[Patch 2/3] ksym_tracer: Allow bulk removal using empty orwildcard string input

[K.Prasad]

Accept an empty string or wildcard input (of the form *:---) as input for
ksym_trace_filter to perform bulk removal of all monitored entries.

Signed-off-by: K.Prasad <prasad@xxxxxxxxxxxxxxxxxx>
---
 kernel/trace/trace_ksym.c |   75 +++++++++++++++++++++++++---------------------
 1 file changed, 42 insertions(+), 33 deletions(-)

Index: linux-2.6-tip.hbkpt/kernel/trace/trace_ksym.c
===================================================================
--- linux-2.6-tip.hbkpt.orig/kernel/trace/trace_ksym.c
+++ linux-2.6-tip.hbkpt/kernel/trace/trace_ksym.c
@@ -138,6 +138,34 @@ static int ksym_trace_get_access_type(ch
 	return access;
 }
 
+static void ksym_trace_reset(struct trace_array *tr)
+{
+	struct trace_ksym *entry;
+	struct hlist_node *node, *node1;
+
+	ksym_tracing_enabled = 0;
+
+	mutex_lock(&ksym_tracer_mutex);
+	hlist_for_each_entry_safe(entry, node, node1, &ksym_filter_head,
+								ksym_hlist) {
+		unregister_kernel_hw_breakpoint(entry->ksym_hbp);
+		ksym_filter_entry_count--;
+		hlist_del_rcu(&(entry->ksym_hlist));
+		synchronize_rcu();
+		/* Free the 'input_string' only if reset
+		 * after startup self-test
+		 */
+#ifdef CONFIG_FTRACE_SELFTEST
+		if (strncmp(entry->ksym_hbp->info.name, KSYM_SELFTEST_ENTRY,
+					strlen(KSYM_SELFTEST_ENTRY)) != 0)
+#endif /* CONFIG_FTRACE_SELFTEST*/
+			kfree(entry->ksym_hbp->info.name);
+		kfree(entry->ksym_hbp);
+		kfree(entry);
+	}
+	mutex_unlock(&ksym_tracer_mutex);
+}
+
 /*
  * There can be several possible malformed requests and we attempt to capture
  * all of them. We enumerate some of the rules
@@ -163,7 +191,7 @@ static int parse_ksym_trace_str(char *in
 	/* Check for malformed request: (2), (1) and (5) */
 	if ((!input_string) ||
 		(strlen(input_string) != (KSYM_TRACER_OP_LEN + 1)) ||
-			(*addr == 0))
+			((*addr == 0) && strncmp(*ksymname, "*", strlen("*"))))
 		goto return_code;
 	ret = ksym_trace_get_access_type(input_string);
 
@@ -211,6 +239,7 @@ int process_new_ksym_entry(char *ksymnam
 	}
 	hlist_add_head_rcu(&(entry->ksym_hlist), &ksym_filter_head);
 	ksym_filter_entry_count++;
+	ksym_tracing_enabled = 1;
 
 	return 0;
 }
@@ -220,7 +249,7 @@ static ssize_t ksym_trace_filter_read(st
 {
 	struct trace_ksym *entry;
 	struct hlist_node *node;
-	char buf[KSYM_FILTER_ENTRY_LEN * KSYM_TRACER_MAX];
+	char buf[KSYM_FILTER_ENTRY_LEN * KSYM_TRACER_MAX] = "\0";
 	ssize_t ret, cnt = 0;
 
 	mutex_lock(&ksym_tracer_mutex);
@@ -251,9 +280,11 @@ static ssize_t ksym_trace_filter_write(s
 	unsigned long ksym_addr = 0;
 	int ret, op, changed = 0;
 
-	/* Ignore echo "" > ksym_trace_filter */
-	if (count == 0)
-		return 0;
+	/* Clear all breakpoint requests if echo "" > ksym_trace_filter */
+	if (count == 1) {
+		ksym_trace_reset(NULL);
+		return count;
+	}
 
 	input_string = kzalloc(count, GFP_KERNEL);
 	if (!input_string)
@@ -269,6 +300,12 @@ static ssize_t ksym_trace_filter_write(s
 		kfree(input_string);
 		return ret;
 	}
+	/* Clear all breakpoints if echo "*:---" > ksym_trace_filter */
+	if ((strncmp(ksymname, "*", strlen("*")) == 0) && (op == 0)) {
+		ksym_trace_reset(NULL);
+		kfree(input_string);
+		return count;
+	}
 
 	mutex_lock(&ksym_tracer_mutex);
 
@@ -325,34 +362,6 @@ static const struct file_operations ksym
 	.write		= ksym_trace_filter_write,
 };
 
-static void ksym_trace_reset(struct trace_array *tr)
-{
-	struct trace_ksym *entry;
-	struct hlist_node *node, *node1;
-
-	ksym_tracing_enabled = 0;
-
-	mutex_lock(&ksym_tracer_mutex);
-	hlist_for_each_entry_safe(entry, node, node1, &ksym_filter_head,
-								ksym_hlist) {
-		unregister_kernel_hw_breakpoint(entry->ksym_hbp);
-		ksym_filter_entry_count--;
-		hlist_del_rcu(&(entry->ksym_hlist));
-		synchronize_rcu();
-		/* Free the 'input_string' only if reset
-		 * after startup self-test
-		 */
-#ifdef CONFIG_FTRACE_SELFTEST
-		if (strncmp(entry->ksym_hbp->info.name, KSYM_SELFTEST_ENTRY,
-					strlen(KSYM_SELFTEST_ENTRY)) != 0)
-#endif /* CONFIG_FTRACE_SELFTEST*/
-			kfree(entry->ksym_hbp->info.name);
-		kfree(entry->ksym_hbp);
-		kfree(entry);
-	}
-	mutex_unlock(&ksym_tracer_mutex);
-}
-
 static int ksym_trace_init(struct trace_array *tr)
 {
 	int cpu, ret = 0;

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