From 1301a44e77557e928700f91c7083c5770054c212 Mon Sep 17 00:00:00 2001
From: Namhyung Kim <namhyung.kim@lge.com>
Date: Tue, 26 Nov 2013 15:21:04 +0900
Subject: tracing/probes: Move 'symbol' fetch method to kprobes

Move existing functions to trace_kprobe.c and add NULL entries to the
uprobes fetch type table.  I don't make them static since some generic
routines like update/free_XXX_fetch_param() require pointers to the
functions.

Acked-by: Oleg Nesterov <oleg@redhat.com>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Cc: zhangwei(Jovi) <jovi.zhangwei@huawei.com>
Cc: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
---
 kernel/trace/trace_kprobe.c | 59 +++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 59 insertions(+)

(limited to 'kernel/trace/trace_kprobe.c')

diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
index 389f9e4744c8..d2a4fd2fd8c1 100644
--- a/kernel/trace/trace_kprobe.c
+++ b/kernel/trace/trace_kprobe.c
@@ -88,6 +88,51 @@ static int kprobe_dispatcher(struct kprobe *kp, struct pt_regs *regs);
 static int kretprobe_dispatcher(struct kretprobe_instance *ri,
 				struct pt_regs *regs);
 
+/* Memory fetching by symbol */
+struct symbol_cache {
+	char		*symbol;
+	long		offset;
+	unsigned long	addr;
+};
+
+unsigned long 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;
+}
+
+void free_symbol_cache(struct symbol_cache *sc)
+{
+	kfree(sc->symbol);
+	kfree(sc);
+}
+
+struct symbol_cache *alloc_symbol_cache(const char *sym, long offset)
+{
+	struct symbol_cache *sc;
+
+	if (!sym || strlen(sym) == 0)
+		return NULL;
+
+	sc = kzalloc(sizeof(struct symbol_cache), GFP_KERNEL);
+	if (!sc)
+		return NULL;
+
+	sc->symbol = kstrdup(sym, GFP_KERNEL);
+	if (!sc->symbol) {
+		kfree(sc);
+		return NULL;
+	}
+	sc->offset = offset;
+	update_symbol_cache(sc);
+
+	return sc;
+}
+
 /*
  * Kprobes-specific fetch functions
  */
@@ -103,6 +148,20 @@ DEFINE_BASIC_FETCH_FUNCS(stack)
 #define fetch_stack_string	NULL
 #define fetch_stack_string_size	NULL
 
+#define DEFINE_FETCH_symbol(type)					\
+__kprobes void FETCH_FUNC_NAME(symbol, type)(struct pt_regs *regs,	\
+					  void *data, void *dest)	\
+{									\
+	struct symbol_cache *sc = data;					\
+	if (sc->addr)							\
+		fetch_memory_##type(regs, (void *)sc->addr, dest);	\
+	else								\
+		*(type *)dest = 0;					\
+}
+DEFINE_BASIC_FETCH_FUNCS(symbol)
+DEFINE_FETCH_symbol(string)
+DEFINE_FETCH_symbol(string_size)
+
 /* Fetch type information table */
 const struct fetch_type kprobes_fetch_type_table[] = {
 	/* Special types */
-- 
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