perf/ebpf library + llvm/clang infrastructure

Infrastructure:
 
 - library for interfacing with the kernel eBPF infrastructure, with
   tools/perf/ targeted as a first user (Wang Nan)
 
 - llvm/clang infrastructure for building BPF object files from C source
   code (Wang Nan)
 
 Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
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Merge tag 'perf-ebpf-for-mingo' of git://git.kernel.org/pub/scm/linux/kernel/git/acme/linux into perf/core

Pull perf/ebpf library + llvm/clang infrastructure changes from Arnaldo Carvalho de Melo:

Infrastructure changes:

  - Add library for interfacing with the kernel eBPF infrastructure, with
    tools/perf/ targeted as a first user. (Wang Nan)

  - Add llvm/clang infrastructure for building BPF object files from C source
    code. (Wang Nan)

Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>

tools/build/feature/Makefile

@@ -33,7 +33,8 @@ FILES=					\
 	test-compile-32.bin		\
 	test-compile-x32.bin		\
 	test-zlib.bin			\
-	test-lzma.bin
+	test-lzma.bin			\
+	test-bpf.bin
 
 CC := $(CROSS_COMPILE)gcc -MD
 PKG_CONFIG := $(CROSS_COMPILE)pkg-config
@@ -156,6 +157,9 @@ test-zlib.bin:
 test-lzma.bin:
 	$(BUILD) -llzma
 
+test-bpf.bin:
+	$(BUILD)
+
 -include *.d
 
 ###############################

tools/build/feature/test-bpf.c

@@ -0,0 +1,18 @@
+#include <linux/bpf.h>
+
+int main(void)
+{
+	union bpf_attr attr;
+
+	attr.prog_type = BPF_PROG_TYPE_KPROBE;
+	attr.insn_cnt = 0;
+	attr.insns = 0;
+	attr.license = 0;
+	attr.log_buf = 0;
+	attr.log_size = 0;
+	attr.log_level = 0;
+	attr.kern_version = 0;
+
+	attr = attr;
+	return 0;
+}

