December 2015 - kernelnewbies@kernelnewbies.org

How to handle Hotplug with UIO userspace driver
by Mandeep Sandhu Sept. 28, 2017

Sept. 28, 2017

Hi All, We're working on a custom PCIe based hardware, which can be hotplugged into the system. We're using the UIO approach of having a minimal kernel driver which basically handles the interrupt and provides a mmap of the device memory to userspace and userspace driver which mmap's the provided memory and manages the device. We're using systemd and udev rules to spawn off a user process whenever the hardware is plugged into the system. Now my question is, how can we gracefully inform the userspace process if someone pulls out the hardware (sitting on a PCI slot). Even with full hotplug support, there can always be a case of "surprise removal", where someone yanks the board without going through the whole "attention button" routine. While the kernel driver has no problem with hot-removal, I see that if I "unregister" our UIO driver in response to the removal, then the mapping for the hardware's physical memory would become "invalid" (done by UIO on unregsiter). This could possibly cause the user-space process to crash due to illegal memory access. Is there a "standard" way to handle this scenario, i.e for hotpluggable hardware using UIO? Basically, we'd want to "unregister" the UIO device only after the userspace process is informed of the removal so that it could unmap/close the device and exit gracefully. We could try doing it using some systemd trick, where we put a dependency on one of the UIO created files (/dev/uioX), so that when the file is destroyed, systemd could kill/shutdown the process. Although, there's no guarantee that the userspace process won't try to access the mmaped space during that interval, so this isn't a reliable solution either. Any hints, thoughts? Thanks., -mandeep

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Re: Developing environments used for kernel development
by Daniel. Jan. 14, 2016

Jan. 14, 2016

Hey Jeff, thanks for the reply, what I realy don't like in IDEs is tying building and editing at same tool. I'm a simple guy so I like to keep things simple. I never heard of anybody using IDE's for building C code in linux. I'm considering back to vim since emacs indenting is making me crazy Regards 2015-12-22 17:59 GMT-02:00 Jeff Haran <Jeff.Haran(a)citrix.com>: > Off list. > > > > I use gvim, make, all the old style tools for kernel development and have > been doing so for about 15 years now, but I am an old fart. Your boss needs > to understand that a lot of these IDEs, though useful for user space > development, don’t help much in kernel space. When the kernel goes bad, the > IDE goes with it. > > > > If he is uneducatable on this, you might want to check out this package > called kdevelop. You can keep it running in one desktop to make him happy > and then do the real work using the tried and true command line tools in > another desktop. > > > > Good luck, > > > > Jeff Haran > > > > > > > > From: kernelnewbies-bounces(a)kernelnewbies.org > [mailto:kernelnewbies-bounces@kernelnewbies.org] On Behalf Of Daniel. > Sent: Tuesday, December 22, 2015 11:28 AM > To: kernelnewbies > Subject: Developing environments used for kernel development > > > > My boss came to my desk today raiging that I should use more productive > tools for developing. Well I don't want to begin an editor war but, yes, I > use emacs. I used to use vim before but the integration of emacs and gdb has > caught my attention. > > To be clear, as "more productive tools" he understands graphical eye candy > tools. My argument to use an "simple editor plus makefiles" was, it just > works and thats it. So before to downloading eclipse just to make my boss's > eyes happy I've decided to make a little research. > > What you guys are using today to develope kenrel code? > > > > Best Regards, > > - dhs > > > -- > > "Do or do not. There is no try" > Yoda Master -- "Do or do not. There is no try" Yoda Master

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Re: Developing environments used for kernel development
by Daniel. Jan. 14, 2016

