November 2011 - kernelnewbies@kernelnewbies.org

Serial console temporarily garbled
by Neil Baylis Nov. 22, 2011

Nov. 22, 2011

I'm working on an embedded system running a 2.6.32 kernel originally derived from RHEL6. The hardware architecture is similar to a PC. The device is a specialized server. It uses an 8250 compatible serial port for the console. When it's booting up, everything looks fine until it initializes the serial driver. At that point the output to the console becomes garbled until (I think...) getty runs for the console port. Then it's readable again. It looks as though the initialization of the serial driver is setting the wrong baud rate, or perhaps some other configuration. During the boot process, this garbled output happens for about 1 second, during which probably a few thousand characters of garbage are output. The grub boot parameter specifies "console=ttys0,57600" The getty line for the console specifies "T0:23:respawn:/sbin/getty -L ttys0 57600 vt100" It's not clear to me how the serial driver is supposed to be initialized to the right baud rate. Is the parameter from the boot line supposed to be used? (Just to complicate matters, we're using a Debian userspace with this kernel). Here's how it looks on the console: [ 4.429923] Non-volatile memory driver v1.3 [ 4.438325] Serial: 8250/16550 driver, 4 ports, IRQ sharing enabled ÿ[ 4.615305] serial8250: ttyS0 at I/O 0x3f8 (irq = 4) is a ST16650V2 ;s¶6T=$É½¤©;s¶v´=Ä½ÁÔP%1D²äÍÓÉK æÑ- %1¹©;s¶5V=ÔÍê£!¬E¹)¥°? U000&ÉP%19)$%°©;s61v=¡ 0¦0¦1r2CÔJ °æÁ0424¬Ñ6/F3d °0 ÕÁ4! Much garbage deleted... Ø¤µ!V°ÉD¨«Í'µõ;Ðs°W¶G=dÉ©¥®5ÕV$´Ô¥½Y§ ³°&V%jê;Ðs1&·Ë=t²E%²ÑiÑ)¤D!6f¸ÕêLoading, please wait... PuTTYPuTTYPuTTYBegin: Loading essential drivers ... done. Begin: Running /scripts/init-premount ... PuTTYPuTTYPuTTYPuTTYPuTTYPuTTYPuTTYPuTTYdone. Begin: Mounting root file system ... Begin: Running /scripts/local-top ... done. If anyone can point me in the right direction to understand this, that would be great. I think the repeated 'PuTTY' strings result from control characters being sent to the terminal, which is PuTTY. It's answerback string is 'PuTTY' by default. Thanks, Neil Baylis

2 2

Freeing work_struct memory
by Kai Meyer Nov. 22, 2011

Nov. 22, 2011

I've got a bug I'm having trouble identifying. It seems like it could be related to my work_struct usage. I essentially have this: struct my_worker { work_struct work; /* some other data */ }; void worker_fn(struct work_struct *work) { struct my_worker *worker = container_of(work, struct my_worker, work); /* ... do some stuff ... */ kfree(worker); } void worker_caller() { struct my_worker *worker = kmalloc(sizeof(*worker), GFP_KERNEL); INIT_WORK(&worker->work, worker_fn); /* ... add some other stuff to *worker ... */ schedule_work(&worker->work); } I frequently get a kernel panic with a specific test, but the stack trace is rarely the same, which seems to indicate to me that I'm corrupting data somewhere. So my question is: Can I free the memory for "struct my_worker *worker" inside worker_fn? Or does the work_queue stuff need to continue to use the "struct work_struct work" member after the end of worker_fn? -Kai Meyer

2 1

(no subject)
by Jimmy Pan Nov. 22, 2011

Nov. 22, 2011

..Do you want to feel something new? Do you want to feel new unforgettable sensations? This is for you! http://un-ocean.fr/p.g.php?wellink_friend_id=14ox0

