March 2020 - kernelnewbies@kernelnewbies.org - Kernelnewbies Mailing Lists

Accessing rpmsg_device in sysfs attribute functions
by Pelle Windestam March 24, 2020

March 24, 2020

Hi, I am trying to develop a simple driver for the rpmsg bus, in order to send various commands from user space in Linux to a secondary CPU (A Cortex M4). I'm trying to keep things as simple as possible, so my idea was to create a driver that just has a few attributes which can be set in /sys which would trigger commands to be sent to the M4 CPU. I have the communication between the CPU:s up and running, but where I'm having trouble moving forward is how to access the "struct rpmsg_device *" that I need in order to communicate with the endpoint for the M4 CPU from the store/show function of the sysfs attributes. What my driver does is to register a rpmsg_driver in the init function: register_rpmsg_driver(&pwm_rpmsg_driver); the device_driver member of my rpmsg_driver struct has its groups member set to my driver attribute groups array: static struct rpmsg_driver pwm_rpmsg_driver = { .probe = pwm_rpmsg_probe, .remove = pwm_rpmsg_remove, .callback = pwm_rpmsg_cb, .id_table = pwm_rpmsg_device_id_table, .drv = { .groups = driver_pwm_groups, .name = "pwm_rpmsg", }, }; My issue is that that I am not sure how to access the struct "rpmsg_device *" (i.e. from the probe() function) in the show/store functions for the sysfs attributes, which have a "struct device_driver *" argument: static int pwm_rpmsg_probe(struct rpmsg_device *rpdev) /* rpmsg_device->ept is needed to send messages to the other CPU */ static ssize_t duty_cycle_store(struct device_driver *dev, const char *buf, size_t count); /* Can I use the device_driver struct to somehow access the rpmsg_device? */ I am very much a novice when it comes to driver development, so I might be approaching this from a completely wrong direction. Any advice would be very much appreciated! Thanks, Pelle

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Unknown symbol reboot_mode
by Tomek The Messenger March 23, 2020

March 23, 2020

Hi When I insert external kernel module which is compiled out of tree I got error: root:/run# insmod ./my_module.ko [ 137.443823] my_module: Unknown symbol reboot_mode (err 0) I investigated that I have attached in my my_module.c file: #include <linux/reboot.h> and in this file we have: extern enum reboot_mode reboot_mode; However reboot_mode symbol is not exported with macro EXPORT_SYMBOL_GPL. Probably this is the reason why symbol is not seen in my module. Then why the same issue doesn't occur here: /arch/arm/kernel/setup.c /arch/arm64/kernel/process.c Those linux files also use global variable reboot_mode.

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the use case of MODULE_SOFTDEP
by Tomek The Messenger March 22, 2020

March 22, 2020

What is the use case of using: MODULE_SOFTDEP("pre: another-external-kernel-module..."); because I completely don't understand. If I have phandle to another-external-kernel-module in dts which is mandatory in my kernel driver then should I put this line in my kernel driver code? If I use function of core.c which is my framework and this is also as external module then should I put this line in my kernel driver code: MODULE_SOFTDEP("pre: testframework-core"); Who knows please respond as this is black magic for me.

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Writing framework in kernel
by Tomek The Messenger March 22, 2020

March 22, 2020

Hi I am writing some framework for my kernel drivers. I delegated to framework the code which is common amongs all kernel drivers. So my framework module core.c has none probe, remove functions. It has also none module_init, module_exit functions at those are not needed. 1.) When I do modprobe of my core.ko I got error: 15.092976] testframework_core: module license 'unspecified' taints kernel. [ 15.129532] testframework_core : Unknown symbol regmap_write (err 0) [ 15.129554] testframework_core : Unknown symbol devm_kmalloc (err 0) [ 15.129573] rstctl_core testframework_core : Unknown symbol of_property_read_variable_u32_array (err 0) [ 15.129598] testframework_core : Unknown symbol sysfs_remove_groups (err 0) etc So I suppose I need to put in my core.c line: MODULE_LICENSE("GPL v2"); at the end of file in order to get rid of above problems. I will check if it helps. However when I am looking at build-in frameworks in linux kernel nobody put line: MODULE_LICENSE("GPL v2"); So why I have to and for example here: https://elixir.bootlin.com/linux/latest/source/drivers/reset/core.c there is none such line and everything works? This is what I completely don't understand. My framework is external module, maybe this is the reason???