Jan. 14, 2016

Hey Lucas, thanks for the reply. Did you use gdb inside eclipse? It works fine? For code browsing I use cscope. Best Regards, -dhs Em 22/12/2015 19:04, "Lucas Tanure" <tanurelinux(a)gmail.com> escreveu: > I use eclipse, but I had to expand my RAM, 24GB added. I tried Kdevelop, > but doesn't work for big projects. Tried a few LLVM code browsers but none > was good enough. > Vim for minor modifications. > > Thanks > > On Tue, Dec 22, 2015 at 5:27 PM, Daniel. <danielhilst(a)gmail.com> wrote: > >> My boss came to my desk today raiging that I should use more productive >> tools for developing. Well I don't want to begin an editor war but, yes, I >> use emacs. I used to use vim before but the integration of emacs and gdb >> has caught my attention. >> >> To be clear, as "more productive tools" he understands graphical eye >> candy tools. My argument to use an "simple editor plus makefiles" was, it >> just works and thats it. So before to downloading eclipse just to make my >> boss's eyes happy I've decided to make a little research. >> >> What you guys are using today to develope kenrel code? >> >> Best Regards, >> - dhs >> >> -- >> *"Do or do not. There is no try"* >> *Yoda Master* >> >> _______________________________________________ >> Kernelnewbies mailing list >> Kernelnewbies(a)kernelnewbies.org >> http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies >> >> >

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Does the Community use Coverity ?
by pavi1729 Jan. 7, 2016

Jan. 7, 2016

Hi, May I know if the community uses the Coverity tool and, if yes where can I find a repo of Coverity scans of kernels and IGNORE LIST; cause there obviously would be false positives. Cheers, Pavi

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skb_clone related query
by pavi1729 Jan. 5, 2016

Jan. 5, 2016

Hi, Just out of curisity, I was looking at Kernel 3.14, skb_clone function in f_ncm.c http://lxr.free-electrons.com/source/drivers/usb/gadget/f_ncm.c?v=3.14#L1063 QUERY : Shouldn't a kfree_skb(skb2); happen before goto err @1070 ? Is this not a memleak ? 1068 if (!skb_pull(skb2, index)) { 1069 ret = -EOVERFLOW; 1070 goto err; 1071 } Thanks, Pavi

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Re: eudyptula challenge, stuck at task 06 - no reply for four weeks
by chuckleberryfinn Dec. 31, 2015