tools/lib/bpf/.gitignore

@@ -0,0 +1,2 @@
+libbpf_version.h
+FEATURE-DUMP

tools/lib/bpf/Build

@@ -0,0 +1 @@
+libbpf-y := libbpf.o bpf.o

tools/lib/bpf/Makefile

@@ -0,0 +1,195 @@
+# Most of this file is copied from tools/lib/traceevent/Makefile
+
+BPF_VERSION = 0
+BPF_PATCHLEVEL = 0
+BPF_EXTRAVERSION = 1
+
+MAKEFLAGS += --no-print-directory
+
+
+# Makefiles suck: This macro sets a default value of $(2) for the
+# variable named by $(1), unless the variable has been set by
+# environment or command line. This is necessary for CC and AR
+# because make sets default values, so the simpler ?= approach
+# won't work as expected.
+define allow-override
+  $(if $(or $(findstring environment,$(origin $(1))),\
+            $(findstring command line,$(origin $(1)))),,\
+    $(eval $(1) = $(2)))
+endef
+
+# Allow setting CC and AR, or setting CROSS_COMPILE as a prefix.
+$(call allow-override,CC,$(CROSS_COMPILE)gcc)
+$(call allow-override,AR,$(CROSS_COMPILE)ar)
+
+INSTALL = install
+
+# Use DESTDIR for installing into a different root directory.
+# This is useful for building a package. The program will be
+# installed in this directory as if it was the root directory.
+# Then the build tool can move it later.
+DESTDIR ?=
+DESTDIR_SQ = '$(subst ','\'',$(DESTDIR))'
+
+LP64 := $(shell echo __LP64__ | ${CC} ${CFLAGS} -E -x c - | tail -n 1)
+ifeq ($(LP64), 1)
+  libdir_relative = lib64
+else
+  libdir_relative = lib
+endif
+
+prefix ?= /usr/local
+libdir = $(prefix)/$(libdir_relative)
+man_dir = $(prefix)/share/man
+man_dir_SQ = '$(subst ','\'',$(man_dir))'
+
+export man_dir man_dir_SQ INSTALL
+export DESTDIR DESTDIR_SQ
+
+include ../../scripts/Makefile.include
+
+# copy a bit from Linux kbuild
+
+ifeq ("$(origin V)", "command line")
+  VERBOSE = $(V)
+endif
+ifndef VERBOSE
+  VERBOSE = 0
+endif
+
+ifeq ($(srctree),)
+srctree := $(patsubst %/,%,$(dir $(shell pwd)))
+srctree := $(patsubst %/,%,$(dir $(srctree)))
+srctree := $(patsubst %/,%,$(dir $(srctree)))
+#$(info Determined 'srctree' to be $(srctree))
+endif
+
+FEATURE_DISPLAY = libelf libelf-getphdrnum libelf-mmap bpf
+FEATURE_TESTS = libelf bpf
+
+INCLUDES = -I. -I$(srctree)/tools/include -I$(srctree)/arch/$(ARCH)/include/uapi -I$(srctree)/include/uapi
+FEATURE_CHECK_CFLAGS-bpf = $(INCLUDES)
+
+include $(srctree)/tools/build/Makefile.feature
+
+export prefix libdir src obj
+
+# Shell quotes
+libdir_SQ = $(subst ','\'',$(libdir))
+libdir_relative_SQ = $(subst ','\'',$(libdir_relative))
+plugin_dir_SQ = $(subst ','\'',$(plugin_dir))
+
+LIB_FILE = libbpf.a libbpf.so
+
+VERSION		= $(BPF_VERSION)
+PATCHLEVEL	= $(BPF_PATCHLEVEL)
+EXTRAVERSION	= $(BPF_EXTRAVERSION)
+
+OBJ		= $@
+N		=
+
+LIBBPF_VERSION = $(BPF_VERSION).$(BPF_PATCHLEVEL).$(BPF_EXTRAVERSION)
+
+# Set compile option CFLAGS
+ifdef EXTRA_CFLAGS
+  CFLAGS := $(EXTRA_CFLAGS)
+else
+  CFLAGS := -g -Wall
+endif
+
+ifeq ($(feature-libelf-mmap), 1)
+  override CFLAGS += -DHAVE_LIBELF_MMAP_SUPPORT
+endif
+
+ifeq ($(feature-libelf-getphdrnum), 1)
+  override CFLAGS += -DHAVE_ELF_GETPHDRNUM_SUPPORT
+endif
+
+# Append required CFLAGS
+override CFLAGS += $(EXTRA_WARNINGS)
+override CFLAGS += -Werror -Wall
+override CFLAGS += -fPIC
+override CFLAGS += $(INCLUDES)
+
+ifeq ($(VERBOSE),1)
+  Q =
+else
+  Q = @
+endif
+
+# Disable command line variables (CFLAGS) overide from top
+# level Makefile (perf), otherwise build Makefile will get
+# the same command line setup.
+MAKEOVERRIDES=
+
+export srctree OUTPUT CC LD CFLAGS V
+build := -f $(srctree)/tools/build/Makefile.build dir=. obj
+
+BPF_IN    := $(OUTPUT)libbpf-in.o
+LIB_FILE := $(addprefix $(OUTPUT),$(LIB_FILE))
+
+CMD_TARGETS = $(LIB_FILE)
+
+TARGETS = $(CMD_TARGETS)
+
+all: $(VERSION_FILES) all_cmd
+
+all_cmd: $(CMD_TARGETS)
+
+$(BPF_IN): force elfdep bpfdep
+	$(Q)$(MAKE) $(build)=libbpf
+
+$(OUTPUT)libbpf.so: $(BPF_IN)
+	$(QUIET_LINK)$(CC) --shared $^ -o $@
+
+$(OUTPUT)libbpf.a: $(BPF_IN)
+	$(QUIET_LINK)$(RM) $@; $(AR) rcs $@ $^
+
+define update_dir
+  (echo $1 > $@.tmp;				\
+   if [ -r $@ ] && cmp -s $@ $@.tmp; then	\
+     rm -f $@.tmp;				\
+   else						\
+     echo '  UPDATE                 $@';	\
+     mv -f $@.tmp $@;				\
+   fi);
+endef
+
+define do_install
+	if [ ! -d '$(DESTDIR_SQ)$2' ]; then		\
+		$(INSTALL) -d -m 755 '$(DESTDIR_SQ)$2';	\
+	fi;						\
+	$(INSTALL) $1 '$(DESTDIR_SQ)$2'
+endef
+
+install_lib: all_cmd
+	$(call QUIET_INSTALL, $(LIB_FILE)) \
+		$(call do_install,$(LIB_FILE),$(libdir_SQ))
+
+install: install_lib
+
+### Cleaning rules
+
+config-clean:
+	$(call QUIET_CLEAN, config)
+	$(Q)$(MAKE) -C $(srctree)/tools/build/feature/ clean >/dev/null
+
+clean:
+	$(call QUIET_CLEAN, libbpf) $(RM) *.o *~ $(TARGETS) *.a *.so $(VERSION_FILES) .*.d \
+		$(RM) LIBBPF-CFLAGS
+	$(call QUIET_CLEAN, core-gen) $(RM) $(OUTPUT)FEATURE-DUMP
+
+
+
+PHONY += force elfdep bpfdep
+force:
+
+elfdep:
+	@if [ "$(feature-libelf)" != "1" ]; then echo "No libelf found"; exit -1 ; fi
+
+bpfdep:
+	@if [ "$(feature-bpf)" != "1" ]; then echo "BPF API too old"; exit -1 ; fi
+
+# Declare the contents of the .PHONY variable as phony.  We keep that
+# information in a variable so we can use it in if_changed and friends.
+.PHONY: $(PHONY)

