On my Linux machine when i run
uname -v
it gives me
#83-Ubuntu SMP Wed Jan 4 11:12:07 UTC 2012
Now i am building my custom kernel and i need to show some flag/text info about build in this string ..
i want something like
if some config are on then add BUILD-XYZ in that string
#83-Ubuntu SMP Wed Jan 4 11:12:07 UTC 2012 BUILD-XYZ
if not then add BUILD-ABC in that.
#83-Ubuntu SMP Wed Jan 4 11:12:07 UTC 2012 BUILD-ABC
The variable CONFIG_LOCALVERSION (inside your kernel .config file) let you set a custom string that will be appended to the kernel release number, thus shown when using 'uname'.
Is that what you want?
There's a few ways to do this using GNU awk, here's one:
uname -v | awk '{ printf (/some config/) ? $0" BUILD-XYZ\n" : $0" BUILD-ABC\n" }'
Related
I have some kernel module which prints to log like
printk(KERN_INFO "Something\n");
When module was loaded I found that the time in dmesg outruns the current time in date:
-bash-4.4$ dmesg -T | grep some_driver
[Sat May 16 22:25:03 2020] some_driver: Something
-bash-4.4$ date
Sat May 16 22:22:02 UTC 2020
What could be the reason?
P.S. Linux kernel version is 4.4, it lives in VMware vSphere VM.
I'm trying to compile the same lib on two x86 separate machines.
Both use the same toolchain (exactly same set of files) but have different Glibc versions.
When I run command LD_DEBUG=libs /lib64/ld-linux-x86-64.so.2 --list ./libl2ps.so I notice the following discrepancy between the 2 Linux loaders:
Machine 1 (with Glibc 2.12):
19943: find library=libm.so.6 [0]; searching
19943: search path=/ebs/frperies/repo/gnb/uplane/build/prefix-root/asik-x86_64-ps_lfs-dynamic-linker-on/toolchain/sysroots/core2-64-pc-linux-gnu/usr/lib64:...:/ebs/frperies/repo/gnb/uplane/build_bbp/l2_ps/build/. (RPATH from file ./libl2ps.so)
19943: trying file=/ebs/frperies/repo/gnb/uplane/build/prefix-root/asik-x86_64-ps_lfs-dynamic-linker-on/toolchain/sysroots/core2-64-pc-linux-gnu/usr/lib64/libm.so.6
19943:
19943: find library=libgcc_s.so.1 [0]; searching
...
In this case the Linux loader selects lib libm.so.6 from the toolchain path based on RPATH of lib libl2ps.so.
Machine 2 (with Glibc 2.17):
10699: find library=libm.so.6 [0]; searching
10699: search path=/home/frperies/repo/gnb/uplane/build/prefix-root/asik-x86_64-ps_lfs-dynamic-linker-on/toolchain/sysroots/core2-64-pc-linux-gnu/usr/lib64:/home/frperies/repo/gnb/uplane/build/prefix-root/asik-x86_64-ps_lfs-dynamic-linker-on/toolchain/sysroots/core2-64-pc-linux-gnu/lib64:/home/frperies/repo/gnb/uplane/build/prefix-root/asik-x86_64-ps_lfs-dynamic-linker-on/toolchain/sysroots/core2-64-pc-linux-gnu/usr/lib:/home/frperies/repo/gnb/uplane/build_bbp/l2_ps/build/. (RPATH from file ./libl2ps.so)
10699: trying file=/home/frperies/repo/gnb/uplane/build/prefix-root/asik-x86_64-ps_lfs-dynamic-linker-on/toolchain/sysroots/core2-64-pc-linux-gnu/usr/lib64/libm.so.6
10699: trying file=/home/frperies/repo/gnb/uplane/build/prefix-root/asik-x86_64-ps_lfs-dynamic-linker-on/toolchain/sysroots/core2-64-pc-linux-gnu/lib64/libm.so.6
10699: trying file=/home/frperies/repo/gnb/uplane/build/prefix-root/asik-x86_64-ps_lfs-dynamic-linker-on/toolchain/sysroots/core2-64-pc-linux-gnu/usr/lib/libm.so.6
10699: trying file=/home/frperies/repo/gnb/uplane/build_bbp/l2_ps/build/./libm.so.6
10699: search cache=/etc/ld.so.cache
10699: trying file=/lib64/libm.so.6
As for Machine 1, the loader attempts from RPATH of libl2ps.so to select lib libm.so.6 from toolchain path but skip it for some reason and try further other paths. Finally it selects libm.so.6from the system path /lib64/.
