: Song Liu <song@kernel.org> Cc: Stanislav Fomichev <sdf@google.com> Cc: Steven Rostedt (VMware) <rostedt@goodmis.org> Cc: Yonghong Song <yonghong.song@linux.dev> Cc: Zhang Rui <rui.zhang@intel.com> Link: https://lore.kernel.org/r/20250213-quiet_tools-v3-1-07de4482a581@rivosinc.com Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
2025-01-09perf tools: Create generic syscall table supportCharlie Jenkins1-0/+409
Currently each architecture in perf independently generates syscall headers. Adapt the work that has gone into unifying syscall header implementations in the kernel to work with perf tools. Introduce this framework with riscv at first. riscv previously relied on libaudit, but with this change, perf tools for riscv no longer needs this external dependency. Signed-off-by: Charlie Jenkins <charlie@rivosinc.com> Cc: Adrian Hunter <adrian.hunter@intel.com> Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com> Cc: Arnd Bergmann <arnd@arndb.de> Cc: Christian Brauner <brauner@kernel.org> Cc: Guo Ren <guoren@kernel.org> Cc: Günther Noack <gnoack@google.com> Cc: Ian Rogers <irogers@google.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: James Clark <james.clark@linaro.org> Cc: Jiri Olsa <jolsa@kernel.org> Cc: John Garry <john.g.garry@oracle.com> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Leo Yan <leo.yan@linux.dev> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Mickaël Salaün <mic@digikod.net> Cc: Mike Leach <mike.leach@linaro.org> Cc: Namhyung Kim <namhyung@kernel.org> Cc: Palmer Dabbelt <palmer@dabbelt.com> Cc: Paul Walmsley <paul.walmsley@sifive.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Will Deacon <will@kernel.org> Link: https://lore.kernel.org/r/20250108-perf_syscalltbl-v6-1-7543b5293098@rivosinc.com Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
2024-11-29tools: Override makefile ARCH variable if defined, but emptyBjörn Töpel1-2/+2
There are a number of tools (bpftool, selftests), that require a "bootstrap" build. Here, a bootstrap build is a build host variant of a target. E.g., assume that you're performing a bpftool cross-build on x86 to riscv, a bootstrap build would then be an x86 variant of bpftool. The typical way to perform the host build variant, is to pass "ARCH=" in a sub-make. However, if a variable has been set with a command argument, then ordinary assignments in the makefile are ignored. This side-effect results in that ARCH, and variables depending on ARCH are not set. Workaround by overriding ARCH to the host arch, if ARCH is empty. Fixes: 8859b0da5aac ("tools/bpftool: Fix cross-build") Signed-off-by: Björn Töpel <bjorn@rivosinc.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Tested-by: Alexandre Ghiti <alexghiti@rivosinc.com> Reviewed-by: Jean-Philippe Brucker <jean-philippe@linaro.org> Reviewed-by: Namhyung Kim <namhyung@kernel.org> Reviewed-by: Toke Høiland-Jørgensen <toke@redhat.com> Acked-by: Quentin Monnet <qmo@kernel.org> Acked-by: Jiri Olsa <jolsa@kernel.org> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Link: https://lore.kernel.org/bpf/20241127101748.165693-1-bjorn@kernel.org
2024-02-23treewide: remove meaningless assignments in MakefilesMasahiro Yamada1-1/+1
In Makefiles, $(error ), $(warning ), and $(info ) expand to the empty string, as explained in the GNU Make manual [1]: "The result of the expansion of this function is the empty string." Therefore, they are no-op except for logging purposes. $(shell ...) expands to the output of the command. It expands to the empty string when the command does not print anything to stdout. Hence, $(shell mkdir ...) is no-op except for creating the directory. Remove meaningless assignments. [1]: https://www.gnu.org/software/make/manual/make.html#Make-Control-Functions Signed-off-by: Masahiro Yamada <masahiroy@kernel.org> Reviewed-by: Arnaldo Carvalho de Melo <acme@redhat.com> Reviewed-by: Ian Rogers <irogers@google.com> Link: https://lore.kernel.org/r/20240221134201.2656908-1-masahiroy@kernel.org Signed-off-by: Namhyung Kim <namhyung@kernel.org> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Adrian Hunter <adrian.hunter@intel.com> Cc: Arnaldo Carvalho de Melo <acme@kernel.org> Cc: Jiri Olsa <jolsa@kernel.org> Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: linux-kbuild@vger.kernel.org Cc: linux-kernel@vger.kernel.org Cc: linux-perf-users@vger.kernel.org
2023-10-18tools/build: Fix -s detection code in tools/scripts/Makefile.includeJiri Olsa1-1/+9