tools/lib/bpf/bpf.c

@@ -0,0 +1,85 @@
+/*
+ * common eBPF ELF operations.
+ *
+ * Copyright (C) 2013-2015 Alexei Starovoitov <ast@kernel.org>
+ * Copyright (C) 2015 Wang Nan <wangnan0@huawei.com>
+ * Copyright (C) 2015 Huawei Inc.
+ */
+
+#include <stdlib.h>
+#include <memory.h>
+#include <unistd.h>
+#include <asm/unistd.h>
+#include <linux/bpf.h>
+#include "bpf.h"
+
+/*
+ * When building perf, unistd.h is override. Define __NR_bpf is
+ * required to be defined.
+ */
+#ifndef __NR_bpf
+# if defined(__i386__)
+#  define __NR_bpf 357
+# elif defined(__x86_64__)
+#  define __NR_bpf 321
+# elif defined(__aarch64__)
+#  define __NR_bpf 280
+# else
+#  error __NR_bpf not defined. libbpf does not support your arch.
+# endif
+#endif
+
+static __u64 ptr_to_u64(void *ptr)
+{
+	return (__u64) (unsigned long) ptr;
+}
+
+static int sys_bpf(enum bpf_cmd cmd, union bpf_attr *attr,
+		   unsigned int size)
+{
+	return syscall(__NR_bpf, cmd, attr, size);
+}
+
+int bpf_create_map(enum bpf_map_type map_type, int key_size,
+		   int value_size, int max_entries)
+{
+	union bpf_attr attr;
+
+	memset(&attr, '\0', sizeof(attr));
+
+	attr.map_type = map_type;
+	attr.key_size = key_size;
+	attr.value_size = value_size;
+	attr.max_entries = max_entries;
+
+	return sys_bpf(BPF_MAP_CREATE, &attr, sizeof(attr));
+}
+
+int bpf_load_program(enum bpf_prog_type type, struct bpf_insn *insns,
+		     size_t insns_cnt, char *license,
+		     u32 kern_version, char *log_buf, size_t log_buf_sz)
+{
+	int fd;
+	union bpf_attr attr;
+
+	bzero(&attr, sizeof(attr));
+	attr.prog_type = type;
+	attr.insn_cnt = (__u32)insns_cnt;
+	attr.insns = ptr_to_u64(insns);
+	attr.license = ptr_to_u64(license);
+	attr.log_buf = ptr_to_u64(NULL);
+	attr.log_size = 0;
+	attr.log_level = 0;
+	attr.kern_version = kern_version;
+
+	fd = sys_bpf(BPF_PROG_LOAD, &attr, sizeof(attr));
+	if (fd >= 0 || !log_buf || !log_buf_sz)
+		return fd;
+
+	/* Try again with log */
+	attr.log_buf = ptr_to_u64(log_buf);
+	attr.log_size = log_buf_sz;
+	attr.log_level = 1;
+	log_buf[0] = 0;
+	return sys_bpf(BPF_PROG_LOAD, &attr, sizeof(attr));
+}

tools/lib/bpf/bpf.h

@@ -0,0 +1,23 @@
+/*
+ * common eBPF ELF operations.
+ *
+ * Copyright (C) 2013-2015 Alexei Starovoitov <ast@kernel.org>
+ * Copyright (C) 2015 Wang Nan <wangnan0@huawei.com>
+ * Copyright (C) 2015 Huawei Inc.
+ */
+#ifndef __BPF_BPF_H
+#define __BPF_BPF_H
+
+#include <linux/bpf.h>
+
+int bpf_create_map(enum bpf_map_type map_type, int key_size, int value_size,
+		   int max_entries);
+
+/* Recommend log buffer size */
+#define BPF_LOG_BUF_SIZE 65536
+int bpf_load_program(enum bpf_prog_type type, struct bpf_insn *insns,
+		     size_t insns_cnt, char *license,
+		     u32 kern_version, char *log_buf,
+		     size_t log_buf_sz);
+
+#endif