The RPATH of the 2 libs lib2ps.so are exactly the same. The two files libm.so.6 are also exactly the same on both machines (checked with md5sum).
I don't understand this differences of behavior between the 2 Linux loaders.
Do you see any reason what would explain this discrepancy ?
Thank you very much for your answers.
Update:
Thank you yugr for your answer.
Output of readelf -h gives only differences on fields "Entry point address" and "Start of section headers" and there is no other differences so I think it will not help.
Regarding using dlopen()/dlerror(), I've done a little executable with the following statement:
dlopen("/home/frperies/repo/gnb/uplane/build/prefix-root/asik-x86_64-ps_lfs-dynamic-linker-on/toolchain/sysroots/core2-64-pc-linux-gnu/usr/lib64/libm-2.28.so", RTLD_LAZY);
On machine 1 it works as expected:
C++ dlopen demo
Opening libm-2.28.so...
Closing library...
On machine 2 it fails and dlerror() gives the following output:
Cannot open library: /home/frperies/repo/gnb/uplane/build/prefix-root/asik-x86_64-ps_lfs-dynamic-linker-on/toolchain/sysroots/core2-64-pc-linux-gnu/usr/lib64/libm-2.28.so: cannot open shared object file: No such file or directory
but the file libm-2-28.so really exists on my file system:
$ ls -l /home/frperies/repo/gnb/uplane/build/prefix-root/asik-x86_64-ps_lfs-dynamic-linker-on/toolchain/sysroots/core2-64-pc-linux-gnu/usr/lib64/libm-2.28.so
-rwxr-xr-x 1 frperies linseeusers_lte_espoo 1682944 Oct 5 13:50 /home/frperies/repo/gnb/uplane/build/prefix-root/asik-x86_64-ps_lfs-dynamic- linker-on/toolchain/sysroots/core2-64-pc-linux-gnu/usr/lib64/libm-2.28.so
This is very weird, what could lead to this situation ???
Thanks
Update 2:
That is true that I haven't pointed out that machine 1 is a RHEL6.8 distro while machine 2 is RHEL7.4 distro. I (naively?) didn't think this really matters...
On machine 1:
$ cat /proc/sys/kernel/osrelease
4.4.115-1.NSN.el6.x86_64
$ uname -a
Linux sq24-3 4.4.115-1.NSN.el6.x86_64 #1 SMP Mon Feb 12 12:35:46 CET 2018 x86_64 x86_64 x86_64 GNU/Linux
$ readelf -n libl2ps.so
Notes at offset 0x00000270 with length 0x00000024:
Owner Data size Description
GNU 0x00000014 NT_GNU_BUILD_ID (unique build ID bitstring)
Build ID: b598468830fdf2f61eda25553b9a367c4d28cdc9
On machine 2:
$ cat /proc/sys/kernel/osrelease
3.10.0-693.el7.x86_64
$ uname -a
Linux localhost.localdomain 3.10.0-693.el7.x86_64 #1 SMP Thu Jul 6 19:56:57 EDT 2017 x86_64 x86_64 x86_64 GNU/Linux
$ readelf -n libl2ps.so
Displaying notes found at file offset 0x00000270 with length 0x00000024:
Owner Data size Description
GNU 0x00000014 NT_GNU_BUILD_ID (unique build ID bitstring)
Build ID: 5829181bc0502233748149369108915ea7b10e8f
Does it help ?
Thanks
Update 3:
$ readelf -n libm.so.6
Notes at offset 0x00000238 with length 0x00000024:
Owner Data size Description
GNU 0x00000014 NT_GNU_BUILD_ID (unique build ID bitstring)
Build ID: 0d84c7247dd76008c096719043e5592735a1c4bd
Notes at offset 0x0000025c with length 0x00000020:
Owner Data size Description
GNU 0x00000010 NT_GNU_ABI_TAG (ABI version tag)
OS: Linux, ABI: 4.4.0
So, how to interpret this ABI version number set to 4.4.0 ??
Thanks
Thank you yugr and Employed Russian for your answers!!
I will give it a try by upgrading my Kernel version on Machine 2.
Thanks
Regards
The error message that you see is the infamously confusing ENOENT errno. I see two instances of it in dl-load.c:
checking OS compatibility
loading non-setuid to setuid process
I suspect the first one fails in your case which would mean that OS kernel is incompatible between two machines. ld.so manpage indeed says that
Each shared object can inform the dynamic linker of the
minimum kernel ABI version that it requires. (This
requirement is encoded in an ELF note section that is viewable
via readelf -n as a section labeled NT_GNU_ABI_TAG.) At run
time, the dynamic linker determines the ABI version of the
running kernel and will reject loading shared objects that
specify minimum ABI versions that exceed that ABI version.
