From 19aaafb584c6317b3d0f6a1fbb346e15c0227be1 Mon Sep 17 00:00:00 2001 From: "Masami Hiramatsu (Google)" Date: Wed, 8 Jun 2022 01:11:02 +0900 Subject: [PATCH] fprobe, samples: Add use_trace option and show hit/missed counter Add use_trace option to use trace_printk() instead of pr_info() so that the handler doesn't involve the RCU operations. And show the hit and missed counter so that the user can check how many times the probe handler hit and missed. Signed-off-by: Masami Hiramatsu (Google) Signed-off-by: Daniel Borkmann Acked-by: Jiri Olsa Link: https://lore.kernel.org/bpf/165461826247.280167.11939123218334322352.stgit@devnote2 --- samples/fprobe/fprobe_example.c | 29 +++++++++++++++++++++++++---- 1 file changed, 25 insertions(+), 4 deletions(-) diff --git a/samples/fprobe/fprobe_example.c b/samples/fprobe/fprobe_example.c index 24d3cf1091407..01ee6c8c83829 100644 --- 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) -- 2.39.5