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Re: [PATCH tracing/kprobes v3 4/7] tracing/kprobes: Avoid field name confliction
- From: Frederic Weisbecker <fweisbec at gmail dot com>
- To: Masami Hiramatsu <mhiramat at redhat dot com>
- Cc: Steven Rostedt <rostedt at goodmis dot org>, Ingo Molnar <mingo at elte dot hu>, lkml <linux-kernel at vger dot kernel dot org>, systemtap <systemtap at sources dot redhat dot com>, DLE <dle-develop at lists dot sourceforge dot net>, Thomas Gleixner <tglx at linutronix dot de>, Arnaldo Carvalho de Melo <acme at redhat dot com>, Mike Galbraith <efault at gmx dot de>, Paul Mackerras <paulus at samba dot org>, Peter Zijlstra <a dot p dot zijlstra at chello dot nl>, Christoph Hellwig <hch at infradead dot org>, Ananth N Mavinakayanahalli <ananth at in dot ibm dot com>, Jim Keniston <jkenisto at us dot ibm dot com>, "Frank Ch. Eigler" <fche at redhat dot com>
- Date: Mon, 12 Oct 2009 19:37:54 +0200
- Subject: Re: [PATCH tracing/kprobes v3 4/7] tracing/kprobes: Avoid field name confliction
- References: <20091007222733.1684.32035.stgit@dhcp-100-2-132.bos.redhat.com> <20091007222807.1684.26880.stgit@dhcp-100-2-132.bos.redhat.com>
On Wed, Oct 07, 2009 at 06:28:07PM -0400, Masami Hiramatsu wrote:
> Check whether the argument name is conflict with other field names.
>
> Changes in v3:
> - Check strcmp() == 0 instead of !strcmp().
>
> Changes in v2:
> - Add common_lock_depth to reserved name list.
>
> Signed-off-by: Masami Hiramatsu <mhiramat@redhat.com>
> Cc: Frederic Weisbecker <fweisbec@gmail.com>
> Cc: Ingo Molnar <mingo@elte.hu>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
> Cc: Steven Rostedt <rostedt@goodmis.org>
> Cc: Mike Galbraith <efault@gmx.de>
> Cc: Paul Mackerras <paulus@samba.org>
> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
> Cc: Christoph Hellwig <hch@infradead.org>
> Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
> Cc: Jim Keniston <jkenisto@us.ibm.com>
> Cc: Frank Ch. Eigler <fche@redhat.com>
> ---
>
> kernel/trace/trace_kprobe.c | 65 +++++++++++++++++++++++++++++++++++--------
> 1 files changed, 53 insertions(+), 12 deletions(-)
>
> diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
> index 030f28c..e3b824a 100644
> --- a/kernel/trace/trace_kprobe.c
> +++ b/kernel/trace/trace_kprobe.c
> @@ -38,6 +38,25 @@
> #define MAX_EVENT_NAME_LEN 64
> #define KPROBE_EVENT_SYSTEM "kprobes"
>
> +/* Reserved field names */
> +#define FIELD_STRING_IP "ip"
> +#define FIELD_STRING_NARGS "nargs"
> +#define FIELD_STRING_RETIP "ret_ip"
> +#define FIELD_STRING_FUNC "func"
> +
> +const char *reserved_field_names[] = {
> + "common_type",
> + "common_flags",
> + "common_preempt_count",
> + "common_pid",
> + "common_tgid",
> + "common_lock_depth",
> + FIELD_STRING_IP,
> + FIELD_STRING_NARGS,
> + FIELD_STRING_RETIP,
> + FIELD_STRING_FUNC,
> +};
> +
> /* currently, trace_kprobe only supports X86. */
>
> struct fetch_func {
> @@ -537,6 +556,20 @@ static int parse_probe_arg(char *arg, struct fetch_func *ff, int is_return)
> return ret;
> }
>
> +/* Return 1 if name is reserved or already used by another argument */
> +static int conflict_field_name(const char *name,
> + struct probe_arg *args, int narg)
> +{
> + int i;
> + for (i = 0; i < ARRAY_SIZE(reserved_field_names); i++)
> + if (strcmp(reserved_field_names[i], name) == 0)
> + return 1;
> + for (i = 0; i < narg; i++)
> + if (strcmp(args[i].name, name) == 0)
> + return 1;
> + return 0;
> +}
> +
> static int create_trace_probe(int argc, char **argv)
> {
> /*
> @@ -637,6 +670,12 @@ static int create_trace_probe(int argc, char **argv)
> *arg++ = '\0';
> else
> arg = argv[i];
> +
> + if (conflict_field_name(argv[i], tp->args, i)) {
> + ret = -EINVAL;
The conflict issue might not be obvious for a user desperately trying to set
a kprobe. Even for other failcases, it might not be obvious (blacklisted
symbols, syntax errors...)
May be should you improve the error granularity and print a KERN_DEBUG
message?
Thanks.