I have a simple Kernel module:
void GPIO_LED(void) {
printk(" GPIO: set PC8: '0');
at91_set_gpio_value(AT91_PIN_PC8, 1);
}
//
int init_module(void) {
GPIO_LED();
return 0;
}
MODULE_LICENSE("GPL");
When using it with mdev device management. everything works just fine. But using it with a udev device management, while executing insmod
insmod /usr/modules/measurement_gpio.ko
the following message appeared:
insmod: can't insert '/usr/modules/measurement_gpio.ko': invalid module format
Another test showed that when using a device table instead of mdev/udev leads to the same Error. Every setting stayed the same (especially the kernel version) but the device management changes during this Test, so actually the module should be fine.
How can that be and how to solve it?
[Edit:] after making the kernel be able for load modules for multiple versions i receive the following message, which confuses me even more:
measurement_gpio: version magic '2.6.39 mod_unload modversions ARMv5 ' should be '2.6.39 mod_unload ARMv5
[Edit2:]
The way I build my module is:
with Buildroot I'm generating an Image, on the way a Linux
2.6.39 is installed.
Afterwards I'm compiling the kernelmodule with the path to the Linux 2.6.39, that buildroot has downloaded.
When the module is created I'm putting it into a fs-overlay
directory, so it will be included into the image on next build.
I hit another "make" on buildroot and i got everything together and a bootable Image.
I change nothing, that's why it confuses me even more
Related
I want to make my own protocol driver for my custom made spi board. The platform on which I want to attach it is a raspberry Pi4 with arm32. I want to load it dynamically with an overlay device tree.
I can build the driver file but the following isn't clear:
Where should the driver exactly placed? I tried /lib/modules/5.4.79-v7, /lib/modules/5.4.79-v7/build
I made in the config.txt an entry dtoverlays= driver.ko and placed the dtbo under /boot/overlays. Is this correct?
Can the driver be loaded at runtime without a second reboot after I placed the overlay file in the right folder.
Is the driver first loaded if the function "spi_new_device" is called or can it be done in this way?
If I call sudo insmod .ko the driver is loaded with:
rpi4: loading out-of-tree module taints kernel.
The probe function isn't called yet.
Where should the driver exactly placed? I tried /lib/modules/5.4.79-v7, /lib/modules/5.4.79-v7/build
Answer: The driver is placed under /lib/modules/5.4.79-v7/extra if it is an extra module and build with.
make -C /lib/modules/`uname -r`/build M=$PWD modules_install
I made in the config.txt an entry dtoverlays= driver.ko and placed the dtbo under /boot/overlays. Is this correct?
Answer: It can be done in this way with rpi.
Can the driver be loaded at runtime without a second reboot after I placed the overlay file in the right folder.
Answer: If the driver is installed under extra it is not loaded. Also it is not loaded after reboot. The driver must be loaded with "modprobe" but without the extension ".ko". Modprobe search the driver under lib/modules.
My desktop is Intel x86_64 processor with Ubuntu operating system.
I know there is perf tool to get a list of statistics of a program.
But what I am trying to do is read performance counter directly without using the perf tool.
First Question
First Questions is I downloaded this code from Github: Github Code Reference.
It compiled successfully with linux-headers-5.3.0-40-generic kernel without any errors. Once I use "insmod" the .ko file, the system hangs. The .ko file is not inserted when I checked the dmesg, so I have to cease it after I do "insmod" the .ko file. Does it happen because I attempted unauthorized access? If there are suggestions that I can try, I am glad to hear that.