NT_GNU_ABI_TAG is 4.4.0 which means that you run a program expecting a minimum 4.4 kernel on a 3.10 kernel. Theoretically newer Glibc should run on older kernels as well but in your case Glibc was probly built with explicit --enable-kernel flag which prevents it's usage on kernels before 4.4 (see e.g. this explanation of --enable-kernel).
As a workaround, you may try to fool Glibc by overriding kernel version on machine 2 via
export LD_ASSUME_KERNEL=4.4.0
but it may not work if libm makes 4.4-specific syscalls that are not really present on 3.10.
Background
$ uname -a
CYGWIN_NT-6.1 Owner-PC 1.7.34(0.285/5/3) 2015-02-04 12:14 x86_64 Cygwin
PS: just updated Cygwin 15 days ago. Should be razor close to current.
$ date --version
date (GNU coreutils) 8.23
Packaged by Cygwin (8.23-4)
Copyright (C) 2014 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>.
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.
Written by David MacKenzie.
Extracted from man date page on cygwin:
%c locale's date and time (e.g., Thu Mar 3 23:05:25 2005)
output from C runtime (dtime is tiny piece of code):
$ ./dtime -f "%c"
Tue Feb 5 17:04:45 2030
Looks good to me...
To avert questions like: what does the code look like:
strcpy(p->fmt, "%c");
....
strftime(tmp, 80, p->fmt, localtime(<));
printf("%s\n", tmp);
dtime and other time routines I wrote in the C library behave as expected per standards. No problem.
On the other hand the date command is not correct AFAICT:
Owner#Owner-PC ~
$ date
Sun, Feb 22, 2015 11:41:44 AM
Owner#Owner-PC ~
$ date +%c
Sun, Feb 22, 2015 11:41:55 AM
The second line of output does not match the man page - or standards, I believe.
Question:
A bug? Something else I am missing?
Edit: per suggestion quote the format string. No. That is only need if there are white spaces in the format
Owner#Owner-PC ~
$ date '+%c'
Sun, Feb 22, 2015 3:13:51 PM
This seems related to the locale settings. Your C program uses the C locale by default, date will behave according to the environment variables LANG, LC_TIME and LC_ALL. What are the values of these variables ? Can you test this:
LC_ALL="C" date '+%c'
Ages ago, I remember there was a command-line Unix program that
would print out major holidays in the USA. With command-line
options, it could print out Islamic, Discordian, and even Canadian
holidays.
I can't seem to find this program now. The closest I can get is
emacs' "list-holidays" function. It's possible the program I
remember just called an emacs function from the command line or
something.
EDIT: In addition to 'calendar', 'gcal' will do this too.
Are you looking for calendar?
This will show all the upcoming holidays.
$ calendar
Jul 26 Bilbo rescued from Wargs by Eagles
Jul 26 Independence Day in Liberia
Jul 26 National Day in Maldives
This shows all US bank holidays upcoming in the next +1 days.
$ calendar -f /usr/share/calendar/calendar.usholiday -W +1
Nov 11 Veterans' Day
This package is maintained by the BSD community and can be installed in debian and ubuntu from bsdmainutils.
For some reason i am not able to attach to my very own processes?! Works fine if i try strace as root.
$ ./list8 &
[1] 3141
$ child4 starts...
$ strace -p 3141
attach: ptrace(PTRACE_ATTACH, ...): Operation not permitted
Could not attach to process. If your uid matches the uid of the target
process, check the setting of /proc/sys/kernel/yama/ptrace_scope, or try
again as the root user. For more details, see /etc/sysctl.d/10-ptrace.conf
$ cat /proc/sys/kernel/yama/ptrace_scope
1
Running on lubuntu 13.10
Linux goal 3.8.0-19-generic #29-Ubuntu SMP Wed Apr 17 18:19:42 UTC 2013 i686 i686 i686 GNU/Linux
So then how does gdb attach to user's own processes without having to muck around with kernel settings (ptrace_scope)??
Looks like you answered your own question -- you have ptrace_scope set to 1, so you can only trace direct children. To allow tracing any process belonging to the same user, set it to 0. This is also required to use the gdb attach command.
READ the /etc/sysctl.d/10-ptrace.conf file as your error message suggested...
If strace fails as root, try checking whether... gdb or strace is not running in the background (that was my case).
Command: ps aux | grep "gdb\|strace"
If this fails as root, I had a problem stracing enlightenment (e17) and the reason was that you can't strace a process already being straced or run under gdb, which some programs will do so that they can get their own debugging info.