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can kernel platform driver name be different than module name?
by Tomek The Messenger March 22, 2020

March 22, 2020

I suppose the response is yes but I would like to make sure: Is below acceptable: some_module_name.c: #define DRIVER_NAME "some-driver-name" ... static struct platform_driver some_driver = { .driver = { .name = DRIVER_NAME, .of_match_table = of_match_ptr(some_of_match), }, vs Makefile: SRC := $(shell pwd) obj-m += some_module_name.o some_module_name-m := directoryInWhichThereIsUsFile/ some_module_name.o all: $(MAKE) -C $(KERNEL_SRC) M=$(SRC) modules_install: $(MAKE) -C $(KERNEL_SRC) M=$(SRC) modules_install

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difference between /usr/lib/modules and /lib/modules
by Fabien R March 22, 2020

March 22, 2020

Hello, Being used to cross-compile my kernel on a faster machine, I noticed the existence of both directories after installing it with update-grub. Since 'du' showed that they have the same size, it's a waste of space. Is it possible to use only one of them ? Is it inherent to grub ? -- Fabien

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How can I compile a rc kernel myself?
by Raphael March 21, 2020

March 21, 2020

Hi! This is my first email to this list. I was wondering how I can compile a rc kernel, since rc is only a patch and I have to apply this patch to a stable kernel first. On which stable kernel do I have to do this? The latest stable kernel, which in this case would be 5.5.11, or another? Best regards, Lockna

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Best way to debug an invalid opcode
by Karaoui mohamed lamine March 19, 2020

