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Subject[RFC PATCH tracing/kprobes 5/5] perf: kprobe command supports without libdwarf
Date
Enables perf-kprobe even if libdwarf is installed. If libdwarf is not found,
perf-kprobe just disables dwarf support. Users can use perf-kprobe to set
up new events by using kprobe_events format.

Signed-off-by: Masami Hiramatsu <mhiramat@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.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>
---
tools/perf/Makefile | 6 +++---
tools/perf/builtin-kprobe.c | 42 +++++++++++++++++++++++++++++++++-------
tools/perf/perf.c | 2 --
tools/perf/util/probe-finder.h | 2 ++
4 files changed, 40 insertions(+), 12 deletions(-)
diff --git a/tools/perf/Makefile b/tools/perf/Makefile
index 1379e3f..3b0307a 100644
--- a/tools/perf/Makefile
+++ b/tools/perf/Makefile
@@ -385,6 +385,7 @@ BUILTIN_OBJS += builtin-stat.o
BUILTIN_OBJS += builtin-timechart.o
BUILTIN_OBJS += builtin-top.o
BUILTIN_OBJS += builtin-trace.o
+BUILTIN_OBJS += builtin-kprobe.o

PERFLIBS = $(LIB_FILE)

@@ -420,13 +421,12 @@ ifneq ($(shell sh -c "(echo '\#include <libelf.h>'; echo 'int main(void) { Elf *
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 kprobe support. Please install libdwarf-dev/libdwarf-devel);
+ msg := $(warning No libdwarf.h found, disables dwarf support. Please install libdwarf-dev/libdwarf-devel);
+ BASIC_CFLAGS += -DNO_LIBDWARF
else
EXTLIBS += -lelf -ldwarf
LIB_H += util/probe-finder.h
LIB_OBJS += util/probe-finder.o
- BUILTIN_OBJS += builtin-kprobe.o
- BASIC_CFLAGS += -DSUPPORT_DWARF
endif

ifdef NO_DEMANGLE
diff --git a/tools/perf/builtin-kprobe.c b/tools/perf/builtin-kprobe.c
index 9e4596b..d8ae476 100644
--- a/tools/perf/builtin-kprobe.c
+++ b/tools/perf/builtin-kprobe.c
@@ -53,6 +53,7 @@ const char *default_search_path[NR_SEARCH_PATH] = {
static struct {
char *vmlinux;
char *release;
+ int need_dwarf;
int nr_probe;
struct probe_point probes[MAX_PROBES];
char *events[MAX_PROBES];
@@ -132,21 +133,27 @@ static int parse_probepoint(const struct option *opt __used,
debug("symbol:%s file:%s offset:%d\n",
pp->function, pp->file, pp->offset);
}
+ if (pp->file)
+ session.need_dwarf = 1;

pp->nr_args = argc - 1;
if (pp->nr_args > 0) {
pp->args = (char **)malloc(sizeof(char *) * pp->nr_args);
memcpy(pp->args, &argv[1], sizeof(char *) * pp->nr_args);
}
- if (retp)
- for (i = 0; i < pp->nr_args; i++)
- if (is_c_varname(pp->args[i]))
+ for (i = 0; i < pp->nr_args; i++)
+ if (is_c_varname(pp->args[i])) {
+ if (retp)
semantic_error("You can't specify local"
" variable for kretprobe");
+ session.need_dwarf = 1;
+ }
+
debug("%d arguments\n", pp->nr_args);
return 0;
}

+#ifndef NO_LIBDWARF
static int open_default_vmlinux(void)
{
struct utsname uts;
@@ -176,6 +183,7 @@ static int open_default_vmlinux(void)
}
return fd;
}
+#endif

static const char * const kprobe_usage[] = {
"perf kprobe [<options>] -P PROBEDEF [-P PROBEDEF ...]",
@@ -183,11 +191,17 @@ static const char * const kprobe_usage[] = {
};