The corresponding code is below.
static void set_pce(void *arg)
{
int to_val = (arg != 0);
u_int64_t cr4_val;
cr4_val = __read_cr4();
if (to_val) {
cr4_val |= X86_CR4_PCE;
} else {
cr4_val &= ~X86_CR4_PCE;
}
__write_cr4(cr4_val);
}
static int __init user_rdpmc_init(void){
int cpu;
num_cpus = num_online_cpus();
printk(KERN_INFO "Enabling RDPMC from ring 3 for %d CPUs\n", num_cpus);
for (cpu = 0; cpu < num_cpus; cpu++) {
smp_call_function_single(cpu, set_pce, (void *) 1, 1);
}
return 0;
}
Second Question
Second question is I am using linux-headers-5.3.0-40-generic kernel version in my Ubuntu desktop. I downloaded kernel code version 5.5.3 from kernel.org. I followed the perf code given in the 5.5.3 kernel code thoroughly and discovered that core.c file under linux-5.5.3/arch/x86/events/intel directory actually does setting and reading the performance counters. I used the core.c file contents to make it as a module to read the performance counter. When I compile it, it creates a bunch of errors because I use linux-headers-5.3.0-40-generic to build the module but my ubuntu kernel doesn't have all header files linked to the core.c file from kernel code from kernel.org.
How can I make my Ubuntu kernel use all the files linked to core.c from kernel.org and build the .ko file?
Or Is there any module source code that has x86 performance counter reading that I can use as a reference?
Thank you for your help in advance.
I know there is perf tool to get a list of statistics of a program. But what I am trying to do is read performance counter directly without using the perf tool.
If you do not want to use perf tool, you can try to use oprofile tool or intel vtune or https://github.com/RRZE-HPC/likwid or https://github.com/opcm/pcm. Or you can use perf_event_open syscall which is how perf tool works (you can study or modify perf tool sources from https://mirrors.edge.kernel.org/pub/linux/kernel/tools/perf/ - and perf tool version may not be equal to kernel version).
If you want to access msr registers as root, use modprobe msr (this is standard kernel module, already compiled for your kernel in ubuntu) and wrmsr and rdmsr tools (msr-tools deb/ubuntu package, by intel), like in slide 27 of Performance Monitoring Chris Dahnken Intel SSG EMEA HPCTC presentation.
I don't understand why do you want to work with performance counters without perf tool. If you want to get counter readings from inside of your program, for example before and after some loops, you can use perf_event_open syscall (with specific ioctls) directly. (Or try to use perf stat + same ioctls PERF_EVENT_IOC_* or try to learn perf + JIT integration)
Or you can use existing kernel module which will export msr register access to root user - the msr.ko. And msr tools - https://01.org/msr-tools. Or with this msr+pmc example https://technicalandstuff.wordpress.com/2015/05/15/using-intels-pcm-in-linux-and-inside-c/ + https://software.intel.com/en-us/articles/intel-performance-counter-monitor (https://github.com/opcm/pcm)
There are also some examples of perf counters usage in https://github.com/RRZE-HPC/likwid.
You can also use PAPI library to access counters from your code, it will handle most of perf_event_open stuff for you. http://icl.cs.utk.edu/projects/papi/wiki/PAPITopics:Getting_Started
First Questions is I downloaded this code https://github.com/softdevteam/user_rdpmc ... "insmod" the .ko file, the system hangs.
There are too low "Stars" rating and the code is too old (2016) to really doing any investigations on the hang. Direct access of PMC may interfere with NMI watchdog (do echo 0 > /proc/sys/kernel/nmi_watchdog as root) or other perf session. It is safer to use perf_event_open syscall.
Second question ... discovered that core.c file under linux-5.5.3/arch/x86/events/intel directory actually does setting and reading the performance counters
This file is part of perf_event_open syscall implementation (perf_events subsystem of the kernel, https://github.com/torvalds/linux/tree/master/kernel/events + https://github.com/torvalds/linux/tree/master/arch/x86/events).
To use this code you can use the perf tool or perf_event_open syscall.
You should not compile the perf_events subsystem of the kernel as separate module because it is already compiled into your kernel (intel/amd specific part can be partially ko) and the Subsystem itself does not support compilation as module:
https://github.com/torvalds/linux/tree/master/kernel/events
Makefile: obj-y := core.o ring_buffer.o callchain.o
How can I make my Ubuntu kernel use all the files linked to core.c from kernel.org and build the .ko file?
