Commit 76d0de57 authored by Masami Hiramatsu (Google)'s avatar Masami Hiramatsu (Google) Committed by Steven Rostedt (Google)
Browse files

fprobe: Pass entry_data to handlers 

Pass the private entry_data to the entry and exit handlers so that
they can share the context data, something like saved function
arguments etc.
User must specify the private entry_data size by @entry_data_size
field before registering the fprobe.

Link: https://lkml.kernel.org/r/167526696173.433354.17408372048319432574.stgit@mhiramat.roam.corp.google.com



Cc: Florent Revest <revest@chromium.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: default avatarMasami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: default avatarSteven Rostedt (Google) <rostedt@goodmis.org>
parent e11b521a

include/linux/fprobe.h

+6 −2
Original line number Diff line number Diff line
@@ -13,6 +13,7 @@ 
 * @nmissed: The counter for missing events.

 * @flags: The status flag.

 * @rethook: The rethook data structure. (internal data)

 * @entry_data_size: The private data storage size.

 * @entry_handler: The callback function for function entry.

 * @exit_handler: The callback function for function exit.

 */
@@ -29,9 +30,12 @@ struct fprobe { 
	unsigned long		nmissed;

	unsigned int		flags;

	struct rethook		*rethook;

	size_t			entry_data_size;



	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);

	void (*entry_handler)(struct fprobe *fp, unsigned long entry_ip,

			      struct pt_regs *regs, void *entry_data);

	void (*exit_handler)(struct fprobe *fp, unsigned long entry_ip,

			     struct pt_regs *regs, void *entry_data);

};



/* This fprobe is soft-disabled. */

kernel/trace/bpf_trace.c

+1 −1
Original line number Diff line number Diff line
@@ -2646,7 +2646,7 @@ kprobe_multi_link_prog_run(struct bpf_kprobe_multi_link *link, 


static void

kprobe_multi_link_handler(struct fprobe *fp, unsigned long fentry_ip,

			  struct pt_regs *regs)

			  struct pt_regs *regs, void *data)

{

	struct bpf_kprobe_multi_link *link;

kernel/trace/fprobe.c

+14 −7
Original line number Diff line number Diff line
@@ -17,14 +17,16 @@ 
struct fprobe_rethook_node {

	struct rethook_node node;

	unsigned long entry_ip;

	char data[];

};



static void fprobe_handler(unsigned long ip, unsigned long parent_ip,

			   struct ftrace_ops *ops, struct ftrace_regs *fregs)

{

	struct fprobe_rethook_node *fpr;

	struct rethook_node *rh;

	struct rethook_node *rh = NULL;

	struct fprobe *fp;

	void *entry_data = NULL;

	int bit;



	fp = container_of(ops, struct fprobe, ops);
@@ -37,9 +39,6 @@ static void fprobe_handler(unsigned long ip, unsigned long parent_ip, 
		return;

	}



	if (fp->entry_handler)

		fp->entry_handler(fp, ip, ftrace_get_regs(fregs));



	if (fp->exit_handler) {

		rh = rethook_try_get(fp->rethook);

		if (!rh) {
@@ -48,9 +47,16 @@ static void fprobe_handler(unsigned long ip, unsigned long parent_ip, 
		}

		fpr = container_of(rh, struct fprobe_rethook_node, node);

		fpr->entry_ip = ip;

		rethook_hook(rh, ftrace_get_regs(fregs), true);

		if (fp->entry_data_size)

			entry_data = fpr->data;

	}



	if (fp->entry_handler)

		fp->entry_handler(fp, ip, ftrace_get_regs(fregs), entry_data);



	if (rh)

		rethook_hook(rh, ftrace_get_regs(fregs), true);



out:

	ftrace_test_recursion_unlock(bit);

}
@@ -81,7 +87,8 @@ static void fprobe_exit_handler(struct rethook_node *rh, void *data, 


	fpr = container_of(rh, struct fprobe_rethook_node, node);



	fp->exit_handler(fp, fpr->entry_ip, regs);

	fp->exit_handler(fp, fpr->entry_ip, regs,

			 fp->entry_data_size ? (void *)fpr->data : NULL);

}

NOKPROBE_SYMBOL(fprobe_exit_handler);
@@ -146,7 +153,7 @@ static int fprobe_init_rethook(struct fprobe *fp, int num) 
	for (i = 0; i < size; i++) {

		struct fprobe_rethook_node *node;



		node = kzalloc(sizeof(*node), GFP_KERNEL);

		node = kzalloc(sizeof(*node) + fp->entry_data_size, GFP_KERNEL);

		if (!node) {

			rethook_free(fp->rethook);

			fp->rethook = NULL;

lib/test_fprobe.c

+4 −2
Original line number Diff line number Diff line
@@ -30,7 +30,8 @@ static noinline u32 fprobe_selftest_target2(u32 value) 
	return (value / div_factor) + 1;

}



static notrace void fp_entry_handler(struct fprobe *fp, unsigned long ip, struct pt_regs *regs)

static notrace void fp_entry_handler(struct fprobe *fp, unsigned long ip,

				     struct pt_regs *regs, void *data)

{

	KUNIT_EXPECT_FALSE(current_test, preemptible());

	/* This can be called on the fprobe_selftest_target and the fprobe_selftest_target2 */
@@ -39,7 +40,8 @@ static notrace void fp_entry_handler(struct fprobe *fp, unsigned long ip, struct 
	entry_val = (rand1 / div_factor);

}



static notrace void fp_exit_handler(struct fprobe *fp, unsigned long ip, struct pt_regs *regs)

static notrace void fp_exit_handler(struct fprobe *fp, unsigned long ip,

				    struct pt_regs *regs, void *data)

{

	unsigned long ret = regs_return_value(regs);

samples/fprobe/fprobe_example.c

+4 −2
Original line number Diff line number Diff line
@@ -48,7 +48,8 @@ static void show_backtrace(void) 
	stack_trace_print(stacks, len, 24);

}



static void sample_entry_handler(struct fprobe *fp, unsigned long ip, struct pt_regs *regs)

static void sample_entry_handler(struct fprobe *fp, unsigned long ip,

				 struct pt_regs *regs, void *data)

{

	if (use_trace)

		/*
@@ -63,7 +64,8 @@ static void sample_entry_handler(struct fprobe *fp, unsigned long ip, struct pt_ 
		show_backtrace();

}



static void sample_exit_handler(struct fprobe *fp, unsigned long ip, struct pt_regs *regs)

static void sample_exit_handler(struct fprobe *fp, unsigned long ip, struct pt_regs *regs,

				void *data)

{

	unsigned long rip = instruction_pointer(regs);