May 2011 - kernelnewbies@kernelnewbies.org - Kernelnewbies Mailing Lists

UDP socket not receiving full data.
by Prabhu nath May 20, 2011

May 20, 2011

Dear All, I have connected two machines A <---> B. B is sending 35 packets (packet size = 1042 bytes) of data to A over UDP socket. But, the application A is receiving only 12 packets. TCPDUMP on machine A is showing all the packets received on machine A. I suspect the erroneous buffer handling in TCP/IP stack. Can anyone please let me know the function which is responsible to transfer data from the kernel space to user space, the function which does copy_to_user() kind of stuff. Or any hint on the control path of data from the driver to the application will be helpful. Thanks, Prabhu

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first downtown ottawa linux kernel geek-up, next tuesday, may 24
by Robert P. J. Day May 20, 2011

May 20, 2011

http://crashcourse.ca/blog/201105/inaugural-downtown-ottawa-linux-geek-tues… rday -- ======================================================================== Robert P. J. Day Ottawa, Ontario, CANADA http://crashcourse.ca Twitter: http://twitter.com/rpjday LinkedIn: http://ca.linkedin.com/in/rpjday ========================================================================

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Re: LSM skeleton module printk message not showing in dmesg
by toqeer ali May 20, 2011

May 20, 2011

Hi Mosta, I am using klogd and its running and also at boot time. I also search my printk message in these files /var/log/kern.log /var/log/boot, /var/log/dmesg, /var/log/messages, but no luck, anything else i need to look for? Regards On Fri, May 20, 2011 at 2:51 PM, mosta <mosta.me(a)googlemail.com> wrote: > This depends on your kernel logger. Do you use klogd/ sysklogd or > another one? > > On 05/20/11 08:40, toqeer ali wrote: > > Hi Mosta, > > > > Thanks for the prompt reply, I added the same printk message in the > > other kernel files like here /usr/src/linux-2.6.33.3/init/calibrate.c > > > > int lps_precision = LPS_PREC; > > printk("*** Just testing prinkt to work ***\n"); > > static bool printed; > > > > and recompiled the kernel and its showing in the dmesg. Is this means > > kernel logger is fine? > > > > also can please verify the steps i made to make lsm module just for > > pirnkt message. > > > > Regards > > > > On Fri, May 20, 2011 at 1:56 PM, mosta <mosta.me > > <http://mosta.me>@googlemail.com <http://googlemail.com>> wrote: > > > > you have to check at what level you're kernel logger is and set it to > > the according level. > > > > > > greetings mosta > > > > On 05/20/11 06:29, toqeer ali wrote: > > > Hi All, > > > > > > > > > I am writing a skeleton LSM module to only print the message at > boot > > > time, but I could not see any printk message in the dmesg. > > > > > > Below are steps i did to enable the printk messages in the LSM > > module. > > > > > > What i did is download linux kernel 2.6.33.3. > > > > > > 1) added the line source security/lsmcustommod/Kconfig in > > > linuxsrc/security/Kconfig near ima/Kconfig. > > > 2) added "subdir-$(CONFIG_SECURITY_LSMCUSTOMMOD) += > > > lsmcustommod" line at linuxsrc/security/Makefile > > > 3) created a directory in linuxsrc/security/lsmcustommod and putted > > > three files > > > > > > i) lsmcustommod.c > > > ii) Kconfig > > > iii) Makefile > > > > > > *Kconfig file contents* > > > > > > config SECURITY_LSMCUSTOMMOD > > > bool "LSMCUSTOMMOD Support" > > > depends on SECURITY > > > select NETWORK_SECMARK > > > default n > > > help > > > > > > *Makefile Contents* > > > > > > obj-$(CONFIG_SECURITY_LSMCUSTOMMOD) := lsmcustommod.o > > > > > > *lsmcustommod.c* contents > > > > > > static __init lsmcustommod_init(void){ > > > /* register the hooks */ > > > > > > if (register_security(&lsmcustommod_ops)) > > > panic("lsmcustommod: Unable to register > lsmcustommod > > > with kernel.\n"); > > > else > > > printk("lsmcustommod: registered with the > > kernel\n"); > > > > > > return 0; > > > } > > > > > > static void __exit lsmcustommod_exit (void) > > > { > > > return; > > > } > > > > > > > > > > > > module_init (lsmcustommod_init); > > > module_exit (lsmcustommod_exit); > > > > > > MODULE_DESCRIPTION("lsmcustommod"); > > > MODULE_LICENSE("GPL"); > > > #endif /* CONFIG_SECURITY_LSMCUSTOMMOD */ > > > > > > > > > > > > After that I also added some return 0 and printk statments in the > > > lsmcustommod_ops stucture. > > > > > > lastly disabled all modules in make menuconfig and select > > LSMCUTOMMOD > > > in security sections of the menufile and compile the kernel by the > > > following command. > > > > > > make && make modules && make modules_install && make install > > > updategrub2 > > > > > > > > > -- > > > Toqeer Ali Syed > > > > > > Red Hat Certified Engineer > > > > > > mob: +60166205504 <tel:%2B60166205504> <tel:%2B60166205504> > > > mob: +92 321 9059916 <tel:%2B92%20321%209059916> > > <tel:%2B92%20321%209059916> > > > > > > > > > _______________________________________________ > > > Kernelnewbies mailing list > > > Kernelnewbies(a)kernelnewbies.org > > <mailto:Kernelnewbies@kernelnewbies.org> > > > http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies > > > > > > > > > > -- > > Toqeer Ali Syed > > > > Red Hat Certified Engineer > > > > mob: +60166205504 > > mob: +92 321 9059916 > > -- Toqeer Ali Syed Red Hat Certified Engineer mob: +60166205504 mob: +92 321 9059916

