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tracing: Add kprobe event command generation functions

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Add functions used to generate kprobe event commands, built on top of
the dynevent_cmd interface.

kprobe_event_gen_cmd_start() is used to create a kprobe event command
using a variable arg list, and kretprobe_event_gen_cmd_start() does
the same for kretprobe event commands.  kprobe_event_add_fields() can
be used to add single fields one by one or as a group.  Once all
desired fields are added, kprobe_event_gen_cmd_end() or
kretprobe_event_gen_cmd_end() respectively are used to actually
execute the command and create the event.

Link: http://lkml.kernel.org/r/95cc4696502bb6017f9126f306a45ad19b4cc14f.1580323897.git.zanussi@kernel.org

Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Tom Zanussi <zanussi@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
This commit is contained in:
Tom Zanussi 2020-01-29 12:59:29 -06:00 committed by Steven Rostedt (VMware)
parent 9fe41efaca
commit 2a588dd1d5
2 changed files with 192 additions and 0 deletions
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31
include/linux/trace_events.h
View File

@ -358,6 +358,7 @@ extern void trace_put_event_file(struct trace_event_file *file);
enum dynevent_type {
DYNEVENT_TYPE_SYNTH = 1,
DYNEVENT_TYPE_KPROBE,
DYNEVENT_TYPE_NONE,
};
@ -442,6 +443,36 @@ extern int synth_event_add_val(const char *field_name, u64 val,
struct synth_event_trace_state *trace_state);
extern int synth_event_trace_end(struct synth_event_trace_state *trace_state);
extern int kprobe_event_delete(const char *name);
extern void kprobe_event_cmd_init(struct dynevent_cmd *cmd,
char *buf, int maxlen);
#define kprobe_event_gen_cmd_start(cmd, name, loc, ...) \
__kprobe_event_gen_cmd_start(cmd, false, name, loc, ## __VA_ARGS__, NULL)
#define kretprobe_event_gen_cmd_start(cmd, name, loc, ...) \
__kprobe_event_gen_cmd_start(cmd, true, name, loc, ## __VA_ARGS__, NULL)
extern int __kprobe_event_gen_cmd_start(struct dynevent_cmd *cmd,
bool kretprobe,
const char *name,
const char *loc, ...);
#define kprobe_event_add_fields(cmd, ...) \
__kprobe_event_add_fields(cmd, ## __VA_ARGS__, NULL)
#define kprobe_event_add_field(cmd, field) \
__kprobe_event_add_fields(cmd, field, NULL)
extern int __kprobe_event_add_fields(struct dynevent_cmd *cmd, ...);
#define kprobe_event_gen_cmd_end(cmd) \
dynevent_create(cmd)
#define kretprobe_event_gen_cmd_end(cmd) \
dynevent_create(cmd)
/*
* Event file flags:
* ENABLED - The event is enabled

