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>
This commit is contained in:
Kay Sievers
Greg Kroah-Hartman
Родитель
7ff9554bb5
Коммит
e11fea92e1
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@ -807,65 +807,6 @@ static const struct file_operations oldmem_fops = {
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};
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#endif
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static ssize_t kmsg_writev(struct kiocb *iocb, const struct iovec *iv,
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unsigned long count, loff_t pos)
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{
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char *buf, *line;
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int i;
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int level = default_message_loglevel;
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int facility = 1; /* LOG_USER */
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size_t len = iov_length(iv, count);
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ssize_t ret = len;
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if (len > 1024)
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return -EINVAL;
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buf = kmalloc(len+1, GFP_KERNEL);
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if (buf == NULL)
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return -ENOMEM;
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line = buf;
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for (i = 0; i < count; i++) {
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if (copy_from_user(line, iv[i].iov_base, iv[i].iov_len))
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goto out;
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line += iv[i].iov_len;
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}
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/*
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* Extract and skip the syslog prefix <[0-9]*>. Coming from userspace
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* the decimal value represents 32bit, the lower 3 bit are the log
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* level, the rest are the log facility.
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*
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* If no prefix or no userspace facility is specified, we
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* enforce LOG_USER, to be able to reliably distinguish
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* kernel-generated messages from userspace-injected ones.
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*/
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line = buf;
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if (line[0] == '<') {
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char *endp = NULL;
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i = simple_strtoul(line+1, &endp, 10);
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if (endp && endp[0] == '>') {
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level = i & 7;
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if (i >> 3)
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facility = i >> 3;
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endp++;
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len -= endp - line;
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line = endp;
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}
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}
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line[len] = '\0';
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printk_emit(facility, level, NULL, 0, "%s", line);
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out:
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kfree(buf);
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return ret;
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}
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static const struct file_operations kmsg_fops = {
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.aio_write = kmsg_writev,
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.llseek = noop_llseek,
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};
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static const struct memdev {
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const char *name;
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umode_t mode;
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@ -884,7 +825,7 @@ static const struct memdev {
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[7] = { "full", 0666, &full_fops, NULL },
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[8] = { "random", 0666, &random_fops, NULL },
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[9] = { "urandom", 0666, &urandom_fops, NULL },
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[11] = { "kmsg", 0, &kmsg_fops, NULL },
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[11] = { "kmsg", 0644, &kmsg_fops, NULL },
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#ifdef CONFIG_CRASH_DUMP
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[12] = { "oldmem", 0, &oldmem_fops, NULL },
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#endif
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@ -300,6 +300,8 @@ extern void dump_stack(void) __cold;
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no_printk(KERN_DEBUG pr_fmt(fmt), ##__VA_ARGS__)
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#endif
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extern const struct file_operations kmsg_fops;
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enum {
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DUMP_PREFIX_NONE,
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DUMP_PREFIX_ADDRESS,
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313
kernel/printk.c
313
kernel/printk.c
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@ -41,6 +41,7 @@
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#include <linux/cpu.h>
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#include <linux/notifier.h>
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#include <linux/rculist.h>
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#include <linux/poll.h>
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#include <asm/uaccess.h>
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@ -149,6 +150,48 @@ static int console_may_schedule;
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* length of the message text is stored in the header, the stored message
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* is not terminated.
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*
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* Optionally, a message can carry a dictionary of properties (key/value pairs),
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* to provide userspace with a machine-readable message context.
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*
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* Examples for well-defined, commonly used property names are:
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* DEVICE=b12:8 device identifier
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* b12:8 block dev_t
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* c127:3 char dev_t
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* n8 netdev ifindex
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* +sound:card0 subsystem:devname
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* SUBSYSTEM=pci driver-core subsystem name
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*
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* Valid characters in property names are [a-zA-Z0-9.-_]. The plain text value
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* follows directly after a '=' character. Every property is terminated by
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* a '\0' character. The last property is not terminated.
