[PATCH v6 1/8] tracing/probes: add traceprobe_expand_dentry_args() helper

[Ye Bin <yebin10@huawei.com>]

Add traceprobe_expand_dentry_args() to expand dentry args. this API is
prepare to support "%pd" print format for kprobe.

Signed-off-by: Ye Bin <yebin10@huawei.com>
---
 kernel/trace/trace_probe.c | 50 ++++++++++++++++++++++++++++++++++++++
 kernel/trace/trace_probe.h |  2 ++
 2 files changed, 52 insertions(+)

diff --git a/kernel/trace/trace_probe.c b/kernel/trace/trace_probe.c
index 34289f9c6707..a27567e16c36 100644
--- a/kernel/trace/trace_probe.c
+++ b/kernel/trace/trace_probe.c
@@ -1569,6 +1569,56 @@ const char **traceprobe_expand_meta_args(int argc, const char *argv[],
 	return ERR_PTR(ret);
 }
 
+/* @buf: *buf must be equal to NULL. Caller must to free *buf */
+int traceprobe_expand_dentry_args(int argc, const char *argv[], char **buf)
+{
+	int i, used, ret;
+	const int bufsize = MAX_DENTRY_ARGS_LEN;
+	char *tmpbuf = NULL;
+
+	if (*buf)
+		return -EINVAL;
+
+	used = 0;
+	for (i = 0; i < argc; i++) {
+		if (glob_match("*:%pd", argv[i])) {
+			char *tmp;
+			char *equal;
+
+			if (!tmpbuf) {
+				tmpbuf = kmalloc(bufsize, GFP_KERNEL);
+				if (!tmpbuf)
+					return -ENOMEM;
+			}
+
+			tmp = kstrdup(argv[i], GFP_KERNEL);
+			if (!tmp)
+				goto nomem;
+
+			equal = strchr(tmp, '=');
+			if (equal)
+				*equal = '\0';
+			tmp[strlen(argv[i]) - 4] = '\0';
+			ret = snprintf(tmpbuf + used, bufsize - used,
+				       "%s%s+0x0(+0x%zx(%s)):string",
+				       equal ? tmp : "", equal ? "=" : "",
+				       offsetof(struct dentry, d_name.name),
+				       equal ? equal + 1 : tmp);
+			kfree(tmp);
+			if (ret >= bufsize - used)
+				goto nomem;
+			argv[i] = tmpbuf + used;
+			used += ret + 1;
+		}
+	}
+
+	*buf = tmpbuf;
+	return 0;
+nomem:
+	kfree(tmpbuf);
+	return -ENOMEM;
+}
+
 void traceprobe_finish_parse(struct traceprobe_parse_context *ctx)
 {
 	clear_btf_context(ctx);
diff --git a/kernel/trace/trace_probe.h b/kernel/trace/trace_probe.h
index c1877d018269..3d22fba4b63f 100644
--- a/kernel/trace/trace_probe.h
+++ b/kernel/trace/trace_probe.h
@@ -34,6 +34,7 @@
 #define MAX_ARRAY_LEN		64
 #define MAX_ARG_NAME_LEN	32
 #define MAX_BTF_ARGS_LEN	128
+#define MAX_DENTRY_ARGS_LEN	256
 #define MAX_STRING_SIZE		PATH_MAX
 #define MAX_ARG_BUF_LEN		(MAX_TRACE_ARGS * MAX_ARG_NAME_LEN)
 
@@ -402,6 +403,7 @@ extern int traceprobe_parse_probe_arg(struct trace_probe *tp, int i,
 const char **traceprobe_expand_meta_args(int argc, const char *argv[],
 					 int *new_argc, char *buf, int bufsize,
 					 struct traceprobe_parse_context *ctx);
+extern int traceprobe_expand_dentry_args(int argc, const char *argv[], char **buf);
 
 extern int traceprobe_update_arg(struct probe_arg *arg);
 extern void traceprobe_free_probe_arg(struct probe_arg *arg);
-- 
2.31.1