tools/lib/bpf/libbpf.h

@@ -0,0 +1,81 @@
+/*
+ * Common eBPF ELF object loading operations.
+ *
+ * Copyright (C) 2013-2015 Alexei Starovoitov <ast@kernel.org>
+ * Copyright (C) 2015 Wang Nan <wangnan0@huawei.com>
+ * Copyright (C) 2015 Huawei Inc.
+ */
+#ifndef __BPF_LIBBPF_H
+#define __BPF_LIBBPF_H
+
+#include <stdio.h>
+#include <stdbool.h>
+
+/*
+ * In include/linux/compiler-gcc.h, __printf is defined. However
+ * it should be better if libbpf.h doesn't depend on Linux header file.
+ * So instead of __printf, here we use gcc attribute directly.
+ */
+typedef int (*libbpf_print_fn_t)(const char *, ...)
+	__attribute__((format(printf, 1, 2)));
+
+void libbpf_set_print(libbpf_print_fn_t warn,
+		      libbpf_print_fn_t info,
+		      libbpf_print_fn_t debug);
+
+/* Hide internal to user */
+struct bpf_object;
+
+struct bpf_object *bpf_object__open(const char *path);
+struct bpf_object *bpf_object__open_buffer(void *obj_buf,
+					   size_t obj_buf_sz);
+void bpf_object__close(struct bpf_object *object);
+
+/* Load/unload object into/from kernel */
+int bpf_object__load(struct bpf_object *obj);
+int bpf_object__unload(struct bpf_object *obj);
+
+struct bpf_object *bpf_object__next(struct bpf_object *prev);
+#define bpf_object__for_each_safe(pos, tmp)			\
+	for ((pos) = bpf_object__next(NULL),		\
+		(tmp) = bpf_object__next(pos);		\
+	     (pos) != NULL;				\
+	     (pos) = (tmp), (tmp) = bpf_object__next(tmp))
+
+/* Accessors of bpf_program. */
+struct bpf_program;
+struct bpf_program *bpf_program__next(struct bpf_program *prog,
+				      struct bpf_object *obj);
+
+#define bpf_object__for_each_program(pos, obj)		\
+	for ((pos) = bpf_program__next(NULL, (obj));	\
+	     (pos) != NULL;				\
+	     (pos) = bpf_program__next((pos), (obj)))
+
+typedef void (*bpf_program_clear_priv_t)(struct bpf_program *,
+					 void *);
+
+int bpf_program__set_private(struct bpf_program *prog, void *priv,
+			     bpf_program_clear_priv_t clear_priv);
+
+int bpf_program__get_private(struct bpf_program *prog,
+			     void **ppriv);
+
+const char *bpf_program__title(struct bpf_program *prog, bool dup);
+
+int bpf_program__fd(struct bpf_program *prog);
+
+/*
+ * We don't need __attribute__((packed)) now since it is
+ * unnecessary for 'bpf_map_def' because they are all aligned.
+ * In addition, using it will trigger -Wpacked warning message,
+ * and will be treated as an error due to -Werror.
+ */
+struct bpf_map_def {
+	unsigned int type;
+	unsigned int key_size;
+	unsigned int value_size;
+	unsigned int max_entries;
+};
+
+#endif

tools/perf/MANIFEST

@@ -18,6 +18,7 @@ tools/arch/x86/include/asm/atomic.h
 tools/arch/x86/include/asm/rmwcc.h
 tools/lib/traceevent
 tools/lib/api
+tools/lib/bpf
 tools/lib/hweight.c
 tools/lib/rbtree.c
 tools/lib/symbol/kallsyms.c

tools/perf/tests/Build

@@ -32,6 +32,7 @@ perf-y += sample-parsing.o
 perf-y += parse-no-sample-id-all.o
 perf-y += kmod-path.o
 perf-y += thread-map.o
+perf-y += llvm.o
 
 perf-$(CONFIG_X86) += perf-time-to-tsc.o
 

tools/perf/tests/builtin-test.c

@@ -174,6 +174,10 @@ static struct test {
 		.desc = "Test thread map",
 		.func = test__thread_map,
 	},
+	{
+		.desc = "Test LLVM searching and compiling",
+		.func = test__llvm,
+	},
 	{
 		.func = NULL,
 	},

