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SubjectRe: [PATCH 2/3] tracing/boottime: Fix kprobe event API usage
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Hi Masami,

On Sat, 2020-04-25 at 14:49 +0900, Masami Hiramatsu wrote:
> Fix boottime kprobe events to use API correctly for
> multiple events.
>
> For example, when we set a multiprobe kprobe events in
> bootconfig like below,
>
> ftrace.event.kprobes.myevent {
> probes = "vfs_read $arg1 $arg2", "vfs_write $arg1 $arg2"
> }
>
> This cause an error;
>
> trace_boot: Failed to add probe: p:kprobes/myevent (null) vfs_read
> $arg1 $arg2 vfs_write $arg1 $arg2
>
> This shows the 1st argument becomes NULL and multiprobes
> are merged to 1 probe.
>
> Fixes: 29a154810546 ("tracing: Change trace_boot to use kprobe_event
> interface")
> Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
> Cc: stable@vger.kernel.org

Thanks for fixing this!

Reviewed-by: Tom Zanussi <zanussi@kernel.org>


> ---
> kernel/trace/trace_boot.c | 20 ++++++++------------
> 1 file changed, 8 insertions(+), 12 deletions(-)
>
> diff --git a/kernel/trace/trace_boot.c b/kernel/trace/trace_boot.c
> index 06d7feb5255f..9de29bb45a27 100644
> --- a/kernel/trace/trace_boot.c
> +++ b/kernel/trace/trace_boot.c
> @@ -95,24 +95,20 @@ trace_boot_add_kprobe_event(struct xbc_node
> *node, const char *event)
> struct xbc_node *anode;
> char buf[MAX_BUF_LEN];
> const char *val;
> - int ret;
> + int ret = 0;
>
> - kprobe_event_cmd_init(&cmd, buf, MAX_BUF_LEN);
> + xbc_node_for_each_array_value(node, "probes", anode, val) {
> + kprobe_event_cmd_init(&cmd, buf, MAX_BUF_LEN);
>
> - ret = kprobe_event_gen_cmd_start(&cmd, event, NULL);
> - if (ret)
> - return ret;
> + ret = kprobe_event_gen_cmd_start(&cmd, event, val);
> + if (ret)
> + break;
>
> - xbc_node_for_each_array_value(node, "probes", anode, val) {
> - ret = kprobe_event_add_field(&cmd, val);
> + ret = kprobe_event_gen_cmd_end(&cmd);
> if (ret)
> - return ret;
> + pr_err("Failed to add probe: %s\n", buf);
> }
>
> - ret = kprobe_event_gen_cmd_end(&cmd);
> - if (ret)
> - pr_err("Failed to add probe: %s\n", buf);
> -
> return ret;
> }
> #else
>

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