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    Subject[PATCH RESEND] trace_uprobe: support reference counter in fd-based uprobe
    Date
    This patch enables uprobes with reference counter in fd-based uprobe.
    Highest 40 bits of perf_event_attr.config is used to stored offset
    of the reference counter (semaphore).

    Format information in /sys/bus/event_source/devices/uprobe/format/ is
    updated to reflect this new feature.

    Signed-off-by: Song Liu <songliubraving@fb.com>
    Reviewed-and-tested-by: Ravi Bangoria <ravi.bangoria@linux.ibm.com>
    Cc: Masami Hiramatsu <mhiramat@kernel.org>
    Cc: Oleg Nesterov <oleg@redhat.com>
    Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
    Cc: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
    Cc: Steven Rostedt (VMware) <rostedt@goodmis.org>
    ---
    include/linux/trace_events.h | 3 +-
    kernel/events/core.c | 49 ++++++++++++++++++++++++++-------
    kernel/trace/trace_event_perf.c | 7 +++--
    kernel/trace/trace_probe.h | 3 +-
    kernel/trace/trace_uprobe.c | 4 ++-
    5 files changed, 50 insertions(+), 16 deletions(-)

    diff --git a/include/linux/trace_events.h b/include/linux/trace_events.h
    index 78a010e19ed4..4130a5497d40 100644
    --- a/include/linux/trace_events.h
    +++ b/include/linux/trace_events.h
    @@ -575,7 +575,8 @@ extern int bpf_get_kprobe_info(const struct perf_event *event,
    bool perf_type_tracepoint);
    #endif
    #ifdef CONFIG_UPROBE_EVENTS
    -extern int perf_uprobe_init(struct perf_event *event, bool is_retprobe);
    +extern int perf_uprobe_init(struct perf_event *event,
    + unsigned long ref_ctr_offset, bool is_retprobe);
    extern void perf_uprobe_destroy(struct perf_event *event);
    extern int bpf_get_uprobe_info(const struct perf_event *event,
    u32 *fd_type, const char **filename,
    diff --git a/kernel/events/core.c b/kernel/events/core.c
    index c80549bf82c6..a4ad5235ec9b 100644
    --- a/kernel/events/core.c
    +++ b/kernel/events/core.c
    @@ -8368,30 +8368,39 @@ static struct pmu perf_tracepoint = {
    *
    * PERF_PROBE_CONFIG_IS_RETPROBE if set, create kretprobe/uretprobe
    * if not set, create kprobe/uprobe
    + *
    + * The following values specify a reference counter (or semaphore in the
    + * terminology of tools like dtrace, systemtap, etc.) Userspace Statically
    + * Defined Tracepoints (USDT). Currently, we use 40 bit for the offset.
    + *
    + * PERF_UPROBE_REF_CTR_OFFSET_BITS # of bits in config as th offset
    + * PERF_UPROBE_REF_CTR_OFFSET_SHIFT # of bits to shift left
    */
    enum perf_probe_config {
    PERF_PROBE_CONFIG_IS_RETPROBE = 1U << 0, /* [k,u]retprobe */
    + PERF_UPROBE_REF_CTR_OFFSET_BITS = 40,
    + PERF_UPROBE_REF_CTR_OFFSET_SHIFT = 64 - PERF_UPROBE_REF_CTR_OFFSET_BITS,
    };

    PMU_FORMAT_ATTR(retprobe, "config:0");
    +#endif

    -static struct attribute *probe_attrs[] = {
    +#ifdef CONFIG_KPROBE_EVENTS
    +static struct attribute *kprobe_attrs[] = {
    &format_attr_retprobe.attr,
    NULL,
    };

    -static struct attribute_group probe_format_group = {
    +static struct attribute_group kprobe_format_group = {
    .name = "format",
    - .attrs = probe_attrs,
    + .attrs = kprobe_attrs,
    };

    -static const struct attribute_group *probe_attr_groups[] = {
    - &probe_format_group,
    +static const struct attribute_group *kprobe_attr_groups[] = {
    + &kprobe_format_group,
    NULL,
    };
    -#endif

    -#ifdef CONFIG_KPROBE_EVENTS
    static int perf_kprobe_event_init(struct perf_event *event);
    static struct pmu perf_kprobe = {
    .task_ctx_nr = perf_sw_context,
    @@ -8401,7 +8410,7 @@ static struct pmu perf_kprobe = {
    .start = perf_swevent_start,
    .stop = perf_swevent_stop,
    .read = perf_swevent_read,
    - .attr_groups = probe_attr_groups,
    + .attr_groups = kprobe_attr_groups,
    };

    static int perf_kprobe_event_init(struct perf_event *event)
    @@ -8433,6 +8442,24 @@ static int perf_kprobe_event_init(struct perf_event *event)
    #endif /* CONFIG_KPROBE_EVENTS */

