perf: Add perf probe subcommand, a kprobe-event setup helper

Add perf probe subcommand that implements a kprobe-event setup helper
to the perf command.
This allows user to define kprobe events using C expressions (C line
numbers, C function names, and C local variables).

Usage
-----
 perf probe [<options>] -P 'PROBEDEF' [-P 'PROBEDEF' ...]

    -k, --vmlinux <file>  vmlinux/module pathname
    -P, --probe <p|r:[GRP/]NAME FUNC[+OFFS][@SRC]|@SRC:LINE [ARG ...]>
                          probe point definition, where
		p:	kprobe probe
		r:	kretprobe probe
		GRP:	Group name (optional)
		NAME:	Event name
		FUNC:	Function name
		OFFS:	Offset from function entry (in byte)
		SRC:	Source code path
		LINE:	Line number
		ARG:	Probe argument (local variable name or
			kprobe-tracer argument format is supported.)

Changes in v4:
 - Add _GNU_SOURCE macro for strndup().

Changes in v3:
 - Remove -r option because perf always be used for online kernel.
 - Check malloc/calloc results.

Changes in v2:
 - Check synthesized string length.
 - Rename perf kprobe to perf probe.
 - Use spaces for separator and update usage comment.
 - Check error paths in parse_probepoint().
 - Check optimized-out variables.
Signed-off-by: Masami Hiramatsu <mhiramat@redhat.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: Jim Keniston <jkenisto@us.ibm.com>
Cc: Frank Ch. Eigler <fche@redhat.com>
LKML-Reference: <20091008211737.29299.14784.stgit@dhcp-100-2-132.bos.redhat.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>

tools/perf/Makefile

@@ -419,6 +419,16 @@ ifneq ($(shell sh -c "(echo '\#include <libelf.h>'; echo 'int main(void) { Elf *
 	msg := $(error No libelf.h/libelf found, please install libelf-dev/elfutils-libelf-devel);
 endif
 
+ifneq ($(shell sh -c "(echo '\#include <libdwarf/dwarf.h>'; echo '\#include <libdwarf/libdwarf.h>'; echo 'int main(void) { Dwarf_Debug dbg; Dwarf_Error err; dwarf_init(0, DW_DLC_READ, 0, 0, &dbg, &err); return (long)dbg; }') | $(CC) -x c - $(ALL_CFLAGS) -D_LARGEFILE64_SOURCE -D_FILE_OFFSET_BITS=64 -ldwarf -lelf -o /dev/null $(ALL_LDFLAGS) > /dev/null 2>&1 && echo y"), y)
+	msg := $(warning No libdwarf.h found, disables probe subcommand. Please install libdwarf-dev/libdwarf-devel);
+else
+	EXTLIBS += -lelf -ldwarf
+	LIB_H += util/probe-finder.h
+	LIB_OBJS += util/probe-finder.o
+	BUILTIN_OBJS += builtin-probe.o
+	BASIC_CFLAGS += -DSUPPORT_DWARF
+endif
+
 ifdef NO_DEMANGLE
 	BASIC_CFLAGS += -DNO_DEMANGLE
 else

