October 2022 - kernelnewbies@kernelnewbies.org

work one webcam out of two webcam connect to xhci controller for 2 usb3.0 ports
by Malatesh Oct. 13, 2022

Oct. 13, 2022

*Hi Team,* *Good Morning/Afternoon/Evening.* I connect two usb webcameras and one mouse, one keyboard to xhci controller, which has 4 usb v3.x ports. Here, keyboard and mouse works fine without any issue. But out of two cameras, only one camera works( I mean when I click preview only one camera show and one camera show blank ) *Debug log:* kernel: xhci_ep_clear_stall: <3057.043240> -------------------------- xhci_configure_reset_endpoint ------------ <3057.043272> ------------------------>dev:11,bEndpointAddress:81,ep_status:0,epno:3,xfer:0xfffffe0036ebc148 <3057.043296> xhci_cmd_configure_ep: <3057.043545> xhci_check_command: Received command event <3057.289866> xhci_timeout: xfer=0xfffffe0036ebc148 <3057.290055> -------------------------- xhci_configure_reset_endpoint ------------ <3057.290079> ------------------------>dev:11,bEndpointAddress:81,ep_status:0,epno:3,xfer:0xfffffe0036ebc148 <3057.290102> xhci_cmd_reset_ep: <3057.290145> xhci_check_command:Received command event <3057.290198> [ERROR] - xhci_configure_reset_endpoint: Could not set dequeue ptr for endpoint 3, 0 <3057.290221> xhci_cmd_set_tr_dequeue_ptr: <3057.290282> xhci_check_command: Received command event [ERROR] - xhci_configure_reset_endpoint: Error to set dequeue ptr for endpoint 3, 81, err 18, 0 <3057.290350> xhci_cmd_evaluate_ctx: <3057.290403> xhci_check_command: Received command event kernel: <> xhci_timeout: xfer=0xfffffe0036ebc148 It is great if you provide some inputs. Thank you in advance!!! Regards, Malatesh

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mabe a bug in kernel 5.4 since patchlevel 159 - dma error because use ttynull?
by Simon Lindhorst Oct. 13, 2022

Oct. 13, 2022

Hello all, when I updated my Kernel from version 5.4.155 to 5.4.215 I get an strange xhci error: /xhci-hcd f10f0000.usb3: ERROR unknown event type 37// //xhci-hcd f10f0000.usb3: ERROR Transfer event TRB DMA ptr not part of current TD ep_index 2 comp_code 13// / After a lot of this messages, my hardware makes a reboot without any more outputs. The error only occures when i add /console=null/ to my kernel bootargs. When I add instead console=/ttyS0,115200/ no error occured. Now I go back in kernelversions. The error occured first in version 5.4.159. Between patchlevel 158 and 159 there is a change: /--- linux-5.4.158/kernel/printk/printk.c 2021-11-06 13:59:45.000000000 +0100// //+++ linux-5.4.159/kernel/printk/printk.c 2021-11-12 14:43:05.000000000 +0100// //@@ -2193,8 +2193,15 @@// // char *s, *options, *brl_options = NULL;// // int idx;// //// //- if (str[0] == 0)// //+ /*// //+ * console="" or console=null have been suggested as a way to// //+ * disable console output. Use ttynull that has been created// //+ * for exacly this purpose.// //+ */// //+ if (str[0] == 0 || strcmp(str, "null") == 0) {// //+ __add_preferred_console("ttynull", 0, NULL, NULL);// // return 1;// //+ }// //// // if (_braille_console_setup(&str, &brl_options))// // return 1;/ I checked my kernelconfig and found that I have no ttynull device configured (/CONFIG_NULL_TTY=n/). Add /CONFIG_NULL_TTY=y/ to my kernelconfig doesn't made a change. When I undo the change above, everything works fine. Does anybody know, what could be the main trigger for the error above? Regards, Sarah -- Unsere Aussagen koennen Irrtuemer und Missverstaendnisse enthalten. Bitte pruefen Sie die Aussagen fuer Ihren Fall, bevor Sie Entscheidungen auf Grundlage dieser Aussagen treffen. Wiesemann & Theis GmbH, Porschestr. 12, D-42279 Wuppertal Geschaeftsfuehrer: Dipl.-Ing. Ruediger Theis Registergericht: Amtsgericht Wuppertal, HRB 6377 Infos zum Datenschutz: https://www.wut.de/datenschutz Tel. +49-202/2680-0, Fax +49-202/2680-265, https://www.wut.de

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howto strip trailing newline from a format string at compile-time ?
by jim.cromie＠gmail.com Oct. 12, 2022

