创建proc项，write函数调用copy_from_user读取换行符的疑问 - Chinaunix

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/proc_fs.h>
#include<linux/sched.h>
#include <asm/uaccess.h>
#include <linux/slab.h>
#include <linux/string.h>
int len,temp;
char *msg;
int read_proc(struct file *filp,char *buf,size_t count,loff_t *offp)
{
if(count>temp)
{
count=temp;
}
temp=temp-count;
printk("read\n");
printk("count = %d\n", count);
printk("strlen(msg) = %d\n", strlen(msg));
copy_to_user(buf,msg, count);
if(count==0)
temp=len;
return count;
}
int write_proc(struct file *filp,const char *buf,size_t count,loff_t *offp)
{
if (copy_from_user(msg,buf,count))
return -EFAULT;
len=count;
temp=len;
printk("write\n");
printk("count = %d\n", count);
printk("strlen(msg) = %d\n", strlen(msg));
return count;
}
struct file_operations proc_fops = {
read: read_proc,
write: write_proc
};
void create_new_proc_entry()
{
proc_create("hello",0,NULL,&proc_fops);
msg=kmalloc(GFP_KERNEL,10*sizeof(char));
}
int proc_init (void) {
create_new_proc_entry();
return 0;
}
void proc_cleanup(void) {
remove_proc_entry("hello",NULL);
}
MODULE_LICENSE("GPL");
module_init(proc_init);
module_exit(proc_cleanup);

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obj-m += proc_rw.o
KDIR := /lib/modules/$(shell uname -r)/build
PWD := $(shell pwd)
EXTRA_CFLAGS = -g -O0 -std=gnu99 -Wno-declaration-after-statement
all:
make -C $(KDIR) M=$(PWD) modules
rm -rf *.ko.unsigned *.mod.c *.mod.o *.symvers *.o
.PHONY: clean
clean:
make -C $(KDIR) M=$(PWD) clean

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echo -ne "a b c" > /proc/hello

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# cat /proc/hello
a b c

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echo -ne "a b c\td \ne f" > /proc/hello

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# cat /proc/hello
e f

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int write_proc(struct file *filp,const char *buf,size_t count,loff_t *offp)
{
printk("buf size: %d\n", strlen_user(buf));
if (copy_from_user(msg,buf,count))
return -EFAULT;
len=count;
temp=len;
printk("write\n");
printk("count = %d\n", count);
printk("strlen(msg) = %d\n", strlen(msg));
return count;
}

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echo -ne "a b c\td \ne f" > /proc/hello

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# dmesg
[76143.461257] buf size: 1613
[76143.461261] write
[76143.461262] count = 9
[76143.461262] strlen(msg) = 16
[76143.461268] buf size: 1613
[76143.461269] write
[76143.461270] count = 5
[76143.461270] strlen(msg) = 16

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cat /proc/hello
e f

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# dmesg
[76143.461257] buf size: 1613
[76143.461261] write
[76143.461262] count = 9
[76143.461262] strlen(msg) = 16
[76143.461268] buf size: 1613
[76143.461269] write
[76143.461270] count = 5
[76143.461270] strlen(msg) = 16
[76157.239084] read
[76157.239088] count = 5
[76157.239090] strlen(msg) = 16
[76157.239102] read
[76157.239103] count = 0
[76157.239104] strlen(msg) = 16

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[76143.461257] buf size: 1613
[76143.461261] write
[76143.461262] count = 9
[76143.461262] strlen(msg) = 16
[76143.461268] buf size: 1613
[76143.461269] write
[76143.461270] count = 5
[76143.461270] strlen(msg) = 16
[76157.239084] read
[76157.239088] count = 5
[76157.239090] strlen(msg) = 16
[76157.239102] read
[76157.239103] count = 0
[76157.239104] strlen(msg) = 16

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printk("read\n");
printk("count = %d\n", count);
printk("strlen(msg) = %d\n", strlen(msg));

