linux-kernel - [PATCH -tip -v12 09/11] tracing: Kprobe-tracer supports more than 6 arguments

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Date:	Thu, 16 Jul 2009 11:57:48 -0400
From:	Masami Hiramatsu <mhiramat@...hat.com>
To:	Ingo Molnar <mingo@...e.hu>, Steven Rostedt <rostedt@...dmis.org>,
	lkml <linux-kernel@...r.kernel.org>
Cc:	systemtap <systemtap@...rces.redhat.com>,
	kvm <kvm@...r.kernel.org>,
	DLE <dle-develop@...ts.sourceforge.net>,
	Masami Hiramatsu <mhiramat@...hat.com>,
	Ananth N Mavinakayanahalli <ananth@...ibm.com>,
	Christoph Hellwig <hch@...radead.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Ingo Molnar <mingo@...e.hu>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Tom Zanussi <tzanussi@...il.com>
Subject: [PATCH -tip -v12 09/11] tracing: Kprobe-tracer supports more than 6
	arguments

Support up to 128 arguments for each kprobes event.

Signed-off-by: Masami Hiramatsu <mhiramat@...hat.com>
Cc: Ananth N Mavinakayanahalli <ananth@...ibm.com>
Cc: Christoph Hellwig <hch@...radead.org>
Cc: Steven Rostedt <rostedt@...dmis.org>
Cc: Ingo Molnar <mingo@...e.hu>
Cc: Frederic Weisbecker <fweisbec@...il.com>
Cc: Tom Zanussi <tzanussi@...il.com>
---

 Documentation/trace/kprobetrace.txt |    2 +-
 kernel/trace/trace_kprobe.c         |   21 +++++++++++++--------
 2 files changed, 14 insertions(+), 9 deletions(-)

diff --git a/Documentation/trace/kprobetrace.txt b/Documentation/trace/kprobetrace.txt
index 9ad907c..b29a54b 100644
--- a/Documentation/trace/kprobetrace.txt
+++ b/Documentation/trace/kprobetrace.txt
@@ -32,7 +32,7 @@ Synopsis of kprobe_events
  SYMBOL[+offs|-offs]	: Symbol+offset where the probe is inserted.
  MEMADDR		: Address where the probe is inserted.
 
- FETCHARGS		: Arguments.
+ FETCHARGS		: Arguments. Each probe can have up to 128 args.
   %REG	: Fetch register REG
   sN	: Fetch Nth entry of stack (N >= 0)
   @ADDR	: Fetch memory at ADDR (ADDR should be in kernel)
diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
index ad33073..67c33e1 100644
--- a/kernel/trace/trace_kprobe.c
+++ b/kernel/trace/trace_kprobe.c
@@ -32,7 +32,7 @@
 #include "trace.h"
 #include "trace_output.h"
 
-#define TRACE_KPROBE_ARGS 6
+#define MAX_TRACE_ARGS 128
 #define MAX_ARGSTR_LEN 63
 
 /* currently, trace_kprobe only supports X86. */
@@ -178,11 +178,15 @@ struct trace_probe {
 		struct kretprobe	rp;
 	};
 	const char		*symbol;	/* symbol name */
-	unsigned int		nr_args;
-	struct fetch_func	args[TRACE_KPROBE_ARGS];
 	struct ftrace_event_call	call;
+	unsigned int		nr_args;
+	struct fetch_func	args[];
 };
 
+#define SIZEOF_TRACE_PROBE(n)			\
+	(offsetof(struct trace_probe, args) +	\
+	(sizeof(struct fetch_func) * (n)))
+
 static int kprobe_trace_func(struct kprobe *kp, struct pt_regs *regs);
 static int kretprobe_trace_func(struct kretprobe_instance *ri,
 				struct pt_regs *regs);
@@ -255,11 +259,11 @@ static DEFINE_MUTEX(probe_lock);
 static LIST_HEAD(probe_list);
 
 static struct trace_probe *alloc_trace_probe(const char *symbol,
-					     const char *event)
+					     const char *event, int nargs)
 {
 	struct trace_probe *tp;
 
-	tp = kzalloc(sizeof(struct trace_probe), GFP_KERNEL);
+	tp = kzalloc(SIZEOF_TRACE_PROBE(nargs), GFP_KERNEL);
 	if (!tp)
 		return ERR_PTR(-ENOMEM);
 
@@ -559,9 +563,10 @@ static int create_trace_probe(int argc, char **argv)
 		if (offset && is_return)
 			return -EINVAL;
 	}
+	argc -= 2; argv += 2;
 
 	/* setup a probe */
-	tp = alloc_trace_probe(symbol, event);
+	tp = alloc_trace_probe(symbol, event, argc);
 	if (IS_ERR(tp))
 		return PTR_ERR(tp);
 
@@ -580,8 +585,8 @@ static int create_trace_probe(int argc, char **argv)
 		kp->addr = addr;
 
 	/* parse arguments */
-	argc -= 2; argv += 2; ret = 0;
-	for (i = 0; i < argc && i < TRACE_KPROBE_ARGS; i++) {
+	ret = 0;
+	for (i = 0; i < argc && i < MAX_TRACE_ARGS; i++) {
 		if (strlen(argv[i]) > MAX_ARGSTR_LEN) {
 			pr_info("Argument%d(%s) is too long.\n", i, argv[i]);
 			ret = -ENOSPC;


-- 
Masami Hiramatsu

Software Engineer
Hitachi Computer Products (America), Inc.
Software Solutions Division

e-mail: mhiramat@...hat.com
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