kmsg: export printk records to the /dev/kmsg interface
Support for multiple concurrent readers of /dev/kmsg, with read(),
seek(), poll() support. Output of message sequence numbers, to allow
userspace log consumers to reliably reconnect and reconstruct their
state at any given time. After open("/dev/kmsg"), read() always
returns *all* buffered records. If only future messages should be
read, SEEK_END can be used. In case records get overwritten while
/dev/kmsg is held open, or records get faster overwritten than they
are read, the next read() will return -EPIPE and the current reading
position gets updated to the next available record. The passed
sequence numbers allow the log consumer to calculate the amount of
lost messages.
[root@mop ~]# cat /dev/kmsg
5,0,0;Linux version 3.4.0-rc1+ (kay@mop) (gcc version 4.7.0 20120315 ...
6,159,423091;ACPI: PCI Root Bridge [PCI0] (domain 0000 [bus 00-ff])
7,160,424069;pci_root PNP0A03:00: host bridge window [io 0x0000-0x0cf7] (ignored)
SUBSYSTEM=acpi
DEVICE=+acpi:PNP0A03:00
6,339,5140900;NET: Registered protocol family 10
30,340,5690716;udevd[80]: starting version 181
6,341,6081421;FDC 0 is a S82078B
6,345,6154686;microcode: CPU0 sig=0x623, pf=0x0, revision=0x0
7,346,6156968;sr 1:0:0:0: Attached scsi CD-ROM sr0
SUBSYSTEM=scsi
DEVICE=+scsi:1:0:0:0
6,347,6289375;microcode: CPU1 sig=0x623, pf=0x0, revision=0x0
Cc: Karel Zak <kzak@redhat.com>
Tested-by: William Douglas <william.douglas@intel.com>
Signed-off-by: Kay Sievers <kay@vrfy.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/drivers/char/mem.c b/drivers/char/mem.c
index cf56614..0e7fbfc 100644
--- a/drivers/char/mem.c
+++ b/drivers/char/mem.c
@@ -807,65 +807,6 @@
};
#endif
-static ssize_t kmsg_writev(struct kiocb *iocb, const struct iovec *iv,
- unsigned long count, loff_t pos)
-{
- char *buf, *line;
- int i;
- int level = default_message_loglevel;
- int facility = 1; /* LOG_USER */
- size_t len = iov_length(iv, count);
- ssize_t ret = len;
-
- if (len > 1024)
- return -EINVAL;
- buf = kmalloc(len+1, GFP_KERNEL);
- if (buf == NULL)
- return -ENOMEM;
-
- line = buf;
- for (i = 0; i < count; i++) {
- if (copy_from_user(line, iv[i].iov_base, iv[i].iov_len))
- goto out;
- line += iv[i].iov_len;
- }
-
- /*
- * Extract and skip the syslog prefix <[0-9]*>. Coming from userspace
- * the decimal value represents 32bit, the lower 3 bit are the log
- * level, the rest are the log facility.
- *
- * If no prefix or no userspace facility is specified, we
- * enforce LOG_USER, to be able to reliably distinguish
- * kernel-generated messages from userspace-injected ones.
- */
- line = buf;
- if (line[0] == '<') {
- char *endp = NULL;
-
- i = simple_strtoul(line+1, &endp, 10);
- if (endp && endp[0] == '>') {
- level = i & 7;
- if (i >> 3)
- facility = i >> 3;
- endp++;
- len -= endp - line;
- line = endp;
- }
- }
- line[len] = '\0';
-
- printk_emit(facility, level, NULL, 0, "%s", line);
-out:
- kfree(buf);
- return ret;
-}
-
-static const struct file_operations kmsg_fops = {
- .aio_write = kmsg_writev,
- .llseek = noop_llseek,
-};
-
static const struct memdev {
const char *name;
umode_t mode;
@@ -884,7 +825,7 @@
[7] = { "full", 0666, &full_fops, NULL },
[8] = { "random", 0666, &random_fops, NULL },
[9] = { "urandom", 0666, &urandom_fops, NULL },
- [11] = { "kmsg", 0, &kmsg_fops, NULL },
+ [11] = { "kmsg", 0644, &kmsg_fops, NULL },
#ifdef CONFIG_CRASH_DUMP
[12] = { "oldmem", 0, &oldmem_fops, NULL },
#endif