For the moment the library provides only one method for writing to
tracefs files, that is:
int tracefs_instance_file_write()
This method first truncates the size of the file to 0 (clearing it),
then writes new content to this file. Essentially this method overwrites
(clear + write). In this patch we add two additional methids:
int tracefs_instance_file_append()
which writes without clearing and
int tracefs_instance_file_clear()
which clears without writing anything. Those two new APIs have various
use-cases. For example one can use the two methods when adding/clearing
kprobes.
Signed-off-by: Yordan Karadzhov (VMware) <y.karadz@xxxxxxxxx>
---
include/tracefs.h | 4 +++
src/tracefs-instance.c | 65 ++++++++++++++++++++++++++++++++----------
2 files changed, 54 insertions(+), 15 deletions(-)
diff --git a/include/tracefs.h b/include/tracefs.h
index 55ee867..551c37c 100644
--- a/include/tracefs.h
+++ b/include/tracefs.h
@@ -33,6 +33,10 @@ tracefs_instance_get_file(struct tracefs_instance *instance, const char *file);
char *tracefs_instance_get_dir(struct tracefs_instance *instance);
int tracefs_instance_file_write(struct tracefs_instance *instance,
const char *file, const char *str);
+int tracefs_instance_file_append(struct tracefs_instance *instance,
+ const char *file, const char *str);
+int tracefs_instance_file_clear(struct tracefs_instance *instance,
+ const char *file);
char *tracefs_instance_file_read(struct tracefs_instance *instance,
const char *file, int *psize);
int tracefs_instance_file_read_number(struct tracefs_instance *instance,
diff --git a/src/tracefs-instance.c b/src/tracefs-instance.c
index b8ce36f..e9dbba4 100644
--- a/src/tracefs-instance.c
+++ b/src/tracefs-instance.c
@@ -337,21 +337,41 @@ const char *tracefs_instance_get_trace_dir(struct tracefs_instance *instance)
return NULL;
}
-static int write_file(const char *file, const char *str)
+static int write_file(const char *file, const char *str, int flags)
{
- int ret;
+ int ret = 0;
int fd;
- fd = open(file, O_WRONLY | O_TRUNC);
+ fd = open(file, flags);
if (fd < 0) {
tracefs_warning("Failed to open '%s'", file);
return -1;
}
- ret = write(fd, str, strlen(str));
+
+ if (str)
+ ret = write(fd, str, strlen(str));
+
close(fd);
return ret;
}
+static int instance_file_write(struct tracefs_instance *instance,
+ const char *file, const char *str, int flags)
+{
+ struct stat st;
+ char *path;
+ int ret;
+
+ path = tracefs_instance_get_file(instance, file);
+ if (!path)
+ return -1;
+ ret = stat(path, &st);
+ if (ret == 0)
+ ret = write_file(path, str, flags);
+ tracefs_put_tracing_file(path);
+
+ return ret;
+}
/**
* tracefs_instance_file_write - Write in trace file of specific instance.
@@ -364,19 +384,34 @@ static int write_file(const char *file, const char *str)
int tracefs_instance_file_write(struct tracefs_instance *instance,
const char *file, const char *str)
{
- struct stat st;
- char *path;
- int ret;
+ return instance_file_write(instance, file, str, O_WRONLY | O_TRUNC);
+}
- path = tracefs_instance_get_file(instance, file);
- if (!path)
- return -1;
- ret = stat(path, &st);
- if (ret == 0)
- ret = write_file(path, str);
- tracefs_put_tracing_file(path);
+/**
+ * tracefs_instance_file_write - Append to a trace file of specific instance.
+ * @instance: ftrace instance, can be NULL for the top instance
+ * @file: name of the file
+ * @str: nul terminated string, that will be appended to the file.
+ *
+ * Returns the number of appended bytes, or -1 in case of an error.
+ */
+int tracefs_instance_file_append(struct tracefs_instance *instance,
+ const char *file, const char *str)
+{
+ return instance_file_write(instance, file, str, O_WRONLY);
+}
- return ret;
+/**
+ * tracefs_instance_file_write - Clear a trace file of specific instance.
+ * @instance: ftrace instance, can be NULL for the top instance
+ * @file: name of the file
+ *
+ * Returns 0 on success, or -1 in case of an error.
+ */
+int tracefs_instance_file_clear(struct tracefs_instance *instance,
+ const char *file)
+{
+ return instance_file_write(instance, file, NULL, O_WRONLY | O_TRUNC);
}
/**
--
2.25.1
|