1 1

Path for STOLEN Packets!!!
by Kesava Srinivas Nov. 22, 2011

Nov. 22, 2011

Hi , Even after lot of google; didn't get the accurate answer for this. After STEALING Packets (NF_STOLEN); want to send the Manipulated Packet (added extra header) to some of the available net devices. Please let me know what is the Function that I Should call to do this step ?? Also; once the skb was expanded by 20 bytes to add new ip header; do I need to reassign the skb pointer to the new location ?? -Thanks in Advance, VKS

2 1

a few questions regarding acpi and kernel configuration
by Littlefield, Tyler Nov. 22, 2011

Nov. 22, 2011

Hello all: I have a few questions, I was hoping someone could help me out here. First, I'll start off by saying that my netbook is a sort of PDA for me. I just boot it up and when I'm taking care of stuff for work running around getting info and that, I can use it to grab the info. I use Linux for this, but my battery dies kind of quickly. I'm also looking to optomize performance as much as possible. So, I sat down and tried to optomize a kernel. Both to save space (since this is a smaller drive), and to make things a bit quicker, even by a little bit. I put the config here: http://tds-solutions.net/config.tar.bz2 First, I'm curious what else I can yank out of there to make everything smaller. I'd like to cut down on the drivers and all that, and just include the driver for my specific harddrive if that's possible, as well as the wireless card. Can I turn off scsi/pata/ata since I have a sata drive? Is there other stuff I missed that I could take out? Finally, my last two questions. 1) Is there a way to access acpi so I can put the computer into standby quickly? I'm not sure how to pull that off from the cli, but doing it with code would work. 2) Is there a way for me to detect when the lid of my laptop has been closed and put it into standby, and/or set an idle timer to put it into standby? If there are clients out there that can interface with acpi and help with this, awesome. If not, and I need to code something up, that works too. Finally, I'm trying to find a way, since I do not use it to turn off the display. Is this possible? -- Take care, Ty Web: http://tds-solutions.net The Aspen project: a light-weight barebones mud engine http://code.google.com/p/aspenmud Sent from my toaster.

3 2

x86: Executing a raw vmlinux image (embedded environment)
by Graeme Russ Nov. 22, 2011

Nov. 22, 2011

Hi All, Firstly, a little introduction an background - I am currently the maintainer for the x86 port of Das U-Boot (or more simply U-Boot). While the x86 port is not as well known as the more major ports like ARM and PPC, it is starting to gain more attention and more developer input which has beed nice to see after my solo efforts over the last few years. One of my biggest annoyances with the x86 U-Boot port is that, while it is an embedded boot loader, it still tries to boot Linux as if it was a conventional PC - i.e. it has 'real mode' and 'BIOS' implementation and loads a bzImage. But this approach is completely unnecessary and only adds to the boot time (load bzImage from storage into RAM, decompress, then run). So I want to shortcut bzImage and migrate towards treating the loading of the Linux kernel from U-Boot like any other embedded environment: - Decompress vmlinux directly from storage into the appropriate memory location - Setup required data structures - Jump into vmlinux U-Boot has it's own compressed kernel image container (uImage) and support code which will allow me to decompress the vmlinux directly from storage into RAM. In my current situation, I have ~1.7MB of onboard (i.e. cached) flash memory where I plan to store the compressed kernel and an MMC where I plan to store the file system. So after building a very stripped down kernel (no TCP/IP for example) I get: /vmlinux 2,629,659 bytes /vmlinux.o 2,889,050 bytes /arch/i386/boot/bzImage 1,104,864 bytes /arch/x86/boot/bzImage 1,104,864 bytes /arch/x86/boot/vmlinux.bin 1,092,060 bytes /arch/x86/boot/compressed/vmlinux 1,099,538 bytes /arch/x86/boot/compressed/vmlinux.bin 2,094,132 bytes /arch/x86/boot/compressed/vmlinux.bin.gz 1,074,711 bytes I understand that /arch/x86/boot/compressed/vmlinux.bin.gz is a compressed version of /arch/x86/boot/compressed/vmlinux.bin, and /arch/i386/boot/bzImage and /arch/x86/boot/bzImage are the same file and that it is the 16-bit boot code + /arch/x86/boot/compressed/vmlinux.bin.gz but I don't understand the rest... My guess is that /vmlinux.o is the ELF image generated by the compiler + linker stage and /vmlinux may be /vmlinux.o objdump'd into a raw binary and perhaps /arch/x86/boot/vmlinux.bin is a further stripped version of/vmlinux, but I'm at a loss with /arch/x86/boot/compressed/vmlinux In any event, it looks like either /arch/x86/boot/compressed/vmlinux.bin or /vmlinux is what I need to copy into RAM @ 0x100000 (1MiB) which is where my non-relocatable kernel is compiled to. I also have looked at the documentation for the x86 32-boot protocol found in linux/Documentation/x86/boot.txt So what I'm needing is: - Confirmation of exactly which vmlinux to use - Confirmation that I do load it @ 0x100000 - How to setup the memory map (keeping in mind I have 2GB of contiguous memory with no BIOS/ACPI etc to worry about clobbering - Any other tricks I need to be aware of.. Any help will be greatly appreciated Thanks, Graeme