Oct. 12, 2022

hi all So Im (always) hacking on dynamic-debug.. Ive added a 'T' flag, which causes dyndbg to send its message to /sys/kernel/tracing/trace instead of syslog (p does that). trouble is, pr_debug() calls almost always have a trailing newline, and ftrace adds its own, so the tracefile has empty lines after each pr_debug's message. I would like to fix this in the format-string, with a macro, and add the newline explicitly, when given originally, for the 'p'/syslog case. While still needing an add-newline? decision, it avoids scanning format or sprint-d bufs for the trailing newline. ie #define strip_trailing_newline(str) ..... #define has_trailing_newline(str) ... theyd get used in: #define DEFINE_DYNAMIC_DEBUG_METADATA_CLS(name, cls, fmt) \ ... .format = strip_trailing_newline(fmt), \ .add_nl = has_trailing_newline(fmt), \ that new .add_nl bit-field might be difficult - the other flags in _ddebug are not individual bit-fields, but I think this would have to be separate to be initializable in the macro. maybe no big deal. and how to fix the 'fmt expanded 2x' problem ?

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Re: Can KASAN be used with loadable modules?
by John Ousterhout Oct. 12, 2022

Oct. 12, 2022

Responding to my own message: It turns out that I had somehow botched the installation of the KASAN-ified kernel, so that the module compilation was using old information that didn't include KASAN. Once I got the KASAN-ified kernel properly installed, my module compiled cleanly with KASAN and KASAN did indeed detect memory problems. Sorry for the false alarm. On Tue, Oct 11, 2022 at 9:43 PM John Ousterhout <ouster(a)cs.stanford.edu> wrote: > > Responding to my own message: > > It turns out that I had somehow botched the installation of the > KASAN-ified kernel, so that the module compilation was using old > information that didn't include KASAN. Once I got the KASAN-ified > kernel properly installed, my module compiled cleanly with KASAN and > KASAN did indeed detect memory problems. > > Sorry for the false alarm. > > > On Tue, Oct 11, 2022 at 2:47 PM John Ousterhout > <john.ousterhout(a)gmail.com> wrote: > > > > I'm trying to use the address sanitizer (KASAN) with a loadable module, but so far haven't been able to make it work. I compiled a kernel with KASAN and tested to see that it detects errors properly with kernel files, but when I compile a loadable module with that kernel, the module is not configured for KASAN (e.g. missing CFLAGS switches). Furthermore, I found that the lib/include/config/auto.conf file in the /lib/modules/xxx directory is different from the one in the kernel build directory. I tried copying the auto.conf file from the kernel directory to lib/modules/xxx, but then the module build fails during the link step with missing symbols such as __asan_handle_no_return. > > > > Is KASAN known to work with modules? If so, is any additional configuration needed for a module to use KASAN? > > > > Thanks in advance for any help you can provide. > > > > -John-

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Can KASAN be used with loadable modules?
by John Ousterhout Oct. 11, 2022

Oct. 11, 2022

I'm trying to use the address sanitizer (KASAN) with a loadable module, but so far haven't been able to make it work. I compiled a kernel with KASAN and tested to see that it detects errors properly with kernel files, but when I compile a loadable module with that kernel, the module is not configured for KASAN (e.g. missing CFLAGS switches). Furthermore, I found that the lib/include/config/auto.conf file in the /lib/modules/xxx directory is different from the one in the kernel build directory. I tried copying the auto.conf file from the kernel directory to lib/modules/xxx, but then the module build fails during the link step with missing symbols such as __asan_handle_no_return. Is KASAN known to work with modules? If so, is any additional configuration needed for a module to use KASAN? Thanks in advance for any help you can provide. -John-

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only one element get stored in kfifo
by chrishell Oct. 11, 2022

