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    Subject[PATCH 1/2 v3] tracing/uprobes: Support ftrace_event_file base multibuffer
    Support multi-buffer on uprobe-based dynamic events by
    using ftrace_event_file.

    This patch is based kprobe-based dynamic events multibuffer
    support work initially, commited by Masami(commit 41a7dd420c),
    but revised as below:

    Oleg changed the kprobe-based multibuffer design from
    array-pointers of ftrace_event_file into simple list,
    so this patch also change to the list degisn.

    rcu_read_lock/unlock added into uprobe_trace_func/uretprobe_trace_func,
    to synchronize with ftrace_event_file list add and delete.

    Even though we allow multi-uprobes instances now,
    but TP_FLAG_PROFILE/TP_FLAG_TRACE are still mutually exclusive
    in probe_event_enable currently, this means we cannot allow
    one user is using uprobe-tracer, and another user is using
    perf-probe on same uprobe concurrently.
    (Perhaps this will be fix in future, kprobe dont't have this
    limitation now)

    Signed-off-by: zhangwei(Jovi) <jovi.zhangwei@huawei.com>
    Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
    Cc: Frederic Weisbecker <fweisbec@gmail.com>
    Cc: Oleg Nesterov <oleg@redhat.com>
    Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
    ---
    kernel/trace/trace_uprobe.c | 118 +++++++++++++++++++++++++++++++++++--------
    1 file changed, 97 insertions(+), 21 deletions(-)

    diff --git a/kernel/trace/trace_uprobe.c b/kernel/trace/trace_uprobe.c
    index 32494fb0..dbbb4a9 100644
    --- a/kernel/trace/trace_uprobe.c
    +++ b/kernel/trace/trace_uprobe.c
    @@ -53,6 +53,7 @@ struct trace_uprobe {
    struct list_head list;
    struct ftrace_event_class class;
    struct ftrace_event_call call;
    + struct list_head files;
    struct trace_uprobe_filter filter;
    struct uprobe_consumer consumer;
    struct inode *inode;
    @@ -65,6 +66,11 @@ struct trace_uprobe {
    struct probe_arg args[];
    };

    +struct event_file_link {
    + struct ftrace_event_file *file;
    + struct list_head list;
    +};
    +
    #define SIZEOF_TRACE_UPROBE(n) \
    (offsetof(struct trace_uprobe, args) + \
    (sizeof(struct probe_arg) * (n)))
    @@ -124,6 +130,7 @@ alloc_trace_uprobe(const char *group, const char *event, int nargs, bool is_ret)
    goto error;

    INIT_LIST_HEAD(&tu->list);
    + INIT_LIST_HEAD(&tu->files);
    tu->consumer.handler = uprobe_dispatcher;
    if (is_ret)
    tu->consumer.ret_handler = uretprobe_dispatcher;
    @@ -511,7 +518,8 @@ static const struct file_operations uprobe_profile_ops = {
    };

    static void uprobe_trace_print(struct trace_uprobe *tu,
    - unsigned long func, struct pt_regs *regs)
    + unsigned long func, struct pt_regs *regs,
    + struct ftrace_event_file *ftrace_file)
    {
    struct uprobe_trace_entry_head *entry;
    struct ring_buffer_event *event;
    @@ -520,9 +528,12 @@ static void uprobe_trace_print(struct trace_uprobe *tu,
    int size, i;
    struct ftrace_event_call *call = &tu->call;

    + WARN_ON(call != ftrace_file->event_call);
    +
    size = SIZEOF_TRACE_ENTRY(is_ret_probe(tu));
    - event = trace_current_buffer_lock_reserve(&buffer, call->event.type,
    - size + tu->size, 0, 0);
    + event = trace_event_buffer_lock_reserve(&buffer, ftrace_file,
    + call->event.type,
    + size + tu->size, 0, 0);
    if (!event)
    return;

    @@ -546,15 +557,28 @@ static void uprobe_trace_print(struct trace_uprobe *tu,
    /* uprobe handler */
    static int uprobe_trace_func(struct trace_uprobe *tu, struct pt_regs *regs)
    {
    - if (!is_ret_probe(tu))
    - uprobe_trace_print(tu, 0, regs);
    + struct event_file_link *link;
    +
    + if (is_ret_probe(tu))
    + return 0;
    +
    + rcu_read_lock();
    + list_for_each_entry(link, &tu->files, list)
    + uprobe_trace_print(tu, 0, regs, link->file);
    + rcu_read_unlock();
    +
    return 0;
    }

    static void uretprobe_trace_func(struct trace_uprobe *tu, unsigned long func,
    struct pt_regs *regs)
    {
    - uprobe_trace_print(tu, func, regs);
    + struct event_file_link *link;
    +
    + rcu_read_lock();
    + list_for_each_entry(link, &tu->files, list)
    + uprobe_trace_print(tu, func, regs, link->file);
    + rcu_read_unlock();
    }