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*
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* Example of a message structure:
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* 0000 ff 8f 00 00 00 00 00 00 monotonic time in nsec
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* 0008 34 00 record is 52 bytes long
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* 000a 0b 00 text is 11 bytes long
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* 000c 1f 00 dictionary is 23 bytes long
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* 000e 03 00 LOG_KERN (facility) LOG_ERR (level)
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* 0010 69 74 27 73 20 61 20 6c "it's a l"
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* 69 6e 65 "ine"
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* 001b 44 45 56 49 43 "DEVIC"
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* 45 3d 62 38 3a 32 00 44 "E=b8:2\0D"
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* 52 49 56 45 52 3d 62 75 "RIVER=bu"
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* 67 "g"
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* 0032 00 00 00 padding to next message header
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*
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* The 'struct log' buffer header must never be directly exported to
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* userspace, it is a kernel-private implementation detail that might
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* need to be changed in the future, when the requirements change.
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*
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* /dev/kmsg exports the structured data in the following line format:
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* "level,sequnum,timestamp;<message text>\n"
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*
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* The optional key/value pairs are attached as continuation lines starting
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* with a space character and terminated by a newline. All possible
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* non-prinatable characters are escaped in the "\xff" notation.
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*
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* Users of the export format should ignore possible additional values
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* separated by ',', and find the message after the ';' character.
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*/
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struct log {
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@ -297,6 +340,276 @@ static void log_store(int facility, int level,
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log_next_seq++;
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}
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/* /dev/kmsg - userspace message inject/listen interface */
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struct devkmsg_user {
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u64 seq;
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u32 idx;
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struct mutex lock;
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char buf[8192];
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};
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static ssize_t devkmsg_writev(struct kiocb *iocb, const struct iovec *iv,
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unsigned long count, loff_t pos)
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{
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char *buf, *line;
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int i;
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int level = default_message_loglevel;
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int facility = 1; /* LOG_USER */
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size_t len = iov_length(iv, count);
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ssize_t ret = len;
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if (len > LOG_LINE_MAX)
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return -EINVAL;
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buf = kmalloc(len+1, GFP_KERNEL);
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if (buf == NULL)
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return -ENOMEM;
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line = buf;
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for (i = 0; i < count; i++) {
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if (copy_from_user(line, iv[i].iov_base, iv[i].iov_len))
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goto out;
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line += iv[i].iov_len;
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}
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/*
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* Extract and skip the syslog prefix <[0-9]*>. Coming from userspace
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* the decimal value represents 32bit, the lower 3 bit are the log
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* level, the rest are the log facility.
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*
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* If no prefix or no userspace facility is specified, we
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* enforce LOG_USER, to be able to reliably distinguish
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* kernel-generated messages from userspace-injected ones.
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*/
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line = buf;
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if (line[0] == '<') {
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char *endp = NULL;
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i = simple_strtoul(line+1, &endp, 10);
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if (endp && endp[0] == '>') {
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level = i & 7;
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if (i >> 3)
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facility = i >> 3;
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endp++;
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len -= endp - line;
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line = endp;
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}
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}
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line[len] = '\0';
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printk_emit(facility, level, NULL, 0, "%s", line);
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out:
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kfree(buf);
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return ret;
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}
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static ssize_t devkmsg_read(struct file *file, char __user *buf,
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size_t count, loff_t *ppos)
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{
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struct devkmsg_user *user = file->private_data;
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struct log *msg;
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size_t i;
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size_t len;
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ssize_t ret;
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if (!user)
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return -EBADF;
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mutex_lock(&user->lock);
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raw_spin_lock(&logbuf_lock);
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while (user->seq == log_next_seq) {
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if (file->f_flags & O_NONBLOCK) {
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ret = -EAGAIN;
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raw_spin_unlock(&logbuf_lock);
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goto out;
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}
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raw_spin_unlock(&logbuf_lock);
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ret = wait_event_interruptible(log_wait,
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user->seq != log_next_seq);
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if (ret)
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goto out;
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raw_spin_lock(&logbuf_lock);
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}
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if (user->seq < log_first_seq) {
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/* our last seen message is gone, return error and reset */
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user->idx = log_first_idx;
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user->seq = log_first_seq;
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ret = -EPIPE;
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raw_spin_unlock(&logbuf_lock);
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goto out;
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}
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msg = log_from_idx(user->idx);
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len = sprintf(user->buf, "%u,%llu,%llu;",
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msg->level, user->seq, msg->ts_nsec / 1000);
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/* escape non-printable characters */
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for (i = 0; i < msg->text_len; i++) {
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char c = log_text(msg)[i];