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Putting artificial delays in a char driver
by Mandeep Sandhu May 20, 2011

May 20, 2011

Hi All, I was fiddling around with an IR remote driver for my embedded platform to see if I can make the IR LED light (connected to GPIO's) blink on IR activity. The IR driver behaves like a char driver. The way to make the LED on/off is to simply write to some GPIO reg with a 1/0. So I was switching on the LED at the beginning of the function that reads data (in ISR context) and then switching it off at the end of that function. The problem was that all this happens too fats and I'm barely able to see the LED blink (there's only a faint flicker)! :) I tired various places in the driver to keep on/off calls as "far" as possible (ON in ISR and then OFF _after_ a copy_to_user()), but that did not help much. Whats the recommended way of solving this issue? I'm working on drivers after a really long time (last time I worked on a driver was when LDD 2nd ed was published!) so I'm not sure if bottom-halves or work-queues should be used. I was thinking what if I introduce an artificial delay in my driver where I "sleep/wait" for a few millsecs after switching on the LED and then switch it off after the incoming data has been processed. Is that a good idea? TIA, -mandeep

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Re: LSM skeleton module printk message not showing in dmesg
by toqeer ali May 20, 2011

May 20, 2011

Hi Mosta, Thanks for the prompt reply, I added the same printk message in the other kernel files like here /usr/src/linux-2.6.33.3/init/calibrate.c int lps_precision = LPS_PREC; printk("*** Just testing prinkt to work ***\n"); static bool printed; and recompiled the kernel and its showing in the dmesg. Is this means kernel logger is fine? also can please verify the steps i made to make lsm module just for pirnkt message. Regards On Fri, May 20, 2011 at 1:56 PM, mosta <mosta.me(a)googlemail.com> wrote: > you have to check at what level you're kernel logger is and set it to > the according level. > > > greetings mosta > > On 05/20/11 06:29, toqeer ali wrote: > > Hi All, > > > > > > I am writing a skeleton LSM module to only print the message at boot > > time, but I could not see any printk message in the dmesg. > > > > Below are steps i did to enable the printk messages in the LSM module. > > > > What i did is download linux kernel 2.6.33.3. > > > > 1) added the line source security/lsmcustommod/Kconfig in > > linuxsrc/security/Kconfig near ima/Kconfig. > > 2) added "subdir-$(CONFIG_SECURITY_LSMCUSTOMMOD) += > > lsmcustommod" line at linuxsrc/security/Makefile > > 3) created a directory in linuxsrc/security/lsmcustommod and putted > > three files > > > > i) lsmcustommod.c > > ii) Kconfig > > iii) Makefile > > > > *Kconfig file contents* > > > > config SECURITY_LSMCUSTOMMOD > > bool "LSMCUSTOMMOD Support" > > depends on SECURITY > > select NETWORK_SECMARK > > default n > > help > > > > *Makefile Contents* > > > > obj-$(CONFIG_SECURITY_LSMCUSTOMMOD) := lsmcustommod.o > > > > *lsmcustommod.c* contents > > > > static __init lsmcustommod_init(void){ > > /* register the hooks */ > > > > if (register_security(&lsmcustommod_ops)) > > panic("lsmcustommod: Unable to register lsmcustommod > > with kernel.\n"); > > else > > printk("lsmcustommod: registered with the kernel\n"); > > > > return 0; > > } > > > > static void __exit lsmcustommod_exit (void) > > { > > return; > > } > > > > > > > > module_init (lsmcustommod_init); > > module_exit (lsmcustommod_exit); > > > > MODULE_DESCRIPTION("lsmcustommod"); > > MODULE_LICENSE("GPL"); > > #endif /* CONFIG_SECURITY_LSMCUSTOMMOD */ > > > > > > > > After that I also added some return 0 and printk statments in the > > lsmcustommod_ops stucture. > > > > lastly disabled all modules in make menuconfig and select LSMCUTOMMOD > > in security sections of the menufile and compile the kernel by the > > following command. > > > > make && make modules && make modules_install && make install > > updategrub2 > > > > > > -- > > Toqeer Ali Syed > > > > Red Hat Certified Engineer > > > > mob: +60166205504 <tel:%2B60166205504> > > mob: +92 321 9059916 <tel:%2B92%20321%209059916> > > > > > > _______________________________________________ > > Kernelnewbies mailing list > > Kernelnewbies(a)kernelnewbies.org > > http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies > > -- Toqeer Ali Syed Red Hat Certified Engineer mob: +60166205504 mob: +92 321 9059916