2 2

LPC bus access howto
by Andre Haupt Nov. 22, 2011

Nov. 22, 2011

Hi all, We have a FPGA which will be connected to the LPC bus. This FPGA will provide some GPIO functionality, a rotary encoder, etc. Now i want to write a kernel driver to talk to this FPGA. I am unsure how to get access to the LPC bus in the first place. What kernel APIs should i use? How to get the memory mapping right, etc? I would appreciate any pointers to documentation or examples. cheers, Andre

2 2

sock_buff is NULL !
by Kesava Srinivas Nov. 21, 2011

Nov. 21, 2011

HI Team, Trying to make this code work; but some how it is entering the if condition mentioned below.sock_buff is still a NULL Pointer.I can see that Function was registered with the Ipv4 Hooks. Any ideas/scenarios where the sock_buff remains as NULL Pointer??? Testing this code by trying to do ssh with this machine. Any Help is really appreciated !! ######### static struct nf_hook_ops netfilter_ops; struct sk_buff *sock_buff; unsigned int main_hook(unsigned int hooknum,struct sk_buff **skb,const struct net_device *in,const struct net_device *out,int (*okfn)(struct sk_buff*)) { sock_buff = *skb; if(!sock_buff){ printk(KERN_ERR "Entered unexpected loop \n"); return NF_ACCEPT; }/* Check for sk_buff NULL */ } int init_module() { netfilter_ops.hook = (nf_hookfn *) main_hook; netfilter_ops.hooknum = NF_INET_PRE_ROUTING; netfilter_ops.pf = PF_INET; netfilter_ops.priority = NF_IP_PRI_FIRST; nf_register_hook(&netfilter_ops); } ###################### -Thnx, VKS

2 3

Delivery Status Notification
by Enes Albay - انس الباى Nov. 20, 2011

Nov. 20, 2011

Hi! anybody knows that where is set_user_nice() function called in the kernel? i couldn't find that. i just found that in forking operation do_fork()->copy_process()->dup_task_struct() called then set_user_nice() called but i couldn't find that where. Also how/where do_fork() function called in kernel i couldn't find. Thanks in advance... -- Enes Albay

1 1

Regarding data transfer per beat in AXI.
by mindentropy Nov. 19, 2011

Nov. 19, 2011

Hi, Can somebody explain to me what a 'beat' is in data transfer in AXI protocol ? The documentations says: Burst size ------------------ Table 4-2 shows how the ARSIZE or AWSIZE signal specifies the maximum number of data bytes to transfer in each beat, or data transfer, within a burst. Table 4-2 Burst size encoding ARSIZE[2:0] AWSIZE[2:0] Bytes in transfer b000 1 b001 2 b010 4 b011 8 b100 16 b101 32 b110 64 b111 128 The AXI determines from the transfer address which byte lanes of the data bus to use for each transfer. For incrementing or wrapping bursts with transfer sizes narrower than the data bus, data transfers are on different byte lanes for each beat of the burst. The address of a fixed burst remains constant, and every transfer uses the same byte lanes. The size of any transfer must not exceed the data bus width of the components in the transaction. Thanks.

1 0