linux-kernel - [RFC PATCH 1/2] tracing: Don't update sc->addr in update_symbol

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Message-ID: <20131126174423.GC14028@redhat.com>
Date:	Tue, 26 Nov 2013 18:44:23 +0100
From:	Oleg Nesterov <oleg@...hat.com>
To:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
Cc:	Steven Rostedt <rostedt@...dmis.org>,
	Namhyung Kim <namhyung.kim@....com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Ingo Molnar <mingo@...hat.com>, Jiri Olsa <jolsa@...hat.com>,
	linux-kernel@...r.kernel.org, Rusty Russell <rusty@...tcorp.com.au>
Subject: [RFC PATCH 1/2] tracing: Don't update sc->addr in
	update_symbol_cache()

Preparation for the next changes. Shift "+= offset" from
update_symbol_cache() to ->fetch[FETCH_MTD_symbol], this
allows to detect the per-cpu symbols.

Also remove the !offset check in traceprobe_split_symbol_offset(),
it is never called with offset == NULL.

Signed-off-by: Oleg Nesterov <oleg@...hat.com>
---
 kernel/trace/trace_probe.c |   13 +++----------
 1 files changed, 3 insertions(+), 10 deletions(-)

diff --git a/kernel/trace/trace_probe.c b/kernel/trace/trace_probe.c
index fce222f..097cc80 100644
--- a/kernel/trace/trace_probe.c
+++ b/kernel/trace/trace_probe.c
@@ -219,14 +219,9 @@ struct symbol_cache {
 	unsigned long	addr;
 };
 
-static unsigned long update_symbol_cache(struct symbol_cache *sc)
+static void update_symbol_cache(struct symbol_cache *sc)
 {
 	sc->addr = (unsigned long)kallsyms_lookup_name(sc->symbol);
-
-	if (sc->addr)
-		sc->addr += sc->offset;
-
-	return sc->addr;
 }
 
 static void free_symbol_cache(struct symbol_cache *sc)
@@ -262,8 +257,9 @@ static __kprobes void FETCH_FUNC_NAME(symbol, type)(struct pt_regs *regs,\
 					  void *data, void *dest)	\
 {									\
 	struct symbol_cache *sc = data;					\
+	long off = sc->offset;						\
 	if (sc->addr)							\
-		fetch_memory_##type(regs, (void *)sc->addr, dest);	\
+		fetch_memory_##type(regs, (void *)sc->addr + off, dest);\
 	else								\
 		*(type *)dest = 0;					\
 }
@@ -485,9 +481,6 @@ int traceprobe_split_symbol_offset(char *symbol, unsigned long *offset)
 	char *tmp;
 	int ret;
 
-	if (!offset)
-		return -EINVAL;
-
 	tmp = strchr(symbol, '+');
 	if (tmp) {
 		/* skip sign because kstrtoul doesn't accept '+' */
-- 
1.5.5.1


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