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echo -ne "a b c \n d e \n f \n gh \n wxyz" > /proc/hello
[root@super memory]# cat /proc/hello
wxyz[root@super memory]# dmesg
[87130.808871] buf size: 1613
[87130.808875] write
[87130.808876] count = 7
[87130.808877] strlen(msg) = 16
[87130.808881] buf size: 1613
[87130.808882] write
[87130.808883] count = 6
[87130.808883] strlen(msg) = 16
[87130.808887] buf size: 1613
[87130.808888] write
[87130.808889] count = 4
[87130.808889] strlen(msg) = 16
[87130.808894] buf size: 1613
[87130.808894] write
[87130.808895] count = 5
[87130.808896] strlen(msg) = 16
[87130.808901] buf size: 1613
[87130.808901] write
[87130.808902] count = 5
[87130.808903] strlen(msg) = 16
[87134.014814] read
[87134.014819] count = 5
[87134.014820] strlen(msg) = 16
[87134.014840] read
[87134.014841] count = 0
[87134.014842] strlen(msg) = 16

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const struct file_operations *proc_fops;

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ssize_t (*read) (struct file *file, char __user *buf, size_t count, loff_t *offset);
ssize_t (*write) (struct file *file, const char __user *buf, size_t count, loff_t *offset);

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有点问题

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linux-mkov:~/jerry # cat hh.c
#include <linux/module.h>
#include <linux/mm.h>
#include <linux/gfp.h>
#include <linux/kernel.h>
#include <linux/proc_fs.h>
#include <asm/uaccess.h>
#include <linux/slab.h>
#include <linux/string.h>
struct cir_list {
unsigned int num ;
struct list_head * cir_entry ;
struct list_head * write;
struct list_head * read;
};
struct cir_node {
struct list_head list;
int w_off_set ;
int r_off_set ;
char * buff ;
int ok ;
};
struct cir_list * jerry;
int add_node (struct cir_list *c, struct cir_node * n)
{
if(c == NULL) return 0;
if(n == NULL) return 0;
if(c->cir_entry == NULL){
c->cir_entry = &n->list;
c->write = &n->list;
c->read = &n->list;
printk("create the first node\n");
return 1;
}else {
printk("add the new node to the list\n");
list_add(&n->list,c->cir_entry);
c->num +=1;
printk("the num of c %d \n", c->num);
return 1;
}
}
struct cir_list * gen_cir(int n){
struct cir_list * hello_list;
hello_list = kmalloc(sizeof(struct cir_list),GFP_KERNEL);
if(hello_list == NULL){
return NULL;
}
//init the list
hello_list->cir_entry = NULL;
hello_list->write = NULL;
hello_list->num = 0;
hello_list->read = NULL;
struct cir_node * hello_node;
int i;
printk("start to generate nodes in total %d \n",n);
for(i=0;i<n;i++){
printk("start to generate %d \n",i);
hello_node = kmalloc(sizeof(struct cir_node),GFP_KERNEL);
if(hello_node == NULL) {
printk("not enough mem\n");
//TO DO #free all the node already allocated;
return NULL;
}
//init the node
hello_node->list.next = &hello_node->list;
hello_node->list.prev = &hello_node->list;
hello_node->w_off_set = 0;
hello_node->r_off_set = 0;
hello_node->buff = get_zeroed_page(GFP_KERNEL);
hello_node->ok = 1;
printk("start to generate %d add_node func\n",i);
add_node(hello_list,hello_node);
}
return hello_list;
}
void clean_list_node(struct cir_list * c)
{
struct cir_node * n;
struct list_head * l;
printk("start to free\n");
list_for_each(l,c->cir_entry) {
printk("in for each loop free\n");
n = list_entry(l, struct cir_node, list);
if(n==NULL) return;
free_page(n->buff);
printk("in for each loop free free_page\n");
kfree(n);
printk("in for each loop free node\n");
}
printk("out for each loop free list\n");
//free the head
printk("free the head \n");
n = list_entry(c->cir_entry, struct cir_node, list);
free_page(n->buff);
printk("head free_page\n");
kfree(n);
printk("head node\n");
kfree(c);
printk("free the list descriptor\n");
}
