kprobes: treewide: Cleanup the error messages for kprobes

This clean up the error/notification messages in kprobes related code.
Basically this defines 'pr_fmt()' macros for each files and update
the messages which describes

 - what happened,
 - what is the kernel going to do or not do,
 - is the kernel fine,
 - what can the user do about it.

Also, if the message is not needed (e.g. the function returns unique
error code, or other error message is already shown.) remove it,
and replace the message with WARN_*() macros if suitable.

Link: https://lkml.kernel.org/r/163163036568.489837.14085396178727185469.stgit@devnote2

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

1 files changed, 16 insertions, 20 deletions

diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index 30199bfcc74a..7663c8a51889 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -18,6 +18,9 @@
  *		<jkenisto@us.ibm.com> and Prasanna S Panchamukhi
  *		<prasanna@in.ibm.com> added function-return probes.
  */
+
+#define pr_fmt(fmt) "kprobes: " fmt
+
 #include <linux/kprobes.h>
 #include <linux/hash.h>
 #include <linux/init.h>
@@ -892,7 +895,7 @@ static void optimize_all_kprobes(void)
 				optimize_kprobe(p);
 	}
 	cpus_read_unlock();
-	printk(KERN_INFO "Kprobes globally optimized\n");
+	pr_info("kprobe jump-optimization is enabled. All kprobes are optimized if possible.\n");
 out:
 	mutex_unlock(&kprobe_mutex);
 }
@@ -925,7 +928,7 @@ static void unoptimize_all_kprobes(void)
 
 	/* Wait for unoptimizing completion */
 	wait_for_kprobe_optimizer();
-	printk(KERN_INFO "Kprobes globally unoptimized\n");
+	pr_info("kprobe jump-optimization is disabled. All kprobes are based on software breakpoint.\n");
 }
 
 static DEFINE_MUTEX(kprobe_sysctl_mutex);
@@ -1003,7 +1006,7 @@ static int reuse_unused_kprobe(struct kprobe *ap)
 	 * unregistered.
 	 * Thus there should be no chance to reuse unused kprobe.
 	 */
-	printk(KERN_ERR "Error: There should be no unused kprobe here.\n");
+	WARN_ON_ONCE(1);
 	return -EINVAL;
 }
 
@@ -1040,18 +1043,13 @@ static int __arm_kprobe_ftrace(struct kprobe *p, struct ftrace_ops *ops,
 	int ret = 0;
 
 	ret = ftrace_set_filter_ip(ops, (unsigned long)p->addr, 0, 0);
-	if (ret) {
-		pr_debug("Failed to arm kprobe-ftrace at %pS (%d)\n",
-			 p->addr, ret);
+	if (WARN_ONCE(ret < 0, "Failed to arm kprobe-ftrace at %pS (error %d)\n", p->addr, ret))
 		return ret;
-	}
 
 	if (*cnt == 0) {
 		ret = register_ftrace_function(ops);
-		if (ret) {
-			pr_debug("Failed to init kprobe-ftrace (%d)\n", ret);
+		if (WARN(ret < 0, "Failed to register kprobe-ftrace (error %d)\n", ret))
 			goto err_ftrace;
-		}
 	}
 
 	(*cnt)++;
@@ -1083,14 +1081,14 @@ static int __disarm_kprobe_ftrace(struct kprobe *p, struct ftrace_ops *ops,
 
 	if (*cnt == 1) {
 		ret = unregister_ftrace_function(ops);
-		if (WARN(ret < 0, "Failed to unregister kprobe-ftrace (%d)\n", ret))
+		if (WARN(ret < 0, "Failed to unregister kprobe-ftrace (error %d)\n", ret))
 			return ret;
 	}
 
 	(*cnt)--;
 
 	ret = ftrace_set_filter_ip(ops, (unsigned long)p->addr, 1, 0);
-	WARN_ONCE(ret < 0, "Failed to disarm kprobe-ftrace at %pS (%d)\n",
+	WARN_ONCE(ret < 0, "Failed to disarm kprobe-ftrace at %pS (error %d)\n",
 		  p->addr, ret);
 	return ret;
 }
@@ -1880,7 +1878,7 @@ unsigned long __kretprobe_trampoline_handler(struct pt_regs *regs,
 
 		node = node->next;
 	}
-	pr_err("Oops! Kretprobe fails to find correct return address.\n");
+	pr_err("kretprobe: Return address not found, not execute handler. Maybe there is a bug in the kernel.\n");
 	BUG_ON(1);
 
 found:
@@ -2209,8 +2207,7 @@ EXPORT_SYMBOL_GPL(enable_kprobe);
 /* Caller must NOT call this in usual path. This is only for critical case */
 void dump_kprobe(struct kprobe *kp)
 {
-	pr_err("Dumping kprobe:\n");
-	pr_err("Name: %s\nOffset: %x\nAddress: %pS\n",
+	pr_err("Dump kprobe:\n.symbol_name = %s, .offset = %x, .addr = %pS\n",
 	       kp->symbol_name, kp->offset, kp->addr);
 }
 NOKPROBE_SYMBOL(dump_kprobe);
@@ -2473,8 +2470,7 @@ static int __init init_kprobes(void)
 	err = populate_kprobe_blacklist(__start_kprobe_blacklist,
 					__stop_kprobe_blacklist);
 	if (err) {
-		pr_err("kprobes: failed to populate blacklist: %d\n", err);
-		pr_err("Please take care of using kprobes.\n");
+		pr_err("Failed to populate blacklist (error %d), kprobes not restricted, be careful using them!\n", err);
 	}
 
 	if (kretprobe_blacklist_size) {
@@ -2483,7 +2479,7 @@ static int __init init_kprobes(void)
 			kretprobe_blacklist[i].addr =
 				kprobe_lookup_name(kretprobe_blacklist[i].name, 0);
 			if (!kretprobe_blacklist[i].addr)
-				printk("kretprobe: lookup failed: %s\n",
+				pr_err("Failed to lookup symbol '%s' for kretprobe blacklist. Maybe the target function is removed or renamed.\n",
 				       kretprobe_blacklist[i].name);
 		}
 	}
@@ -2687,7 +2683,7 @@ static int arm_all_kprobes(void)
 	}
 
 	if (errors)
-		pr_warn("Kprobes globally enabled, but failed to arm %d out of %d probes\n",
+		pr_warn("Kprobes globally enabled, but failed to enable %d out of %d probes. Please check which kprobes are kept disabled via debugfs.\n",
 			errors, total);
 	else
 		pr_info("Kprobes globally enabled\n");
@@ -2730,7 +2726,7 @@ static int disarm_all_kprobes(void)
 	}
 
 	if (errors)
-		pr_warn("Kprobes globally disabled, but failed to disarm %d out of %d probes\n",
+		pr_warn("Kprobes globally disabled, but failed to disable %d out of %d probes. Please check which kprobes are kept enabled via debugfs.\n",
 			errors, total);
 	else
 		pr_info("Kprobes globally disabled\n");