Added two functions to test how to write string events:
* Using tp_copy_string_from_user
* can't enforce string length
* can't enforce '\0' at EOL
* can't return the number of bytes written to the caller
* Using tp_memcpy_from_user
* can't enforce '\0' at EOL
* this TP doesn't show-up with lttng list -k, maybe miss usage of the
TRACE_EVENT macro?
Also, adding a small script to quickly test experiments with various files.
---
do-user-event-experiment.sh | 15 ++++
instrumentation/events/lttng-module/lttng.h | 34 +++++++++
probes/lttng-user-event.c | 97 +++++++++++++++++++++-----
3 files changed, 127 insertions(+), 19 deletions(-)
create mode 100755 do-user-event-experiment.sh
diff --git a/do-user-event-experiment.sh b/do-user-event-experiment.sh
new file mode 100755
index 0000000..d41d8e4
--- /dev/null
+++ b/do-user-event-experiment.sh
@@ -0,0 +1,15 @@
+#!/bin/bash
+
+rmmod lttng-user-event
+modprobe lttng-user-event
+lttng create test
+lttng enable-event lttng_uevent_memcpy -k
+lttng enable-event lttng_uevent_cfu -k
+lttng enable-event lttng_uevent -k
+lttng start
+echo -n "bidon" > /proc/lttng_user_event
+echo -n "bidon" > /proc/lttng_user_event_cfu
+echo -n "bidon" > /proc/lttng_user_event_memcpy
+lttng stop
+lttng view
+lttng destroy
diff --git a/instrumentation/events/lttng-module/lttng.h
b/instrumentation/events/lttng-module/lttng.h
index 9da3c7e..e505c21 100644
--- a/instrumentation/events/lttng-module/lttng.h
+++ b/instrumentation/events/lttng-module/lttng.h
@@ -47,6 +47,40 @@ TRACE_EVENT(lttng_uevent,
TP_printk("text=%s", __entry->text)
)
+TRACE_EVENT(lttng_uevent_cfu,
+
+ TP_PROTO(const char *str),
+
+ TP_ARGS(str),
+
+ TP_STRUCT__entry(
+ __string_from_user( str, str )
+ ),
+
+ TP_fast_assign(
+ tp_copy_string_from_user(str, str)
+ ),
+
+ TP_printk()
+)
+
+TRACE_EVENT(lttng_uevent_memcpy,
+
+ TP_PROTO(const char *str, size_t len),
+
+ TP_ARGS(str, len),
+
+ TP_STRUCT__entry(
+ __string( text, str )
+ ),
+
+ TP_fast_assign(
+ tp_memcpy_from_user(text, str, len)
+ ),
+
+ TP_printk("text=%s", __entry->text)
+)
+
#endif /* _TRACE_LTTNG_H */
/* This part must be outside protection */
diff --git a/probes/lttng-user-event.c b/probes/lttng-user-event.c
index d3b66e6..db45ad4 100644
--- a/probes/lttng-user-event.c
+++ b/probes/lttng-user-event.c
@@ -8,7 +8,7 @@
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; only
- * version 2.1 of the License.
+ * version 2 of the License.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
@@ -37,11 +37,12 @@
#include "../instrumentation/events/lttng-module/lttng.h"
DEFINE_TRACE(lttng_uevent);
+DEFINE_TRACE(lttng_uevent_cfu);
+DEFINE_TRACE(lttng_uevent_memcpy);
#define LTTNG_UEVENT_FILE "lttng_user_event"
-
-struct proc_dir_entry *lttng_root;
-static struct proc_dir_entry *write_file;
+#define LTTNG_UEVENT_FILE_CFU "lttng_user_event_cfu"
+#define LTTNG_UEVENT_FILE_MEMCPY "lttng_user_event_memcpy"
/**
* write_event - write a userspace string into the trace system
@@ -114,41 +115,99 @@ ssize_t write_event(struct file *file, const char __user
*user_buf,
return written;
}
+/* CFU stands for Copy From User */
+static
+ssize_t write_event_copy_from_user(struct file *file, const char __user
*user_buf,
+ size_t count, loff_t *fpos)
+{
+ /* How do we know how much data is written? Otherwise,
+ * this function can't return the appropriate value.