tools/perf/builtin-probe.c

+/*
+ * builtin-probe.c
+ *
+ * Builtin probe command: Set up probe events by C expression
+ *
+ * Written by Masami Hiramatsu <mhiramat@redhat.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
+ *
+ */
+#define _GNU_SOURCE
+#include <sys/utsname.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <errno.h>
+#include <stdio.h>
+#include <unistd.h>
+#include <stdlib.h>
+#include <string.h>
+
+#undef _GNU_SOURCE
+#include "perf.h"
+#include "builtin.h"
+#include "util/util.h"
+#include "util/parse-options.h"
+#include "util/parse-events.h"	/* For debugfs_path */
+#include "util/probe-finder.h"
+
+/* Default vmlinux search paths */
+#define NR_SEARCH_PATH 3
+const char *default_search_path[NR_SEARCH_PATH] = {
+"/lib/modules/%s/build/vmlinux",		/* Custom build kernel */
+"/usr/lib/debug/lib/modules/%s/vmlinux",	/* Red Hat debuginfo */
+"/boot/vmlinux-debug-%s",			/* Ubuntu */
+};
+
+#define MAX_PATH_LEN 256
+#define MAX_PROBES 128
+
+/* Session management structure */
+static struct {
+	char *vmlinux;
+	char *release;
+	int nr_probe;
+	struct probe_point probes[MAX_PROBES];
+	char *events[MAX_PROBES];
+} session;
+
+static void semantic_error(const char *msg)
+{
+	fprintf(stderr, "Semantic error: %s\n", msg);
+	exit(1);
+}
+
+static void perror_exit(const char *msg)
+{
+	perror(msg);
+	exit(1);
+}
+
+#define MAX_PROBE_ARGS 128
+
+static int parse_probepoint(const struct option *opt __used,
+			    const char *str, int unset __used)
+{
+	char *argv[MAX_PROBE_ARGS + 2];	/* Event + probe + args */
+	int argc, i;
+	char *arg, *ptr;
+	struct probe_point *pp = &session.probes[session.nr_probe];
+	char **event = &session.events[session.nr_probe];
+	int retp = 0;
+
+	if (!str)	/* The end of probe points */
+		return 0;
+
+	debug("Probe-define(%d): %s\n", session.nr_probe, str);
+	if (++session.nr_probe == MAX_PROBES)
+		semantic_error("Too many probes");
+
+	/* Separate arguments, similar to argv_split */
+	argc = 0;
+	do {
+		/* Skip separators */
+		while (isspace(*str))
+			str++;
+
+		/* Add an argument */
+		if (*str != '\0') {
+			const char *s = str;
+
+			/* Skip the argument */
+			while (!isspace(*str) && *str != '\0')
+				str++;
+
+			/* Duplicate the argument */
+			argv[argc] = strndup(s, str - s);
+			if (argv[argc] == NULL)
+				perror_exit("strndup");
+			if (++argc == MAX_PROBE_ARGS)
+				semantic_error("Too many arguments");
+			debug("argv[%d]=%s\n", argc, argv[argc - 1]);
+		}
+	} while (*str != '\0');
+	if (argc < 2)
+		semantic_error("Need event-name and probe-point at least.");
+
+	/* Parse the event name */
+	if (argv[0][0] == 'r')
+		retp = 1;
+	else if (argv[0][0] != 'p')
+		semantic_error("You must specify 'p'(kprobe) or"
+				" 'r'(kretprobe) first.");
+	/* TODO: check event name */
+	*event = argv[0];
+
+	/* Parse probe point */
+	arg = argv[1];
+	if (arg[0] == '@') {
+		/* Source Line */
+		arg++;
+		ptr = strchr(arg, ':');
+		if (!ptr || !isdigit(ptr[1]))
+			semantic_error("Line number is required.");
+		*ptr++ = '\0';
+		if (strlen(arg) == 0)
+			semantic_error("No file name.");
+		pp->file = strdup(arg);
+		pp->line = atoi(ptr);
+		if (!pp->file || !pp->line)
+			semantic_error("Failed to parse line.");
+		debug("file:%s line:%d\n", pp->file, pp->line);
+	} else {
+		/* Function name */
+		ptr = strchr(arg, '+');
+		if (ptr) {
+			if (!isdigit(ptr[1]))
+				semantic_error("Offset is required.");
+			*ptr++ = '\0';
+			pp->offset = atoi(ptr);
+		} else
+			ptr = arg;
+		ptr = strchr(ptr, '@');
+		if (ptr) {
+			*ptr++ = '\0';
+			pp->file = strdup(ptr);
+		}
+		pp->function = strdup(arg);
+		debug("symbol:%s file:%s offset:%d\n",
+		      pp->function, pp->file, pp->offset);
+	}
+	free(argv[1]);
+
+	/* Copy arguments */
+	pp->nr_args = argc - 2;
+	if (pp->nr_args > 0) {
+		pp->args = (char **)malloc(sizeof(char *) * pp->nr_args);
+		if (!pp->args)
+			perror_exit("malloc");
+		memcpy(pp->args, &argv[2], sizeof(char *) * pp->nr_args);
+	}
+
+	/* Ensure return probe has no C argument */
+	if (retp)
+		for (i = 0; i < pp->nr_args; i++)
+			if (is_c_varname(pp->args[i]))
+				semantic_error("You can't specify local"
+						" variable for kretprobe");
+	debug("%d arguments\n", pp->nr_args);
+	return 0;
+}
+
