(2013/09/03 14:44), Namhyung Kim wrote:
> From: Namhyung Kim <namhyung....@lge.com>
>
> Fetching from user space should be done in a non-atomic context. So
> use a per-cpu buffer and copy its content to the ring buffer
> atomically. Note that we can migrate during accessing user memory
> thus use a per-cpu mutex to protect concurrent accesses.
>
> This is needed since we'll be able to fetch args from an user memory
> which can be swapped out. Before that uprobes could fetch args from
> registers only which saved in a kernel space.
>
> While at it, use __get_data_size() and store_trace_args() to reduce
> code duplication.
>
> Cc: Masami Hiramatsu <masami.hiramatsu...@hitachi.com>
> Cc: Srikar Dronamraju <sri...@linux.vnet.ibm.com>
> Cc: Oleg Nesterov <o...@redhat.com>
> Cc: zhangwei(Jovi) <jovi.zhang...@huawei.com>
> Cc: Arnaldo Carvalho de Melo <a...@ghostprotocols.net>
> Signed-off-by: Namhyung Kim <namhy...@kernel.org>
> ---
> kernel/trace/trace_uprobe.c | 97
> +++++++++++++++++++++++++++++++++++++--------
> 1 file changed, 81 insertions(+), 16 deletions(-)
>
> diff --git a/kernel/trace/trace_uprobe.c b/kernel/trace/trace_uprobe.c
> index 9f2d12d2311d..9ede401759ab 100644
> --- a/kernel/trace/trace_uprobe.c
> +++ b/kernel/trace/trace_uprobe.c
> @@ -530,21 +530,46 @@ static const struct file_operations uprobe_profile_ops
> = {
> .release = seq_release,
> };
>
> +static atomic_t uprobe_buffer_ref = ATOMIC_INIT(0);
> +static void __percpu *uprobe_cpu_buffer;
> +static DEFINE_PER_CPU(struct mutex, uprobe_cpu_mutex);
> +
> static void uprobe_trace_print(struct trace_uprobe *tu,
> unsigned long func, struct pt_regs *regs)
> {
> struct uprobe_trace_entry_head *entry;
> struct ring_buffer_event *event;
> struct ring_buffer *buffer;
> - void *data;
> - int size, i;
> + struct mutex *mutex;
> + void *data, *arg_buf;
> + int size, dsize, esize;
> + int cpu;
> struct ftrace_event_call *call = &tu->p.call;
>
> - size = SIZEOF_TRACE_ENTRY(is_ret_probe(tu));
> + dsize = __get_data_size(&tu->p, regs);
> + esize = SIZEOF_TRACE_ENTRY(is_ret_probe(tu));
> +
> + if (WARN_ON_ONCE(!uprobe_cpu_buffer || tu->p.size + dsize > PAGE_SIZE))
> + return;
> +
> + cpu = raw_smp_processor_id();
> + mutex = &per_cpu(uprobe_cpu_mutex, cpu);
> + arg_buf = per_cpu_ptr(uprobe_cpu_buffer, cpu);
> +
> + /*
> + * Use per-cpu buffers for fastest access, but we might migrate
> + * so the mutex makes sure we have sole access to it.
> + */
> + mutex_lock(mutex);
> + store_trace_args(esize, &tu->p, regs, arg_buf, dsize);
> +
> + size = esize + tu->p.size + dsize;
> event = trace_current_buffer_lock_reserve(&buffer, call->event.type,
> - size + tu->p.size, 0, 0);
> - if (!event)
> + size, 0, 0);
> + if (!event) {
> + mutex_unlock(mutex);
> return;
Just for a maintenance reason, I personally like to use "goto" in this case
to fold up the mutex_unlock. :)
Other parts are good for me.
Reviewed-by: Masami Hiramatsu <masami.hiramatsu...@hitachi.com>
Thank you!
--
Masami HIRAMATSU
IT Management Research Dept. Linux Technology Center
Hitachi, Ltd., Yokohama Research Laboratory
E-mail: masami.hiramatsu...@hitachi.com
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