[PATCH tracing/kprobes v3 1/7] tracing/kprobes: Add $ prefix tospecial variables

[Masami Hiramatsu]

Add $ prefix to the special variables(e.g. sa, rv) of kprobe-tracer.
This resolves consistency issue between kprobe_events and perf-kprobe.

Signed-off-by: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
Cc: Frederic Weisbecker <fweisbec@xxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
Cc: Mike Galbraith <efault@xxxxxx>
Cc: Paul Mackerras <paulus@xxxxxxxxx>
Cc: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxxxxxxxxx>
Cc: Ananth N Mavinakayanahalli <ananth@xxxxxxxxxx>
Cc: Jim Keniston <jkenisto@xxxxxxxxxx>
Cc: Frank Ch. Eigler <fche@xxxxxxxxxx>
---

 Documentation/trace/kprobetrace.txt |   20 ++++++------
 kernel/trace/trace_kprobe.c         |   60 ++++++++++++++++++++++-------------
 2 files changed, 47 insertions(+), 33 deletions(-)

diff --git a/Documentation/trace/kprobetrace.txt b/Documentation/trace/kprobetrace.txt
index 9b8f7c6..33f5318 100644
--- a/Documentation/trace/kprobetrace.txt
+++ b/Documentation/trace/kprobetrace.txt
@@ -36,13 +36,13 @@ Synopsis of kprobe_events
 
  FETCHARGS	: Arguments. Each probe can have up to 128 args.
   %REG	: Fetch register REG
-  sN	: Fetch Nth entry of stack (N >= 0)
-  sa	: Fetch stack address.
   @ADDR	: Fetch memory at ADDR (ADDR should be in kernel)
   @SYM[+|-offs]	: Fetch memory at SYM +|- offs (SYM should be a data symbol)
-  aN	: Fetch function argument. (N >= 0)(*)
-  rv	: Fetch return value.(**)
-  ra	: Fetch return address.(**)
+  $sN	: Fetch Nth entry of stack (N >= 0)
+  $sa	: Fetch stack address.
+  $aN	: Fetch function argument. (N >= 0)(*)
+  $rv	: Fetch return value.(**)
+  $ra	: Fetch return address.(**)
   +|-offs(FETCHARG) : Fetch memory at FETCHARG +|- offs address.(***)
   NAME=FETCHARG: Set NAME as the argument name of FETCHARG.
 
@@ -85,13 +85,13 @@ Usage examples
 To add a probe as a new event, write a new definition to kprobe_events
 as below.
 
-  echo p:myprobe do_sys_open dfd=a0 filename=a1 flags=a2 mode=a3 > /sys/kernel/debug/tracing/kprobe_events
+  echo p:myprobe do_sys_open dfd=$a0 filename=$a1 flags=$a2 mode=$a3 > /sys/kernel/debug/tracing/kprobe_events
 
  This sets a kprobe on the top of do_sys_open() function with recording
 1st to 4th arguments as "myprobe" event. As this example shows, users can
 choose more familiar names for each arguments.
 
-  echo r:myretprobe do_sys_open rv ra >> /sys/kernel/debug/tracing/kprobe_events
+  echo r:myretprobe do_sys_open $rv $ra >> /sys/kernel/debug/tracing/kprobe_events
 
  This sets a kretprobe on the return point of do_sys_open() function with
 recording return value and return address as "myretprobe" event.
@@ -138,11 +138,11 @@ events, you need to enable it.
 #           TASK-PID    CPU#    TIMESTAMP  FUNCTION
 #              | |       |          |         |
            <...>-1447  [001] 1038282.286875: myprobe: (do_sys_open+0x0/0xd6) dfd=3 filename=7fffd1ec4440 flags=8000 mode=0
-           <...>-1447  [001] 1038282.286878: myretprobe: (sys_openat+0xc/0xe <- do_sys_open) rv=fffffffffffffffe ra=ffffffff81367a3a
+           <...>-1447  [001] 1038282.286878: myretprobe: (sys_openat+0xc/0xe <- do_sys_open) $rv=fffffffffffffffe $ra=ffffffff81367a3a
            <...>-1447  [001] 1038282.286885: myprobe: (do_sys_open+0x0/0xd6) dfd=ffffff9c filename=40413c flags=8000 mode=1b6
-           <...>-1447  [001] 1038282.286915: myretprobe: (sys_open+0x1b/0x1d <- do_sys_open) rv=3 ra=ffffffff81367a3a
+           <...>-1447  [001] 1038282.286915: myretprobe: (sys_open+0x1b/0x1d <- do_sys_open) $rv=3 $ra=ffffffff81367a3a
            <...>-1447  [001] 1038282.286969: myprobe: (do_sys_open+0x0/0xd6) dfd=ffffff9c filename=4041c6 flags=98800 mode=10
-           <...>-1447  [001] 1038282.286976: myretprobe: (sys_open+0x1b/0x1d <- do_sys_open) rv=3 ra=ffffffff81367a3a
+           <...>-1447  [001] 1038282.286976: myretprobe: (sys_open+0x1b/0x1d <- do_sys_open) $rv=3 $ra=ffffffff81367a3a
 