Your ubuntu kernel already have all perf_events subsystem files compiled, some are linked into the kernel image and other are .ko files already installed like intel-rapl-perf.ko
$ grep _PERF_ /boot/config-`uname -r`
$ ls -l /lib/modules/`uname -r`/kernel/arch/x86/events/intel
I'm trying to cross compile the Linux kernel 4.10.8 for arm, but get this error:
CC [M] drivers/vhost/vhost.o
In file included from ./include/uapi/linux/stddef.h:1:0,
from ./include/linux/stddef.h:4,
from ./include/uapi/linux/posix_types.h:4,
from ./include/uapi/linux/types.h:13,
from ./include/linux/types.h:5,
from ./include/uapi/asm-generic/fcntl.h:4,
from ./arch/arm/include/uapi/asm/fcntl.h:9,
from ./include/uapi/linux/fcntl.h:4,
from ./include/linux/fcntl.h:4,
from ./include/linux/eventfd.h:11,
from drivers/vhost/vhost.c:14:
drivers/vhost/vhost.c: In function ‘vhost_vring_ioctl’:
./include/linux/compiler.h:518:38: error: call to ‘__compiletime_assert_1357’ declared with attribute error: BUILD_BUG_ON failed: __alignof__ *vq->avail > VRING_AVAIL_ALIGN_SIZE
_compiletime_assert(condition, msg, __compiletime_assert_, __LINE__)enter
Any idea how to solve this?
I dont know what this module is used for, so I dont know if I actually need to compile it, but I cant find where in menuconfig to disable this module?
This module (CONFIG_VHOST) usually requires when you need virtualization support. If you don't require it disable it in the make menuconfig.
If you don't need virtualization, you can ignore it and proceed your build.
I want to use the LSM framework with kernel ubuntu 2.6.36.
When I compiled the kernel module, it wrote:
WARNING: "register_security " undefined!
After a lot of googlings, I found the reason is that the register_security() symbol is no longer exported in the 2.6 kernel.
So I added EXPORT_SYMBOL(register_security) in the ../security/security.c file, and recompiled the kernel.
After booting with the new kernel, I added extern int register_security(struct security_operations *ops) in my kernel module file, and compiled the module again.
However, the WARNING information still existed. If I continued to insmode the module, the dmesg told me that
Unknown symbol register_security
What should I do? How can I register a Linux Security Module?
Make sure newly loaded kernel is the one, which is compiled by you.
Check the Licence of your module (Ref: http://lists.jammed.com/linux-security-module/2004/08/0053.html)
In modern kernels register_security symbol does not exported. It means that you can't register LSM module as a module. But if you really wish to do that you can do that :) Look at the exported LSM-symbols like security_sb_copy_data. They are simple wrappers over the security_ops->some_lsm_method. So, you can use their code to determine security_ops pointer value. It needs disassembler though.
Unknown symbol register_security
Happened at the line that you unregister your LSM.
So add unregister_security() in security.c and export it:
/**
* unregister_security - allows security modules to be moved
* #ops : a pointer to the struct security_options that had been registered before.
*/
int unregister_security(struct security_operations *ops)
{
if (ops != security_ops)
{
printk (KERN_INFO "%s: trying to unregister "
"a security_opts structure that is not "
"registered, failing.\n", __FUNCTION__);
return -EINVAL;
}
security_ops = &dummy_security_ops;
return 0;
}
EXPORT_SYMBOL(unregister_security);
And recompiled the kernel.
I'm compiling a custom kernel under Ubuntu and I'm running into the problem that my kernel doesn't seem to know where to look for firmware. Under Ubuntu 8.04, firmware is tied to kernel version the same way driver modules are. For example, kernel 2.6.24-24-generic stores its kernel modules in:
/lib/modules/2.6.24-24-generic
and its firmware in:
/lib/firmware/2.6.24-24-generic
When I compile the 2.6.24-24-generic Ubuntu kernel according the "Alternate Build Method: The Old-Fashioned Debian Way" I get the appropriate modules directory and all my devices work except those requiring firmware such as my Intel wireless card (ipw2200 module).