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LSM skeleton module printk message not showing in dmesg
by toqeer ali May 20, 2011

May 20, 2011

Hi All, I am writing a skeleton LSM module to only print the message at boot time, but I could not see any printk message in the dmesg. Below are steps i did to enable the printk messages in the LSM module. What i did is download linux kernel 2.6.33.3. 1) added the line source security/lsmcustommod/Kconfig in linuxsrc/security/Kconfig near ima/Kconfig. 2) added "subdir-$(CONFIG_SECURITY_LSMCUSTOMMOD) += lsmcustommod" line at linuxsrc/security/Makefile 3) created a directory in linuxsrc/security/lsmcustommod and putted three files i) lsmcustommod.c ii) Kconfig iii) Makefile *Kconfig file contents* config SECURITY_LSMCUSTOMMOD bool "LSMCUSTOMMOD Support" depends on SECURITY select NETWORK_SECMARK default n help *Makefile Contents* obj-$(CONFIG_SECURITY_LSMCUSTOMMOD) := lsmcustommod.o *lsmcustommod.c* contents static __init lsmcustommod_init(void){ /* register the hooks */ if (register_security(&lsmcustommod_ops)) panic("lsmcustommod: Unable to register lsmcustommod with kernel.\n"); else printk("lsmcustommod: registered with the kernel\n"); return 0; } static void __exit lsmcustommod_exit (void) { return; } module_init (lsmcustommod_init); module_exit (lsmcustommod_exit); MODULE_DESCRIPTION("lsmcustommod"); MODULE_LICENSE("GPL"); #endif /* CONFIG_SECURITY_LSMCUSTOMMOD */ After that I also added some return 0 and printk statments in the lsmcustommod_ops stucture. lastly disabled all modules in make menuconfig and select LSMCUTOMMOD in security sections of the menufile and compile the kernel by the following command. make && make modules && make modules_install && make install updategrub2 -- Toqeer Ali Syed Red Hat Certified Engineer mob: +60166205504 mob: +92 321 9059916

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Re: [Kgdb-bugreport] KGDB problem at first breakpoint
by Prabhu nath May 20, 2011

