tracing/kprobe: Add kprobe_event= boot parameter

Add kprobe_event= boot parameter to define kprobe events
at boot time.
The definition syntax is similar to tracefs/kprobe_events
interface, but use ',' and ';' instead of ' ' and '\n'
respectively. e.g.

  kprobe_event=p,vfs_read,$arg1,$arg2

This puts a probe on vfs_read with argument1 and 2, and
enable the new event.

Link: http://lkml.kernel.org/r/155851395498.15728.830529496248543583.stgit@devnote2

Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

2 files changed, 27 insertions, 0 deletions

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 138f6664b2e2..11b9ffb265eb 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -2007,6 +2007,19 @@
 			Built with CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=y,
 			the default is off.
 
+	kprobe_event=[probe-list]
+			[FTRACE] Add kprobe events and enable at boot time.
+			The probe-list is a semicolon delimited list of probe
+			definitions. Each definition is same as kprobe_events
+			interface, but the parameters are comma delimited.
+			For example, to add a kprobe event on vfs_read with
+			arg1 and arg2, add to the command line;
+
+			      kprobe_event=p,vfs_read,$arg1,$arg2
+
+			See also Documentation/trace/kprobetrace.rst "Kernel
+			Boot Parameter" section.
+
 	kpti=		[ARM64] Control page table isolation of user
 			and kernel address spaces.
 			Default: enabled on cores which need mitigation.
diff --git a/Documentation/trace/kprobetrace.rst b/Documentation/trace/kprobetrace.rst
index 09ff474493e1..af776989caca 100644
--- a/Documentation/trace/kprobetrace.rst
+++ b/Documentation/trace/kprobetrace.rst
@@ -146,6 +146,20 @@ You can check the total number of probe hits and probe miss-hits via
 The first column is event name, the second is the number of probe hits,
 the third is the number of probe miss-hits.
 
+Kernel Boot Parameter
+---------------------
+You can add and enable new kprobe events when booting up the kernel by
+"kprobe_event=" parameter. The parameter accepts a semicolon-delimited
+kprobe events, which format is similar to the kprobe_events.
+The difference is that the probe definition parameters are comma-delimited
+instead of space. For example, adding myprobe event on do_sys_open like below
+
+  p:myprobe do_sys_open dfd=%ax filename=%dx flags=%cx mode=+4($stack)
+
+should be below for kernel boot parameter (just replace spaces with comma)
+
+  p:myprobe,do_sys_open,dfd=%ax,filename=%dx,flags=%cx,mode=+4($stack)
+
 
 Usage examples
 --------------