diff options
| -rw-r--r-- | Documentation/ABI/testing/dev-kmsg | 5 | ||||
| -rw-r--r-- | kernel/printk/printk.c | 10 |
2 files changed, 15 insertions, 0 deletions
diff --git a/Documentation/ABI/testing/dev-kmsg b/Documentation/ABI/testing/dev-kmsg index f307506eb54c..1e6c28b1942b 100644 --- a/Documentation/ABI/testing/dev-kmsg +++ b/Documentation/ABI/testing/dev-kmsg @@ -56,6 +56,11 @@ Description: The /dev/kmsg character device node provides userspace access seek after the last record available at the time the last SYSLOG_ACTION_CLEAR was issued. + Due to the record nature of this interface with a "read all" + behavior and the specific positions each seek operation sets, + SEEK_CUR is not supported, returning -ESPIPE (invalid seek) to + errno whenever requested. + The output format consists of a prefix carrying the syslog prefix including priority and facility, the 64 bit message sequence number and the monotonic timestamp in microseconds, diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c index 525038745a14..35cc5f548860 100644 --- a/kernel/printk/printk.c +++ b/kernel/printk/printk.c @@ -974,6 +974,16 @@ static loff_t devkmsg_llseek(struct file *file, loff_t offset, int whence) user->idx = log_next_idx; user->seq = log_next_seq; break; + case SEEK_CUR: + /* + * It isn't supported due to the record nature of this + * interface: _SET _DATA and _END point to very specific + * record positions, while _CUR would be more useful in case + * of a byte-based log. Because of that, return the default + * errno value for invalid seek operation. + */ + ret = -ESPIPE; + break; default: ret = -EINVAL; } |