May 20, 2011

Enabling CONFIG_DEBUG_RODATA also didn't work. -Prabhu On Thu, May 19, 2011 at 6:45 AM, Dongdong Deng <libfetion(a)gmail.com> wrote: > On Wed, May 18, 2011 at 7:23 PM, Prabhu nath <gprabhunath(a)gmail.com> > wrote: > > Dear All, > > > > There is a problem with the KGDB at the very first break point > after > > executing the gdb command "target remote /dev/ttyS0" from the host. > > I have verbatim, followed the KGDB document > > http://kernel.org/pub/linux/kernel/people/jwessel/kdb/ > > > > Problem Logs: > > --------------------- > > > > Details of my hardware and system software: > > ------------------------------------------------------------------- > > > > *Host (Development machine): * > > Intel Pentium IV Machine with Fedora Core 12 > > Linux Version : 2.6.31.5-127.fc12.i686.PAE > > gdb version : GNU gdb (GDB) Fedora (7.0-3.fc12) > > > > *Target:* > > Intel Pentium IV Machine with Fedora Core 12 > > Customized Linux Version : 2.6.38 > > > > Host is connected to Target via a null modem cable > > > > *Snapshot of .config of linux version 2.6.38 on the target * > > * > > * > > # CONFIG_DEBUG_RODATA is not set > > > Hi Prabhu, > > The CONFIG_DEBUG_RODATA was suggested to set at KGDB, > Could you enable it? > > CONFIG_DEBUG_RODATA = y > > Dongdong > > > > > > > CONFIG_HAVE_ARCH_KGDB=y > > CONFIG_FRAME_POINTER=y > > CONFIG_DEBUG_INFO=y > > CONFIG_KGDB=y > > CONFIG_KGDB_SERIAL_CONSOLE=y > > CONFIG_KGDB_LOW_LEVEL_TRAP=y > > > > *Grub config on the target machine* > > * > > * > > title Fedora (2.6.38) > > root (hd0,0) > > kernel /boot/vmlinuz-2.6.38 ro > > root=UUID=fb7800fb-cfe7-438d-bc7f-c153ba4353d1 LANG=en_US.UTF-8 > > SYSFONT=latarcyrheb-sun16 KEYBOARDTYPE=pc > KEYTABLE=us*console=ttyS0,115200n8 > > kgdboc=ttyS0 kgdbwai*t > > initrd /boot/initrd-2.6.38.img > > > > > > On power on of the target, linux kernel boots and the logs are seen on > the > > minicom console of the host and it will wait for the gdb on the host to > > connect. Here is the last 4 lines of the logs seen on the minicom > > > > Serial: 8250/16550 driver, 4 ports, IRQ sharing disabled > > serial8250: ttyS0 at I/O 0x3f8 (irq = 4) is a 16550A > > 00:06: ttyS0 at I/O 0x3f8 (irq = 4) is a 16550A > > kgdb: Registered I/O driver kgdboc. > > kgdb: Waiting for connection from remote gdb.. > > > > *--- Now I close the minicom console (Ctrl-A X) and start the gdb on the > > host. Here is the steps I follow. * > > * > > * > > *On the host machine:* > > * > > * > > > > [root@localhost kgdb]# gdb vmlinux > > > > GNU gdb (GDB) Fedora (7.0-3.fc12) > > Copyright (C) 2009 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. Type "show > copying" > > and "show warranty" for details. > > This GDB was configured as "i686-redhat-linux-gnu". > > For bug reporting instructions, please see: > > <http://www.gnu.org/software/gdb/bugs/>... > > Reading symbols from /root/kgdb/vmlinux...done. > > > > (gdb) set remotebaud 115200 > > (gdb) set debug remote 1 > > (gdb) target remote /dev/ttyS0 > > Remote debugging using /dev/ttyS0 > > Sending packet: $qSupported#37...Ack > > Packet received: > > Packet qSupported (supported-packets) is NOT supported > > Sending packet: $Hg0#df...Ack > > Packet received: OK > > Sending packet: $?#3f...Ack > > Packet received: S05 > > Sending packet: $Hc-1#09...Ack > > Packet received: OK > > Sending packet: $qC#b4...Ack > > Packet received: QC01 > > Sending packet: $qAttached#8f...Ack > > Packet received: > > Packet qAttached (query-attached) is NOT supported > > Sending packet: $qOffsets#4b...Ack > > Packet received: > > Sending packet: $g#67...Ack > > Packet received: > > > 36000000ffffffff0abaffff20d98bc06c3f86de783f86de803ac8dd803f86de885747c00202000060000000680000007b00c8dd7b0086deffff0000ffff0000 > > Sending packet: $mc0475788,1#a4...Ack > > Packet received: 0f > > Sending packet: $mc0475788,8#ab...Ack > > Packet received: 0faef889f6ff0d08 > > Sending packet: $mc0475788,7#aa...Ack > > Packet received: 0faef889f6ff0d > > 0xc0475788 in ?? () > > Sending packet: $qSymbol::#5b...Ack > > Packet received: > > Packet qSymbol (symbol-lookup) is NOT supported > > (gdb) s > > Cannot find bounds of current function > > (gdb) > > > > > > *Observation:* > > *1.* Ideally the kernel being debugged should break > at > > legitimate address and the corresponding line number should > > be displayed instead of " 0xc0475788 in ?? ()". > > > > 2. On inspecting section header in vmlinux > executable, > > I found the .text section address range is from > > 0xC1000000 to 0xC1326e58 and no section's > contents > > associate with the address 0xC0475788. > > > > *3.* Hence on single stepping, gdb logs the error > > as* "Cannot > > find bounds of current function"* > > * > > * > > Humbly request you to help me in addressing this issue. > > > > Thanks and Regards, > > Prabhu > > > ------------------------------------------------------------------------------ > > What Every C/C++ and Fortran developer Should Know! > > Read this article and learn how Intel has extended the reach of its > > next-generation tools to help Windows* and Linux* C/C++ and Fortran > > developers boost performance applications - including clusters. > > http://p.sf.net/sfu/intel-dev2devmay > > _______________________________________________ > > Kgdb-bugreport mailing list > > Kgdb-bugreport(a)lists.sourceforge.net > > https://lists.sourceforge.net/lists/listinfo/kgdb-bugreport > > >

