From 2a588dd1d5d649a183a2ff6fa1b80e870cf821d8 Mon Sep 17 00:00:00 2001 From: Tom Zanussi Date: Wed, 29 Jan 2020 12:59:29 -0600 Subject: [PATCH] tracing: Add kprobe event command generation functions 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 Signed-off-by: Tom Zanussi Signed-off-by: Steven Rostedt (VMware) --- include/linux/trace_events.h | 31 +++++++ kernel/trace/trace_kprobe.c | 161 +++++++++++++++++++++++++++++++++++ 2 files changed, 192 insertions(+) diff --git a/include/linux/trace_events.h b/include/linux/trace_events.h index bf03d12efb28..7c307a7c9c6a 100644 --- a/include/linux/trace_events.h +++ b/include/linux/trace_events.h @@ -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 diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c index bf20cd7f2666..f43548b466d0 100644 --- a/kernel/trace/trace_kprobe.c +++ b/kernel/trace/trace_kprobe.c @@ -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); -- 2.30.2