March 19, 2020

Hi list, I am currently encountering a kernel oops that indicate an "invalid opcode: 0000 [#1] SMP" I am working on this project https://github.com/GiantVM/Linux-DSM The full log of the bug can be found here: https://github.com/GiantVM/Linux-DSM/pull/3 (at the end) Here is a snippet of the log: [ 107.980285] ------------[ cut here ]------------ [ 107.980995] kernel BUG at arch/x86/kvm/dsm-util.c:214! [ 107.981706] invalid opcode: 0000 [#1] SMP [ 107.982423] Modules linked in: ccm arc4 iwlmvm joydev mac80211 mei_wdt hid_alps snd_soc_skl snd_soc_skl_ipc snd_hda_codec_hdmi snd_soc_sst_ipc snd_soc_sst_dsp snd_hda_codec_realtek snd_hda_ext_core snd_hda_codec_generic dell_wmi snd_soc_sst_match dell_smbios snd_soc_core snd_compress snd_pcm_dmaengine ac97_bus dcdbas dell_smm_hwmon iwlwifi snd_hda_intel snd_hda_codec cfg80211 intel_rapl snd_hda_core x86_pkg_temp_thermal intel_powerclamp coretemp snd_hwdep snd_pcm snd_timer snd input_leds serio_raw soundcore idma64 virt_dma hci_uart uvcvideo mei_me btusb mei videobuf2_vmalloc btrtl videobuf2_memops videobuf2_v4l2 videobuf2_core btbcm videodev btqca btintel bluetooth media intel_pch_thermal intel_lpss_pci processor_thermal_device intel_soc_dts_iosf acpi_als kfifo_buf intel_hid int3400_thermal intel_lpss_acpi [ 107.985763] acpi_pad intel_lpss dell_smo8800 int3403_thermal industrialio acpi_thermal_rel mac_hid int340x_thermal_zone sparse_keymap iscsi_tcp libiscsi_tcp autofs4 btrfs raid10 raid456 async_raid6_recov async_memcpy async_pq async_xor async_tx xor raid6_pq libcrc32c raid1 raid0 multipath linear i2c_hid i915 crct10dif_pclmul drm_kms_helper crc32_pclmul syscopyarea sysfillrect sysimgblt ghash_clmulni_intel fb_sys_fops drm aesni_intel e1000e aes_x86_64 lrw glue_helper ablk_helper cryptd ahci libahci wmi hid pinctrl_sunrisepoint pinctrl_intel video fjes [ 107.990389] CPU: 1 PID: 1592 Comm: qemu-system-x86 Not tainted 4.9.76+ #5 [ 107.991368] Hardware name: Dell Inc. Latitude 5280/08DMYJ, BIOS 1.9.3 03/08/2018 [ 107.992346] task: ffff92fa7e1f9700 task.stack: ffffa2dc837e4000 [ 107.993310] RIP: 0010:[<ffffffffb606794e>] [<ffffffffb606794e>] dsm_decode_diff+0xbe/0xd0 [ 107.994310] RSP: 0018:ffffa2dc837e7b50 EFLAGS: 00010286 [ 107.995310] RAX: 00000000ffffffff RBX: ffff92fa66090000 RCX: 0000000000001000 [ 107.996294] RDX: ffff92fa66096000 RSI: 0000000000000001 RDI: ffff92fa66090000 [ 107.997297] RBP: ffffa2dc837e7b78 R08: ffffa2dc837e8000 R09: 0000000000001000 [ 107.998292] R10: 0000000000001000 R11: 0000000000000030 R12: ffff92fa66096000 [ 107.999305] R13: ffffa2dc85af31c0 R14: 0000000000078948 R15: 0000000000000001 [ 108.000303] FS: 00007f92cfbff700(0000) GS:ffff92fab1480000(0000) knlGS:0000000000000000 [ 108.001326] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 108.002316] CR2: 00007f5c3c3ca688 CR3: 00000007fdc84000 CR4: 0000000000362670 [ 108.003333] Stack: [ 108.004354] 00000007f9348548 ffffa2dc85b09000 0000000000078948 ffffa2dc85af31c0 [ 108.005379] ffff92fa7dc98000 ffffa2dc837e7bf8 ffffffffb6069713 0000000100000000 [ 108.006427] 000000017e1fa940 ffff92fa66090000 0000000000000000 0000000000000000 [ 108.007480] Call Trace: [ 108.008508] [<ffffffffb6069713>] ivy_kvm_dsm_page_fault+0x573/0x840 [ 108.009572] [<ffffffffb60645e1>] kvm_dsm_page_fault+0x71/0xd0 [ 108.010633] [<ffffffffb606639c>] kvm_dsm_memcpy+0x33c/0x5c0 [ 108.011667] [<ffffffffb6066c76>] kvm_vm_ioctl_dsm+0xc6/0x360 [ 108.012721] [<ffffffffb6035ef9>] kvm_arch_vm_ioctl+0x929/0xbf0 [ 108.013767] [<ffffffffb611b605>] ? update_load_avg+0x75/0x390 [ 108.014806] [<ffffffffb611b605>] ? update_load_avg+0x75/0x390 [ 108.015827] [<ffffffffb60219ea>] kvm_vm_ioctl+0x8a/0x7c0 [ 108.016828] [<ffffffffb60957c5>] ? __switch_to+0x2e5/0x700 [ 108.017842] [<ffffffffb62a2412>] do_vfs_ioctl+0x92/0x5b0 [ 108.018830] [<ffffffffb68f9e12>] ? __sys_recvmsg+0x62/0x80 [ 108.019823] [<ffffffffb62a29a9>] SyS_ioctl+0x79/0x90 [ 108.020806] [<ffffffffb6a3159e>] entry_SYSCALL_64_fastpath+0x1e/0xc9 [ 108.021801] Code: 0f 00 00 48 29 fb 48 29 de 81 c3 00 10 00 00 c1 eb 03 89 d9 f3 48 a5 4c 89 e7 e8 3e f8 1f 00 5b 41 5c 41 5d 41 5e 41 5f 5d f3 c3 <0f> 0b 0f 0b 0f 1f 40 00 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 [ 108.023980] RIP [<ffffffffb606794e>] dsm_decode_diff+0xbe/0xd0 [ 108.025003] RSP <ffffa2dc837e7b50> AFAIK, this is a memory corruption problem. There maybe a function that rewrite the kernel code and set some instruction to 0x0? Ideas?

