BPF custom kfunc : calling kernel function %s is not allowed
I am writing some codes for my thesis using ebpf and I need to create a custom kfunc to call within my bpf program. To do so I started by following the example here...
View ArticleTuning Apache (Event MPM); Many Intensive Rewrites
My loadbalacned website (Server version: Apache/2.4.37) has many mod_rewrite expressions using the ipmatch flag to forbid/block single IPs as well as entire ranges of IPs. I'm using info from these...
View ArticlePCI Express AER driver doesn't insert /dev/aer_inject as device
Currently using the description shown at this site to capture PCI-e AER codes.All the options related to the custom kernel compilation has been enabled as shown belowcat /boot/config-6.8.0-48-generic |...
View ArticleBPF verification error when trying to extract SNI from TLS packet
I am trying to get the server name from the SNI extension of a TLS hello packet in a XDP program. When I try to load it, I get the following error from the BPF verifier:math between pkt pointer and...
View Articlehow to find Linux module path
in the linux, lsmod lists a lot of modules. but how can we find where those module loaded from.for some modules,linux command "modprobe -i" shows a path but some are not.editedi also tried "find" and...
View Articleunable to understand kernel panic logs from /var/log/kern.log [closed]
The ubuntu system that stored these logs crashed. When we later restarted the system and viewed the logs at /var/log/kern.log we found unusual logs starting with "echo 0 >...
View ArticleGeneric clock consumer in the common clock framework
In my setup, there is a clock generator that use the common clock framework in the Linux kernel. The clock generator has an output clock that I would like to feed to an external connector. If I have...
View Articledevice-tree entry for an i2c to spi multiplexer that shares logic with a GPIO...
I have the following setup (from external; this cannot be changed):+------+ I2C | I2C |--------------------- Device 0--------| to |------------ Device 1 | MISO0 | SPI |--- Device 2 | MISO1 |+------+ |...
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eBPF program fails with "libbpf: failed to find valid kernel BTF" after...
I'm learning how to use eBPF in Linux environments via the libbpf library. I have a simple eBPF program that compiles and runs successfully on kernel version 5.15.0-125-generic, but after upgrading my...
View ArticlePCIe driver, Bus Mastering DMA and dma_alloc_coherent
I a trying to write a linux-driver for a PCIe device which should have bus mastering capabilities. I am encountering the problem that the buffer space, when initialized with dma_alloc_coherent() is not...
View ArticleWhy is Linux interrupting processing every second even with isolated core
I'm working in a real-time system Linux with the PREEMPT_RT kernel, multi-core Xeon processor. I have an isolated core, and turned off irqaffinity and am using the nohz_full option on the isolated...
View ArticleCross-compiling Linux kernel for ARM on Windows using Sourcery Toolchain
I am trying to cross-compile a Linux kernel for an ARM-target (Freescale i.Mx28) on a Windows host. I know that this approach is not the best one compared to using a Linux host, but unfortunately it's...
View ArticleWhat is the interface for ARM system calls and where is it defined in the...
I have read about system calls in Linux, and everywhere descriptions are given regarding x86 architecture (0x80 interrupt and SYSENTER). But I am not able to track down the files and process for a...
View ArticleIn Linux kernel, where's the function that prints a character to a text VGA...
I am reading Linux's source code, hoping to build a better understanding of its architecture. My goal is to reduce it to a minimal "hello, world" binary, removing as much unrelated code as possible....
View ArticleDifference between Linux Loadable and built-in modules
What's the difference between loadable modules and built-in (statically linked) modules?I got this question while finding out an answer for difference between system calls subsys_initcall() and...
View ArticleLinux device node for sd card as mmcblk to access CSD register
I am trying to access the CSD (Card Specific Data) register on a SD card. The only way I know to do this is by having the linux system recognize it as a mmc device (Multi Media Card?) (eg....
View ArticleHow to test shpc on qemu
Contextualizing the ProblemI am a beginner contributor to the Linux kernel.Recently, I made a change to the SHPC (Standard Hot-Plug Controller) drivers, where I replaced the request_irq() function with...
View ArticleDoes the Linux scheduler need to execute on every core in a multicore?
Is it possible for a kernel scheduler thread executing on one core to handle the scheduling of threads/processes for a different remote core, or is it necessary for every core to have their own kernel...
View ArticleSeveral `/dev/uioX` devices fail to enumerate for uio_pdrv_genirq driver
I use the uio_pdrv_genirq driver to control a number of FPGA modules on a Xilinx MPSoC system. I've used this for several months with quite a few FPGA modules (~170) and never had any difficulties...
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PCIe BAR alignment issue under Linux
I am using kernel 5.4.93 (with Ubuntu 20.04 rootfs) on an ARMv8-based embedded system. The "BIOS" is U-boot which does not include PCIe feature thus the PCIe bus enumeration is solely done by...
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