[PATCH v3 3/5] tracing: Use __free() for kprobe events to cleanup

["Masami Hiramatsu (Google)" <mhiramat@kernel.org>]

From: Masami Hiramatsu (Google) <mhiramat@kernel.org>

Use __free() in trace_kprobe.c to cleanup code.

Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
---
 Changes in v3:
  - Rename to __free(free_trace_kprobe) to clarify what function will be called.
  - Add !IS_ERR_OR_NULL() check because alloc_trace_kprobe() returns an error code.
  - Prevent freeing 'tk' in create_local_trace_kprobe() when succeeded to register.
 Changes in v2:
  - Instead of using no_free_ptr(), just assign NULL to the registered pointer.
---
 kernel/trace/trace_kprobe.c |   63 +++++++++++++++++++++----------------------
 1 file changed, 31 insertions(+), 32 deletions(-)

diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
index fb9d4dffa66e..2d8b5ef47e96 100644
--- a/kernel/trace/trace_kprobe.c
+++ b/kernel/trace/trace_kprobe.c
@@ -8,6 +8,7 @@
 #define pr_fmt(fmt)	"trace_kprobe: " fmt
 
 #include <linux/bpf-cgroup.h>
+#include <linux/cleanup.h>
 #include <linux/security.h>
 #include <linux/module.h>
 #include <linux/uaccess.h>
@@ -257,6 +258,9 @@ static void free_trace_kprobe(struct trace_kprobe *tk)
 	}
 }
 
+DEFINE_FREE(free_trace_kprobe, struct trace_kprobe *,
+	if (!IS_ERR_OR_NULL(_T)) free_trace_kprobe(_T))
+
 /*
  * Allocate new trace_probe and initialize it (including kprobes).
  */
@@ -268,7 +272,7 @@ static struct trace_kprobe *alloc_trace_kprobe(const char *group,
 					     int maxactive,
 					     int nargs, bool is_return)
 {
-	struct trace_kprobe *tk;
+	struct trace_kprobe *tk __free(free_trace_kprobe) = NULL;
 	int ret = -ENOMEM;
 
 	tk = kzalloc(struct_size(tk, tp.args, nargs), GFP_KERNEL);
@@ -277,12 +281,12 @@ static struct trace_kprobe *alloc_trace_kprobe(const char *group,
 
 	tk->nhit = alloc_percpu(unsigned long);
 	if (!tk->nhit)
-		goto error;
+		return ERR_PTR(ret);
 
 	if (symbol) {
 		tk->symbol = kstrdup(symbol, GFP_KERNEL);
 		if (!tk->symbol)
-			goto error;
+			return ERR_PTR(ret);
 		tk->rp.kp.symbol_name = tk->symbol;
 		tk->rp.kp.offset = offs;
 	} else
@@ -299,13 +303,10 @@ static struct trace_kprobe *alloc_trace_kprobe(const char *group,
 
 	ret = trace_probe_init(&tk->tp, event, group, false, nargs);
 	if (ret < 0)
-		goto error;
+		return ERR_PTR(ret);
 
 	dyn_event_init(&tk->devent, &trace_kprobe_ops);
-	return tk;
-error:
-	free_trace_kprobe(tk);
-	return ERR_PTR(ret);
+	return_ptr(tk);
 }
 
 static struct trace_kprobe *find_trace_kprobe(const char *event,
@@ -866,11 +867,12 @@ static int __trace_kprobe_create(int argc, const char *argv[])
 	 * Type of args:
 	 *  FETCHARG:TYPE : use TYPE instead of unsigned long.
 	 */
-	struct trace_kprobe *tk = NULL;
+	struct trace_kprobe *tk __free(free_trace_kprobe) = NULL;
 	int i, len, new_argc = 0, ret = 0;
 	bool is_return = false;
-	char *symbol = NULL, *tmp = NULL;
-	const char **new_argv = NULL;
+	char *symbol __free(kfree) = NULL;
+	char *tmp = NULL;
+	const char **new_argv __free(kfree) = NULL;
 	const char *event = NULL, *group = KPROBE_EVENT_SYSTEM;
 	enum probe_print_type ptype;
 	int maxactive = 0;
@@ -879,7 +881,7 @@ static int __trace_kprobe_create(int argc, const char *argv[])
 	char buf[MAX_EVENT_NAME_LEN];
 	char gbuf[MAX_EVENT_NAME_LEN];
 	char abuf[MAX_BTF_ARGS_LEN];
-	char *dbuf = NULL;
+	char *dbuf __free(kfree) = NULL;
 	struct traceprobe_parse_context ctx = { .flags = TPARG_FL_KERNEL };
 
