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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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