android log.

I'm not sure I understand.  Do you want to use the existing 'logcat' 
program to save the logs, or do you want to write a new program 
that saves logs, while preserving the ability of 'logcat' to also 
show android logs from the command line? 

The loglevel specified in init.rc only affects the logging emitted by 
'init'.  It doesn't affect the logging of any of the rest of the system. 
That is, various parts of the init program issue log messages, with 
log levels, when the program does certain actions.  The init.rc loglevel 
controls which of these will actually be written to the log by the 
'init' program. 

Does 3) mean you want to control what log messages are saved in your 
persistent log file (in the file system)?  Or are you trying to 
control what messages are saved into the kernel log buffers to 
begin with? 

There's a writeup of the logging system, with a nice diagram, at: 
http://elinux.org/Android_Logging_System 

Note that the android logging system is completely separate from 
the Linux kernel log system (which uses printk inside the kernel 
to save messages and dmesg to extract them).   You can write to 
the kernel log from user space by writing to /dev/kmsg. 

I've seen a reference to couple the two together, to redirect 
android messages into the kernel log buffer, using the 'logcat' 
program launched from init, like below: 

service logcat /system/bin/logcat -f /dev/kmsg 
       oneshot 

(See http://groups.google.com/group/android-kernel/browse_thread/thread/87...) 

However, this seems really wasteful of space (and time), since it 
basically buffers each log message twice.  Also, for your intended use 
(saving messages to a file), this re-logging of messages into the kernel 
log buffer seems orthogonal. 

 

 

adb dmesg 

 

cat /proc/kmsg

 

$adb shell dmesg 

 

echo 7 > /proc/sys/kernel/printk

 

Well, it isn't very hard to debug the kernel in the emulator. 
Configure the kernel by hand to include debugging symbols: 
cd kernel 
make menuconfig 
Select Kernel hacking or whatever it is called and select the item 
which says to compile the kernel with debugging info. 
make 
cd .. 
When starting the emulator use sth like: (but change the openbsd refs 
to linux) 
out/host/openbsd-x86_64/bin/emulator -show-kernel -system out/target/ 
product/generic -kernel kernel/arch/arm/boot/zImage  -logcat *:v -qemu 
-monitor telnet::4444,server -s 
then it will sit waiting for you to prepare your gdb session: 
prebuilt/openbsd-x86_64/toolchain/arm-eabi-4.2.1/bin/arm-eabi-gdb 
kernel/vmlinux 
(gdb) br sys_execve   (or some other place you want to gain control) 
(gdb) target remote localhost:1234 
and then, in another window, release qemu by attaching to its monitor: 
telnet localhost 4444 
(qemu) cont 

well it's somewhat from memory, but I suspect, the info given will 
work with perhaps a few modifications... 
I just hope that you are hunting for easier bugs than I am... :-) 

Good luck 

On Nov 29, 5:47 am, allstars <[e-mail]> wrote: 

 

 

I do it all the time. 

Here's a paste of how I start the emulator.  If this does no work you 
are basing it of a different tree than I (do you use cupcake? maybe it's 
changed there?) 

/home/projects/android/mydroid/out/host/openbsd-x86_64/bin/emulator 
-system out/target/product/generic -kernel kernel/arch/arm/boot/zImage 
-show-kernel -logcat *:v -qemu -monitor telnet::4444,server -s 

After this the emulator should start waiting for a telnet connection to 
port 4444.  Then I do: 

telnet localhost 4444 

and issue the "stop" command immediately.  Right after the connect to 
4444, the kernel should start listening on port 1234 for an ARM gdb to 
attach to. 

Niklas 

 

 

printk's output goes to several places:

1. The system console (default is the currently active text mode VT).
2. It gets sent to /proc/kmsg.

/proc/kmsg is a binary interface for retrieving kernel messages and setting kernel logging settings. Normally, the only process using it is klogd, which captures all kernel log messages and passes them on to syslogd. syslogd then multiplexes them to a couple of files, depending on what is configured in /etc/syslog.conf. Normally, messages of the DEBUG priority are discarded, so if you're logging with printk(KERN_DEBUG "..."), syslogd will discard them.

See the syslog(3) and syslogd(8) and syslog.conf(5) manpages for more info on syslogging. I normally add these lines to my /etc/syslog.conf on a new system, in order to be able to see all log messages easily:

Code:

*.* /dev/tty12*.* /var/log/all

Also, there's an ioctl that you can use to redirect the system console output to another terminal -- you open a terminal and run this ioctl with no parameters on it, and the console output will get there. See tty_ioctl(4) for more info. The only program I know of right now that can do this is screen. Run the command C-a : console RET in screen to make it display the console output. I believe, although I'm not sure, that it will not show debug message, however. The best option may be to make syslogd redirect the output where you want it. Remember "tail -f".

 

 

hi guys, 
I am creating a driver under MontaVista Linux. I want the module 
to log its messages to a specific file. I tried editting the 
/etc/syslog.conf file. I was able to redirect all the KERN_ERR kernel 
messages (including other error messages) to a specific file instead 
of logging them to /var/log/messages. However, I have no idea how to 
edit the syslog.conf file to log only the messages generated by my 
driver to a specific file. I want to create my own directory in the 
/var/log directory where I can store the different message levels of 
my driver. Is this possible? Can somebody teach me how? Thank you 
so much! 

 

 

 

http://www.ibm.com/developerworks/linux/library/l-kernel-logging-apis/?ca=drs-

 

 

http://www.onlinehowto.net/Tutorials/System/Enable-kernel-logging/1480

 

 

告诉你两种方法吧，其实本质是一样的。

前提是adb shell能成功。

1.
./adb shell
#cd /data/anr
#cat /proc/kmsg kernel.txt
这时kernel.txt放在emulator中的/data/anr下。
2.
./adb shell cat /proc/kmsg > kernel.txt
这时kernel.txt放在adb所在的目录下。

 

直接运行dmesg