+ *
+ * If the user string is not null-terminated,
+ * then could it leak info beyong the string? : yes
+ *
+ * Assuming the userspace string is well formated
+ * seems not appropriate.
+ */
+ trace_lttng_uevent_cfu(user_buf);
+ return count;
+}
+
+static
+ssize_t write_event_memcpy(struct file *file, const char __user *user_buf,
+ size_t count, loff_t *fpos)
+{
+ if (count >= LTTNG_UEVENT_SIZE)
+ count = LTTNG_UEVENT_SIZE - 1;
+
+ /*
+ * still unable to enforce null terminated string
+ * userspace won't be happy if we change their buffers in-place
+ */
+ trace_lttng_uevent_memcpy(user_buf, count);
+ return count;
+}
+
static const struct file_operations write_file_ops = {
.owner = THIS_MODULE,
.write = write_event
};
-static int __init lttng_user_event_init(void)
+static const struct file_operations write_file_cfu_ops = {
+ .owner = THIS_MODULE,
+ .write = write_event_copy_from_user
+};
+
+static const struct file_operations write_file_memcpy_ops = {
+ .owner = THIS_MODULE,
+ .write = write_event_memcpy
+};
+
+static int init_proc_entry(char *name, const struct file_operations *fops)
{
- int err = 0;
+ struct proc_dir_entry *write_file;
- /* lttng is already a file with the current abi, not a directory */
- /*
- lttng_root = proc_mkdir("lttng", NULL);
- if (lttng_root == NULL)
- return -ENOMEM;
- */
- write_file = create_proc_entry(LTTNG_UEVENT_FILE, 0644, lttng_root);
+ write_file = create_proc_entry(name, 0644, NULL);
if (!write_file) {
- err = -ENOENT;
- goto err_procfs;
+ return -ENOENT;
}
- write_file->proc_fops = &write_file_ops;
+ write_file->proc_fops = fops;
write_file->mode = S_IFREG | S_IWUGO;
write_file->uid = 0;
write_file->gid = 0;
+ return 0;
+}
+
+static int __init lttng_user_event_init(void)
+{
+ int err = 0;
+
+ if ((err = init_proc_entry(LTTNG_UEVENT_FILE, &write_file_ops)) < 0)
+ goto err_1;
+ if ((err = init_proc_entry(LTTNG_UEVENT_FILE_CFU, &write_file_cfu_ops))
< 0)
+ goto err_2;
+ if ((err = init_proc_entry(LTTNG_UEVENT_FILE_MEMCPY,
&write_file_memcpy_ops)) < 0)
+ goto err_3;
+
return err;
-err_procfs:
- remove_proc_entry(LTTNG_UEVENT_FILE, lttng_root);
+ err_3:
+ remove_proc_entry(LTTNG_UEVENT_FILE_MEMCPY, NULL);
+ err_2:
+ remove_proc_entry(LTTNG_UEVENT_FILE_CFU, NULL);
+ err_1:
+ remove_proc_entry(LTTNG_UEVENT_FILE, NULL);
return err;
}
static void __exit lttng_user_event_exit(void)
{
- remove_proc_entry(LTTNG_UEVENT_FILE, lttng_root);
+ remove_proc_entry(LTTNG_UEVENT_FILE, NULL);
printk(KERN_INFO "/proc/%s removed\n", LTTNG_UEVENT_FILE);
+ remove_proc_entry(LTTNG_UEVENT_FILE_CFU, NULL);
+ printk(KERN_INFO "/proc/%s removed\n", LTTNG_UEVENT_FILE_CFU);
+ remove_proc_entry(LTTNG_UEVENT_FILE_MEMCPY, NULL);
+ printk(KERN_INFO "/proc/%s removed\n", LTTNG_UEVENT_FILE_MEMCPY);
}
module_init(lttng_user_event_init);
--
1.7.5.4
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