 	switch (argv[0][0]) {
@@ -936,7 +938,7 @@ static int __trace_kprobe_create(int argc, const char *argv[])
 		/* Check whether uprobe event specified */
 		if (strchr(argv[1], '/') && strchr(argv[1], ':')) {
 			ret = -ECANCELED;
-			goto error;
+			goto out;
 		}
 		/* a symbol specified */
 		symbol = kstrdup(argv[1], GFP_KERNEL);
@@ -1040,7 +1042,7 @@ static int __trace_kprobe_create(int argc, const char *argv[])
 		ctx.offset = 0;
 		ret = traceprobe_parse_probe_arg(&tk->tp, i, argv[i], &ctx);
 		if (ret)
-			goto error;	/* This can be -ENOMEM */
+			goto out;	/* This can be -ENOMEM */
 	}
 	/* entry handler for kretprobe */
 	if (is_return && tk->tp.entry_arg) {
@@ -1051,7 +1053,7 @@ static int __trace_kprobe_create(int argc, const char *argv[])
 	ptype = is_return ? PROBE_PRINT_RETURN : PROBE_PRINT_NORMAL;
 	ret = traceprobe_set_print_fmt(&tk->tp, ptype);
 	if (ret < 0)
-		goto error;
+		goto out;
 
 	ret = register_trace_kprobe(tk);
 	if (ret) {
@@ -1062,21 +1064,20 @@ static int __trace_kprobe_create(int argc, const char *argv[])
 			trace_probe_log_err(0, BAD_PROBE_ADDR);
 		else if (ret != -ENOMEM && ret != -EEXIST)
 			trace_probe_log_err(0, FAIL_REG_PROBE);
-		goto error;
-	}
+	} else
+		/*
+		 * Here, 'tk' has been registered to the list successfully,
+		 * so we don't need to free it.
+		 */
+		tk = NULL;
 
 out:
 	traceprobe_finish_parse(&ctx);
 	trace_probe_log_clear();
-	kfree(new_argv);
-	kfree(symbol);
-	kfree(dbuf);
 	return ret;
 
 parse_error:
 	ret = -EINVAL;
-error:
-	free_trace_kprobe(tk);
 	goto out;
 }
 
@@ -1898,7 +1899,8 @@ create_local_trace_kprobe(char *func, void *addr, unsigned long offs,
 			  bool is_return)
 {
 	enum probe_print_type ptype;
-	struct trace_kprobe *tk;
+	struct trace_kprobe *tk __free(free_trace_kprobe) = NULL;
+	struct trace_probe *tp;
 	int ret;
 	char *event;
 
@@ -1929,19 +1931,16 @@ create_local_trace_kprobe(char *func, void *addr, unsigned long offs,
 
 	ptype = trace_kprobe_is_return(tk) ?
 		PROBE_PRINT_RETURN : PROBE_PRINT_NORMAL;
-	if (traceprobe_set_print_fmt(&tk->tp, ptype) < 0) {
-		ret = -ENOMEM;
-		goto error;
-	}
+	if (traceprobe_set_print_fmt(&tk->tp, ptype) < 0)
+		return ERR_PTR(-ENOMEM);
 
 	ret = __register_trace_kprobe(tk);
 	if (ret < 0)
-		goto error;
+		return ERR_PTR(ret);
 
-	return trace_probe_event_call(&tk->tp);
-error:
-	free_trace_kprobe(tk);
-	return ERR_PTR(ret);
+	tp = &tk->tp;
+	tk = NULL;	/* 'tk' is registered successfully, so do not free. */
+	return trace_probe_event_call(tp);
 }
 
 void destroy_local_trace_kprobe(struct trace_event_call *event_call)