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unlocked_ioctl explanation
by Ezequiel García May 19, 2011

May 19, 2011

I am aware that ioctl has been superseeded by unlocked_ioctl. I've been looking through patches and this seems to be BKL related. Could someone explain further the differences and reasons for the new ioctl prototype and name? I guess 'unlocked' means BKL is no longer held inside ioctl, right? What precautions should we take when using unlocked_ioctl ? Greetings, Ezequiel.

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system timer interrupt targets for SMP platforms with local timer support
by Christopher Harvey May 18, 2011

May 18, 2011

I'm having a hard time finding out by reading documentation and source code if a system timer IRQ is supposed to be directed at all cores of a processor or if just interrupting one core is enough. I know interrupting one core is enough without local timers, because an IPI will be used to interrupt the other. These IPIs are not used with local timers, so does the global timer need to send an IRQ at the same time to both cores in that case? Thanks, -Chris

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Re: How logs will come to UART serial console?
by Haphazard H May 18, 2011

May 18, 2011

> Hi sandeep, > > On Tue, May 17, 2011 at 12:52 AM, sandeep kumar > <coolsandyforyou(a)gmail.com> wrote: > > > > Hi , > > Here is my question. > > when we put 'printk's in kernel code the logs will go to the log_buffer.(i observed that from implementation) > > But when UART is enabled(in the bootloader), the same printk logs?are going to the serial console. > > As per my study printk doesnot implementing anything that writes to the UART console. > > > > Now here are?my questions, > > how this is being achieved??Where this is implemented?(which file) > > When you register your UART driver there is typically an option to > register a console driver at the same time. > > For example, let's take a look at the 8250 serial driver. We'll look > at the file drivers/serial/8250.c Think the file has changed, its now in drivers/tty/serial/8250.c > Search for the function serial8250_console_init, which has a call to > register_console. > > That's the starting point that sets up the console driver. You can > have other drivers call register_console and get your console messages > sent out whatever bizarre device you may have connected to your > system. > You can also have multiple consoles registered at the same time. If so, you can see the output in all the registered ports. > > Where wil be the parsing of the cmdline string sent from the bootloader is done? > > The function console_setup is called when the console= parameter is > passed on the kernel command line. > <http://lxr.linux.no/linux+v2.6.38/kernel/printk.c#L904> In the console_setup function, the struct console's address in stored in a char pointer. If you want to know how the parsing is done, if (str[0] >= '0' && str[0] <= '9') { strcpy(buf, "ttyS"); strncpy(buf + 4, str, sizeof(buf) - 5); } else { strncpy(buf, str, sizeof(buf) - 1); } buf[sizeof(buf) - 1] = 0; if ((options = strchr(str, ',')) != NULL) *(options++) = 0; I they check the str[0], the first element in the received char array, it corresponds to char name[16] // from linux/console.h the name parameter in the static struct console serial8250_console is "ttyS". Basically what the first line does is that, the console device's name should not start with numbers. If not actual name is copied. > The __setup just after the end of the function is what causes it to > call that function when the console= parameter is passed. /harper

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