tools/perf/tests/llvm.c

@@ -0,0 +1,98 @@
+#include <stdio.h>
+#include <bpf/libbpf.h>
+#include <util/llvm-utils.h>
+#include <util/cache.h>
+#include "tests.h"
+#include "debug.h"
+
+static int perf_config_cb(const char *var, const char *val,
+			  void *arg __maybe_unused)
+{
+	return perf_default_config(var, val, arg);
+}
+
+/*
+ * Randomly give it a "version" section since we don't really load it
+ * into kernel
+ */
+static const char test_bpf_prog[] =
+	"__attribute__((section(\"do_fork\"), used)) "
+	"int fork(void *ctx) {return 0;} "
+	"char _license[] __attribute__((section(\"license\"), used)) = \"GPL\";"
+	"int _version __attribute__((section(\"version\"), used)) = 0x40100;";
+
+#ifdef HAVE_LIBBPF_SUPPORT
+static int test__bpf_parsing(void *obj_buf, size_t obj_buf_sz)
+{
+	struct bpf_object *obj;
+
+	obj = bpf_object__open_buffer(obj_buf, obj_buf_sz);
+	if (!obj)
+		return -1;
+	bpf_object__close(obj);
+	return 0;
+}
+#else
+static int test__bpf_parsing(void *obj_buf __maybe_unused,
+			     size_t obj_buf_sz __maybe_unused)
+{
+	fprintf(stderr, " (skip bpf parsing)");
+	return 0;
+}
+#endif
+
+int test__llvm(void)
+{
+	char *tmpl_new, *clang_opt_new;
+	void *obj_buf;
+	size_t obj_buf_sz;
+	int err, old_verbose;
+
+	perf_config(perf_config_cb, NULL);
+
+	/*
+	 * Skip this test if user's .perfconfig doesn't set [llvm] section
+	 * and clang is not found in $PATH, and this is not perf test -v
+	 */
+	if (verbose == 0 && !llvm_param.user_set_param && llvm__search_clang()) {
+		fprintf(stderr, " (no clang, try 'perf test -v LLVM')");
+		return TEST_SKIP;
+	}
+
+	old_verbose = verbose;
+	/*
+	 * llvm is verbosity when error. Suppress all error output if
+	 * not 'perf test -v'.
+	 */
+	if (verbose == 0)
+		verbose = -1;
+
+	if (!llvm_param.clang_bpf_cmd_template)
+		return -1;
+
+	if (!llvm_param.clang_opt)
+		llvm_param.clang_opt = strdup("");
+
+	err = asprintf(&tmpl_new, "echo '%s' | %s", test_bpf_prog,
+		       llvm_param.clang_bpf_cmd_template);
+	if (err < 0)
+		return -1;
+	err = asprintf(&clang_opt_new, "-xc %s", llvm_param.clang_opt);
+	if (err < 0)
+		return -1;
+
+	llvm_param.clang_bpf_cmd_template = tmpl_new;
+	llvm_param.clang_opt = clang_opt_new;
+	err = llvm__compile_bpf("-", &obj_buf, &obj_buf_sz);
+
+	verbose = old_verbose;
+	if (err) {
+		if (!verbose)
+			fprintf(stderr, " (use -v to see error message)");
+		return -1;
+	}
+
+	err = test__bpf_parsing(obj_buf, obj_buf_sz);
+	free(obj_buf);
+	return err;
+}

tools/perf/tests/tests.h

@@ -62,6 +62,7 @@ int test__fdarray__filter(void);
 int test__fdarray__add(void);
 int test__kmod_path__parse(void);
 int test__thread_map(void);
+int test__llvm(void);
 
 #if defined(__x86_64__) || defined(__i386__) || defined(__arm__) || defined(__aarch64__)
 #ifdef HAVE_DWARF_UNWIND_SUPPORT

tools/perf/util/Build

@@ -14,6 +14,7 @@ libperf-y += find_next_bit.o
 libperf-y += help.o
 libperf-y += kallsyms.o
 libperf-y += levenshtein.o
+libperf-y += llvm-utils.o
 libperf-y += parse-options.o
 libperf-y += parse-events.o
 libperf-y += path.o

tools/perf/util/config.c

@@ -12,6 +12,7 @@
 #include "cache.h"
 #include "exec_cmd.h"
 #include "util/hist.h"  /* perf_hist_config */
+#include "util/llvm-utils.h"   /* perf_llvm_config */
 
 #define MAXNAME (256)
 
@@ -408,6 +409,9 @@ int perf_default_config(const char *var, const char *value,
 	if (!prefixcmp(var, "call-graph."))
 		return perf_callchain_config(var, value);
 
+	if (!prefixcmp(var, "llvm."))
+		return perf_llvm_config(var, value);
+
 	/* Add other config variables here. */
 	return 0;
 }