161
kernel/trace/trace_kprobe.c
View File

@ -906,6 +906,167 @@ int trace_kprobe_run_command(const char *command)
return trace_run_command(command, create_or_delete_trace_kprobe);
}
static int trace_kprobe_run_cmd(struct dynevent_cmd *cmd)
{
return trace_run_command(cmd->buf, create_or_delete_trace_kprobe);
}
/**
* kprobe_event_cmd_init - Initialize a kprobe event command object
* @cmd: A pointer to the dynevent_cmd struct representing the new event
* @buf: A pointer to the buffer used to build the command
* @maxlen: The length of the buffer passed in @buf
*
* Initialize a synthetic event command object. Use this before
* calling any of the other kprobe_event functions.
*/
void kprobe_event_cmd_init(struct dynevent_cmd *cmd, char *buf, int maxlen)
{
dynevent_cmd_init(cmd, buf, maxlen, DYNEVENT_TYPE_KPROBE,
trace_kprobe_run_cmd);
}
EXPORT_SYMBOL_GPL(kprobe_event_cmd_init);
/**
* __kprobe_event_gen_cmd_start - Generate a kprobe event command from arg list
* @cmd: A pointer to the dynevent_cmd struct representing the new event
* @name: The name of the kprobe event
* @loc: The location of the kprobe event
* @kretprobe: Is this a return probe?
* @args: Variable number of arg (pairs), one pair for each field
*
* NOTE: Users normally won't want to call this function directly, but
* rather use the kprobe_event_gen_cmd_start() wrapper, which automatically
* adds a NULL to the end of the arg list. If this function is used
* directly, make sure the last arg in the variable arg list is NULL.
*
* Generate a kprobe event command to be executed by
* kprobe_event_gen_cmd_end(). This function can be used to generate the
* complete command or only the first part of it; in the latter case,
* kprobe_event_add_fields() can be used to add more fields following this.
*
* Return: 0 if successful, error otherwise.
*/
int __kprobe_event_gen_cmd_start(struct dynevent_cmd *cmd, bool kretprobe,
const char *name, const char *loc, ...)
{
char buf[MAX_EVENT_NAME_LEN];
struct dynevent_arg arg;
va_list args;
int ret;
if (cmd->type != DYNEVENT_TYPE_KPROBE)
return -EINVAL;
if (kretprobe)
snprintf(buf, MAX_EVENT_NAME_LEN, "r:kprobes/%s", name);
else
snprintf(buf, MAX_EVENT_NAME_LEN, "p:kprobes/%s", name);
ret = dynevent_str_add(cmd, buf);
if (ret)
return ret;
dynevent_arg_init(&arg, NULL, 0);
arg.str = loc;
ret = dynevent_arg_add(cmd, &arg);
if (ret)
return ret;
va_start(args, loc);
for (;;) {
const char *field;
field = va_arg(args, const char *);
if (!field)
break;
if (++cmd->n_fields > MAX_TRACE_ARGS) {
ret = -EINVAL;
break;
}
arg.str = field;
ret = dynevent_arg_add(cmd, &arg);
if (ret)
break;
}
va_end(args);
return ret;
}
EXPORT_SYMBOL_GPL(__kprobe_event_gen_cmd_start);
/**
* __kprobe_event_add_fields - Add probe fields to a kprobe command from arg list
* @cmd: A pointer to the dynevent_cmd struct representing the new event
* @args: Variable number of arg (pairs), one pair for each field
*
* NOTE: Users normally won't want to call this function directly, but
* rather use the kprobe_event_add_fields() wrapper, which
* automatically adds a NULL to the end of the arg list. If this
* function is used directly, make sure the last arg in the variable
* arg list is NULL.
*
* Add probe fields to an existing kprobe command using a variable
* list of args. Fields are added in the same order they're listed.
*
* Return: 0 if successful, error otherwise.
*/
int __kprobe_event_add_fields(struct dynevent_cmd *cmd, ...)
{
struct dynevent_arg arg;
va_list args;
int ret;
if (cmd->type != DYNEVENT_TYPE_KPROBE)
return -EINVAL;
dynevent_arg_init(&arg, NULL, 0);
va_start(args, cmd);
for (;;) {
const char *field;
field = va_arg(args, const char *);
if (!field)
break;
if (++cmd->n_fields > MAX_TRACE_ARGS) {
ret = -EINVAL;
break;
}
arg.str = field;
ret = dynevent_arg_add(cmd, &arg);
if (ret)
break;
}
va_end(args);
return ret;
}
EXPORT_SYMBOL_GPL(__kprobe_event_add_fields);
/**
* kprobe_event_delete - Delete a kprobe event
* @name: The name of the kprobe event to delete
*
* Delete a kprobe event with the give @name from kernel code rather
* than directly from the command line.
*
* Return: 0 if successful, error otherwise.
*/
int kprobe_event_delete(const char *name)
{
char buf[MAX_EVENT_NAME_LEN];
snprintf(buf, MAX_EVENT_NAME_LEN, "-:%s", name);
return trace_run_command(buf, create_or_delete_trace_kprobe);
}
EXPORT_SYMBOL_GPL(kprobe_event_delete);
static int trace_kprobe_release(struct dyn_event *ev)
{
struct trace_kprobe *tk = to_trace_kprobe(ev);