[RFC 6/8] kmsg: add predefined _PID, _TID, _COMM keywords to kmsg* log dict

Marcin Niesluchowski
2015-07-03T10:51:40Z

kmsg* devices write operation wrote no dict along with message
Due to usage of kmsg devices in userspace dict has been added
identifying pid, tid and comm of writing process.

Signed-off-by: Marcin Niesluchowski <m.niesluchow@samsung.com>
---
kernel/printk/printk.c | 40 ++++++++++++++++++++++++++++++++++++----
1 file changed, 36 insertions(+), 4 deletions(-)

diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index abe78c1..2a7f6a4 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -876,7 +876,34 @@ void log_buf_release(struct kref *ref)
kfree(log_b);
}

-static int kmsg_sys_write(int minor, int level, const char *fmt, ...)
+#define MAX_PID_LEN 20
+#define MAX_TID_LEN 20
+/*
+ * Fromat below describes dict appended to message written from userspace:
+ * "_PID=<pid>\0_TID=<tid>\0_COMM=<comm>"
+ * KMSG_DICT_MAX_LEN definition represents maximal length of this dict.
+ */
+#define KMSG_DICT_MAX_LEN (5 + MAX_PID_LEN + 1 + \
+ 5 + MAX_TID_LEN + 1 + \
+ 6 + TASK_COMM_LEN)
+
+static size_t set_kmsg_dict(char *buf)
+{
+ size_t len;
+
+ len = sprintf(buf, "_PID=%d", task_tgid_nr(current)) + 1;
+ len += sprintf(buf + len, "_TID=%d", task_pid_nr(current)) + 1;
+ memcpy(buf + len, "_COMM=", 6);
+ len += 6;
+ get_task_comm(buf + len, current);
+ while (buf[len] != '\0')
+ len++;
+ return len;
+}
+
+static int kmsg_sys_write(int minor, int level,
+ const char *dict, size_t dictlen,
+ const char *fmt, ...)
{
va_list args;
int ret = -ENXIO;
@@ -891,7 +918,7 @@ static int kmsg_sys_write(int minor, int level, const char *fmt, ...)

va_start(args, fmt);
log_format_and_store(log_b, 1 /* LOG_USER */, level,
- NULL, 0, fmt, args);
+ dict, dictlen, fmt, args);
va_end(args);
wake_up_interruptible(&log_b->wait);

@@ -911,6 +938,8 @@ static ssize_t devkmsg_write(struct kiocb *iocb, struct iov_iter *from)
int level = default_message_loglevel;
int facility = 1; /* LOG_USER */
size_t len = iov_iter_count(from);
+ char dict[KMSG_DICT_MAX_LEN];
+ size_t dictlen;
ssize_t ret = len;
int minor = iminor(iocb->ki_filp->f_inode);

@@ -950,10 +979,13 @@ static ssize_t devkmsg_write(struct kiocb *iocb, struct iov_iter *from)
}
}

+ dictlen = set_kmsg_dict(dict);
+
if (minor == log_buf.minor) {
- printk_emit(facility, level, NULL, 0, "%s", line);
+ printk_emit(facility, level, dict, dictlen, "%s", line);
} else {
- int error = kmsg_sys_write(minor, level, "%s", line);
+ int error = kmsg_sys_write(minor, level, dict, dictlen,
+ "%s", line);

if (error)
ret = error;
--
1.9.1