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process descriptor address in kernel stack
by , Samuel March 19, 2020

March 19, 2020

In this book (understanding Linux kernel), the kernel can easily obtain the address of the thread_info structure of the process currently running on a CPU from the value of the esp register. In fact, if the thread_union structure is 8 KB (213 bytes) long, the kernel masks out the 13 least significant bits of esp to obtain the base address of the thread_info structure; on the other hand, if the thread_union struc- ture is 4 KB long, the kernel masks out the 12 least significant bits of esp. This is done by the current_thread_info() function, which produces assembly language instructions like the following: movl $0xffffe000,%ecx or 0xfffff000 for 4KB stacks andl %esp,%ecx movl %ecx,p Why is *"stack pointer(esp) & 0xffffe000"* equal to the process descriptor base address? That means the base address of process descriptor is always *0xXYZ...000*, right? It is weird.

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request_firmware in DMA region
by Lucas Tanure March 18, 2020

March 18, 2020

Hi, I'm sending firmware to usb device with this code: But it`s falling because the request firmware call didn't put my firmware in a DMA capable area. That's my guess. So how to request firmware in DMA capable area? Thanks Lucas [ 30.330081] ------------[ cut here ]------------ [ 30.334782] WARNING: CPU: 1 PID: 557 at /media/workspace/linux/drivers/usb/core/hcd.c:1586 usb_hcd_map_urb_for_dma+0x4f4/0x634 [ 30.346362] transfer buffer not dma capable [ 30.350623] Modules linked in: usb_bridge_boot(+) bnep hci_uart btbcm serdev bluetooth ecdh_generic 8021q garp stp llc bcm2835_codec(C) brcmfmac vc4 brcmutil v4l6 [ 30.406130] CPU: 1 PID: 557 Comm: systemd-udevd Tainted: G C 4.19.108-v7l+ #1 [ 30.414691] Hardware name: BCM2835 [ 30.418148] [<c0212c6c>] (unwind_backtrace) from [<c020d490>] (show_stack+0x20/0x24) [ 30.426009] [<c020d490>] (show_stack) from [<c09c1ac0>] (dump_stack+0xd8/0x11c) [ 30.433428] [<c09c1ac0>] (dump_stack) from [<c0222138>] (__warn+0xf0/0x108) [ 30.440492] [<c0222138>] (__warn) from [<c02221a8>] (warn_slowpath_fmt+0x58/0x74) [ 30.448087] [<c02221a8>] (warn_slowpath_fmt) from [<c079df38>] (usb_hcd_map_urb_for_dma+0x4f4/0x634) [ 30.457357] [<c079df38>] (usb_hcd_map_urb_for_dma) from [<c079e518>] (usb_hcd_submit_urb+0x4a0/0x968) [ 30.466714] [<c079e518>] (usb_hcd_submit_urb) from [<c079fbfc>] (usb_submit_urb+0x354/0x504) [ 30.475277] [<c079fbfc>] (usb_submit_urb) from [<c07a0430>] (usb_start_wait_urb+0x6c/0xf0) [ 30.483663] [<c07a0430>] (usb_start_wait_urb) from [<c07a0588>] (usb_control_msg+0xd4/0x12c) [ 30.492232] [<c07a0588>] (usb_control_msg) from [<bf984270>] (clbrd_probe+0x240/0x43c [usb_bridge_boot]) [ 30.502135] [<bf984270>] (clbrd_probe [usb_bridge_boot]) from [<c07a4f64>] (usb_probe_interface+0xec/0x278) [ 30.512287] [<c07a4f64>] (usb_probe_interface) from [<c071a4d8>] (really_probe+0x1e8/0x2d0) [ 30.520762] [<c071a4d8>] (really_probe) from [<c071a794>] (driver_probe_device+0x70/0x184) [ 30.529149] [<c071a794>] (driver_probe_device) from [<c071a998>] (__driver_attach+0xf0/0xf4) [ 