Ftrace "function" enabling fails with resource busy
I am trying to enable "function" tracer in ftrace after going...
View ArticleLinux suspend/resume operations' userspace notification
I'm working on an embedded linux platform.When I do "echo "mem"> /sys/power/state", system will suspend.I know that kernel and driver can know that suspend operation's coming. But would it be...
View ArticleClik here to view.
How to access the I/O bits of PCI printer card?
In older time on a P4 mother board of my PC there was an integrated parallel printer port with a DB-25 connector. These I/O pins was very handy to communicate with an external digital equipment.I could...
View ArticleIs bool a native C type?
I've noticed that the Linux kernel code uses bool, but I thought that bool was a C++ type. Is bool a standard C extension (e.g., ISO C90) or a GCC extension?
View ArticleeMMC writes randomly takes longer time
I'm analysing how long time it takes to write 1MB to a eMMC. It is supposed to happen during powerfail, thus time is critical.I found that the write can be done in 40 ms, which is fine.However randomly...
View ArticleHow to apply patches to a package in Buildroot?
I am working on an embedded system that uses buildroot as a tool for building the kernel and the root filesystem. I want to apply some patches to this kernel source tree, Can somebody tell me how...
View ArticleCan linux kernel module be removed before module init has completed?
Lets say my kernel module have the init and exit function bellow:module_init(init_module);module_exit(cleanup_module);Can the kernel module be removed, thus calling cleanup_module(), before the module...
View ArticleReboot only userspace
Is it possible to restart only the userspace? Like shutdown everything up to the kernel and then restart from PID 1?I would like to snapshot my root btrfs filesystem and quickly boot on that snapsnot.
View ArticleWhat is memory reclaim in linux
I am very new to Linux memory management concept while reading some memory management related document I had some basic doubt please clarify me.considering below is my config...
View ArticleDevice tree debugging
I have a very basic question about the Linux Device TreI'm trying to build a device tree coming from an existing project, the device tree compiler just refuses like this:Error:...
View ArticleHow to post-date ftrace events
I am currently using ftrace to trace a variety of events on the local system both within my application and the graphics drivers. But, this is a multi-computer setup. And I'm trying to trace things...
View Articlemodule_init macro vs init_module function for built-in kernel modules
I've been trying to do some light kernel development on Android.I'm a bit confused about how built-in (built using obj-y += module_name.o) kernel modules use the module_init macro vs the init_module...
View ArticleLinux Character Device is not registering
I refactored the code for my Hello World device driver, and now the device will not register.The module is listed as expected in /proc/modules after a sudo make load.However, the device itself is no...
View ArticleGetting VBox Guest Addtions for Android x86
I am running Android x86 on VirtualBox, and I want the pointer integration enabled, which needs VirtualBox Guest Additions to be installed on the guest OS. I have searched a lot, but what I have found...
View ArticleGet the executable file name (comm in task_struct) from a PID
I am learning OS in Linux, and want to get the executable file name.I know I can get it from 'comm' located in task_struct, but I don't know how to get it.Thank you!
View ArticleHow can I disable producing paged (non-linear) skb's in Linux kernel?
Suppose I write some LKM with networking (netfilter) activity and I need to do some tampering with skb including skb_pull(). So I have to take care about is skb linear or not before pulling.If I...
View ArticleWhat is an simple example of copy_from_user
There is already a question about copy_from_user, but it is a little bit too advanced for me, I want to see simple example of using the copy_from_user method within kernel module, what is the simplest...
View ArticleCustom system call leads to infinite loop
I am adding a custom system call to the Linux kernel in Ubuntu:SYSCALL_DEFINE1(test_call, int, num){ if (num >= 0 && num <= 6) { char values[7][15] = { "PROC_OVERRIDE", "PROC_ALERT",...
View ArticleWhy netdev_alloc_skb_ip_align allocates different size of sk_buffers?
The next issue is regarding linux kernel buffers for managing network packets, as known as sk_buff.I'm running a code that every time that some event occurs it calls netdev_alloc_skb_ip_align to...
View ArticleWhy ARMv7-A crashes when flushing the stack pointer from the cache
I am trying to evict the memory address in which the stack pointer is pointing to it in an ARM Cortex-A8 processor. I am trying to do that with the below code:cpy r3, spmcr p15, 0x0, r3, cr7, cr6, 0x1I...
View Article