As Dmitry described in [1] changelog the current way of detecting -s option is broken for new make. Changing the tools/build -s option detection the same way as it was fixed for root Makefile in [1]. [1] 4bf73588165b ("kbuild: Port silent mode detection to future gnu make.") Cc: Dmitry Goncharov <dgoncharov@users.sf.net> Signed-off-by: Jiri Olsa <jolsa@kernel.org> Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com> Acked-by: Namhyung Kim <namhyung@kernel.org> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: KP Singh <kpsingh@chromium.org> Cc: Martin KaFai Lau <kafai@fb.com> Cc: Song Liu <songliubraving@fb.com> Cc: Yonghong Song <yhs@fb.com> Cc: John Fastabend <john.fastabend@gmail.com> Cc: Hao Luo <haoluo@google.com> Cc: Ian Rogers <irogers@google.com> Cc: Stanislav Fomichev <sdf@google.com> Cc: Daniel Borkmann <daniel@iogearbox.net> Cc: Quentin Monnet <quentin@isovalent.com> Cc: Arnaldo Carvalho de Melo <acme@kernel.org> Cc: Andrii Nakryiko <andrii@kernel.org> Cc: Alexei Starovoitov <ast@kernel.org> Cc: Ingo Molnar <mingo@kernel.org> Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com> Cc: bpf@vger.kernel.org Cc: linux-perf-users@vger.kernel.org Link: https://lore.kernel.org/r/20231008212251.236023-3-jolsa@kernel.org Signed-off-by: Namhyung Kim <namhyung@kernel.org>
2023-08-03tools build: Add 3-component logical version comparatorsArnaldo Carvalho de Melo1-0/+20
The next cset needs to compare if a flex version is greater or equal/less than another, but since there is no canonical, generally available way to compare versions in the command line (sort -V, yeah, but...), just use awk to canonicalize the versions like is also done in scripts/rust_is_available.sh. There was a problem spotted in linux-next where a bashism, here documents, aka the '<<<' stdin redirector, for strings to be used as the stdin for awk. Use $(shell echo | awk ...) instead. Cc: Adrian Hunter <adrian.hunter@intel.com> Cc: Ian Rogers <irogers@google.com> Cc: Jiri Olsa <jolsa@kernel.org> Cc: Namhyung Kim <namhyung@kernel.org> Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
2023-04-27Merge tag 'sh-for-v6.4-tag1' of ↵Linus Torvalds1-5/+0
git://git.kernel.org/pub/scm/linux/kernel/git/glaubitz/sh-linux Pull sh updates from John Paul Adrian Glaubitz: "This is a bit larger than my previous one and mainly consists of clean-up work in the arch/sh directory by Geert Uytterhoeven and Randy Dunlap. Additionally, this fixes a bug in the Storage Queue code that was discovered while I was reviewing a patch to switch the code to the bitmap API by Christophe Jaillet. So this contains both a fix for the original bug in the Storage Queue code that can be backported later as well as the Christophe's patch to swich the code to the bitmap API. Summary: - Use generic GCC library routines - sq: Use the bitmap API when applicable - sq: Fix incorrect element size for allocating bitmap buffer - pci: Remove unused variable in SH-7786 PCI Express code - mcount.S: fix build error when PRINTK is not enabled - remove sh5/sh64 last fragments - math-emu: fix macro redefined warning - init: use OF_EARLY_FLATTREE for early init - nmi_debug: fix return value of __setup handler - SH2007: drop the bad URL info" * tag 'sh-for-v6.4-tag1' of git://git.kernel.org/pub/scm/linux/kernel/git/glaubitz/sh-linux: sh: Replace <uapi/asm/types.h> by <asm-generic/int-ll64.h> sh: Use generic GCC library routines sh: sq: Use the bitmap API when applicable sh: sq: Fix incorrect element size for allocating bitmap buffer sh: pci: Remove unused variable in SH-7786 PCI Express code sh: mcount.S: fix build error when PRINTK is not enabled sh: remove sh5/sh64 last fragments sh: math-emu: fix macro redefined warning sh: init: use OF_EARLY_FLATTREE for early init sh: nmi_debug: fix return value of __setup handler sh: SH2007: drop the bad URL info
2023-03-23sh: remove sh5/sh64 last fragmentsRandy Dunlap1-5/+0
A previous patch removed most of the sh5 (sh64) support from the kernel tree. Now remove the last stragglers. Fixes: 37744feebc08 ("sh: remove sh5 support") Signed-off-by: Randy Dunlap <rdunlap@infradead.org> Cc: Geert Uytterhoeven <geert+renesas@glider.be> Cc: Arnd Bergmann <arnd@arndb.de> Cc: Rich Felker <dalias@libc.org> Cc: Yoshinori Sato <ysato@users.sourceforge.jp> Cc: John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de> Cc: linux-sh@vger.kernel.org Acked-by: John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de> Reviewed-by: John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de> Link: https://lore.kernel.org/r/20230306040037.20350-6-rdunlap@infradead.org Signed-off-by: John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>
