Commit 56b11a21 authored Aug 11, 2023 by Ian Rogers Committed by Arnaldo Carvalho de Melo Aug 15, 2023

perf bpf: Remove support for embedding clang for compiling BPF events (-e foo.c)



This never was in the default build for perf, is difficult to maintain
as it uses clang/llvm internals so ditch it, keeping, for now, the
external compilation of .c BPF into .o bytecode and its subsequent
loading, that is also going to be removed, do it separately to help
bisection and to properly document what is being removed and why.

Committer notes:

Extracted from a larger patch and removed some leftovers, namely
deleting these now unused feature tests:

    tools/build/feature/test-clang.cpp
    tools/build/feature/test-cxx.cpp
    tools/build/feature/test-llvm-version.cpp
    tools/build/feature/test-llvm.cpp

Testing the use of BPF events after applying this patch:

To use the external clang/llvm toolchain to compile a .c event and then
use libbpf to load it, to get the syscalls:sys_enter_open* tracepoints
and read the filename pointer, putting it into the ring buffer right
after the usual tracepoint payload for 'perf trace' to then print it:

  [root@quaco ~]# perf trace -e /home/acme/git/perf-tools-next/tools/perf/examples/bpf/augmented_raw_syscalls.c,open* --max-events=10
     0.000 systemd-oomd/959 openat(dfd: CWD, filename: "/proc/meminfo", flags: RDONLY|CLOEXEC) = 12
     0.083 abrt-dump-jour/1453 openat(dfd: CWD, filename: "/var/log/journal/d6a97235307247e09f13f326fb607e3c/system.journal", flags: RDONLY|CLOEXEC|NONBLOCK) = 4
     0.063 abrt-dump-jour/1454 openat(dfd: CWD, filename: "/var/log/journal/d6a97235307247e09f13f326fb607e3c/system.journal", flags: RDONLY|CLOEXEC|NONBLOCK) = 4
     0.082 abrt-dump-jour/1455 openat(dfd: CWD, filename: "/var/log/journal/d6a97235307247e09f13f326fb607e3c/system.journal", flags: RDONLY|CLOEXEC|NONBLOCK) = 4
   250.124 systemd-oomd/959 openat(dfd: CWD, filename: "/proc/meminfo", flags: RDONLY|CLOEXEC) = 12
   250.521 systemd-oomd/959 openat(dfd: CWD, filename: "/sys/fs/cgroup/user.slice/user-1000.slice/user@1000.service/app.slice/memory.pressure", flags: RDONLY|CLOEXEC) = 12
   251.047 systemd-oomd/959 openat(dfd: CWD, filename: "/sys/fs/cgroup/user.slice/user-1000.slice/user@1000.service/app.slice/memory.current", flags: RDONLY|CLOEXEC) = 12
   251.162 systemd-oomd/959 openat(dfd: CWD, filename: "/sys/fs/cgroup/user.slice/user-1000.slice/user@1000.service/app.slice/memory.min", flags: RDONLY|CLOEXEC) = 12
   251.242 systemd-oomd/959 openat(dfd: CWD, filename: "/sys/fs/cgroup/user.slice/user-1000.slice/user@1000.service/app.slice/memory.low", flags: RDONLY|CLOEXEC) = 12
   251.353 systemd-oomd/959 openat(dfd: CWD, filename: "/sys/fs/cgroup/user.slice/user-1000.slice/user@1000.service/app.slice/memory.swap.current", flags: RDONLY|CLOEXEC) = 12
  [root@quaco ~]#

Same thing, but with a prebuilt .o BPF bytecode:

  [root@quaco ~]# perf trace -e /home/acme/git/perf-tools-next/tools/perf/examples/bpf/augmented_raw_syscalls.o,open* --max-events=10
     0.000 systemd-oomd/959 openat(dfd: CWD, filename: "/proc/meminfo", flags: RDONLY|CLOEXEC) = 12
     0.083 abrt-dump-jour/1453 openat(dfd: CWD, filename: "/var/log/journal/d6a97235307247e09f13f326fb607e3c/system.journal", flags: RDONLY|CLOEXEC|NONBLOCK) = 4
     0.083 abrt-dump-jour/1455 openat(dfd: CWD, filename: "/var/log/journal/d6a97235307247e09f13f326fb607e3c/system.journal", flags: RDONLY|CLOEXEC|NONBLOCK) = 4
     0.062 abrt-dump-jour/1454 openat(dfd: CWD, filename: "/var/log/journal/d6a97235307247e09f13f326fb607e3c/system.journal", flags: RDONLY|CLOEXEC|NONBLOCK) = 4
   249.985 systemd-oomd/959 openat(dfd: CWD, filename: "/proc/meminfo", flags: RDONLY|CLOEXEC) = 12
   466.763 thermald/1234 openat(dfd: CWD, filename: "/sys/class/powercap/intel-rapl/intel-rapl:0/intel-rapl:0:2/energy_uj") = 13
   467.145 thermald/1234 openat(dfd: CWD, filename: "/sys/class/powercap/intel-rapl/intel-rapl:0/energy_uj") = 13
   467.311 thermald/1234 openat(dfd: CWD, filename: "/sys/class/thermal/thermal_zone2/temp") = 13
   500.040 cgroupify/24006 openat(dfd: 4, filename: ".", flags: RDONLY|CLOEXEC|DIRECTORY|NONBLOCK) = 5
   500.295 cgroupify/24006 openat(dfd: 4, filename: "24616/cgroup.procs") = 5
  [root@quaco ~]#

Signed-off-by: Ian Rogers <irogers@google.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Andrii Nakryiko <andrii@kernel.org>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Athira Rajeev <atrajeev@linux.vnet.ibm.com>
Cc: Brendan Gregg <brendan.d.gregg@gmail.com>
Cc: Carsten Haitzler <carsten.haitzler@arm.com>
Cc: Eduard Zingerman <eddyz87@gmail.com>
Cc: Fangrui Song <maskray@google.com>
Cc: He Kuang <hekuang@huawei.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: James Clark <james.clark@arm.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Leo Yan <leo.yan@linaro.org>
Cc: Madhavan Srinivasan <maddy@linux.ibm.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Nathan Chancellor <nathan@kernel.org>
Cc: "Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ravi Bangoria <ravi.bangoria@amd.com>
Cc: Rob Herring <robh@kernel.org>
Cc: Tiezhu Yang <yangtiezhu@loongson.cn>
Cc: Tom Rix <trix@redhat.com>
Cc: Wang Nan <wangnan0@huawei.com>
Cc: Wang ShaoBo <bobo.shaobowang@huawei.com>
Cc: Yang Jihong <yangjihong1@huawei.com>
Cc: Yonghong Song <yhs@fb.com>
Cc: YueHaibing <yuehaibing@huawei.com>
Link: https://lore.kernel.org/lkml/ZNZWsAXg2px1sm2h@kernel.org


Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

parent 6f769c34

tools/build/feature/test-clang.cpp

deleted100644 → 0

+0 −28

Original line number	Diff line number	Diff line
		// SPDX-License-Identifier: GPL-2.0
		#include "clang/Basic/Version.h"
		#if CLANG_VERSION_MAJOR < 8
		#include "clang/Basic/VirtualFileSystem.h"
		#endif
		#include "clang/Driver/Driver.h"
		#include "clang/Frontend/TextDiagnosticPrinter.h"
		#include "llvm/ADT/IntrusiveRefCntPtr.h"
		#include "llvm/Support/ManagedStatic.h"
		#if CLANG_VERSION_MAJOR >= 8
		#include "llvm/Support/VirtualFileSystem.h"
		#endif
		#include "llvm/Support/raw_ostream.h"

		using namespace clang;
		using namespace clang::driver;

		int main()
		{
		IntrusiveRefCntPtr<DiagnosticIDs> DiagID(new DiagnosticIDs());
		IntrusiveRefCntPtr<DiagnosticOptions> DiagOpts = new DiagnosticOptions();