30.537712] [<c071a998>] (__driver_attach) from [<c07183f4>] (bus_for_each_dev+0x84/0xc4) [ 30.546011] [<c07183f4>] (bus_for_each_dev) from [<c0719ddc>] (driver_attach+0x2c/0x30) [ 30.554133] [<c0719ddc>] (driver_attach) from [<c07197bc>] (bus_add_driver+0x19c/0x220) [ 30.562254] [<c07197bc>] (bus_add_driver) from [<c071b184>] (driver_register+0x84/0x118) [ 30.570464] [<c071b184>] (driver_register) from [<c07a3d84>] (usb_register_driver+0x80/0x144) [ 30.579117] [<c07a3d84>] (usb_register_driver) from [<bf989030>] (clbrd_driver_init+0x30/0x1000 [usb_bridge_boot]) [ 30.589889] [<bf989030>] (clbrd_driver_init [usb_bridge_boot]) from [<c0203138>] (do_one_initcall+0x50/0x214) [ 30.600218] [<c0203138>] (do_one_initcall) from [<c02bdcb8>] (do_init_module+0x74/0x224) [ 30.608429] [<c02bdcb8>] (do_init_module) from [<c02bcce8>] (load_module+0x202c/0x25dc) [ 30.616552] [<c02bcce8>] (load_module) from [<c02bd4d8>] (sys_finit_module+0xbc/0xe8) [ 30.624497] [<c02bd4d8>] (sys_finit_module) from [<c02011a4>] (__sys_trace_return+0x0/0x1c) [ 30.632969] Exception stack(0xdafdffa8 to 0xdafdfff0) [ 30.638091] ffa0: fda1c800 01e30b08 00000006 b6d8f8e0 00000000 b6d903f4 [ 30.646388] ffc0: fda1c800 01e30b08 00000000 0000017b 01e5c418 0057f1dc 01e5d0c8 00000000 [ 30.654684] ffe0: bea80180 bea80170 b6d869d8 b6e76af0 [ 30.659823] ---[ end trace fa96d8b137009b49 ]--- static int fx3_ram_write(struct usb_device *udev, u32 *buf, u32 ramAddress, size_t len) { size_t index = 0, size; int ret; while(len > 0) { size = (len > MAX_WRITE_SIZE) ? MAX_WRITE_SIZE : len; ret = usb_control_msg(udev, usb_sndctrlpipe(udev, 0), 0xA0, 0x40, ramAddress & 0xFFFF, ramAddress >> 16, &buf[index], size, VENDORCMD_TIMEOUT); if (ret != size) { ret = (ret < 0) ? ret : -EIO; dev_err(&udev->dev, "Error: Vendor write to FX3 RAM failed: %d\n", ret); return ret; } ramAddress += size; index += size; len -= size; } return 0; } static int clbrd_probe(struct usb_interface *intf, const struct usb_device_id *id) { struct device *dev = &intf->dev; struct usb_device *udev = interface_to_usbdev(intf); const struct firmware *firmware; struct fx3_img *img; struct fx3_sector *sector; int ret; dev_info(&intf->dev, "%s\n", __func__); ret = request_firmware(&firmware, FW_NAME, dev); if (ret) dev_err(dev, "request_firmware failed '%s' = %d (check files)\n", FW_NAME, ret); img = (struct fx3_img*)firmware->data; print_img_header(dev, img); sector = (struct fx3_sector*)img->sectors; while ((u8*)sector < firmware->data + firmware->size) { dev_dbg(&intf->dev, "0x%.4x 0x%.4x\n", sector->dLength , sector->dAddress); if (sector->dLength == 0) { ret = usb_control_msg(udev, usb_sndctrlpipe(udev, 0), 0xA0, 0x40, (sector->dAddress & 0xFFFF), (sector->dAddress >> 16), NULL, 0, VENDORCMD_TIMEOUT); if (ret < 0) dev_err(dev, "Fail to write last sector: %d\n", ret); break; } ret = fx3_ram_write(udev, sector->dData, sector->dAddress, sector->dLength * 4); if (ret < 0) dev_err(dev, "Fail to write sector: %d\n", ret); sector += sizeof(sector->dLength) + sizeof(sector->dAddress) + (sector->dLength * 4); } release_firmware(firmware); return ret; }

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