tools/perf/util/llvm-utils.c

@@ -0,0 +1,408 @@
+/*
+ * Copyright (C) 2015, Wang Nan <wangnan0@huawei.com>
+ * Copyright (C) 2015, Huawei Inc.
+ */
+
+#include <stdio.h>
+#include <sys/utsname.h>
+#include "util.h"
+#include "debug.h"
+#include "llvm-utils.h"
+#include "cache.h"
+
+#define CLANG_BPF_CMD_DEFAULT_TEMPLATE				\
+		"$CLANG_EXEC -D__KERNEL__ $CLANG_OPTIONS "	\
+		"$KERNEL_INC_OPTIONS -Wno-unused-value "	\
+		"-Wno-pointer-sign -working-directory "		\
+		"$WORKING_DIR -c \"$CLANG_SOURCE\" -target bpf -O2 -o -"
+
+struct llvm_param llvm_param = {
+	.clang_path = "clang",
+	.clang_bpf_cmd_template = CLANG_BPF_CMD_DEFAULT_TEMPLATE,
+	.clang_opt = NULL,
+	.kbuild_dir = NULL,
+	.kbuild_opts = NULL,
+	.user_set_param = false,
+};
+
+int perf_llvm_config(const char *var, const char *value)
+{
+	if (prefixcmp(var, "llvm."))
+		return 0;
+	var += sizeof("llvm.") - 1;
+
+	if (!strcmp(var, "clang-path"))
+		llvm_param.clang_path = strdup(value);
+	else if (!strcmp(var, "clang-bpf-cmd-template"))
+		llvm_param.clang_bpf_cmd_template = strdup(value);
+	else if (!strcmp(var, "clang-opt"))
+		llvm_param.clang_opt = strdup(value);
+	else if (!strcmp(var, "kbuild-dir"))
+		llvm_param.kbuild_dir = strdup(value);
+	else if (!strcmp(var, "kbuild-opts"))
+		llvm_param.kbuild_opts = strdup(value);
+	else
+		return -1;
+	llvm_param.user_set_param = true;
+	return 0;
+}
+
+static int
+search_program(const char *def, const char *name,
+	       char *output)
+{
+	char *env, *path, *tmp = NULL;
+	char buf[PATH_MAX];
+	int ret;
+
+	output[0] = '\0';
+	if (def && def[0] != '\0') {
+		if (def[0] == '/') {
+			if (access(def, F_OK) == 0) {
+				strlcpy(output, def, PATH_MAX);
+				return 0;
+			}
+		} else if (def[0] != '\0')
+			name = def;
+	}
+
+	env = getenv("PATH");
+	if (!env)
+		return -1;
+	env = strdup(env);
+	if (!env)
+		return -1;
+
+	ret = -ENOENT;
+	path = strtok_r(env, ":",  &tmp);
+	while (path) {
+		scnprintf(buf, sizeof(buf), "%s/%s", path, name);
+		if (access(buf, F_OK) == 0) {
+			strlcpy(output, buf, PATH_MAX);
+			ret = 0;
+			break;
+		}
+		path = strtok_r(NULL, ":", &tmp);
+	}
+
+	free(env);
+	return ret;
+}
+
+#define READ_SIZE	4096
+static int
+read_from_pipe(const char *cmd, void **p_buf, size_t *p_read_sz)
+{
+	int err = 0;
+	void *buf = NULL;
+	FILE *file = NULL;
+	size_t read_sz = 0, buf_sz = 0;
+
+	file = popen(cmd, "r");
+	if (!file) {
+		pr_err("ERROR: unable to popen cmd: %s\n",
+		       strerror(errno));
+		return -EINVAL;
+	}
+
+	while (!feof(file) && !ferror(file)) {
+		/*
+		 * Make buf_sz always have obe byte extra space so we
+		 * can put '\0' there.
+		 */
+		if (buf_sz - read_sz < READ_SIZE + 1) {
+			void *new_buf;
+
+			buf_sz = read_sz + READ_SIZE + 1;
+			new_buf = realloc(buf, buf_sz);
+
+			if (!new_buf) {
+				pr_err("ERROR: failed to realloc memory\n");
+				err = -ENOMEM;
+				goto errout;
+			}
+
+			buf = new_buf;
+		}
+		read_sz += fread(buf + read_sz, 1, READ_SIZE, file);
+	}
+
+	if (buf_sz - read_sz < 1) {
+		pr_err("ERROR: internal error\n");
+		err = -EINVAL;
+		goto errout;
+	}
+
+	if (ferror(file)) {
+		pr_err("ERROR: error occurred when reading from pipe: %s\n",
+		       strerror(errno));
+		err = -EIO;
+		goto errout;
+	}
+
+	err = WEXITSTATUS(pclose(file));
+	file = NULL;
+	if (err) {
+		err = -EINVAL;
+		goto errout;
+	}
+
+	/*
+	 * If buf is string, give it terminal '\0' to make our life
+	 * easier. If buf is not string, that '\0' is out of space
+	 * indicated by read_sz so caller won't even notice it.
+	 */
+	((char *)buf)[read_sz] = '\0';
+
+	if (!p_buf)
+		free(buf);
+	else
+		*p_buf = buf;
+
+	if (p_read_sz)
+		*p_read_sz = read_sz;
+	return 0;
+
+errout:
+	if (file)
+		pclose(file);
+	free(buf);
+	if (p_buf)
+		*p_buf = NULL;
+	if (p_read_sz)
+		*p_read_sz = 0;
+	return err;
+}
+
+static inline void
+force_set_env(const char *var, const char *value)
+{
+	if (value) {
+		setenv(var, value, 1);
+		pr_debug("set env: %s=%s\n", var, value);
+	} else {
+		unsetenv(var);
+		pr_debug("unset env: %s\n", var);
+	}
+}
+
+static void
+version_notice(void)
+{
+	pr_err(
+"     \tLLVM 3.7 or newer is required. Which can be found from http://llvm.org\n"
+"     \tYou may want to try git trunk:\n"
+"     \t\tgit clone http://llvm.org/git/llvm.git\n"
+"     \t\t     and\n"
+"     \t\tgit clone http://llvm.org/git/clang.git\n\n"
+"     \tOr fetch the latest clang/llvm 3.7 from pre-built llvm packages for\n"
+"     \tdebian/ubuntu:\n"
+"     \t\thttp://llvm.org/apt\n\n"
+"     \tIf you are using old version of clang, change 'clang-bpf-cmd-template'\n"
+"     \toption in [llvm] section of ~/.perfconfig to:\n\n"
+"     \t  \"$CLANG_EXEC $CLANG_OPTIONS $KERNEL_INC_OPTIONS \\\n"
+"     \t     -working-directory $WORKING_DIR -c $CLANG_SOURCE \\\n"
+"     \t     -emit-llvm -o - | /path/to/llc -march=bpf -filetype=obj -o -\"\n"
+"     \t(Replace /path/to/llc with path to your llc)\n\n"
+);
+}
+
+static int detect_kbuild_dir(char **kbuild_dir)
+{
+	const char *test_dir = llvm_param.kbuild_dir;
+	const char *prefix_dir = "";
+	const char *suffix_dir = "";
+
+	char *autoconf_path;
