fprobe, samples: Add use_trace option and show hit/missed counter

[sfrench/cifs-2.6.git] / samples / fprobe / fprobe_example.c

diff --git a/samples/fprobe/fprobe_example.c b/samples/fprobe/fprobe_example.c
index 24d3cf1091407cd6f7b4bb415f102a64074080db..01ee6c8c8382921d253e0a130b8a05df3c60ebc1 100644 (file)
--- a/samples/fprobe/fprobe_example.c
+++ b/samples/fprobe/fprobe_example.c
@@ -21,6 +21,7 @@
 #define BACKTRACE_DEPTH 16
 #define MAX_SYMBOL_LEN 4096
 struct fprobe sample_probe;
+static unsigned long nhit;
 
 static char symbol[MAX_SYMBOL_LEN] = "kernel_clone";
 module_param_string(symbol, symbol, sizeof(symbol), 0644);
@@ -28,6 +29,8 @@ static char nosymbol[MAX_SYMBOL_LEN] = "";
 module_param_string(nosymbol, nosymbol, sizeof(nosymbol), 0644);
 static bool stackdump = true;
 module_param(stackdump, bool, 0644);
+static bool use_trace = false;
+module_param(use_trace, bool, 0644);
 
 static void show_backtrace(void)
 {
@@ -40,7 +43,15 @@ static void show_backtrace(void)
 
 static void sample_entry_handler(struct fprobe *fp, unsigned long ip, struct pt_regs *regs)
 {
-       pr_info("Enter <%pS> ip = 0x%p\n", (void *)ip, (void *)ip);
+       if (use_trace)
+               /*
+                * This is just an example, no kernel code should call
+                * trace_printk() except when actively debugging.
+                */
+               trace_printk("Enter <%pS> ip = 0x%p\n", (void *)ip, (void *)ip);
+       else
+               pr_info("Enter <%pS> ip = 0x%p\n", (void *)ip, (void *)ip);
+       nhit++;
        if (stackdump)
                show_backtrace();
 }
@@ -49,8 +60,17 @@ static void sample_exit_handler(struct fprobe *fp, unsigned long ip, struct pt_r
 {
        unsigned long rip = instruction_pointer(regs);
 
-       pr_info("Return from <%pS> ip = 0x%p to rip = 0x%p (%pS)\n",
-               (void *)ip, (void *)ip, (void *)rip, (void *)rip);
+       if (use_trace)
+               /*
+                * This is just an example, no kernel code should call
+                * trace_printk() except when actively debugging.
+                */
+               trace_printk("Return from <%pS> ip = 0x%p to rip = 0x%p (%pS)\n",
+                       (void *)ip, (void *)ip, (void *)rip, (void *)rip);
+       else
+               pr_info("Return from <%pS> ip = 0x%p to rip = 0x%p (%pS)\n",
+                       (void *)ip, (void *)ip, (void *)rip, (void *)rip);
+       nhit++;
        if (stackdump)
                show_backtrace();
 }
@@ -112,7 +132,8 @@ static void __exit fprobe_exit(void)
 {
        unregister_fprobe(&sample_probe);
 
-       pr_info("fprobe at %s unregistered\n", symbol);
+       pr_info("fprobe at %s unregistered. %ld times hit, %ld times missed\n",
+               symbol, nhit, sample_probe.nmissed);
 }
 
 module_init(fprobe_init)