[英]Unable to create directories in /proc from a custom kernel module
In the /proc directory a custom module should create two directories lkm and mem to get a hierarchy like /proc/lkm/mem .在 /proc 目录中,自定义模块应创建两个目录lkm和mem以获得类似/proc/lkm/mem的层次结构。
A simple refactoring now broke what was working without obvious reason.一个简单的重构现在在没有明显原因的情况下破坏了工作。
After the refactoring the module is not creating the hierarchy /proc/lkm/mem anymore.重构后,模块不再创建层次结构/proc/lkm/mem 。 It only creates lkm and then stops.
它只创建lkm然后停止。 There're no messages in the Kernel Ring Buffer.
内核环缓冲区中没有消息。 I was wondering what did I break with that refactoring?
我想知道我在重构中破坏了什么? I hope you can help me finding the issue.
我希望你能帮我找到问题。
Manual tests have been run with a fresh started VM and with usual insmod/rmmod and following versions:手动测试已使用新启动的 VM 和通常的 insmod/rmmod 和以下版本运行:
In the following you can see the original and the refactored code.在下面,您可以看到原始代码和重构代码。 At the bottom I put the a minimum source file and the Makefile.
在底部,我放了一个最小的源文件和 Makefile。 There is also a repository , an issue and the breaking commit .
还有一个存储库、一个问题和破坏性提交。 Of course I could revert that commit, but other refactorings are coming and I want to know the reason, before I break something similar.
当然,我可以恢复那个提交,但其他重构即将到来,我想知道原因,然后再破坏类似的东西。
Thanks in advance :)提前致谢 :)
Original code prior to refactoring重构前的原始代码
static int __init lkm_mem_init(void)
{
lkm_proc_parent = proc_mkdir(LKM_PROC_PARENT, NULL);
if (lkm_proc_parent == NULL) {
printk(KERN_ERR "lkm_mem: Failed to create parent /proc/%s for lkm.\n",
LKM_PROC_PARENT);
return 1;
}
mem_proc_parent = proc_mkdir(LKM_MEM_PROC_PARENT, lkm_proc_parent);
if (mem_proc_parent == NULL) {
printk(KERN_ERR
"lkm_mem: Failed to create parent /proc/%s/%s for mem.\n",
LKM_PROC_PARENT, LKM_MEM_PROC_PARENT);
return 1;
}
// ...
}
Refactored code重构代码
static int __init lkm_mem_init(void)
{
lkm_proc_mkdir(lkm_proc_parent, LKM_PROC_PARENT, NULL);
lkm_proc_mkdir(mem_proc_parent, LKM_MEM_PROC_PARENT, lkm_proc_parent);
// ...
}
void lkm_proc_mkdir(struct proc_dir_entry *entry, const char *name,
struct proc_dir_entry *parent)
{
entry = proc_mkdir(name, parent);
if (entry == NULL) {
printk(KERN_ERR
"lkm_mem: Failed to create parent %s in proc.\n",
name);
// todo: How to abort loading module in gentle way?
}
}
// ...
Minimum source code最小源代码
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/module.h>
#include <linux/proc_fs.h>
#include <linux/seq_file.h>
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Thomas Piekarski");
MODULE_DESCRIPTION("Exposing separated memory and swap statistics to /proc");
MODULE_VERSION("0.1");
#define LKM_PROC_PERMISSION 0444
#define LKM_PROC_PARENT "lkm"
#define LKM_MEM_PROC_PARENT "mem"
#define LKM_MEM_PROC_TOTAL_ENTRY "total"
#define LKM_MEM_PROC_FREE_ENTRY "free"
struct sysinfo si;
struct proc_dir_entry *lkm_proc_parent;
struct proc_dir_entry *mem_proc_parent;
struct proc_dir_entry *mem_proc_total_entry;
struct proc_dir_entry *mem_proc_free_entry;
static int lkm_value_show(struct seq_file *seq, void *v)
{
seq_put_decimal_ull(seq, "", *(unsigned long *)seq->private);
seq_putc(seq, '\n');
return 0;
}
void lkm_proc_create_single_data(struct proc_dir_entry *entry,
unsigned long *value, const char *name)
{
entry = proc_create_single_data(name, LKM_PROC_PERMISSION,
