Hi ,
That is my first post here. I'm studying kernel and more especific /proc. I'm trying to receive a pid on write using /proc ,find uid and print all tasks with the same uid.Like this :
# ps aux
root 4713
0.0 0.0 1592 500 tty1 Ss+ Jan09 0:00
/sbin/getty 38400 tty1
root 4714 0.0 0.0 1592 504 tty2 Ss+ Jan09 0:00
/sbin/getty 38400 tty2
root 4715
0.0 0.0 1596 508 tty3 Ss+ Jan09 0:00
/sbin/getty 38400 tty3
root 4716 0.0 0.0 1596 504 tty4 Ss+ Jan09 0:00
/sbin/getty 38400 tty4
root 4717 0.0 0.0 1592 504 tty5 Ss+ Jan09 0:00
/sbin/getty 38400 tty5
root 4718 0.0 0.0 1592 504 tty6 Ss+ Jan09 0:00
/sbin/getty 38400 tty6
foo 29661 0.0 0.0 3696 2064 pts/0 Ss Jan10 0:00 bash
foo 1794 0.0 0.0 3672 2036 pts/3 Ss Jan10 0:00 bash
foo 26631 0.0 0.1 3660 2328 pts/1 S+ 16:09 0:00 vim foo.txt
root 718 0.0 0.0 592 500 ? Ss+ Jan09 0:00 /sbin/cron
# echo "1794" > /proc/entrada
# cat /proc/entrada
<29661, bash>
<1794, bash>
<26631, vim>
I wrote some changes and created a patch (end of file),the new kernel is crashing.
root@darkstar:~# cat /proc/entrada
< 1 , init >
< 2 , migration/0 >
< 3 , ksoftirqd/0 >
< 4 , watchdog/0 >
< 5 , events/0 >
< 6 , khelper >
< 7 , kthread >
< 8 , kblockd/0 >
< 22 , pdflush >
< 23 , pdflush >
< 25 , aio/0 >
< 24 , kswapd0 >
< 673 , syslogd >
< 676 , klogd >
< 712 , inetd >
< 721 , crond >
< 724 , bash >
< 741 , agetty >
< 742 , agetty >
< 743 , agetty >
< 757 , cat >
root@darkstar:~# su - foo
[42949478.160000] Kernel panic - not syncing: Kernel mode fault at addr 0x61202d68, ip 0x400ab0b8
[42949478.160000] [42949478.160000]
My first patch :)
Index: linux-2.6.15.7/fs/proc/proc_misc.c
===================================================================
--- linux-2.6.15.7.orig/fs/proc/proc_misc.c 2006-08-11 10:08:20.000000000 -0400
+++ linux-2.6.15.7/fs/proc/proc_misc.c 2006-08-11 10:08:38.000000000 -0400
@@ -13,6 +13,8 @@
* Changes:
* Fulton Green : Encapsulated position metric calculations.
* <kernel@xxxxxxxxxxxxxxx>
+ * Changes Francisco Keppler Silva Alecrim (
alecrim@xxxxxxxxx)
+ * Create "entrada" on /proc to read a pid number and return all processes of its owner.
*/
#include <linux/types.h>
@@ -67,7 +69,8 @@
extern int get_exec_domain_list(char *);
extern int get_dma_list(char *);
extern int get_locks_status (char *, char **, off_t, int);
-
+static struct proc_dir_entry *proc_entry_file;
+int process_number=0;
static int proc_calc_metrics(char *page, char **start, off_t off,
int count, int *eof, int len)
{
@@ -563,6 +566,55 @@
entry->proc_fops = f;
}
+
+/*function called when someone try to read /proc/entrada
+ * It returns all processes of a owner*/
+static int proc_entry_file_read(char *page, char **start, off_t off,
+ int count, int *eof, void *data)
+{
+ int len; //length - used to store the page length
+ char *out,*item; // out - store all info
+ struct task_struct *p,*c=find_task_by_pid(process_number);//p - pointer process - used to check all processes // c - pointer for current process
+ if(!c)//if not not found
+ {
+ len=sprintf(page,"Current pid=%d does not exist! :p\n",process_number);//store on page : not found
+ return len; //returning length of page used
+ }
+ out=kmalloc(200,GFP_KERNEL);
+ item=kmalloc(20,GFP_KERNEL);
+ strcpy(out,"");
+ for_each_process(p)//pointer p will run for all process
+ {
+ if(c->uid == p->uid)//some uid = user identifier
+ {
+ sprintf(item,"< %d , %s >\n",p->pid,p->comm);//store on task identifier and name on item
+ strcat(out,item); //acumulate item to out
+ }
+ }
+ len=sprintf(page,"%s",out);//store on page : all task of a user
+ return len;
+}
+/*function called when someone try to write /proc/entrada
+ * It stores a process number giving by someone on process_number*/
+static int proc_entry_file_write (struct file *file, const char *buffer,unsigned long count, void *data)
+{
+ char *input = kmalloc (count,GFP_KERNEL) ;// pointer to store buffer number
+ if (!input)
+ {
+ return -ENOMEM ; // Out of memory
+ }
+ if(copy_from_user(input,buffer,count))//copy value stored on buffer to input
+ {
+ kfree(input);
+ return -EFAULT; //Bad address
+ }
+ process_number=simple_strtoul(input,NULL,10); // convert string to unsigned integer and store on process_number
+ printk(KERN_INFO "proc_entry_file - received process number %d \n",process_number);
+ kfree(input);
+ return count ;
+}
+
+
void __init proc_misc_init(void)
{
struct proc_dir_entry *entry;
@@ -629,4 +681,7 @@
if (entry)
entry->proc_fops = &proc_sysrq_trigger_operations;
#endif
+ proc_entry_file=create_proc_entry("entrada",S_IRUGO | S_IWUSR,NULL); // creating a proc entry
+ proc_entry_file->read_proc= proc_entry_file_read; //defining that when file read , execute proc_entry_file_read
+ proc_entry_file->write_proc=proc_entry_file_write; // when write proc_entry_file_read
}
What is wrong ?
Go ahead , give it hell. I'm open for comments and sugestions.
Thanks
--
--
Francisco Keppler Silva Alecrim
Instituto Nokia de Tecnologia (INdT) - OSMRC
