February 2019 - kernelnewbies@kernelnewbies.org

How to dealwith mmap for a filesystem filter driver?
by kipade Feb. 16, 2019

Feb. 16, 2019

Hello all, I created a filter driver for the vfs, for some special file read, I want to replace its data got from the disk and return to the new data to user space, eg. decryption. my hooked read entry like this: int my_hooked_read(struct file* filp, char* buffer, size_t count, loff_t* pos) { int ret = orig_read(filp, buffer, count, pos); if(ret > 0) { //do something } return ret; } the code works file for normal read, but take no sense for read via mmap operations. so, I want to know what should I do to resolve such issue? Thanks.

1 0

Configuring a Conexant USB modem
by Jeffrey Walton Feb. 15, 2019

Feb. 15, 2019

Hi Everyone, I'm having trouble using a USB modem. It is a Conexant modem but it is not responding to AT commands. Sample code is at https://pastebin.com/84YUn9ey . I think the first thing I need to do is verify the kernel configuration for the device. For that: $ sudo setserial -a /dev/ttyACM0 /dev/ttyACM0, Line 0, UART: unknown, Port: 0x0000, IRQ: 0 Baud_base: 115200, close_delay: 12, divisor: 0 closing_wait: 750 Flags: spd_normal At this point I think I need to read some kernel docs. I'm not sure if I should be in https://www.kernel.org/doc/Documentation/serial or https://www.kernel.org/doc/Documentation/usb . Looking through the pages nothing jumps out as specific to the Conexant. Can someone suggest what my next steps are to verify the modem's configuration with respect to the kernel and driver? Thanks in advance.

2 1

Want to improve wiki document
by Bo YU Feb. 14, 2019

Feb. 14, 2019

Hi, I want to improve the page: https://kernelnewbies.org/KernelJanitors/Todo For example, 1. Fix sparse warnings. Read section "Where to get sparse" in Documentation/sparse.txt... As we all know, it has been moved into Documentation/dev-tools/, right? Please consider add me into editor list, thanks!

3 6

how to find out IRQ end user
by Matwey V. Kornilov Feb. 14, 2019

Feb. 14, 2019

Hello, >From /sys/kernel/debug/tracing I see the following points: <idle>-0 [000] d.h1 2388.136032: irq_handler_entry: irq=16 name=gp_timer Is there a simple way to figure out what is the exact final function called to handle this IRQ?

2 3

[Question] Use mr25h40 in a custom DSDT ACPI table
by Flavio Suligoi Feb. 14, 2019

Feb. 14, 2019

Hi all, I work on a custom x86 board. In this board I have to manage an MRAM chip mr25h40 (on the SPI bus). I want to modify the DSDT ACPI table in the BIOS. Unfortunately, the mr25h40 is not Jedec compatible, so, in my DSDT, if I use the classic: {"compatible", "jedec,spi-nor"} the device drivers mtd and m25p80 are loaded, but obviously the MRAM is not initialized: Device (NVR0) { Name (_HID, "PRP0001") Name (_DDN, "Everspin MR25H40 MRAM") Name (_CRS, ResourceTemplate () { SpiSerialBus ( 0, // Chip select PolarityLow, // Chip select is active low FourWireMode, // Full duplex 8, // Bits per word is 8 (byte) ControllerInitiated, // Don't care 10000000, // 10 MHz ClockPolarityLow, // SPI mode 0 ClockPolarityLow ClockPhaseFirst, // SPI mode 0 ClockPhaseFirst "\\_SB.SPI1", // SPI host controller 0 // Must be 0 ) }) Name (_DSD, Package () { ToUUID("daffd814-6eba-4d8c-8a91-bc9bbf4aa301"), Package () { Package () {"compatible", "jedec,spi-nor"}, } }) } Instead if I try to use: Package () {"compatible", "mr25h40"} obviously it doesn't work, because "mr25h40" is not in the m25p_of_table. Does anyone have any ideas? Thanks and best regards, Flavio Suligoi

1 0

SELinux, LSM and ima_policy rules
by Lev Olshvang Feb. 4, 2019

Feb. 4, 2019

Hello everybody. I learned recently that IMA kernel security subsystem can be integrated with LSMs, such as SELinux, Smack, ... https://sourceforge.net/p/linux-ima/wiki/Home/ https://www.kernel.org/doc/Documentation/ABI/testing/ima_policy It was present in kernel since v3.8 but not google does not know much about the usability. Does anybody have any experience or references which I can read to learn restrictions, performance impact or just use cases? ThanX! Lev.

2 1