Oct. 11, 2022

hello, Im struggle with a simple kfifo. I try to do it dynamicly. For the sake of simplicity I changed the code in a way that everything with the kfifo is done in the open function of my module. First of all, I have a struct, in which I store the pointer to that kfifo: struct mymod_private_fops { wait_queue_head_t wait; struct kfifo mymod_fifo; } And the struct in which I store my data: struct mymod_data_pkt { __u8 mbyte; __u8 smfunc; ktime_t ktime; __u16 len; __u16 sequence; char devname[32] void *page; }; this is the open function, which creates the kfifo and stores the pointer to that kfifo for later usage. As I mentioned I simplified the whole thing to have the store operation into the kfifo and the fetch operation, out of the kfifo in one place. Initially I did this in the read and write function. static int mymod_open(struct inode *pinode, struct file *pfile) { int rc = 0, len = 0; struct mymod_private_fops pfops; struct mymod_data_pkt w_cache1, w_cache2, w_cache3 r_cache1, r_cache2, r_cache3; pfops = kzalloc(sizeof(struct mymod_private_fops), GFP_KERNEL); if(pfops == NULL) return -ENOMEM; init_waitqueue_head(&pfops->wait); len = LOG_STACK_SIZE * sizeof(struct mymod_data_pkt); rc = kfifo_alloc(&pfops->mymod_fifo, len, GFP_KERNEL); if(rc) { pr_err("kfifo_alloc failed %d", rc); return rc; } if(! kfifo_initialized(&pfops->mymod_fifo)) { pr_err("kfifo initialized"); } w_cache1.mbyte = 4; w_cache1.len = 245; rc = kfifo_in(&pfops->mymod_fifo, &w_cache1, sizeof(struct mymod_data_pkt)); pr_err("kfifo_in returns %d", rc); w_cache2.mbyte = 42; w_cache2.len = 112; rc = kfifo_in(&pfops->mymod_fifo, &w_cache2, sizeof(struct mymod_data_pkt)); pr_err("kfifo_in returns %d", rc); w_cache3.mbyte = 119; w_cache3.len = 77; rc = kfifo_in(&pfops->mymod_fifo, &w_cache3, sizeof(struct mymod_data_pkt)); pr_err("kfifo_in returns %d", rc); rc = kfifo_len(&pfops->mymod_fifo); pr_err("kfifo_len: %d", rc); memset(&r_cache1, 0, sizeof(struct mymod_data_pkt)); rc = kfifo_get(&pfops->mymod_fifo, &r_cache1); pr_err("kfifo_get returns %d", rc); pr_err("content of kfifo r_cache1->mbyte: %d", r_cache1.mbyte); memset(&r_cache2, 0, sizeof(struct mymod_data_pkt)); rc = kfifo_get(&pfops->mymod_fifo, &r_cache2); pr_err("kfifo_get returns %d", rc); pr_err("content of kfifo r_cache2->mbyte: %d", r_cache2.mbyte); ... pfile->private_data = pfops; ... [ 108.200977] kfifo_in returns 64 [ 108.200985] kfifo_in returns 64 [ 108.200990] kfifo_in returns 64 [ 108.200993] kfifo_len: 192 [ 108.200997] kfifo_get returns 1 [ 108.201000] content of kfifo r_cache1->mbyte: 4 [ 108.201003] kfifo_get returns 1 [ 108.201006] content of kfifo r_cache2->mbyte: 0 [ 108.201010] kfifo_get returns 1 [ 108.201013] content of kfifo r_cache3->mbyte: 0 The initialization worked fine, the store operations went properly. Only pulling data out of the kfifo didn't work as expected. Only the 1st element was correct, the 2nd and 3rd element was just 0 Also the size of the struct and the fifo seems to be okay. The struct has the size of 64 (there is some padding within I think) and after inserting 3 elements the kfifo has the size of 192 Where is the flaw here? Thank you in advance Best regards Christian

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Missing linux-headers
by neutrino network Oct. 10, 2022

Oct. 10, 2022

Hi, How to update linux-headers for kernel (6.0.0) compiled from source in centos? System has kernel 4.18 headers while kernel is 6.0, however userspace program generates error e.g* fatal error: linux/mutex.h: No such file or directory* Regards

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Using printk, how can I know where the kernel jumps after schedule() function?
by Chan Kim Oct. 8, 2022

Oct. 8, 2022

Hello experts, I am faced with a problem on my experiment. (arm64) When the linux kernel boots and after it jumped to /bin/sh in the initramfs (by busybox), it hangs after the program jumps the schedule() function. I can see it comes out of schedule() function using printk, but I don't know where it had gone(or returned). I tried printing the bottom two values in the schedule() function, because the x29(=fp) and x30(=lr) is stored at the stack bottom during any function. But the lr value is somewhere in then init stack(by examining the System.map). So I guessed that lr value, a virtual address is a user virtual address.. Is my guess correct or should the lr value point to a point in kernel text section? Actually I don't know exactly how a user program is interrupted by the schedule function initiated by the timer interrupt so I would be grateful if someone explain it. ( I tried reading part of a book or web posts but didn't get what I want yet). Thank you! Regards, Chan Kim

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Can Cgroup memory subsystem provide estimated available memory, just like /proc/meminfo: MemAvailable?
by 宁静的天空 Oct. 8, 2022

Oct. 8, 2022

Hello cgroup experts, /proc/meminfo: MemAvailable is a very useful mertics, provide estimated available memory, caculated by MemFree, Active(file), Inactive(file), SReclaimable and watermarks. It is implemented by the si_mem_available() function[1]. Can cgroup memory subsystem provide estimated available memory? /proc/meminfo: MemTotal:       63793888 kB MemFree:        21124704 kB MemAvailable:   39106088 kB [1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?…

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Extract patch from kernel mailing list
by neutrino network Oct. 7, 2022

Oct. 7, 2022

Hello, How to extract patches from the kernel mailing list? Best.

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