+static int open_default_vmlinux(void)
+{
+	struct utsname uts;
+	char fname[MAX_PATH_LEN];
+	int fd, ret, i;
+
+	ret = uname(&uts);
+	if (ret) {
+		debug("uname() failed.\n");
+		return -errno;
+	}
+	session.release = uts.release;
+	for (i = 0; i < NR_SEARCH_PATH; i++) {
+		ret = snprintf(fname, MAX_PATH_LEN,
+			       default_search_path[i], session.release);
+		if (ret >= MAX_PATH_LEN || ret < 0) {
+			debug("Filename(%d,%s) is too long.\n", i, uts.release);
+			errno = E2BIG;
+			return -E2BIG;
+		}
+		debug("try to open %s\n", fname);
+		fd = open(fname, O_RDONLY);
+		if (fd >= 0)
+			break;
+	}
+	return fd;
+}
+
+static const char * const probe_usage[] = {
+	"perf probe [<options>] -P 'PROBEDEF' [-P 'PROBEDEF' ...]",
+	NULL
+};
+
+static const struct option options[] = {
+	OPT_STRING('k', "vmlinux", &session.vmlinux, "file",
+		"vmlinux/module pathname"),
+	OPT_CALLBACK('P', "probe", NULL,
+		"p|r:[GRP/]NAME FUNC[+OFFS][@SRC]|@SRC:LINE [ARG ...]",
+		"probe point definition, where\n"
+		"\t\tp:\tkprobe probe\n"
+		"\t\tr:\tkretprobe probe\n"
+		"\t\tGRP:\tGroup name (optional)\n"
+		"\t\tNAME:\tEvent name\n"
+		"\t\tFUNC:\tFunction name\n"
+		"\t\tOFFS:\tOffset from function entry (in byte)\n"
+		"\t\tSRC:\tSource code path\n"
+		"\t\tLINE:\tLine number\n"
+		"\t\tARG:\tProbe argument (local variable name or\n"
+		"\t\t\tkprobe-tracer argument format is supported.)\n",
+		parse_probepoint),
+	OPT_END()
+};
+
+static int write_new_event(int fd, const char *buf)
+{
+	int ret;
+
+	printf("Adding new event: %s\n", buf);
+	ret = write(fd, buf, strlen(buf));
+	if (ret <= 0)
+		perror("Error: Failed to create event");
+
+	return ret;
+}
+
+#define MAX_CMDLEN 256
+
+static int synthesize_probepoint(struct probe_point *pp)
+{
+	char *buf;
+	int i, len, ret;
+	pp->probes[0] = buf = (char *)calloc(MAX_CMDLEN, sizeof(char));
+	if (!buf)
+		perror_exit("calloc");
+	ret = snprintf(buf, MAX_CMDLEN, "%s+%d", pp->function, pp->offset);
+	if (ret <= 0 || ret >= MAX_CMDLEN)
+		goto error;
+	len = ret;
+
+	for (i = 0; i < pp->nr_args; i++) {
+		ret = snprintf(&buf[len], MAX_CMDLEN - len, " %s",
+			       pp->args[i]);
+		if (ret <= 0 || ret >= MAX_CMDLEN - len)
+			goto error;
+		len += ret;
+	}
+	pp->found = 1;
+	return pp->found;
+error:
+	free(pp->probes[0]);
+	if (ret > 0)
+		ret = -E2BIG;
+	return ret;
+}
+
+int cmd_probe(int argc, const char **argv, const char *prefix __used)
+{
+	int i, j, fd, ret, need_dwarf = 0;
+	struct probe_point *pp;
+	char buf[MAX_CMDLEN];
+
+	argc = parse_options(argc, argv, options, probe_usage,
+		PARSE_OPT_STOP_AT_NON_OPTION);
+	if (argc || session.nr_probe == 0)
+		usage_with_options(probe_usage, options);
+
+	/* Synthesize return probes */
+	for (j = 0; j < session.nr_probe; j++) {
+		if (session.events[j][0] != 'r') {
+			need_dwarf = 1;
+			continue;
+		}
+		ret = synthesize_probepoint(&session.probes[j]);
+		if (ret == -E2BIG)
+			semantic_error("probe point is too long.");
+		else if (ret < 0) {
+			perror("snprintf");
+			return -1;
+		}
+	}
+
+	if (!need_dwarf)
+		goto setup_probes;
+
+	if (session.vmlinux)
+		fd = open(session.vmlinux, O_RDONLY);
+	else
+		fd = open_default_vmlinux();
+	if (fd < 0) {
+		perror("vmlinux/module file open");
+		return -1;
+	}
+
+	/* Searching probe points */
+	for (j = 0; j < session.nr_probe; j++) {
+		pp = &session.probes[j];
+		if (pp->found)
+			continue;
+
+		lseek(fd, SEEK_SET, 0);
+		ret = find_probepoint(fd, pp);
+		if (ret <= 0) {
+			fprintf(stderr, "Error: No probe point found.\n");
+			return -1;
+		}
+		debug("probe event %s found\n", session.events[j]);
+	}
+	close(fd);
+
+setup_probes:
+	/* Settng up probe points */
+	snprintf(buf, MAX_CMDLEN, "%s/../kprobe_events", debugfs_path);
+	fd = open(buf, O_WRONLY, O_APPEND);
+	if (fd < 0) {
+		perror("kprobe_events open");
+		return -1;
+	}
+	for (j = 0; j < session.nr_probe; j++) {
+		pp = &session.probes[j];
+		if (pp->found == 1) {
+			snprintf(buf, MAX_CMDLEN, "%s %s\n",
+				session.events[j], pp->probes[0]);
+			write_new_event(fd, buf);
+		} else
+			for (i = 0; i < pp->found; i++) {
+				snprintf(buf, MAX_CMDLEN, "%s%d %s\n",
+					session.events[j], i, pp->probes[i]);
+				write_new_event(fd, buf);
+			}
+	}
+	close(fd);
+	return 0;
+}
+

