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