    /* Event entry printers */
    @@ -605,33 +629,84 @@ typedef bool (*filter_func_t)(struct uprobe_consumer *self,
    struct mm_struct *mm);

    static int
    -probe_event_enable(struct trace_uprobe *tu, int flag, filter_func_t filter)
    +probe_event_enable(struct trace_uprobe *tu, struct ftrace_event_file *file,
    + filter_func_t filter)
    {
    + int enabled = 0;
    int ret = 0;

    + /* we cannot call uprobe_register twice for same tu */
    if (is_trace_uprobe_enabled(tu))
    - return -EINTR;
    + enabled = 1;
    +
    + if (file) {
    + struct event_file_link *link;
    +
    + if (tu->flags & TP_FLAG_PROFILE)
    + return -EINTR;
    +
    + link = kmalloc(sizeof(*link), GFP_KERNEL);
    + if (!link)
    + return -ENOMEM;
    +
    + link->file = file;
    + list_add_rcu(&link->list, &tu->files);
    +
    + tu->flags |= TP_FLAG_TRACE;
    + } else {
    + if (tu->flags & TP_FLAG_TRACE)
    + return -EINTR;
    +
    + tu->flags |= TP_FLAG_PROFILE;
    + }

    WARN_ON(!uprobe_filter_is_empty(&tu->filter));

    - tu->flags |= flag;
    - tu->consumer.filter = filter;
    - ret = uprobe_register(tu->inode, tu->offset, &tu->consumer);
    - if (ret)
    - tu->flags &= ~flag;
    + if (!enabled) {
    + tu->consumer.filter = filter;
    + ret = uprobe_register(tu->inode, tu->offset, &tu->consumer);
    + if (ret)
    + tu->flags &= file ? ~TP_FLAG_TRACE : ~TP_FLAG_PROFILE;
    + }

    return ret;
    }

    -static void probe_event_disable(struct trace_uprobe *tu, int flag)
    +static struct event_file_link *
    +find_event_file_link(struct trace_uprobe *tu, struct ftrace_event_file *file)
    {
    - if (!is_trace_uprobe_enabled(tu))
    - return;
    + struct event_file_link *link;
    +
    + list_for_each_entry(link, &tu->files, list)
    + if (link->file == file)
    + return link;
    +
    + return NULL;
    +}
    +
    +static void
    +probe_event_disable(struct trace_uprobe *tu, struct ftrace_event_file *file)
    +{
    + if (file) {
    + struct event_file_link *link;
    +
    + link = find_event_file_link(tu, file);
    + if (!link)
    + return;
    +
    + list_del_rcu(&link->list);
    + /* synchronize with uprobe_trace_func/uretprobe_trace_func */
    + synchronize_sched();
    + kfree(link);
    +
    + if (!list_empty(&tu->files))
    + return;
    + }

    WARN_ON(!uprobe_filter_is_empty(&tu->filter));

    uprobe_unregister(tu->inode, tu->offset, &tu->consumer);
    - tu->flags &= ~flag;
    + tu->flags &= file ? ~TP_FLAG_TRACE : ~TP_FLAG_PROFILE;
    }

    static int uprobe_event_define_fields(struct ftrace_event_call *event_call)
    @@ -867,21 +942,22 @@ static
    int trace_uprobe_register(struct ftrace_event_call *event, enum trace_reg type, void *data)
    {
    struct trace_uprobe *tu = event->data;
    + struct ftrace_event_file *file = data;

    switch (type) {
    case TRACE_REG_REGISTER:
    - return probe_event_enable(tu, TP_FLAG_TRACE, NULL);
    + return probe_event_enable(tu, file, NULL);

    case TRACE_REG_UNREGISTER:
    - probe_event_disable(tu, TP_FLAG_TRACE);
    + probe_event_disable(tu, file);
    return 0;

    #ifdef CONFIG_PERF_EVENTS
    case TRACE_REG_PERF_REGISTER:
    - return probe_event_enable(tu, TP_FLAG_PROFILE, uprobe_perf_filter);
    + return probe_event_enable(tu, NULL, uprobe_perf_filter);

    case TRACE_REG_PERF_UNREGISTER:
    - probe_event_disable(tu, TP_FLAG_PROFILE);
    + probe_event_disable(tu, NULL);
    return 0;

    case TRACE_REG_PERF_OPEN:
    --
    1.7.9.7



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