void write_end(char * buff ,size_t count ,struct cir_list * l )
{
printk("----------------------------------start write--------------------------------\n" );
unsigned int done=0;
unsigned int left_sp_node;
struct cir_node * t_node;
t_node = list_entry(l->write,struct cir_node,list);
left_sp_node = 4096 - t_node->w_off_set;
printk("the left space : %d , woffset : %d\n",left_sp_node,t_node->w_off_set );
while(count > left_sp_node){
printk("----------------------------------loops--------------------------------\n" );
printk(" value lengh %d is bigger than left space %d\n",count,left_sp_node);
copy_from_user(t_node->buff + t_node->w_off_set,buff+done,left_sp_node);
printk(" count %d is decrease space\n",count,left_sp_node);
count -= left_sp_node;
t_node->w_off_set += left_sp_node;
done += left_sp_node;
t_node = list_entry(t_node->list.next,struct cir_node,list);
t_node->r_off_set = 0;
t_node->w_off_set = 0;
left_sp_node = 4096 - t_node->w_off_set;
printk("----------------------------------loope--------------------------------\n" );
}
printk(" value length %d is small than left space %d\n",count,left_sp_node);
printk(" --start to append value %d at offset %d---\n",count,t_node->w_off_set );
copy_from_user(t_node->buff + t_node->w_off_set,buff+done,count);
t_node->w_off_set += count;
done += count;
printk(" finshed append %d , all done is %d in this time\n",count,done);
l->write = &t_node->list;
printk("----------------------------------end--------------------------------\n" );
return 1;
}
int read_to_write (struct cir_list * l,char * buff,size_t count)
{
struct cir_node * t_node;
int o_left;
t_node = list_entry(l->read,struct cir_node,list);
if(l->read != l->write){
printk("cross read\n");
o_left = 4096 - t_node->r_off_set;
printk("cross read this node have left %d , the request count is %d \n",o_left,count);
printk("cross area read woffset : %d , roffset : %d \n",t_node->w_off_set,t_node->r_off_set);
if(count <= o_left){
printk("cross read count is <= o_left \n");
copy_to_user(buff,t_node->buff + t_node->r_off_set,count);
printk("cross area read copy to user %d \n",count);
t_node->r_off_set += count;
return count;
}else{
copy_to_user(buff ,t_node->buff + t_node->r_off_set,o_left);
t_node->r_off_set = 4096;
t_node = list_entry(t_node->list.next,struct cir_node,list);
l->read = &t_node->list;
return o_left;
}
} else {
printk("same area read\n");
o_left = t_node->w_off_set - t_node->r_off_set;
printk("same area read woffset : %d , roffset : %d \n",t_node->w_off_set,t_node->r_off_set);
if(o_left==0) return 0;
if(count <= o_left){
copy_to_user(buff,t_node->buff + t_node->r_off_set,count);
t_node->r_off_set += count;
return count;
}else{
copy_to_user(buff ,t_node->buff + t_node->r_off_set,o_left);
t_node->r_off_set += o_left;
return o_left;
}
}
}
int read_proc(struct file *filp,char *buf,size_t count,loff_t *offp)
{
printk("read\n");
int real_count;
real_count = read_to_write(jerry,buf,count);
return real_count;
}
int write_proc(struct file *filp,const char *buf,size_t count,loff_t *offp)
{
printk("write\n");
write_end(buf,count,jerry);
return count;
}
struct file_operations proc_fops = {
read: read_proc,
write: write_proc
};
void create_new_proc_entry()
{
proc_create("hello",0,NULL,&proc_fops);
}
int proc_init (void) {
jerry = gen_cir(4);
create_new_proc_entry();
return 0;
}
void proc_cleanup(void) {
remove_proc_entry("hello",NULL);
clean_list_node(jerry);
}
MODULE_LICENSE("GPL");
module_init(proc_init);
module_exit(proc_cleanup);

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ssize_t (*read) (struct file *file, char __user *buf, size_t count, loff_t *offset);
ssize_t (*write) (struct file *file, const char __user *buf, size_t count, loff_t *offset);

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