3rd-party/linux-kernel-module-cheat
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split kernel module api docs to README

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Ciro Santilli
2018-07-01 23:37:37 +01:00
parent 8f37cd0d22
commit 6c241279a6
18 changed files with 490 additions and 296 deletions
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66
kernel_module/dep.c
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@@ -1,76 +1,22 @@
/*
Exports the lkmc_dep which dep2.ko uses.
/* https://github.com/cirosantilli/linux-kernel-module-cheat#kernel-module-dependencies */
insmod /dep.ko
# dmesg => 0
# dmesg => 0
# dmesg => ...
insmod /dep2.ko
# dmesg => 1
# dmesg => 2
# dmesg => ...
rmmod dep
# Fails because dep2 uses it.
rmmod dep2
# Dmesg stops incrementing.
rmmod dep
sys visibility:
dmesg -n 1
insmod /dep.ko
insmod /dep2.ko
ls -l /sys/module/dep/holders
# => ../../dep2
cat refcnt
# => 1
proc visibility:
grep lkmc_dep /proc/kallsyms
Requires "CONFIG_KALLSYMS_ALL=y".
depmod:
grep dep "/lib/module/"*"/depmod"
# extra/dep2.ko: extra/dep.ko
# extra/dep.ko:
modprobe dep
# lsmod
# Both dep and dep2 were loaded.
TODO: at what point does buildroot / busybox generate that file?
*/
#include <linux/delay.h> /* usleep_range */
#include <linux/debugfs.h>
#include <linux/kernel.h>
#include <linux/kthread.h>
#include <linux/module.h>
int lkmc_dep = 0;
u32 lkmc_dep = 0;
EXPORT_SYMBOL(lkmc_dep);
static struct task_struct *kthread;
static int work_func(void *data)
{
while (!kthread_should_stop()) {
pr_info("%d\n", lkmc_dep);
usleep_range(1000000, 1000001);
}
return 0;
}
static struct dentry *debugfs_file;
static int myinit(void)
{
kthread = kthread_create(work_func, NULL, "mykthread");
wake_up_process(kthread);
debugfs_file = debugfs_create_u32("lkmc_dep", S_IRUSR | S_IWUSR, NULL, &lkmc_dep);
return 0;
}
static void myexit(void)
{
kthread_stop(kthread);
debugfs_remove(debugfs_file);
}
module_init(myinit)