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>

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 138f666..11b9ffb 100644 (file)
--- 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 09ff474..af77698 100644 (file)
--- 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
 --------------

diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
index 2c5357d..004fffd 100644 (file)
--- a/kernel/trace/trace_kprobe.c
+++ b/kernel/trace/trace_kprobe.c
@@ -12,6 +12,8 @@
 #include <linux/rculist.h>
 #include <linux/error-injection.h>
 
+#include <asm/setup.h>  /* for COMMAND_LINE_SIZE */
+
 #include "trace_dynevent.h"
 #include "trace_kprobe_selftest.h"
 #include "trace_probe.h"
@@ -19,6 +21,17 @@
 
 #define KPROBE_EVENT_SYSTEM "kprobes"
 #define KRETPROBE_MAXACTIVE_MAX 4096
+#define MAX_KPROBE_CMDLINE_SIZE 1024
+
+/* Kprobe early definition from command line */
+static char kprobe_boot_events_buf[COMMAND_LINE_SIZE] __initdata;
+
+static int __init set_kprobe_boot_events(char *str)
+{
+       strlcpy(kprobe_boot_events_buf, str, COMMAND_LINE_SIZE);
+       return 0;
+}
+__setup("kprobe_event=", set_kprobe_boot_events);
 
 static int trace_kprobe_create(int argc, const char **argv);
 static int trace_kprobe_show(struct seq_file *m, struct dyn_event *ev);
@@ -1494,6 +1507,44 @@ void destroy_local_trace_kprobe(struct trace_event_call *event_call)
 }
 #endif /* CONFIG_PERF_EVENTS */
 
+static __init void enable_boot_kprobe_events(void)
+{
+       struct trace_array *tr = top_trace_array();
+       struct trace_event_file *file;
+       struct trace_kprobe *tk;
+       struct dyn_event *pos;
+
+       mutex_lock(&event_mutex);
+       for_each_trace_kprobe(tk, pos) {
+               list_for_each_entry(file, &tr->events, list)
+                       if (file->event_call == &tk->tp.call)
+                               trace_event_enable_disable(file, 1, 0);
+       }
+       mutex_unlock(&event_mutex);
+}
+
+static __init void setup_boot_kprobe_events(void)
+{
+       char *p, *cmd = kprobe_boot_events_buf;
+       int ret;
+
+       strreplace(kprobe_boot_events_buf, ',', ' ');
+
+       while (cmd && *cmd != '\0') {
+               p = strchr(cmd, ';');
+               if (p)
+                       *p++ = '\0';
+
+               ret = trace_run_command(cmd, create_or_delete_trace_kprobe);
+               if (ret)
+                       pr_warn("Failed to add event(%d): %s\n", ret, cmd);
+
+               cmd = p;
+       }
+
+       enable_boot_kprobe_events();
+}
+
 /* Make a tracefs interface for controlling probe points */
 static __init int init_kprobe_trace(void)
 {
@@ -1525,6 +1576,9 @@ static __init int init_kprobe_trace(void)
 
        if (!entry)
                pr_warn("Could not create tracefs 'kprobe_profile' entry\n");
+
+       setup_boot_kprobe_events();
+
        return 0;
 }
 fs_initcall(init_kprobe_trace);