[PATCH v4 2/7] 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 | 36 ++++++++++++++++++++++++++++++++++++
 kernel/trace/trace_probe.h |  2 ++
 2 files changed, 38 insertions(+)

diff --git a/kernel/trace/trace_probe.c b/kernel/trace/trace_probe.c
index 4dc74d73fc1d..cc8bd7ea5341 100644
--- a/kernel/trace/trace_probe.c
+++ b/kernel/trace/trace_probe.c
@@ -1565,6 +1565,42 @@ const char **traceprobe_expand_meta_args(int argc, const char *argv[],
 	return ERR_PTR(ret);
 }
 
+int traceprobe_expand_dentry_args(int argc, const char *argv[], char *buf,
+				  int bufsize)
+{
+	int i, used, ret;
+
+	used = 0;
+	for (i = 0; i < argc; i++) {
+		size_t idx;
+
+		if (str_has_suffix(argv[i], ":%pd", &idx)) {
+			char *tmp = kstrdup(argv[i], GFP_KERNEL);
+			char *equal;
+
+			if (!tmp)
+				return -ENOMEM;
+
+			equal = strchr(tmp, '=');
+			if (equal)
+				*equal = '\0';
+			tmp[idx] = '\0';
+			ret = snprintf(buf + 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)
+				return -ENOMEM;
+			argv[i] = buf + used;
+			used += ret + 1;
+		}
+	}
+
+	return 0;
+}
+
 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 850d9ecb6765..553371a4e0b1 100644
--- a/kernel/trace/trace_probe.h
+++ b/kernel/trace/trace_probe.h
@@ -402,6 +402,8 @@ 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,
+					 int bufsize);
 
 extern int traceprobe_update_arg(struct probe_arg *arg);
 extern void traceprobe_free_probe_arg(struct probe_arg *arg);
-- 
2.31.1