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Commit 4cea3a9c authored by Wang Nan's avatar Wang Nan Committed by Arnaldo Carvalho de Melo
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perf tools: Call clang to compile C source to object code 



This is the core patch for supporting eBPF on-the-fly compiling, does
the following work:

 1. Search clang compiler using search_program().

 2. Run command template defined in llvm-bpf-cmd-template option in
    [llvm] config section using read_from_pipe(). Patch of clang and
    source code path is injected into shell command using environment
    variable using force_set_env().

  Commiter notice:

  When building with DEBUG=1 we get a compiler error that gets fixed with
  the same approach described in commit b2365122:

    perf kmem: Fix compiler warning about may be accessing uninitialized variable

    The last argument to strtok_r doesn't need to be initialized, its
    just a placeholder to make this routine reentrant, but gcc doesn't know
    about that and complains, breaking the build, fix it by setting it to
    NULL.

Signed-off-by: default avatarWang Nan <wangnan0@huawei.com>
Acked-by: default avatarAlexei Starovoitov <ast@plumgrid.com>
Cc: Brendan Gregg <brendan.d.gregg@gmail.com>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: David Ahern <dsahern@gmail.com>
Cc: He Kuang <hekuang@huawei.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Kaixu Xia <xiakaixu@huawei.com>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Zefan Li <lizefan@huawei.com>
Cc: pi3orama@163.com
Link: http://lkml.kernel.org/n/1436445342-1402-14-git-send-email-wangnan0@huawei.com


Signed-off-by: default avatarArnaldo Carvalho de Melo <acme@redhat.com>
parent aa61fd05

tools/perf/util/llvm-utils.c

+226 −0
Original line number Diff line number Diff line
@@ -43,3 +43,229 @@ int perf_llvm_config(const char *var, const char *value) 
		return -1;

	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"

);

}



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;

	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;

	}



	force_set_env("CLANG_EXEC", clang_path);

	force_set_env("CLANG_OPTIONS", clang_opt);

	force_set_env("KERNEL_INC_OPTIONS", NULL);

	force_set_env("WORKING_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;

	}



	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(obj_buf);

	if (p_obj_buf)

		*p_obj_buf = NULL;

	if (p_obj_buf_sz)

		*p_obj_buf_sz = 0;

	return err;

}

tools/perf/util/llvm-utils.h

+3 −0
Original line number Diff line number Diff line
@@ -33,4 +33,7 @@ struct llvm_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);

#endif