+	struct utsname utsname;
+
+	int err;
+
+	if (!test_dir) {
+		err = uname(&utsname);
+		if (err) {
+			pr_warning("uname failed: %s\n", strerror(errno));
+			return -EINVAL;
+		}
+
+		test_dir = utsname.release;
+		prefix_dir = "/lib/modules/";
+		suffix_dir = "/build";
+	}
+
+	err = asprintf(&autoconf_path, "%s%s%s/include/generated/autoconf.h",
+		       prefix_dir, test_dir, suffix_dir);
+	if (err < 0)
+		return -ENOMEM;
+
+	if (access(autoconf_path, R_OK) == 0) {
+		free(autoconf_path);
+
+		err = asprintf(kbuild_dir, "%s%s%s", prefix_dir, test_dir,
+			       suffix_dir);
+		if (err < 0)
+			return -ENOMEM;
+		return 0;
+	}
+	free(autoconf_path);
+	return -ENOENT;
+}
+
+static const char *kinc_fetch_script =
+"#!/usr/bin/env sh\n"
+"if ! test -d \"$KBUILD_DIR\"\n"
+"then\n"
+"	exit -1\n"
+"fi\n"
+"if ! test -f \"$KBUILD_DIR/include/generated/autoconf.h\"\n"
+"then\n"
+"	exit -1\n"
+"fi\n"
+"TMPDIR=`mktemp -d`\n"
+"if test -z \"$TMPDIR\"\n"
+"then\n"
+"    exit -1\n"
+"fi\n"
+"cat << EOF > $TMPDIR/Makefile\n"
+"obj-y := dummy.o\n"
+"\\$(obj)/%.o: \\$(src)/%.c\n"
+"\t@echo -n \"\\$(NOSTDINC_FLAGS) \\$(LINUXINCLUDE) \\$(EXTRA_CFLAGS)\"\n"
+"EOF\n"
+"touch $TMPDIR/dummy.c\n"
+"make -s -C $KBUILD_DIR M=$TMPDIR $KBUILD_OPTS dummy.o 2>/dev/null\n"
+"RET=$?\n"
+"rm -rf $TMPDIR\n"
+"exit $RET\n";
+
+static inline void
+get_kbuild_opts(char **kbuild_dir, char **kbuild_include_opts)
+{
+	int err;
+
+	if (!kbuild_dir || !kbuild_include_opts)
+		return;
+
+	*kbuild_dir = NULL;
+	*kbuild_include_opts = NULL;
+
+	if (llvm_param.kbuild_dir && !llvm_param.kbuild_dir[0]) {
+		pr_debug("[llvm.kbuild-dir] is set to \"\" deliberately.\n");
+		pr_debug("Skip kbuild options detection.\n");
+		return;
+	}
+
+	err = detect_kbuild_dir(kbuild_dir);
+	if (err) {
+		pr_warning(
+"WARNING:\tunable to get correct kernel building directory.\n"
+"Hint:\tSet correct kbuild directory using 'kbuild-dir' option in [llvm]\n"
+"     \tsection of ~/.perfconfig or set it to \"\" to suppress kbuild\n"
+"     \tdetection.\n\n");
+		return;
+	}
+
+	pr_debug("Kernel build dir is set to %s\n", *kbuild_dir);
+	force_set_env("KBUILD_DIR", *kbuild_dir);
+	force_set_env("KBUILD_OPTS", llvm_param.kbuild_opts);
+	err = read_from_pipe(kinc_fetch_script,
+			     (void **)kbuild_include_opts,
+			     NULL);
+	if (err) {
+		pr_warning(
+"WARNING:\tunable to get kernel include directories from '%s'\n"
+"Hint:\tTry set clang include options using 'clang-bpf-cmd-template'\n"
+"     \toption in [llvm] section of ~/.perfconfig and set 'kbuild-dir'\n"
+"     \toption in [llvm] to \"\" to suppress this detection.\n\n",
+			*kbuild_dir);
+
+		free(*kbuild_dir);
+		*kbuild_dir = NULL;
+		return;
+	}
+
+	pr_debug("include option is set to %s\n", *kbuild_include_opts);
+}
+
+int llvm__compile_bpf(const char *path, void **p_obj_buf,
+		      size_t *p_obj_buf_sz)
+{
+	int err;
+	char clang_path[PATH_MAX];
+	const char *clang_opt = llvm_param.clang_opt;
+	const char *template = llvm_param.clang_bpf_cmd_template;
+	char *kbuild_dir = NULL, *kbuild_include_opts = NULL;
+	void *obj_buf = NULL;
+	size_t obj_buf_sz;
+
+	if (!template)
+		template = CLANG_BPF_CMD_DEFAULT_TEMPLATE;
+
+	err = search_program(llvm_param.clang_path,
+			     "clang", clang_path);
+	if (err) {
+		pr_err(
+"ERROR:\tunable to find clang.\n"
+"Hint:\tTry to install latest clang/llvm to support BPF. Check your $PATH\n"
+"     \tand 'clang-path' option in [llvm] section of ~/.perfconfig.\n");
+		version_notice();
+		return -ENOENT;
+	}
+
+	/*
+	 * This is an optional work. Even it fail we can continue our
+	 * work. Needn't to check error return.
+	 */
+	get_kbuild_opts(&kbuild_dir, &kbuild_include_opts);
+
+	force_set_env("CLANG_EXEC", clang_path);
+	force_set_env("CLANG_OPTIONS", clang_opt);
+	force_set_env("KERNEL_INC_OPTIONS", kbuild_include_opts);
+	force_set_env("WORKING_DIR", kbuild_dir ? : ".");
+
+	/*
+	 * Since we may reset clang's working dir, path of source file
+	 * should be transferred into absolute path, except we want
+	 * stdin to be source file (testing).
+	 */
+	force_set_env("CLANG_SOURCE",
+		      (path[0] == '-') ? path :
+		      make_nonrelative_path(path));
+
+	pr_debug("llvm compiling command template: %s\n", template);
+	err = read_from_pipe(template, &obj_buf, &obj_buf_sz);
+	if (err) {
+		pr_err("ERROR:\tunable to compile %s\n", path);
+		pr_err("Hint:\tCheck error message shown above.\n");
+		pr_err("Hint:\tYou can also pre-compile it into .o using:\n");
+		pr_err("     \t\tclang -target bpf -O2 -c %s\n", path);
+		pr_err("     \twith proper -I and -D options.\n");
+		goto errout;
+	}
+
+	free(kbuild_dir);
+	free(kbuild_include_opts);
+	if (!p_obj_buf)
+		free(obj_buf);
+	else
+		*p_obj_buf = obj_buf;
+
+	if (p_obj_buf_sz)
+		*p_obj_buf_sz = obj_buf_sz;
+	return 0;
+errout:
+	free(kbuild_dir);
+	free(kbuild_include_opts);
+	free(obj_buf);
+	if (p_obj_buf)
+		*p_obj_buf = NULL;
+	if (p_obj_buf_sz)
+		*p_obj_buf_sz = 0;
+	return err;
+}
+
+int llvm__search_clang(void)
+{
+	char clang_path[PATH_MAX];
+
+	return search_program(llvm_param.clang_path, "clang", clang_path);
+}