		DiagnosticsEngine Diags(DiagID, &*DiagOpts);
		Driver TheDriver("test", "bpf-pc-linux", Diags);

		llvm::llvm_shutdown();
		return 0;
		}

tools/build/feature/test-cxx.cpp

deleted100644 → 0

+0 −16

Original line number	Diff line number	Diff line
		// SPDX-License-Identifier: GPL-2.0
		#include <iostream>
		#include <memory>

		static void print_str(std::string s)
		{
		std::cout << s << std::endl;
		}

		int main()
		{
		std::string s("Hello World!");
		print_str(std::move(s));
		std::cout << "\|" << s << "\|" << std::endl;
		return 0;
		}

tools/build/feature/test-llvm-version.cpp

deleted100644 → 0

+0 −12

Original line number	Diff line number	Diff line
		// SPDX-License-Identifier: GPL-2.0
		#include <cstdio>
		#include "llvm/Config/llvm-config.h"

		#define NUM_VERSION (((LLVM_VERSION_MAJOR) << 16) + (LLVM_VERSION_MINOR << 8) + LLVM_VERSION_PATCH)
		#define pass int main() {printf("%x\n", NUM_VERSION); return 0;}

		#if NUM_VERSION >= 0x030900
		pass
		#else
		# error This LLVM is not tested yet.
		#endif

tools/build/feature/test-llvm.cpp

deleted100644 → 0

+0 −14

Original line number	Diff line number	Diff line
		// SPDX-License-Identifier: GPL-2.0
		#include "llvm/Support/ManagedStatic.h"
		#include "llvm/Support/raw_ostream.h"
		#define NUM_VERSION (((LLVM_VERSION_MAJOR) << 16) + (LLVM_VERSION_MINOR << 8) + LLVM_VERSION_PATCH)

		#if NUM_VERSION < 0x030900
		# error "LLVM version too low"
		#endif
		int main()
		{
		llvm::errs() << "Hello World!\n";
		llvm::llvm_shutdown();
		return 0;
		}

tools/perf/Makefile.config

+0 −31

Original line number	Diff line number	Diff line
		@@ -1127,37 +1127,6 @@ ifndef NO_JVMTI
		endif
		endif

		USE_CXX = 0
		USE_CLANGLLVM = 0
		ifdef LIBCLANGLLVM
		$(call feature_check,cxx)
		ifneq ($(feature-cxx), 1)
		msg := $(warning No g++ found, disable clang and llvm support. Please install g++)
		else
		$(call feature_check,llvm)
		$(call feature_check,llvm-version)
		ifneq ($(feature-llvm), 1)
		msg := $(warning No suitable libLLVM found, disabling builtin clang and LLVM support. Please install llvm-dev(el) (>= 3.9.0))
		else
		$(call feature_check,clang)
		ifneq ($(feature-clang), 1)
		msg := $(warning No suitable libclang found, disabling builtin clang and LLVM support. Please install libclang-dev(el) (>= 3.9.0))
		else
		CFLAGS += -DHAVE_LIBCLANGLLVM_SUPPORT
		CXXFLAGS += -DHAVE_LIBCLANGLLVM_SUPPORT -I$(shell $(LLVM_CONFIG) --includedir)
		$(call detected,CONFIG_CXX)
		$(call detected,CONFIG_CLANGLLVM)
		USE_CXX = 1
		USE_LLVM = 1
		USE_CLANG = 1
		ifneq ($(feature-llvm-version),1)
		msg := $(warning This version of LLVM is not tested. May cause build errors)
		endif
		endif
		endif
		endif
		endif

		ifndef NO_LIBPFM4
		$(call feature_check,libpfm4)
		ifeq ($(feature-libpfm4), 1)