mem_proc_parent, lkm_value_show, value);
if (entry == NULL) {
printk(KERN_ERR "lkm_mem: Failed to create /proc/%s/%s/%s.\n",
LKM_PROC_PARENT, LKM_MEM_PROC_PARENT, name);
}
}
void lkm_proc_mkdir(struct proc_dir_entry *entry, const char *name,
struct proc_dir_entry *parent)
{
entry = proc_mkdir(name, parent);
if (entry == NULL) {
printk(KERN_ERR
"lkm_mem: Failed to create parent %s in proc.\n",
name);
}
}
void lkm_remove_proc_entry(struct proc_dir_entry *entry, const char *name,
struct proc_dir_entry *parent)
{
if (entry != NULL) {
remove_proc_entry(name, parent);
}
}
static int __init lkm_mem_init(void)
{
lkm_proc_mkdir(lkm_proc_parent, LKM_PROC_PARENT, NULL);
lkm_proc_mkdir(mem_proc_parent, LKM_MEM_PROC_PARENT, lkm_proc_parent);
si_meminfo(&si);
lkm_proc_create_single_data(mem_proc_total_entry, &si.totalram,
LKM_MEM_PROC_TOTAL_ENTRY);
lkm_proc_create_single_data(mem_proc_free_entry, &si.freeram,
LKM_MEM_PROC_FREE_ENTRY);
return 0;
}
static void __exit lkm_mem_exit(void)
{
lkm_remove_proc_entry(mem_proc_total_entry, LKM_MEM_PROC_TOTAL_ENTRY,
mem_proc_parent);
lkm_remove_proc_entry(mem_proc_free_entry, LKM_MEM_PROC_FREE_ENTRY,
mem_proc_parent);
lkm_remove_proc_entry(mem_proc_parent, LKM_MEM_PROC_PARENT,
lkm_proc_parent);
lkm_remove_proc_entry(lkm_proc_parent, LKM_PROC_PARENT, NULL);
}
module_init(lkm_mem_init);
module_exit(lkm_mem_exit);
Makefile生成文件
ccflags-y := -Wall
obj-m += lkm_device.o lkm_mem.o lkm_parameters.o lkm_proc.o lkm_sandbox.o lkm_skeleton.o
all:
$(MAKE) -C /lib/modules/$(shell uname -r)/build M=$(PWD) modules
clean:
$(MAKE) -C /lib/modules/$(shell uname -r)/build M=$(PWD) clean
Edits - Added URLs to repository, issue and commit编辑- 添加了存储库、发布和提交的 URL
struct proc_dir_entry *lkm_proc_parent;
struct proc_dir_entry *mem_proc_parent;
static int __init lkm_mem_init(void)
{
lkm_proc_parent
is NULL
here... lkm_proc_parent
在这里为NULL
...
lkm_proc_mkdir(lkm_proc_parent, LKM_PROC_PARENT, NULL);
and it's still NULL here
, since of course, function arguments in C are passed by value.并且
NULL here
仍然是NULL here
,因为当然,C 中的函数参数是按值传递的。
lkm_proc_mkdir(mem_proc_parent, LKM_MEM_PROC_PARENT, lkm_proc_parent);
So this is calling proc_mkdir("mem", NULL)
.所以这是调用
proc_mkdir("mem", NULL)
。 You'll probably notice that a /proc/mem
directory has been created.您可能会注意到已经创建了一个
/proc/mem
目录。
// ...
}
Meanwhile:同时:
void lkm_proc_mkdir(struct proc_dir_entry *entry, const char *name,
struct proc_dir_entry *parent)
{
entry = proc_mkdir(name, parent);
if (entry == NULL) {
printk(KERN_ERR
"lkm_mem: Failed to create parent %s in proc.\n",
name);
}
}
The value returned by proc_mkdir
is lost when this function returns, since you only assigned it to one of the function arguments, which of course is local to the function.当这个函数返回时,
proc_mkdir
返回的值会丢失,因为你只将它分配给函数参数之一,这当然是函数的本地参数。 Again, arguments are passed by value!同样,参数是按值传递的!
It seems like you probably want lkm_proc_mkdir
to return a struct proc_dir *
, rather than taking one as an argument.看起来您可能希望
lkm_proc_mkdir
返回一个struct proc_dir *
,而不是将其作为参数。 Or possibly you wanted the first argument to be a struct proc_dir **
, but that seems to me like worse style.或者您可能希望第一个参数是
struct proc_dir **
,但在我看来这更像是一种更糟糕的风格。
声明:本站的技术帖子网页,遵循CC BY-SA 4.0协议,如果您需要转载,请注明本站网址或者原文地址。任何问题请咨询:yoyou2525@163.com.