busybox/sysklogd/Config.src
Peter Korsgaard cd776cf967 syslogd: add option to log to Linux kernel printk buffer
Why invent our own shared memory circular buffer when the kernel has a
perfectly fine one already?

This can be used as a smaller/simpler alternative to the syslogd IPC support
(as IPC shmem/klogd/logread aren't needed), while also allowing centralised
logging of everything (kernel messages, userspace bootup and syslog)
when used together with ttyprintk.

Notice that kernel 3.5+ is needed to store syslog facility in printk buffer,
otherwise only the priority is stored.

bloat-o-meter compared to IPC+klogd+logread:
function                                             old     new   delta
get_linux_version_code                                 -      84     +84
lbb_prepare                                           25      90     +65
applet_nameofs                                         6       -      -6
static.stdout@@GLIBC_2                                 8       -      -8
applet_names                                          23       9     -14
bb_msg_standard_output                                16       -     -16
init_sem                                              18       -     -18
xatoull_range                                         19       -     -19
overlapping_strcpy                                    21       -     -21
init_data                                             56      32     -24
applet_main                                           24       -     -24
main                                                 124      99     -25
full_write2_str                                       26       -     -26
error_exit                                            26       -     -26
bb_basename                                           30       -     -30
sem_up                                                32       -     -32
interrupted                                           35       -     -35
fflush_stdout_and_exit                                38       -     -38
bb_banner                                             46       -     -46
find_applet_by_name                                   59       -     -59
bb_signals_recursive_norestart                        90       -     -90
run_applet_no_and_exit                               104       -    -104
timestamp_and_log                                    651     523    -128
syslogd_main                                         798     581    -217
xstrtoull_range_sfx                                  267       -    -267
run_applet_and_exit                                  432       -    -432
klogd_main                                           490       -    -490
logread_main                                         508       -    -508
.rodata                                             1870     937    -933
bb_common_bufsiz1                                   8193       -   -8193
------------------------------------------------------------------------------
(add/remove: 2/26 grow/shrink: 1/6 up/down: 149/-11829)    Total: -11680 bytes

Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>
Signed-off-by: Mike Frysinger <vapier@gentoo.org>
2013-01-06 13:30:50 -05:00

170 lines
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#
# For a description of the syntax of this configuration file,
# see scripts/kbuild/config-language.txt.
#
menu "System Logging Utilities"
INSERT
config SYSLOGD
bool "syslogd"
default y
help
The syslogd utility is used to record logs of all the
significant events that occur on a system. Every
message that is logged records the date and time of the
event, and will generally also record the name of the
application that generated the message. When used in
conjunction with klogd, messages from the Linux kernel
can also be recorded. This is terribly useful,
especially for finding what happened when something goes
wrong. And something almost always will go wrong if
you wait long enough....
config FEATURE_ROTATE_LOGFILE
bool "Rotate message files"
default y
depends on SYSLOGD
help
This enables syslogd to rotate the message files
on his own. No need to use an external rotatescript.
config FEATURE_REMOTE_LOG
bool "Remote Log support"
default y
depends on SYSLOGD
help
When you enable this feature, the syslogd utility can
be used to send system log messages to another system
connected via a network. This allows the remote
machine to log all the system messages, which can be
terribly useful for reducing the number of serial
cables you use. It can also be a very good security
measure to prevent system logs from being tampered with
by an intruder.
config FEATURE_SYSLOGD_DUP
bool "Support -D (drop dups) option"
default y
depends on SYSLOGD
help
Option -D instructs syslogd to drop consecutive messages
which are totally the same.
config FEATURE_SYSLOGD_CFG
bool "Support syslog.conf"
default y
depends on SYSLOGD
help
Supports restricted syslogd config. See docs/syslog.conf.txt
config FEATURE_SYSLOGD_READ_BUFFER_SIZE
int "Read buffer size in bytes"
default 256
range 256 20000
depends on SYSLOGD
help
This option sets the size of the syslog read buffer.
Actual memory usage increases around five times the
change done here.
config FEATURE_IPC_SYSLOG
bool "Circular Buffer support"
default y
depends on SYSLOGD
help
When you enable this feature, the syslogd utility will
use a circular buffer to record system log messages.
When the buffer is filled it will continue to overwrite
the oldest messages. This can be very useful for
systems with little or no permanent storage, since
otherwise system logs can eventually fill up your
entire filesystem, which may cause your system to
break badly.
config FEATURE_IPC_SYSLOG_BUFFER_SIZE
int "Circular buffer size in Kbytes (minimum 4KB)"
default 16
range 4 2147483647
depends on FEATURE_IPC_SYSLOG
help
This option sets the size of the circular buffer
used to record system log messages.
config LOGREAD
bool "logread"
default y
depends on FEATURE_IPC_SYSLOG
help
If you enabled Circular Buffer support, you almost
certainly want to enable this feature as well. This
utility will allow you to read the messages that are
stored in the syslogd circular buffer.
config FEATURE_LOGREAD_REDUCED_LOCKING
bool "Double buffering"
default y
depends on LOGREAD
help
'logread' ouput to slow serial terminals can have
side effects on syslog because of the semaphore.
This option make logread to double buffer copy
from circular buffer, minimizing semaphore
contention at some minor memory expense.
config FEATURE_KMSG_SYSLOG
bool "Linux kernel printk buffer support"
default y
depends on SYSLOGD
select PLATFORM_LINUX
help
When you enable this feature, the syslogd utility will
write system log message to the Linux kernel's printk buffer.
This can be used as a smaller alternative to the syslogd IPC
support, as klogd and logread aren't needed.
NOTICE: Syslog facilities in log entries needs kernel 3.5+.
config KLOGD
bool "klogd"
default y
help
klogd is a utility which intercepts and logs all
messages from the Linux kernel and sends the messages
out to the 'syslogd' utility so they can be logged. If
you wish to record the messages produced by the kernel,
you should enable this option.
comment "klogd should not be used together with syslog to kernel printk buffer"
depends on KLOGD && FEATURE_KMSG_SYSLOG
config FEATURE_KLOGD_KLOGCTL
bool "Use the klogctl() interface"
default y
depends on KLOGD
select PLATFORM_LINUX
help
The klogd applet supports two interfaces for reading
kernel messages. Linux provides the klogctl() interface
which allows reading messages from the kernel ring buffer
independently from the file system.
If you answer 'N' here, klogd will use the more portable
approach of reading them from /proc or a device node.
However, this method requires the file to be available.
If in doubt, say 'Y'.
config LOGGER
bool "logger"
default y
select FEATURE_SYSLOG
help
The logger utility allows you to send arbitrary text
messages to the system log (i.e. the 'syslogd' utility) so
they can be logged. This is generally used to help locate
problems that occur within programs and scripts.
endmenu