The kernel log shows for example that when ipw2200 tries to load the firmware the kernel subsystem controlling the loading of firmware is unable to locate it:
ipw2200: Detected Intel PRO/Wireless 2200BG Network Connection
ipw2200: ipw2200-bss.fw request_firmware failed: Reason -2
errno-base.h defines this as:
#define ENOENT 2 /* No such file or directory */
(The function returning ENOENT puts a minus in front of it.)
I tried creating a symlink in /lib/firmware where my kernel's name pointed to the 2.6.24-24-generic directory, however this resulted in the same error. This firmware is non-GPL, provided by Intel and packed by Ubuntu. I don't believe it has any actual tie to a particular kernel version. cmp shows that the versions in the various directories are identical.
So how does the kernel know where to look for firmware?
Update
I found this solution to the exact problem I'm having, however it no longer works as Ubuntu has eliminated /etc/hotplug.d and no longer stores its firmware in /usr/lib/hotplug/firmware.
Update2
Some more research turned up some more answers. Up until version 92 of udev, the program firmware_helper was the way firmware got loaded. Starting with udev 93 this program was replaced with a script named firmware.sh providing identical functionality as far as I can tell. Both of these hardcode the firmware path to /lib/firmware. Ubuntu still seems to be using the /lib/udev/firmware_helper binary.
The name of the firmware file is passed to firmware_helper in the environment variable $FIRMWARE which is concatenated to the path /lib/firmware and used to load the firmware.
The actual request to load the firmware is made by the driver (ipw2200 in my case) via the system call:
request_firmware(..., "ipw2200-bss.fw", ...);
Now somewhere in between the driver calling request_firmware and firmware_helper looking at the $FIRMWARE environment variable, the kernel package name is getting prepended to the firmware name.
So who's doing it?
From the kernel's perspective, see /usr/src/linux/Documentation/firmware_class/README:
kernel(driver): calls request_firmware(&fw_entry, $FIRMWARE, device)
userspace:
- /sys/class/firmware/xxx/{loading,data} appear.
- hotplug gets called with a firmware identifier in $FIRMWARE
and the usual hotplug environment.
- hotplug: echo 1 > /sys/class/firmware/xxx/loading
kernel: Discard any previous partial load.
userspace:
- hotplug: cat appropriate_firmware_image > \
/sys/class/firmware/xxx/data
kernel: grows a buffer in PAGE_SIZE increments to hold the image as it
comes in.
userspace:
- hotplug: echo 0 > /sys/class/firmware/xxx/loading
kernel: request_firmware() returns and the driver has the firmware
image in fw_entry->{data,size}. If something went wrong
request_firmware() returns non-zero and fw_entry is set to
NULL.
kernel(driver): Driver code calls release_firmware(fw_entry) releasing
the firmware image and any related resource.
The kernel doesn't actually load any firmware at all. It simply informs userspace, "I want a firmware by the name of xxx", and waits for userspace to pipe the firmware image back to the kernel.
Now, on Ubuntu 8.04,
$ grep firmware /etc/udev/rules.d/80-program.rules
# Load firmware on demand
SUBSYSTEM=="firmware", ACTION=="add", RUN+="firmware_helper"
so as you've discovered, udev is configured to run firmware_helper when the kernel asks for firmware.
$ apt-get source udev
Reading package lists... Done
Building dependency tree
Reading state information... Done
Need to get 312kB of source archives.