 
  Each line shows when the kernel hits an event, and <- SYMBOL means kernel
diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
index 97309d4..f63ead0 100644
--- a/kernel/trace/trace_kprobe.c
+++ b/kernel/trace/trace_kprobe.c
@@ -220,24 +220,24 @@ static int probe_arg_string(char *buf, size_t n, struct fetch_func *ff)
 	int ret = -EINVAL;
 
 	if (ff->func == fetch_argument)
-		ret = snprintf(buf, n, "a%lu", (unsigned long)ff->data);
+		ret = snprintf(buf, n, "$a%lu", (unsigned long)ff->data);
 	else if (ff->func == fetch_register) {
 		const char *name;
 		name = regs_query_register_name((unsigned int)((long)ff->data));
 		ret = snprintf(buf, n, "%%%s", name);
 	} else if (ff->func == fetch_stack)
-		ret = snprintf(buf, n, "s%lu", (unsigned long)ff->data);
+		ret = snprintf(buf, n, "$s%lu", (unsigned long)ff->data);
 	else if (ff->func == fetch_memory)
 		ret = snprintf(buf, n, "@0x%p", ff->data);
 	else if (ff->func == fetch_symbol) {
 		struct symbol_cache *sc = ff->data;
 		ret = snprintf(buf, n, "@%s%+ld", sc->symbol, sc->offset);
 	} else if (ff->func == fetch_retvalue)
-		ret = snprintf(buf, n, "rv");
+		ret = snprintf(buf, n, "$rv");
 	else if (ff->func == fetch_ip)
-		ret = snprintf(buf, n, "ra");
+		ret = snprintf(buf, n, "$ra");
 	else if (ff->func == fetch_stack_address)
-		ret = snprintf(buf, n, "sa");
+		ret = snprintf(buf, n, "$sa");
 	else if (ff->func == fetch_indirect) {
 		struct indirect_fetch_data *id = ff->data;
 		size_t l = 0;
@@ -429,12 +429,10 @@ static int split_symbol_offset(char *symbol, unsigned long *offset)
 #define PARAM_MAX_ARGS 16
 #define PARAM_MAX_STACK (THREAD_SIZE / sizeof(unsigned long))
 
-static int parse_probe_arg(char *arg, struct fetch_func *ff, int is_return)
+static int parse_probe_vars(char *arg, struct fetch_func *ff, int is_return)
 {
 	int ret = 0;
 	unsigned long param;
-	long offset;
-	char *tmp;
 
 	switch (arg[0]) {
 	case 'a':	/* argument */
@@ -456,14 +454,6 @@ static int parse_probe_arg(char *arg, struct fetch_func *ff, int is_return)
 		} else
 			ret = -EINVAL;
 		break;
-	case '%':	/* named register */
-		ret = regs_query_register_offset(arg + 1);
-		if (ret >= 0) {
-			ff->func = fetch_register;
-			ff->data = (void *)(unsigned long)ret;
-			ret = 0;
-		}
-		break;
 	case 's':	/* stack */
 		if (arg[1] == 'a') {
 			ff->func = fetch_stack_address;
@@ -478,6 +468,31 @@ static int parse_probe_arg(char *arg, struct fetch_func *ff, int is_return)
 			}
 		}
 		break;
+	default:
+		ret = -EINVAL;
+	}
+	return ret;
+}
+
+static int parse_probe_arg(char *arg, struct fetch_func *ff, int is_return)
+{
+	int ret = 0;
+	unsigned long param;
+	long offset;
+	char *tmp;
+
+	switch (arg[0]) {
+	case '$':
+		ret = parse_probe_vars(arg + 1, ff, is_return);
+		break;
+	case '%':	/* named register */
+		ret = regs_query_register_offset(arg + 1);
+		if (ret >= 0) {
+			ff->func = fetch_register;
+			ff->data = (void *)(unsigned long)ret;
+			ret = 0;
+		}
+		break;
 	case '@':	/* memory or symbol */
 		if (isdigit(arg[1])) {
 			ret = strict_strtoul(arg + 1, 0, &param);
@@ -489,8 +504,7 @@ static int parse_probe_arg(char *arg, struct fetch_func *ff, int is_return)
 			ret = split_symbol_offset(arg + 1, &offset);
 			if (ret)
 				break;
-			ff->data = alloc_symbol_cache(arg + 1,
-							      offset);
+			ff->data = alloc_symbol_cache(arg + 1, offset);
 			if (ff->data)
 				ff->func = fetch_symbol;
 			else
@@ -544,11 +558,11 @@ static int create_trace_probe(int argc, char **argv)
 	 *  - Add kprobe: p[:[GRP/]EVENT] KSYM[+OFFS]|KADDR [FETCHARGS]
 	 *  - Add kretprobe: r[:[GRP/]EVENT] KSYM[+0] [FETCHARGS]
 	 * Fetch args:
-	 *  aN	: fetch Nth of function argument. (N:0-)
-	 *  rv	: fetch return value
-	 *  ra	: fetch return address
-	 *  sa	: fetch stack address
-	 *  sN	: fetch Nth of stack (N:0-)
+	 *  $aN	: fetch Nth of function argument. (N:0-)
+	 *  $rv	: fetch return value
+	 *  $ra	: fetch return address
+	 *  $sa	: fetch stack address
+	 *  $sN	: fetch Nth of stack (N:0-)
 	 *  @ADDR	: fetch memory at ADDR (ADDR should be in kernel)
 	 *  @SYM[+|-offs] : fetch memory at SYM +|- offs (SYM is a data symbol)
 	 *  %REG	: fetch register REG


-- 
Masami Hiramatsu

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

e-mail: mhiramat@xxxxxxxxxx
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