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/[email protected]/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/[email protected]/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/[email protected]/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/[email protected]/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/[email protected]/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 <[email protected]>
Tested-by: Arnaldo Carvalho de Melo <[email protected]>
Cc: Adrian Hunter <[email protected]>
Cc: Alexander Shishkin <[email protected]>
Cc: Andi Kleen <[email protected]>
Cc: Andrii Nakryiko <[email protected]>
Cc: Anshuman Khandual <[email protected]>
Cc: Athira Rajeev <[email protected]>
Cc: Brendan Gregg <[email protected]>
Cc: Carsten Haitzler <[email protected]>
Cc: Eduard Zingerman <[email protected]>
Cc: Fangrui Song <[email protected]>
Cc: He Kuang <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: James Clark <[email protected]>
Cc: Jiri Olsa <[email protected]>
Cc: Kan Liang <[email protected]>
Cc: Leo Yan <[email protected]>
Cc: Madhavan Srinivasan <[email protected]>
Cc: Mark Rutland <[email protected]>
Cc: Namhyung Kim <[email protected]>
Cc: Nathan Chancellor <[email protected]>
Cc: "Naveen N. Rao" <[email protected]>
Cc: Nick Desaulniers <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Ravi Bangoria <[email protected]>
Cc: Rob Herring <[email protected]>
Cc: Tiezhu Yang <[email protected]>
Cc: Tom Rix <[email protected]>
Cc: Wang Nan <[email protected]>
Cc: Wang ShaoBo <[email protected]>
Cc: Yang Jihong <[email protected]>
Cc: Yonghong Song <[email protected]>
Cc: YueHaibing <[email protected]>
Link: https://lore.kernel.org/lkml/[email protected]
Signed-off-by: Arnaldo Carvalho de Melo <[email protected]>

1 files changed, 0 insertions, 225 deletions

diff --git a/tools/perf/util/c++/clang.cpp b/tools/perf/util/c++/clang.cpp
deleted file mode 100644
index 1aad7d6d34aa..000000000000
--- a/tools/perf/util/c++/clang.cpp
+++ /dev/null
@@ -1,225 +0,0 @@
-// SPDX-License-Identifier: GPL-2.0
-/*
- * llvm C frontend for perf. Support dynamically compile C file
- *
- * Inspired by clang example code:
- * http://llvm.org/svn/llvm-project/cfe/trunk/examples/clang-interpreter/main.cpp
- *
- * Copyright (C) 2016 Wang Nan <[email protected]>
- * Copyright (C) 2016 Huawei Inc.
- */
-
-#include "clang/Basic/Version.h"
-#include "clang/CodeGen/CodeGenAction.h"
-#include "clang/Frontend/CompilerInvocation.h"
-#include "clang/Frontend/CompilerInstance.h"
-#include "clang/Frontend/TextDiagnosticPrinter.h"
-#include "clang/Tooling/Tooling.h"
-#include "llvm/IR/LegacyPassManager.h"
-#include "llvm/IR/Module.h"
-#include "llvm/Option/Option.h"
-#include "llvm/Support/FileSystem.h"
-#include "llvm/Support/ManagedStatic.h"
-#if CLANG_VERSION_MAJOR >= 14
-#include "llvm/MC/TargetRegistry.h"
-#else
-#include "llvm/Support/TargetRegistry.h"
-#endif
-#include "llvm/Support/TargetSelect.h"
-#include "llvm/Target/TargetMachine.h"
-#include "llvm/Target/TargetOptions.h"
-#include <memory>
-
-#include "clang.h"
-#include "clang-c.h"
-
-namespace perf {
-
-static std::unique_ptr<llvm::LLVMContext> LLVMCtx;
-
-using namespace clang;
-
-static CompilerInvocation *
-createCompilerInvocation(llvm::opt::ArgStringList CFlags, StringRef& Path,
-			 DiagnosticsEngine& Diags)
-{
-	llvm::opt::ArgStringList CCArgs {
-		"-cc1",
-		"-triple", "bpf-pc-linux",
-		"-fsyntax-only",
-		"-O2",
-		"-nostdsysteminc",
-		"-nobuiltininc",
-		"-vectorize-loops",
-		"-vectorize-slp",
-		"-Wno-unused-value",
-		"-Wno-pointer-sign",
-		"-x", "c"};
-
-	CCArgs.append(CFlags.begin(), CFlags.end());
-	CompilerInvocation *CI = tooling::newInvocation(&Diags, CCArgs
-#if CLANG_VERSION_MAJOR >= 11
-                                                        ,/*BinaryName=*/nullptr
-#endif
-                                                        );
-
-	FrontendOptions& Opts = CI->getFrontendOpts();
-	Opts.Inputs.clear();
-	Opts.Inputs.emplace_back(Path,
-			FrontendOptions::getInputKindForExtension("c"));
-	return CI;
-}
-
-static std::unique_ptr<llvm::Module>
-getModuleFromSource(llvm::opt::ArgStringList CFlags,
-		    StringRef Path, IntrusiveRefCntPtr<vfs::FileSystem> VFS)
-{
-	CompilerInstance Clang;
-	Clang.createDiagnostics();
-
-#if CLANG_VERSION_MAJOR < 9
-	Clang.setVirtualFileSystem(&*VFS);
-#else
-	Clang.createFileManager(&*VFS);
-#endif
-
-#if CLANG_VERSION_MAJOR < 4
-	IntrusiveRefCntPtr<CompilerInvocation> CI =
-		createCompilerInvocation(std::move(CFlags), Path,
-					 Clang.getDiagnostics());
-	Clang.setInvocation(&*CI);
-#else
-	std::shared_ptr<CompilerInvocation> CI(
-		createCompilerInvocation(std::move(CFlags), Path,
-					 Clang.getDiagnostics()));
-	Clang.setInvocation(CI);
-#endif
-
-	std::unique_ptr<CodeGenAction> Act(new EmitLLVMOnlyAction(&*LLVMCtx));
-	if (!Clang.ExecuteAction(*Act))
-		return std::unique_ptr<llvm::Module>(nullptr);
-
-	return Act->takeModule();
-}
-
-std::unique_ptr<llvm::Module>
-getModuleFromSource(llvm::opt::ArgStringList CFlags,
-		    StringRef Name, StringRef Content)
-{
-	using namespace vfs;
-
-	llvm::IntrusiveRefCntPtr<OverlayFileSystem> OverlayFS(
-			new OverlayFileSystem(getRealFileSystem()));
-	llvm::IntrusiveRefCntPtr<InMemoryFileSystem> MemFS(
-			new InMemoryFileSystem(true));
-
-	/*
-	 * pushOverlay helps setting working dir for MemFS. Must call
-	 * before addFile.