static const struct option options[] = {
+#ifndef NO_LIBDWARF
OPT_STRING('k', "vmlinux", &session.vmlinux, "file",
"vmlinux/module pathname"),
OPT_STRING('r', "release", &session.release, "rel", "kernel release"),
+#endif
OPT_CALLBACK('P', "probe", NULL,
+#ifdef NO_LIBDWARF
+ "p|r:[GRP/]NAME,FUNC[+OFFS],ARG[,ARG,...]",
+#else
"p|r:[GRP/]NAME,FUNC[+OFFS][@SRC]|@SRC:LINE,ARG[,ARG,...]",
+#endif
"probe point definition, where\n"
"\t\tp:\tkprobe probe\n"
"\t\tr:\tkretprobe probe\n"
@@ -195,9 +209,13 @@ static const struct option options[] = {
"\t\tNAME:\tEvent name\n"
"\t\tFUNC:\tFunction name\n"
"\t\tOFFS:\tOffset from function entry (in byte)\n"
+#ifdef NO_LIBDWARF
+ "\t\tARG:\tProbe argument (only \n"
+#else
"\t\tSRC:\tSource code path\n"
"\t\tLINE:\tLine number\n"
"\t\tARG:\tProbe argument (local variable name or\n"
+#endif
"\t\t\tkprobe-tracer argument format is supported.)\n",
parse_probepoint),
OPT_END()
@@ -237,7 +255,7 @@ static int synthesize_probepoint(struct probe_point *pp)

int cmd_kprobe(int argc, const char **argv, const char *prefix __used)
{
- int i, j, fd, ret, need_dwarf = 0;
+ int i, j, fd, ret;
struct probe_point *pp;
char buf[MAX_CMDLEN];

@@ -246,18 +264,26 @@ int cmd_kprobe(int argc, const char **argv, const char *prefix __used)
if (argc || session.nr_probe == 0)
usage_with_options(kprobe_usage, options);

- /* Synthesize return probes */
+#ifdef NO_LIBDWARF
+ if (session.need_dwarf)
+ semantic_error("Dwarf-analysis is not supported");
+#endif
+
+ /* Synthesize probes without dwarf */
for (j = 0; j < session.nr_probe; j++) {
+#ifndef NO_LIBDWARF
if (session.events[j][0] != 'r') {
- need_dwarf = 1;
+ session.need_dwarf = 1;
continue;
}
+#endif
ret = synthesize_probepoint(&session.probes[j]);
if (ret < 0)
semantic_error("probe point is too long.");
}

- if (!need_dwarf)
+#ifndef NO_LIBDWARF
+ if (!session.need_dwarf)
goto setup_probes;

if (session.vmlinux)
@@ -286,6 +312,8 @@ int cmd_kprobe(int argc, const char **argv, const char *prefix __used)
close(fd);

setup_probes:
+#endif /* !NO_LIBDWARF */
+
/* Settng up probe points */
snprintf(buf, MAX_CMDLEN, "%s/../kprobe_events", debugfs_path);
fd = open(buf, O_WRONLY, O_APPEND);
diff --git a/tools/perf/perf.c b/tools/perf/perf.c
index c073924..dd77faf 100644
--- a/tools/perf/perf.c
+++ b/tools/perf/perf.c
@@ -295,9 +295,7 @@ 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
{ "kprobe", cmd_kprobe, 0 },
-#endif
};
unsigned int i;
static const char ext[] = STRIP_EXTENSION;
diff --git a/tools/perf/util/probe-finder.h b/tools/perf/util/probe-finder.h
index af920de..306810c 100644
--- a/tools/perf/util/probe-finder.h
+++ b/tools/perf/util/probe-finder.h
@@ -44,6 +44,7 @@ struct probe_point {
char *probes[MAX_PROBES]; /* Output buffers (will be allocated)*/
};

+#ifndef NO_LIBDWARF
extern int find_probepoint(int fd, struct probe_point *pp);

#include <libdwarf/dwarf.h>
@@ -64,5 +65,6 @@ struct probe_finder {
char *buf; /* Current output buffer */
int len; /* Length of output buffer */
};
+#endif /* NO_LIBDWARF */

#endif /*_PROBE_FINDER_H */

--
Masami Hiramatsu

Software Engineer
Hitachi Computer Products (America), Inc.
Software Solutions Division

e-mail: mhiramat@redhat.com


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