linux-kernel - [PATCH RFC v4 net-next 18/26] tracing: allow eBPF programs to be attached to kprobe/kretprobe

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Date:	Wed, 13 Aug 2014 00:57:29 -0700
From:	Alexei Starovoitov <ast@...mgrid.com>
To:	"David S. Miller" <davem@...emloft.net>
Cc:	Ingo Molnar <mingo@...nel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andy Lutomirski <luto@...capital.net>,
	Steven Rostedt <rostedt@...dmis.org>,
	Daniel Borkmann <dborkman@...hat.com>,
	Chema Gonzalez <chema@...gle.com>,
	Eric Dumazet <edumazet@...gle.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	"H. Peter Anvin" <hpa@...or.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Kees Cook <keescook@...omium.org>, linux-api@...r.kernel.org,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH RFC v4 net-next 18/26] tracing: allow eBPF programs to be attached to kprobe/kretprobe

Signed-off-by: Alexei Starovoitov <ast@...mgrid.com>
---
 kernel/trace/trace_kprobe.c |   24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
index 282f6e4e5539..a71e3d521938 100644
--- a/kernel/trace/trace_kprobe.c
+++ b/kernel/trace/trace_kprobe.c
@@ -19,6 +19,7 @@
 
 #include <linux/module.h>
 #include <linux/uaccess.h>
+#include <trace/bpf_trace.h>
 
 #include "trace_probe.h"
 
@@ -930,6 +931,18 @@ __kprobe_trace_func(struct trace_kprobe *tk, struct pt_regs *regs,
 	if (ftrace_trigger_soft_disabled(ftrace_file))
 		return;
 
+	if (call->flags & TRACE_EVENT_FL_BPF) {
+		struct bpf_context __ctx = {};
+		/* get first 3 arguments of the function. x64 syscall ABI uses
+		 * the same 3 registers as x64 calling convention.
+		 * todo: implement it cleanly via arch specific
+		 * regs_get_argument_nth() helper
+		 */
+		syscall_get_arguments(current, regs, 0, 3, &__ctx.arg1);
+		trace_filter_call_bpf(ftrace_file->filter, &__ctx);
+		return;
+	}
+
 	local_save_flags(irq_flags);
 	pc = preempt_count();
 
@@ -978,6 +991,17 @@ __kretprobe_trace_func(struct trace_kprobe *tk, struct kretprobe_instance *ri,
 	if (ftrace_trigger_soft_disabled(ftrace_file))
 		return;
 
+	if (call->flags & TRACE_EVENT_FL_BPF) {
+		struct bpf_context __ctx = {};
+		/* assume that register used to return a value from syscall is
+		 * the same as register used to return a value from a function
+		 * todo: provide arch specific helper
+		 */
+		__ctx.ret = syscall_get_return_value(current, regs);
+		trace_filter_call_bpf(ftrace_file->filter, &__ctx);
+		return;
+	}
+
 	local_save_flags(irq_flags);
 	pc = preempt_count();
 
-- 
1.7.9.5

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