linux-stable/include/linux/fprobe.h
Masami Hiramatsu ab51e15d53 fprobe: Introduce FPROBE_FL_KPROBE_SHARED flag for fprobe
Introduce FPROBE_FL_KPROBE_SHARED flag for sharing fprobe callback with
kprobes safely from the viewpoint of recursion.

Since the recursion safety of the fprobe (and ftrace) is a bit different
from the kprobes, this may cause an issue if user wants to run the same
code from the fprobe and the kprobes.

The kprobes has per-cpu 'current_kprobe' variable which protects the
kprobe handler from recursion in any case. On the other hand, the fprobe
uses only ftrace_test_recursion_trylock(), which will allow interrupt
context calls another (or same) fprobe during the fprobe user handler is
running.

This is not a matter in cases if the common callback shared among the
kprobes and the fprobe has its own recursion detection, or it can handle
the recursion in the different contexts (normal/interrupt/NMI.)
But if it relies on the 'current_kprobe' recursion lock, it has to check
kprobe_running() and use kprobe_busy_*() APIs.

Fprobe has FPROBE_FL_KPROBE_SHARED flag to do this. If your common callback
code will be shared with kprobes, please set FPROBE_FL_KPROBE_SHARED
*before* registering the fprobe, like;

 fprobe.flags = FPROBE_FL_KPROBE_SHARED;

 register_fprobe(&fprobe, "func*", NULL);

This will protect your common callback from the nested call.

Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Tested-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/164735293127.1084943.15687374237275817599.stgit@devnote2
2022-03-17 20:17:02 -07:00

105 lines
2.8 KiB
C

/* SPDX-License-Identifier: GPL-2.0 */
/* Simple ftrace probe wrapper */
#ifndef _LINUX_FPROBE_H
#define _LINUX_FPROBE_H
#include <linux/compiler.h>
#include <linux/ftrace.h>
#include <linux/rethook.h>
/**
* struct fprobe - ftrace based probe.
* @ops: The ftrace_ops.
* @nmissed: The counter for missing events.
* @flags: The status flag.
* @rethook: The rethook data structure. (internal data)
* @entry_handler: The callback function for function entry.
* @exit_handler: The callback function for function exit.
*/
struct fprobe {
#ifdef CONFIG_FUNCTION_TRACER
/*
* If CONFIG_FUNCTION_TRACER is not set, CONFIG_FPROBE is disabled too.
* But user of fprobe may keep embedding the struct fprobe on their own
* code. To avoid build error, this will keep the fprobe data structure
* defined here, but remove ftrace_ops data structure.
*/
struct ftrace_ops ops;
#endif
unsigned long nmissed;
unsigned int flags;
struct rethook *rethook;
void (*entry_handler)(struct fprobe *fp, unsigned long entry_ip, struct pt_regs *regs);
void (*exit_handler)(struct fprobe *fp, unsigned long entry_ip, struct pt_regs *regs);
};
/* This fprobe is soft-disabled. */
#define FPROBE_FL_DISABLED 1
/*
* This fprobe handler will be shared with kprobes.
* This flag must be set before registering.
*/
#define FPROBE_FL_KPROBE_SHARED 2
static inline bool fprobe_disabled(struct fprobe *fp)
{
return (fp) ? fp->flags & FPROBE_FL_DISABLED : false;
}
static inline bool fprobe_shared_with_kprobes(struct fprobe *fp)
{
return (fp) ? fp->flags & FPROBE_FL_KPROBE_SHARED : false;
}
#ifdef CONFIG_FPROBE
int register_fprobe(struct fprobe *fp, const char *filter, const char *notfilter);
int register_fprobe_ips(struct fprobe *fp, unsigned long *addrs, int num);
int register_fprobe_syms(struct fprobe *fp, const char **syms, int num);
int unregister_fprobe(struct fprobe *fp);
#else
static inline int register_fprobe(struct fprobe *fp, const char *filter, const char *notfilter)
{
return -EOPNOTSUPP;
}
static inline int register_fprobe_ips(struct fprobe *fp, unsigned long *addrs, int num)
{
return -EOPNOTSUPP;
}
static inline int register_fprobe_syms(struct fprobe *fp, const char **syms, int num)
{
return -EOPNOTSUPP;
}
static inline int unregister_fprobe(struct fprobe *fp)
{
return -EOPNOTSUPP;
}
#endif
/**
* disable_fprobe() - Disable fprobe
* @fp: The fprobe to be disabled.
*
* This will soft-disable @fp. Note that this doesn't remove the ftrace
* hooks from the function entry.
*/
static inline void disable_fprobe(struct fprobe *fp)
{
if (fp)
fp->flags |= FPROBE_FL_DISABLED;
}
/**
* enable_fprobe() - Enable fprobe
* @fp: The fprobe to be enabled.
*
* This will soft-enable @fp.
*/
static inline void enable_fprobe(struct fprobe *fp)
{
if (fp)
fp->flags &= ~FPROBE_FL_DISABLED;
}
#endif