Get:1 http://us.archive.ubuntu.com hardy-security/main udev 117-8ubuntu0.2 (dsc) [716B]
Get:2 http://us.archive.ubuntu.com hardy-security/main udev 117-8ubuntu0.2 (tar) [245kB]
Get:3 http://us.archive.ubuntu.com hardy-security/main udev 117-8ubuntu0.2 (diff) [65.7kB]
Fetched 312kB in 1s (223kB/s)
gpg: Signature made Tue 14 Apr 2009 05:31:34 PM EDT using DSA key ID 17063E6D
gpg: Can't check signature: public key not found
dpkg-source: extracting udev in udev-117
dpkg-source: unpacking udev_117.orig.tar.gz
dpkg-source: applying ./udev_117-8ubuntu0.2.diff.gz
$ cd udev-117/
$ cat debian/patches/80-extras-firmware.patch
If you read the source, you'll find that Ubuntu wrote a firmware_helper which is hard-coded to first look for /lib/modules/$(uname -r)/$FIRMWARE, then /lib/modules/$FIRMWARE, and no other locations. Translating it to sh, it does approximately this:
echo -n 1 > /sys/$DEVPATH/loading
cat /lib/firmware/$(uname -r)/$FIRMWARE > /sys/$DEVPATH/data \
|| cat /lib/firmware/$FIRMWARE > /sys/$DEVPATH/data
if [ $? = 0 ]; then
echo -n 1 > /sys/$DEVPATH/loading
echo -n -1 > /sys/$DEVPATH/loading
fi
which is exactly the format the kernel expects.
To make a long story short: Ubuntu's udev package has customizations that always look in /lib/firmware/$(uname -r) first. This policy is being handled in userspace.
Wow this is very useful information and it led me to the solution for my problem when making a custom USB kernel module for a device requiring firmware.
Basically, every Ubuntu brings a new rehash of hal,sysfs,devfs,udev,and so on...and things just change. In fact I read they stopped using hal.
So let's reverse engineer this yet again so it's pertinent to the latest [Ubuntu] systems.
On Ubuntu Lucid (the latest at time of writing), /lib/udev/rules.d/50-firmware.rules is used. This file calls the binary /lib/udev/firmware, where magic happens.
Listing: /lib/udev/rules.d/50-firmware.rules
# firmware-class requests, copies files into the kernel
SUBSYSTEM=="firmware", ACTION=="add", RUN+="firmware --firmware=$env{FIRMWARE} --devpath=$env{DEVPATH}"
The magic should be something along these lines (source: Linux Device Drivers, 3rd Ed., Ch. 14: The Linux Device Model):
echo 1 to loading
copy firmware to data
on failure, echo -1 to loading and halt firmware loading process
echo 0 to loading (signal the kernel)
then, a specific kernel module receives the data and pushes it to the device
If you look at Lucid's source page for udev, in udev-151/extras/firmware/firmware.c, the source for that firmware /lib/udev/firmware binary, that's exactly what goes on.
Excerpt: Lucid source, udev-151/extras/firmware/firmware.c
util_strscpyl(datapath, sizeof(datapath), udev_get_sys_path(udev), devpath, "/data", NULL);
if (!copy_firmware(udev, fwpath, datapath, statbuf.st_size)) {
err(udev, "error sending firmware '%s' to device\n", firmware);
set_loading(udev, loadpath, "-1");
rc = 4;
goto exit;
};
set_loading(udev, loadpath, "0");
Additionally, many devices use an Intel HEX format (textish files containing checksum and other stuff) (wiki it i have no reputation and no ability to link). The kernel program ihex2fw (called from Makefile in kernel_source/lib/firmware on .HEX files) converts these HEX files to an arbitrary-designed binary format that the Linux kernel then picks up with request_ihex_firmware, because they thought reading text files in the kernel was silly (it would slow things down).
On current Linux systems, this is handled via udev and the firmware.agent.
Linux 3.5.7 Gentoo, I have the same issue.
SOLVED:
emerge ipw2200-firmware
Then go to /usr/src/linux
make menucofig
on device driver, remove all wirless drivers don't needed, set Intell 2200 as module and recompile.
make
make modules_install
cp arch/x86/boot/bzImage /boot/kernel-yourdefault