From e11fea92e13fb91c50bacca799a6131c81929986 Mon Sep 17 00:00:00 2001 From: Kay Sievers Date: Thu, 3 May 2012 02:29:41 +0200 Subject: 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 Tested-by: William Douglas Signed-off-by: Kay Sievers Signed-off-by: Greg Kroah-Hartman --- drivers/char/mem.c | 61 +----------------------------------------------------- 1 file changed, 1 insertion(+), 60 deletions(-) (limited to 'drivers/char') 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 -- cgit v1.2.3