    #ifdef CONFIG_UPROBE_EVENTS
    +PMU_FORMAT_ATTR(ref_ctr_offset, "config:63-24");
    +
    +static struct attribute *uprobe_attrs[] = {
    + &format_attr_retprobe.attr,
    + &format_attr_ref_ctr_offset.attr,
    + NULL,
    +};
    +
    +static struct attribute_group uprobe_format_group = {
    + .name = "format",
    + .attrs = uprobe_attrs,
    +};
    +
    +static const struct attribute_group *uprobe_attr_groups[] = {
    + &uprobe_format_group,
    + NULL,
    +};
    +
    static int perf_uprobe_event_init(struct perf_event *event);
    static struct pmu perf_uprobe = {
    .task_ctx_nr = perf_sw_context,
    @@ -8442,12 +8469,13 @@ static struct pmu perf_uprobe = {
    .start = perf_swevent_start,
    .stop = perf_swevent_stop,
    .read = perf_swevent_read,
    - .attr_groups = probe_attr_groups,
    + .attr_groups = uprobe_attr_groups,
    };

    static int perf_uprobe_event_init(struct perf_event *event)
    {
    int err;
    + unsigned long ref_ctr_offset;
    bool is_retprobe;

    if (event->attr.type != perf_uprobe.type)
    @@ -8463,7 +8491,8 @@ static int perf_uprobe_event_init(struct perf_event *event)
    return -EOPNOTSUPP;

    is_retprobe = event->attr.config & PERF_PROBE_CONFIG_IS_RETPROBE;
    - err = perf_uprobe_init(event, is_retprobe);
    + ref_ctr_offset = event->attr.config >> PERF_UPROBE_REF_CTR_OFFSET_SHIFT;
    + err = perf_uprobe_init(event, ref_ctr_offset, is_retprobe);
    if (err)
    return err;

    diff --git a/kernel/trace/trace_event_perf.c b/kernel/trace/trace_event_perf.c
    index 69a3fe926e8c..76217bbef815 100644
    --- a/kernel/trace/trace_event_perf.c
    +++ b/kernel/trace/trace_event_perf.c
    @@ -290,7 +290,8 @@ void perf_kprobe_destroy(struct perf_event *p_event)
    #endif /* CONFIG_KPROBE_EVENTS */

    #ifdef CONFIG_UPROBE_EVENTS
    -int perf_uprobe_init(struct perf_event *p_event, bool is_retprobe)
    +int perf_uprobe_init(struct perf_event *p_event,
    + unsigned long ref_ctr_offset, bool is_retprobe)
    {
    int ret;
    char *path = NULL;
    @@ -312,8 +313,8 @@ int perf_uprobe_init(struct perf_event *p_event, bool is_retprobe)
    goto out;
    }

    - tp_event = create_local_trace_uprobe(
    - path, p_event->attr.probe_offset, is_retprobe);
    + tp_event = create_local_trace_uprobe(path, p_event->attr.probe_offset,
    + ref_ctr_offset, is_retprobe);
    if (IS_ERR(tp_event)) {
    ret = PTR_ERR(tp_event);
    goto out;
    diff --git a/kernel/trace/trace_probe.h b/kernel/trace/trace_probe.h
    index 5f52668e165d..03b10f3201a5 100644
    --- a/kernel/trace/trace_probe.h
    +++ b/kernel/trace/trace_probe.h
    @@ -412,6 +412,7 @@ create_local_trace_kprobe(char *func, void *addr, unsigned long offs,
    extern void destroy_local_trace_kprobe(struct trace_event_call *event_call);

    extern struct trace_event_call *
    -create_local_trace_uprobe(char *name, unsigned long offs, bool is_return);
    +create_local_trace_uprobe(char *name, unsigned long offs,
    + unsigned long ref_ctr_offset, bool is_return);
    extern void destroy_local_trace_uprobe(struct trace_event_call *event_call);
    #endif
    diff --git a/kernel/trace/trace_uprobe.c b/kernel/trace/trace_uprobe.c
    index 3a7c73c40007..d09638706fe0 100644
    --- a/kernel/trace/trace_uprobe.c
    +++ b/kernel/trace/trace_uprobe.c
    @@ -1405,7 +1405,8 @@ static int unregister_uprobe_event(struct trace_uprobe *tu)

    #ifdef CONFIG_PERF_EVENTS
    struct trace_event_call *
    -create_local_trace_uprobe(char *name, unsigned long offs, bool is_return)
    +create_local_trace_uprobe(char *name, unsigned long offs,
    + unsigned long ref_ctr_offset, bool is_return)
    {
    struct trace_uprobe *tu;
    struct path path;
    @@ -1437,6 +1438,7 @@ create_local_trace_uprobe(char *name, unsigned long offs, bool is_return)

    tu->offset = offs;
    tu->path = path;
    + tu->ref_ctr_offset = ref_ctr_offset;
    tu->filename = kstrdup(name, GFP_KERNEL);
    init_trace_event_call(tu, &tu->tp.call);

    --
    2.17.1
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