2023-03-09Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/netJakub Kicinski1-1/+10
Documentation/bpf/bpf_devel_QA.rst b7abcd9c656b ("bpf, doc: Link to submitting-patches.rst for general patch submission info") d56b0c461d19 ("bpf, docs: Fix link to netdev-FAQ target") https://lore.kernel.org/all/20230307095812.236eb1be@canb.auug.org.au/ Signed-off-by: Jakub Kicinski <kuba@kernel.org>
2023-02-25tools: Add LoongArch build infrastructureHuacai Chen1-1/+10
We will add tools support for LoongArch (bpf, perf, objtool, etc.), add build infrastructure and common headers for preparation. Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
2023-02-22selftests/bpf: Fix cross compilation with CLANG_CROSS_FLAGSFlorent Revest1-0/+2
I cross-compile my BPF selftests with the following command: CLANG_CROSS_FLAGS="--target=aarch64-linux-gnu --sysroot=/sysroot/" \ make LLVM=1 CC=clang CROSS_COMPILE=aarch64-linux-gnu- SRCARCH=arm64 (Note the use of CLANG_CROSS_FLAGS to specify a custom sysroot instead of letting clang use gcc's default sysroot) However, CLANG_CROSS_FLAGS gets propagated to host tools builds (libbpf and bpftool) and because they reference it directly in their Makefiles, they end up cross-compiling host objects which results in linking errors. This patch ensures that CLANG_CROSS_FLAGS is reset if CROSS_COMPILE isn't set (for example when reaching a BPF host tool build). Signed-off-by: Florent Revest <revest@chromium.org> Link: https://lore.kernel.org/r/20230217151832.27784-1-revest@chromium.org Signed-off-by: Alexei Starovoitov <ast@kernel.org>
2022-03-31Merge tag 'kbuild-v5.18-v2' of ↵Linus Torvalds2-9/+15
git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild Pull Kbuild updates from Masahiro Yamada: - Add new environment variables, USERCFLAGS and USERLDFLAGS to allow additional flags to be passed to user-space programs. - Fix missing fflush() bugs in Kconfig and fixdep - Fix a minor bug in the comment format of the .config file - Make kallsyms ignore llvm's local labels, .L* - Fix UAPI compile-test for cross-compiling with Clang - Extend the LLVM= syntax to support LLVM=<suffix> form for using a particular version of LLVm, and LLVM=<prefix> form for using custom LLVM in a particular directory path. - Clean up Makefiles * tag 'kbuild-v5.18-v2' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild: kbuild: Make $(LLVM) more flexible kbuild: add --target to correctly cross-compile UAPI headers with Clang fixdep: use fflush() and ferror() to ensure successful write to files arch: syscalls: simplify uapi/kapi directory creation usr/include: replace extra-y with always-y certs: simplify empty certs creation in certs/Makefile certs: include certs/signing_key.x509 unconditionally kallsyms: ignore all local labels prefixed by '.L' kconfig: fix missing '# end of' for empty menu kconfig: add fflush() before ferror() check kbuild: replace $(if A,A,B) with $(or A,B) kbuild: Add environment variables for userprogs flags kbuild: unify cmd_copy and cmd_shipped
2022-03-31kbuild: Make $(LLVM) more flexibleNathan Chancellor1-8/+14
The LLVM make variable allows a developer to quickly switch between the GNU and LLVM tools. However, it does not handle versioned binaries, such as the ones shipped by Debian, as LLVM=1 just defines the tool variables with the unversioned binaries. There was some discussion during the review of the patch that introduces LLVM=1 around versioned binaries, ultimately coming to the conclusion that developers can just add the folder that contains the unversioned binaries to their PATH, as Debian's versioned suffixed binaries are really just symlinks to the unversioned binaries in /usr/lib/llvm-#/bin: $ realpath /usr/bin/clang-14 /usr/lib/llvm-14/bin/clang $ PATH=/usr/lib/llvm-14/bin:$PATH make ... LLVM=1 However, that can be cumbersome to developers who are constantly testing series with different toolchains and versions. It is simple enough to support these versioned binaries directly in the Kbuild system by allowing the developer to specify the version suffix with LLVM=, which is shorter than the above suggestion: $ make ... LLVM=-14 It does not change the meaning of LLVM=1 (which will continue to use unversioned binaries) and it does not add too much additional complexity to the existing $(LLVM) code, while allowing developers to quickly test their series with different versions of the whole LLVM suite of tools. Some developers