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authorKay Sievers <kay@vrfy.org>2012-05-03 04:29:41 +0400
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2012-05-08 04:03:27 +0400
commite11fea92e13fb91c50bacca799a6131c81929986 (patch)
tree3b9204f4eccc6b488b843d6d00e65dc982c50160 /drivers/char/mem.c
parent7ff9554bb578ba02166071d2d487b7fc7d860d62 (diff)
downloadlinux-e11fea92e13fb91c50bacca799a6131c81929986.tar.xz
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>
Diffstat (limited to 'drivers/char/mem.c')
-rw-r--r--drivers/char/mem.c61
1 files changed, 1 insertions, 60 deletions
diff --git a/drivers/char/mem.c b/drivers/char/mem.c
index cf56614479ef..0e7fbfcbd6e6 100644
--- a/drivers/char/mem.c
+++ b/drivers/char/mem.c
@@ -807,65 +807,6 @@ static const struct file_operations oldmem_fops = {
};
#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 @@ static const struct memdev {
[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