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SubjectRe: [PATCH 6/7] uprobes/perf: Teach trace_uprobe/perf code to use UPROBE_HANDLER_REMOVE
* Oleg Nesterov <oleg@redhat.com> [2013-02-04 20:03:01]:

> Change uprobe_trace_func() and uprobe_perf_func() to return "int". Change
> Change uprobe_dispatcher() to return "trace_ret | perf_ret" although this
> is not really needed, currently TP_FLAG_TRACE/TP_FLAG_PROFILE are mutually
> exclusive.
>
> The only functional change is that uprobe_perf_func() checks the filtering
> too and returns UPROBE_HANDLER_REMOVE if nobody wants to trace current.
>
> Testing:
>
> # perf probe -x /lib/libc.so.6 syscall
>
> # perf record -e probe_libc:syscall -i perl -e 'fork; syscall -1 for 1..10; wait'
>
> # perf report --show-total-period
> 100.00% 10 perl libc-2.8.so [.] syscall
>
> Before this patch:
>
> # cat /sys/kernel/debug/tracing/uprobe_profile
> /lib/libc.so.6 syscall 20
>
> A child process doesn't have a counter, but still it hits this breakoint
> "copied" by dup_mmap().
>
> After the patch:
>
> # cat /sys/kernel/debug/tracing/uprobe_profile
> /lib/libc.so.6 syscall 11
>
> The child process hits this int3 only once and does unapply_uprobe().
>
> Signed-off-by: Oleg Nesterov <oleg@redhat.com>

Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>

> ---
> kernel/trace/trace_uprobe.c | 21 ++++++++++++++-------
> 1 files changed, 14 insertions(+), 7 deletions(-)
>
> diff --git a/kernel/trace/trace_uprobe.c b/kernel/trace/trace_uprobe.c
> index 5d5a261..1114619 100644
> --- a/kernel/trace/trace_uprobe.c
> +++ b/kernel/trace/trace_uprobe.c
> @@ -483,7 +483,7 @@ static const struct file_operations uprobe_profile_ops = {
> };
>
> /* uprobe handler */
> -static void uprobe_trace_func(struct trace_uprobe *tu, struct pt_regs *regs)
> +static int uprobe_trace_func(struct trace_uprobe *tu, struct pt_regs *regs)
> {
> struct uprobe_trace_entry_head *entry;
> struct ring_buffer_event *event;
> @@ -501,7 +501,7 @@ static void uprobe_trace_func(struct trace_uprobe *tu, struct pt_regs *regs)
> event = trace_current_buffer_lock_reserve(&buffer, call->event.type,
> size, irq_flags, pc);
> if (!event)
> - return;
> + return 0;
>
> entry = ring_buffer_event_data(event);
> entry->ip = instruction_pointer(task_pt_regs(current));
> @@ -511,6 +511,8 @@ static void uprobe_trace_func(struct trace_uprobe *tu, struct pt_regs *regs)
>
> if (!filter_current_check_discard(buffer, call, entry, event))
> trace_buffer_unlock_commit(buffer, event, irq_flags, pc);
> +
> + return 0;
> }
>
> /* Event entry printers */
> @@ -718,7 +720,7 @@ static bool uprobe_perf_filter(struct uprobe_consumer *uc,
> }
>
> /* uprobe profile handler */
> -static void uprobe_perf_func(struct trace_uprobe *tu, struct pt_regs *regs)
> +static int uprobe_perf_func(struct trace_uprobe *tu, struct pt_regs *regs)
> {
> struct ftrace_event_call *call = &tu->call;
> struct uprobe_trace_entry_head *entry;
> @@ -727,11 +729,14 @@ static void uprobe_perf_func(struct trace_uprobe *tu, struct pt_regs *regs)
> int size, __size, i;
> int rctx;
>
> + if (!uprobe_perf_filter(&tu->consumer, 0, current->mm))
> + return UPROBE_HANDLER_REMOVE;
> +
> __size = sizeof(*entry) + tu->size;
> size = ALIGN(__size + sizeof(u32), sizeof(u64));
> size -= sizeof(u32);
> if (WARN_ONCE(size > PERF_MAX_TRACE_SIZE, "profile buffer not large enough"))
> - return;
> + return 0;
>
> preempt_disable();
>
> @@ -749,6 +754,7 @@ static void uprobe_perf_func(struct trace_uprobe *tu, struct pt_regs *regs)
>
> out:
> preempt_enable();
> + return 0;
> }
> #endif /* CONFIG_PERF_EVENTS */
>
> @@ -789,18 +795,19 @@ int trace_uprobe_register(struct ftrace_event_call *event, enum trace_reg type,
> static int uprobe_dispatcher(struct uprobe_consumer *con, struct pt_regs *regs)
> {
> struct trace_uprobe *tu;
> + int ret = 0;
>
> tu = container_of(con, struct trace_uprobe, consumer);
> tu->nhit++;
>
> if (tu->flags & TP_FLAG_TRACE)
> - uprobe_trace_func(tu, regs);
> + ret |= uprobe_trace_func(tu, regs);
>
> #ifdef CONFIG_PERF_EVENTS
> if (tu->flags & TP_FLAG_PROFILE)
> - uprobe_perf_func(tu, regs);
> + ret |= uprobe_perf_func(tu, regs);
> #endif
> - return 0;
> + return ret;
> }
>
> static struct trace_event_functions uprobe_funcs = {
> --
> 1.5.5.1
>

--
Thanks and Regards
Srikar Dronamraju



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