may build LLVM from source but not add the binaries to their PATH, as they may not want to use that toolchain systemwide. Support those developers by allowing them to supply the directory that the LLVM tools are available in, as it is no more complex to support than the version suffix change above. $ make ... LLVM=/path/to/llvm/ Update and reorder the documentation to reflect these new additions. At the same time, notate that LLVM=0 is not the same as just omitting it altogether, which has confused people in the past. Link: https://lore.kernel.org/r/20200317215515.226917-1-ndesaulniers@google.com/ Link: https://lore.kernel.org/r/20220224151322.072632223@infradead.org/ Suggested-by: Masahiro Yamada <masahiroy@kernel.org> Suggested-by: Peter Zijlstra <peterz@infradead.org> Signed-off-by: Nathan Chancellor <nathan@kernel.org> Reviewed-by: Kees Cook <keescook@chromium.org> Reviewed-by: Nick Desaulniers <ndesaulniers@google.com> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
2022-03-08tools: Fix unavoidable GCC call in Clang buildsAdrian Ratiu1-0/+4
In ChromeOS and Gentoo we catch any unwanted mixed Clang/LLVM and GCC/binutils usage via toolchain wrappers which fail builds. This has revealed that GCC is called unconditionally in Clang configured builds to populate GCC_TOOLCHAIN_DIR. Allow the user to override CLANG_CROSS_FLAGS to avoid the GCC call - in our case we set the var directly in the ebuild recipe. In theory Clang could be able to autodetect these settings so this logic could be removed entirely, but in practice as the commit cebdb7374577 ("tools: Help cross-building with clang") mentions, this does not always work, so giving distributions more control to specify their flags & sysroot is beneficial. Suggested-by: Manoj Gupta <manojgupta@chromium.com> Suggested-by: Nathan Chancellor <nathan@kernel.org> Signed-off-by: Adrian Ratiu <adrian.ratiu@collabora.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Acked-by: Nathan Chancellor <nathan@kernel.org> Cc: Nick Desaulniers <ndesaulniers@google.com> Link: https://lore.kernel.org/lkml/87czjk4osi.fsf@ryzen9.i-did-not-set--mail-host-address--so-tickle-me Link: https://lore.kernel.org/bpf/20220308121428.81735-1-adrian.ratiu@collabora.com
2022-02-15kbuild: replace $(if A,A,B) with $(or A,B)Masahiro Yamada1-1/+1
$(or ...) is available since GNU Make 3.81, and useful to shorten the code in some places. Covert as follows: $(if A,A,B) --> $(or A,B) This patch also converts: $(if A, A, B) --> $(or A, B) Strictly speaking, the latter is not an equivalent conversion because GNU Make keeps spaces after commas; if A is not empty, $(if A, A, B) expands to " A", while $(or A, B) expands to "A". Anyway, preceding spaces are not significant in the code hunks I touched. Signed-off-by: Masahiro Yamada <masahiroy@kernel.org> Reviewed-by: Nicolas Schier <nicolas@fjasle.eu>
2022-02-01tools: Ignore errors from `which' when searching a GCC toolchainJean-Philippe Brucker1-1/+1
When cross-building tools with clang, we run `which $(CROSS_COMPILE)gcc` to detect whether a GCC toolchain provides the standard libraries. It is only a helper because some distros put libraries where LLVM does not automatically find them. On other systems, LLVM detects the libc automatically and does not need this. There, it is completely fine not to have a GCC at all, but some versions of `which' display an error when the command is not found: which: no aarch64-linux-gnu-gcc in ($PATH) Since the error can safely be ignored, throw it to /dev/null. Fixes: cebdb7374577 ("tools: Help cross-building with clang") Reported-by: Nathan Chancellor <nathan@kernel.org> Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Tested-by: Nathan Chancellor <nathan@kernel.org> Reviewed-by: Nathan Chancellor <nathan@kernel.org> Link: https://lore.kernel.org/bpf/20220201093119.1713207-1-jean-philippe@linaro.org
2021-12-16tools: Help cross-building with clangJean-Philippe Brucker1-1/+12
Cross-compilation with clang uses the -target parameter rather than a toolchain prefix. Just like the kernel Makefile, add that parameter to CFLAGS when CROSS_COMPILE is set. Unlike the kernel Makefile, we use the --sysroot and --gcc-toolchain options because unlike the kernel, tools require standard libraries. Commit c91d4e47e10e ("Makefile: Remove '--gcc-toolchain' flag") provides some background about --gcc-toolchain. Normally clang finds on its own the additional utilities and libraries that it needs (for example GNU ld or glibc). On some systems however, this autode