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Subject[PATCH 07/15] ftrace: add command interface for function selection
From: Steven Rostedt <srostedt@redhat.com>

Allow for other tracers to add their own commands for function
selection. This interface gives a trace the ability to name a
command for function selection. Right now it is pretty limited
in what it offers, but this is a building step for more features.

The :mod: command is converted to this interface and also serves
as a template for other implementations.

Signed-off-by: Steven Rostedt <srostedt@redhat.com>
---
include/linux/ftrace.h | 16 +++++++
kernel/trace/ftrace.c | 106 +++++++++++++++++++++++++++++++++++++++++++-----
2 files changed, 111 insertions(+), 11 deletions(-)

diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
index 106b790..f0a0ecc 100644
--- a/include/linux/ftrace.h
+++ b/include/linux/ftrace.h
@@ -95,6 +95,13 @@ stack_trace_sysctl(struct ctl_table *table, int write,
loff_t *ppos);
#endif

+struct ftrace_func_command {
+ struct list_head list;
+ char *name;
+ int (*func)(char *func, char *cmd,
+ char *params, int enable);
+};
+
#ifdef CONFIG_DYNAMIC_FTRACE
/* asm/ftrace.h must be defined for archs supporting dynamic ftrace */
#include <asm/ftrace.h>
@@ -119,6 +126,9 @@ struct dyn_ftrace {
int ftrace_force_update(void);
void ftrace_set_filter(unsigned char *buf, int len, int reset);

+int register_ftrace_command(struct ftrace_func_command *cmd);
+int unregister_ftrace_command(struct ftrace_func_command *cmd);
+
/* defined in arch */
extern int ftrace_ip_converted(unsigned long ip);
extern int ftrace_dyn_arch_init(void *data);
@@ -202,6 +212,12 @@ extern void ftrace_enable_daemon(void);
# define ftrace_disable_daemon() do { } while (0)
# define ftrace_enable_daemon() do { } while (0)
static inline void ftrace_release(void *start, unsigned long size) { }
+static inline int register_ftrace_command(struct ftrace_func_command *cmd)
+{
+}
+static inline int unregister_ftrace_command(char *cmd_name)
+{
+}
#endif /* CONFIG_DYNAMIC_FTRACE */

/* totally disable ftrace - can not re-enable after this */
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 340f88b..45a44c4 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -1239,9 +1239,93 @@ static void ftrace_match_module_records(char *buff, char *mod, int enable)
spin_unlock(&ftrace_lock);
}

+/*
+ * We register the module command as a template to show others how
+ * to register the a command as well.
+ */
+
+static int
+ftrace_mod_callback(char *func, char *cmd, char *param, int enable)
+{
+ char *mod;
+
+ /*
+ * cmd == 'mod' because we only registered this func
+ * for the 'mod' ftrace_func_command.
+ * But if you register one func with multiple commands,
+ * you can tell which command was used by the cmd
+ * parameter.
+ */
+
+ /* we must have a module name */
+ if (!param)
+ return -EINVAL;
+
+ mod = strsep(&param, ":");
+ if (!strlen(mod))
+ return -EINVAL;
+
+ ftrace_match_module_records(func, mod, enable);
+ return 0;
+}
+
+static struct ftrace_func_command ftrace_mod_cmd = {
+ .name = "mod",
+ .func = ftrace_mod_callback,
+};
+
+static int __init ftrace_mod_cmd_init(void)
+{
+ return register_ftrace_command(&ftrace_mod_cmd);
+}
+device_initcall(ftrace_mod_cmd_init);
+
+static LIST_HEAD(ftrace_commands);
+static DEFINE_MUTEX(ftrace_cmd_mutex);
+
+int register_ftrace_command(struct ftrace_func_command *cmd)
+{
+ struct ftrace_func_command *p;
+ int ret = 0;
+
+ mutex_lock(&ftrace_cmd_mutex);
+ list_for_each_entry(p, &ftrace_commands, list) {
+ if (strcmp(cmd->name, p->name) == 0) {
+ ret = -EBUSY;
+ goto out_unlock;
+ }
+ }
+ list_add(&cmd->list, &ftrace_commands);
+ out_unlock:
+ mutex_unlock(&ftrace_cmd_mutex);
+
+ return ret;
+}
+
+int unregister_ftrace_command(struct ftrace_func_command *cmd)
+{
+ struct ftrace_func_command *p, *n;
+ int ret = -ENODEV;
+
+ mutex_lock(&ftrace_cmd_mutex);
+ list_for_each_entry_safe(p, n, &ftrace_commands, list) {
+ if (strcmp(cmd->name, p->name) == 0) {
+ ret = 0;
+ list_del_init(&p->list);
+ goto out_unlock;
+ }
+ }
+ out_unlock:
+ mutex_unlock(&ftrace_cmd_mutex);
+
+ return ret;
+}
+
static int ftrace_process_regex(char *buff, int len, int enable)
{
- char *func, *mod, *command, *next = buff;
+ struct ftrace_func_command *p;
+ char *func, *command, *next = buff;
+ int ret = -EINVAL;

func = strsep(&next, ":");

@@ -1250,21 +1334,21 @@ static int ftrace_process_regex(char *buff, int len, int enable)
return 0;
}

- /* command fonud */
+ /* command found */

command = strsep(&next, ":");

- if (strcmp(command, "mod") == 0) {
- /* only match modules */
- if (!next)
- return -EINVAL;
-
- mod = strsep(&next, ":");
- ftrace_match_module_records(func, mod, enable);
- return 0;
+ mutex_lock(&ftrace_cmd_mutex);
+ list_for_each_entry(p, &ftrace_commands, list) {
+ if (strcmp(p->name, command) == 0) {
+ ret = p->func(func, command, next, enable);
+ goto out_unlock;
+ }
}
+ out_unlock:
+ mutex_unlock(&ftrace_cmd_mutex);

- return -EINVAL;
+ return ret;
}

static ssize_t
--
1.5.6.5
--


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