tools/perf/util/llvm-utils.h

@@ -0,0 +1,49 @@
+/*
+ * Copyright (C) 2015, Wang Nan <wangnan0@huawei.com>
+ * Copyright (C) 2015, Huawei Inc.
+ */
+#ifndef __LLVM_UTILS_H
+#define __LLVM_UTILS_H
+
+#include "debug.h"
+
+struct llvm_param {
+	/* Path of clang executable */
+	const char *clang_path;
+	/*
+	 * Template of clang bpf compiling. 5 env variables
+	 * can be used:
+	 *   $CLANG_EXEC:		Path to clang.
+	 *   $CLANG_OPTIONS:		Extra options to clang.
+	 *   $KERNEL_INC_OPTIONS:	Kernel include directories.
+	 *   $WORKING_DIR:		Kernel source directory.
+	 *   $CLANG_SOURCE:		Source file to be compiled.
+	 */
+	const char *clang_bpf_cmd_template;
+	/* Will be filled in $CLANG_OPTIONS */
+	const char *clang_opt;
+	/* Where to find kbuild system */
+	const char *kbuild_dir;
+	/*
+	 * Arguments passed to make, like 'ARCH=arm' if doing cross
+	 * compiling. Should not be used for dynamic compiling.
+	 */
+	const char *kbuild_opts;
+	/*
+	 * Default is false. If one of the above fields is set by user
+	 * explicitly then user_set_llvm is set to true. This is used
+	 * for perf test. If user doesn't set anything in .perfconfig
+	 * and clang is not found, don't trigger llvm test.
+	 */
+	bool user_set_param;
+};
+
+extern struct llvm_param llvm_param;
+extern int perf_llvm_config(const char *var, const char *value);
+
+extern int llvm__compile_bpf(const char *path, void **p_obj_buf,
+			     size_t *p_obj_buf_sz);
+
+/* This function is for test__llvm() use only */
+extern int llvm__search_clang(void);
+#endif