Dec. 31, 2015

I had some replies in November. He's still alive for sure. :) Patience is the biggest requirement for the challenge! ;) > From: "Geyslan G. Bem" <geyslan(a)gmail.com> > Subject: Re: eudyptula challenge, stuck at task 06 - no reply for four > weeks > To: Abner Silva <abnerf(a)gmail.com> > Cc: kernelnewbies <kernelnewbies(a)kernelnewbies.org> > Message-ID: > <CAGG-pURmn_%2BW4Tr6kM0kqhx8ucVfx%3Dbuv_oueV%3DCPPipKy%3Dt%2BQ(a)mail.gmail.com> > Content-Type: text/plain; charset=UTF-8 > > 2015-12-31 12:27 GMT-03:00 Abner Silva <abnerf(a)gmail.com>: >> Anyone heard from Little recently? Got nothing since beginning of Oct. > Mine is stucked in task 6 too. No reply until now. > >> >> On 11/21/2015 12:57 AM, Karthik Nayak wrote: >>> Thanks, I'll check them out. >>> >>> >>> On Sat, Nov 21, 2015, 1:34 AM Drew Fustini <pdp7pdp7(a)gmail.com >>> <mailto:pdp7pdp7@gmail.com>> wrote: >>> >>> yup, that advice has served me well during the challenge. >>> >>> I highly recommend Free Electrons's Embedded Linux kernel and driver >>> development training: >>> >>> slides: >>> http://free-electrons.com/doc/training/linux-kernel/linux-kernel-slides.pdf >>> labs: >>> http://free-electrons.com/doc/training/linux-kernel/linux-kernel-labs.pdf >>> code: >>> http://free-electrons.com/doc/training/linux-kernel/linux-kernel-labs.tar.xz >>> >>> cheers, >>> drew >>> >>> On Fri, Nov 20, 2015 at 7:57 AM, Karthik Nayak >>> <karthik.188(a)gmail.com <mailto:karthik.188@gmail.com>> wrote: >>> > Just wait you'll get it, in the meantime continue reading about >>> Linux =) >>> > >>> > >>> > On Fri, Nov 20, 2015, 6:38 PM Lucas Tanure <tanure(a)linux.com >>> <mailto:tanure@linux.com>> wrote: >>> >> >>> >> Hi, >>> >> >>> >> I'm waiting for task 8 since September 05: >>> >> " Just to provide some information, you are currently number 9 in >>> >> line, and the response that is next is from "05 Sep 2015 >>> 00:53:31 -0400" >>> >> so be aware of the potential wait time. " >>> >> >>> >> Thanks >>> >> >>> >> -- >>> >> Lucas Tanure >>> >> +55 (19) 988176559 >>> >> >>> >> On Thu, Nov 19, 2015 at 11:36 PM, Alexander Ivanov >>> <amivanov(a)gmail.com <mailto:amivanov@gmail.com>> >>> >> wrote: >>> >>> >>> >>> Hi there, >>> >>> >>> >>> Is there anybody stuck at task 06 too? >>> >>> >>> >>> --ami >>> >>> >>> >>> _______________________________________________ >>> >>> Kernelnewbies mailing list >>> >>> Kernelnewbies(a)kernelnewbies.org >>> <mailto:Kernelnewbies@kernelnewbies.org> >>> >>> http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies >>> >> >>> >> >>> >> _______________________________________________ >>> >> Kernelnewbies mailing list >>> >> Kernelnewbies(a)kernelnewbies.org >>> <mailto:Kernelnewbies@kernelnewbies.org> >>> >> http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies >>> > >>> > -- >>> > >>> > Regards, >>> > Karthik >>> > >>> > >>> > _______________________________________________ >>> > Kernelnewbies mailing list >>> > Kernelnewbies(a)kernelnewbies.org >>> <mailto:Kernelnewbies@kernelnewbies.org> >>> > http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies >>> > >>> >>> -- >>> >>> Regards, >>> Karthik >>> >>> >>> >>> _______________________________________________ >>> Kernelnewbies mailing list >>> Kernelnewbies(a)kernelnewbies.org >>> http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies >>> >> >> _______________________________________________ >> Kernelnewbies mailing list >> Kernelnewbies(a)kernelnewbies.org >> http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies > > >

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eudyptula challenge, stuck at task 06 - no reply for four weeks
by Alexander Ivanov Dec. 31, 2015

Dec. 31, 2015

Hi there, Is there anybody stuck at task 06 too? --ami

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回复：Re: some question about arch/x86/kernel/head_64.S
by hitmoon Dec. 30, 2015

Dec. 30, 2015

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some question about arch/x86/kernel/head_64.S
by xiaoqiang zhao Dec. 30, 2015

Dec. 30, 2015

Hello: After kernel is decompressed, the kernel will execute startup_64 and the first two instructions are: leaq _text(%rip), %rbp subq $_text - __START_KERNEL_map, %rbp I tried to understand them but can not figure out what rbp contains after this two instructions. Anybody give me a clear explanation? Thanks a lot!

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Developing environments used for kernel development
by Daniel. Dec. 29, 2015

Dec. 29, 2015

My boss came to my desk today raiging that I should use more productive tools for developing. Well I don't want to begin an editor war but, yes, I use emacs. I used to use vim before but the integration of emacs and gdb has caught my attention. To be clear, as "more productive tools" he understands graphical eye candy tools. My argument to use an "simple editor plus makefiles" was, it just works and thats it. So before to downloading eclipse just to make my boss's eyes happy I've decided to make a little research. What you guys are using today to develope kenrel code? Best Regards, - dhs -- *"Do or do not. There is no try"* *Yoda Master*

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