tools/perf/builtin.h

@@ -25,5 +25,6 @@ extern int cmd_timechart(int argc, const char **argv, const char *prefix);
 extern int cmd_top(int argc, const char **argv, const char *prefix);
 extern int cmd_trace(int argc, const char **argv, const char *prefix);
 extern int cmd_version(int argc, const char **argv, const char *prefix);
+extern int cmd_probe(int argc, const char **argv, const char *prefix);
 
 #endif

tools/perf/perf.c

@@ -295,6 +295,9 @@ static void handle_internal_command(int argc, const char **argv)
 		{ "version", cmd_version, 0 },
 		{ "trace", cmd_trace, 0 },
 		{ "sched", cmd_sched, 0 },
+#ifdef SUPPORT_DWARF
+		{ "probe", cmd_probe, 0 },
+#endif
 	};
 	unsigned int i;
 	static const char ext[] = STRIP_EXTENSION;

tools/perf/util/probe-finder.h

+#ifndef _PROBE_FINDER_H
+#define _PROBE_FINDER_H
+
+#define _stringify(n)	#n
+#define stringify(n)	_stringify(n)
+
+#ifdef DEBUG
+#define debug(fmt ...)	\
+	fprintf(stderr, "DBG(" __FILE__ ":" stringify(__LINE__) "): " fmt)
+#else
+#define debug(fmt ...)	do {} while (0)
+#endif
+
+#define ERR_IF(cnd)	\
+	do { if (cnd) {	\
+		fprintf(stderr, "Error (" __FILE__ ":" stringify(__LINE__) \
+			"): " stringify(cnd) "\n");			\
+		exit(1);						\
+	} } while (0)
+
+#define MAX_PATH_LEN 256
+#define MAX_PROBE_BUFFER 1024
+#define MAX_PROBES 128
+
+static inline int is_c_varname(const char *name)
+{
+	/* TODO */
+	return isalpha(name[0]) || name[0] == '_';
+}
+
+struct probe_point {
+	/* Inputs */
+	char	*file;		/* File name */
+	int	line;		/* Line number */
+
+	char	*function;	/* Function name */
+	int	offset;		/* Offset bytes */
+
+	int	nr_args;	/* Number of arguments */
+	char	**args;		/* Arguments */
+
+	/* Output */
+	int	found;		/* Number of found probe points */
+	char	*probes[MAX_PROBES];	/* Output buffers (will be allocated)*/
+};
+
+extern int find_probepoint(int fd, struct probe_point *pp);
+
+#include <libdwarf/dwarf.h>
+#include <libdwarf/libdwarf.h>
+
+struct probe_finder {
+	struct probe_point	*pp;	/* Target probe point */
+
+	/* For function searching */
+	Dwarf_Addr	addr;		/* Address */
+	Dwarf_Unsigned	fno;		/* File number */
+	Dwarf_Off	inl_offs;	/* Inline offset */
+
+	/* For variable searching */
+	Dwarf_Addr	cu_base;	/* Current CU base address */
+	Dwarf_Locdesc	fbloc;		/* Location of Current Frame Base */
+	const char	*var;		/* Current variable name */
+	char		*buf;		/* Current output buffer */
+	int		len;		/* Length of output buffer */
+};
+
+#endif /*_PROBE_FINDER_H */