-	 */
-	OverlayFS->pushOverlay(MemFS);
-	MemFS->addFile(Twine(Name), 0, llvm::MemoryBuffer::getMemBuffer(Content));
-
-	return getModuleFromSource(std::move(CFlags), Name, OverlayFS);
-}
-
-std::unique_ptr<llvm::Module>
-getModuleFromSource(llvm::opt::ArgStringList CFlags, StringRef Path)
-{
-	IntrusiveRefCntPtr<vfs::FileSystem> VFS(vfs::getRealFileSystem());
-	return getModuleFromSource(std::move(CFlags), Path, VFS);
-}
-
-std::unique_ptr<llvm::SmallVectorImpl<char>>
-getBPFObjectFromModule(llvm::Module *Module)
-{
-	using namespace llvm;
-
-	std::string TargetTriple("bpf-pc-linux");
-	std::string Error;
-	const Target* Target = TargetRegistry::lookupTarget(TargetTriple, Error);
-	if (!Target) {
-		llvm::errs() << Error;
-		return std::unique_ptr<llvm::SmallVectorImpl<char>>(nullptr);
-	}
-
-	llvm::TargetOptions Opt;
-	TargetMachine *TargetMachine =
-		Target->createTargetMachine(TargetTriple,
-					    "generic", "",
-					    Opt, Reloc::Static);
-
-	Module->setDataLayout(TargetMachine->createDataLayout());
-	Module->setTargetTriple(TargetTriple);
-
-	std::unique_ptr<SmallVectorImpl<char>> Buffer(new SmallVector<char, 0>());
-	raw_svector_ostream ostream(*Buffer);
-
-	legacy::PassManager PM;
-	bool NotAdded;
-	NotAdded = TargetMachine->addPassesToEmitFile(PM, ostream
-#if CLANG_VERSION_MAJOR >= 7
-                                                      , /*DwoOut=*/nullptr
-#endif
-#if CLANG_VERSION_MAJOR < 10
-                                                      , TargetMachine::CGFT_ObjectFile
-#else
-                                                      , llvm::CGFT_ObjectFile
-#endif
-                                                      );
-	if (NotAdded) {
-		llvm::errs() << "TargetMachine can't emit a file of this type\n";
-		return std::unique_ptr<llvm::SmallVectorImpl<char>>(nullptr);
-	}
-	PM.run(*Module);
-
-	return Buffer;
-}
-
-}
-
-extern "C" {
-void perf_clang__init(void)
-{
-	perf::LLVMCtx.reset(new llvm::LLVMContext());
-	LLVMInitializeBPFTargetInfo();
-	LLVMInitializeBPFTarget();
-	LLVMInitializeBPFTargetMC();
-	LLVMInitializeBPFAsmPrinter();
-}
-
-void perf_clang__cleanup(void)
-{
-	perf::LLVMCtx.reset(nullptr);
-	llvm::llvm_shutdown();
-}
-
-int perf_clang__compile_bpf(const char *filename,
-			    void **p_obj_buf,
-			    size_t *p_obj_buf_sz)
-{
-	using namespace perf;
-
-	if (!p_obj_buf || !p_obj_buf_sz)
-		return -EINVAL;
-
-	llvm::opt::ArgStringList CFlags;
-	auto M = getModuleFromSource(std::move(CFlags), filename);
-	if (!M)
-		return  -EINVAL;
-	auto O = getBPFObjectFromModule(&*M);
-	if (!O)
-		return -EINVAL;
-
-	size_t size = O->size_in_bytes();
-	void *buffer;
-
-	buffer = malloc(size);
-	if (!buffer)
-		return -ENOMEM;
-	memcpy(buffer, O->data(), size);
-	*p_obj_buf = buffer;
-	*p_obj_buf_sz = size;
-	return 0;
-}
-}