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if (c < ' ' || c >= 128)
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len += sprintf(user->buf + len, "\\x%02x", c);
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else
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user->buf[len++] = c;
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}
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user->buf[len++] = '\n';
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if (msg->dict_len) {
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bool line = true;
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for (i = 0; i < msg->dict_len; i++) {
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char c = log_dict(msg)[i];
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if (line) {
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user->buf[len++] = ' ';
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line = false;
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}
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if (c == '\0') {
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user->buf[len++] = '\n';
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line = true;
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continue;
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}
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if (c < ' ' || c >= 128) {
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len += sprintf(user->buf + len, "\\x%02x", c);
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continue;
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}
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user->buf[len++] = c;
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}
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user->buf[len++] = '\n';
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}
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user->idx = log_next(user->idx);
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user->seq++;
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raw_spin_unlock(&logbuf_lock);
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if (len > count) {
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ret = -EINVAL;
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goto out;
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}
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if (copy_to_user(buf, user->buf, len)) {
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ret = -EFAULT;
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goto out;
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}
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ret = len;
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out:
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mutex_unlock(&user->lock);
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return ret;
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}
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static loff_t devkmsg_llseek(struct file *file, loff_t offset, int whence)
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{
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struct devkmsg_user *user = file->private_data;
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loff_t ret = 0;
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if (!user)
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return -EBADF;
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if (offset)
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return -ESPIPE;
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raw_spin_lock(&logbuf_lock);
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switch (whence) {
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case SEEK_SET:
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/* the first record */
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user->idx = log_first_idx;
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user->seq = log_first_seq;
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break;
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case SEEK_DATA:
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/*
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* The first record after the last SYSLOG_ACTION_CLEAR,
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* like issued by 'dmesg -c'. Reading /dev/kmsg itself
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* changes no global state, and does not clear anything.
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*/
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user->idx = clear_idx;
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user->seq = clear_seq;
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break;
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case SEEK_END:
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/* after the last record */
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user->idx = log_next_idx;
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user->seq = log_next_seq;
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break;
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default:
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ret = -EINVAL;
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}
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raw_spin_unlock(&logbuf_lock);
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return ret;
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}
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static unsigned int devkmsg_poll(struct file *file, poll_table *wait)
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{
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struct devkmsg_user *user = file->private_data;
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int ret = 0;
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if (!user)
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return POLLERR|POLLNVAL;
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poll_wait(file, &log_wait, wait);
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raw_spin_lock(&logbuf_lock);
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if (user->seq < log_next_seq) {
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/* return error when data has vanished underneath us */
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if (user->seq < log_first_seq)
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ret = POLLIN|POLLRDNORM|POLLERR|POLLPRI;
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ret = POLLIN|POLLRDNORM;
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}
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raw_spin_unlock(&logbuf_lock);
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return ret;
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}
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static int devkmsg_open(struct inode *inode, struct file *file)
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{
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struct devkmsg_user *user;
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int err;
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/* write-only does not need any file context */
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if ((file->f_flags & O_ACCMODE) == O_WRONLY)
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return 0;
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err = security_syslog(SYSLOG_ACTION_READ_ALL);
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if (err)
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return err;
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user = kmalloc(sizeof(struct devkmsg_user), GFP_KERNEL);
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if (!user)
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return -ENOMEM;
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mutex_init(&user->lock);
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raw_spin_lock(&logbuf_lock);
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user->idx = log_first_idx;
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user->seq = log_first_seq;
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raw_spin_unlock(&logbuf_lock);
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file->private_data = user;
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return 0;
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}
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static int devkmsg_release(struct inode *inode, struct file *file)
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{
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struct devkmsg_user *user = file->private_data;
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if (!user)
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return 0;
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mutex_destroy(&user->lock);
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kfree(user);
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return 0;
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}
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const struct file_operations kmsg_fops = {
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.open = devkmsg_open,
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.read = devkmsg_read,
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.aio_write = devkmsg_writev,
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.llseek = devkmsg_llseek,
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.poll = devkmsg_poll,
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.release = devkmsg_release,
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};
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#ifdef CONFIG_KEXEC
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/*
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* This appends the listed symbols to /proc/vmcoreinfo
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|
|
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