tracing: probeevent: Return consumed bytes of dynamic area

Cleanup string fetching routine so that returns the consumed
bytes of dynamic area and store the string information as
data_loc format instead of data_rloc.
This simplifies the fetcharg loop.

Link: http://lkml.kernel.org/r/152465874163.26224.12125143907501289031.stgit@devbox

Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

1 files changed, 25 insertions, 29 deletions

diff --git a/kernel/trace/trace_probe_tmpl.h b/kernel/trace/trace_probe_tmpl.h
index c8a5272abf01..3b4aba6f84cc 100644
--- a/kernel/trace/trace_probe_tmpl.h
+++ b/kernel/trace/trace_probe_tmpl.h
@@ -48,24 +48,28 @@ fetch_apply_bitfield(struct fetch_insn *code, void *buf)
 	}
 }
 
-/* Define this for each callsite */
+/*
+ * This must be defined for each callsite.
+ * Return consumed dynamic data size (>= 0), or error (< 0).
+ * If dest is NULL, don't store result and return required dynamic data size.
+ */
 static int
 process_fetch_insn(struct fetch_insn *code, struct pt_regs *regs,
-		   void *dest, bool pre);
+		   void *dest, void *base);
 
 /* Sum up total data length for dynamic arraies (strings) */
 static nokprobe_inline int
 __get_data_size(struct trace_probe *tp, struct pt_regs *regs)
 {
 	struct probe_arg *arg;
-	int i, ret = 0;
-	u32 len;
+	int i, len, ret = 0;
 
 	for (i = 0; i < tp->nr_args; i++) {
 		arg = tp->args + i;
 		if (unlikely(arg->dynamic)) {
-			process_fetch_insn(arg->code, regs, &len, true);
-			ret += len;
+			len = process_fetch_insn(arg->code, regs, NULL, NULL);
+			if (len > 0)
+				ret += len;
 		}
 	}
 
@@ -74,34 +78,26 @@ __get_data_size(struct trace_probe *tp, struct pt_regs *regs)
 
 /* Store the value of each argument */
 static nokprobe_inline void
-store_trace_args(int ent_size, struct trace_probe *tp, struct pt_regs *regs,
-		 u8 *data, int maxlen)
+store_trace_args(void *data, struct trace_probe *tp, struct pt_regs *regs,
+		 int header_size, int maxlen)
 {
 	struct probe_arg *arg;
-	u32 end = tp->size;
-	u32 *dl;	/* Data (relative) location */
-	int i;
+	void *base = data - header_size;
+	void *dyndata = data + tp->size;
+	u32 *dl;	/* Data location */
+	int ret, i;
 
 	for (i = 0; i < tp->nr_args; i++) {
 		arg = tp->args + i;
-		if (unlikely(arg->dynamic)) {
-			/*
-			 * First, we set the relative location and
-			 * maximum data length to *dl
-			 */
-			dl = (u32 *)(data + arg->offset);
-			*dl = make_data_rloc(maxlen, end - arg->offset);
-			/* Then try to fetch string or dynamic array data */
-			process_fetch_insn(arg->code, regs, dl, false);
-			/* Reduce maximum length */
-			end += get_rloc_len(*dl);
-			maxlen -= get_rloc_len(*dl);
-			/* Trick here, convert data_rloc to data_loc */
-			*dl = convert_rloc_to_loc(*dl, ent_size + arg->offset);
-		} else
-			/* Just fetching data normally */
-			process_fetch_insn(arg->code, regs, data + arg->offset,
-					   false);
+		dl = data + arg->offset;
+		/* Point the dynamic data area if needed */
+		if (unlikely(arg->dynamic))
+			*dl = make_data_loc(maxlen, dyndata - base);
+		ret = process_fetch_insn(arg->code, regs, dl, base);
+		if (unlikely(ret < 0 && arg->dynamic))
+			*dl = make_data_loc(0, dyndata - base);
+		else
+			dyndata += ret;
 	}
 }