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What this article shares with you is about how to apply the prctl () function. The editor thinks it is very practical, so I share it with you to learn. I hope you can get something after reading this article.

T prctl (int option,unsigned longarg2,unsigned long arg3,unsigned long arg4,unsigned long arg5)

This system call instruction is designed for the process, and the clear choice depends on the option:

PR_GET_PDEATHSIG: returns the processor signal

PR_SET_PDEATHSIG: arg2 is entered as the processor signal pdeath, which, as the name suggests, is accepted by the process if the parent process is no longer available.

PR_GET_DUMPABLE: returns the processor flag dumpable

PR_SET_DUMPABLE: arg2 is entered as the processor flag dumpable.

PR_GET_NAME: returns the process name of the calling process to the parameter arg2; (Since Linux2.6.9)

PR_SET_NAME: use the parameter arg2 as the frequent name of the calling process. (SinceLinux 2.6.11)

PR_GET_TIMING:

PR_SET_TIMING: determines and modifies process timing mode, which is used to enable traditional process timing mode

PR_TIMING_STATISTICAL, or to enable timestamp-based process timing mode

PR_TIMING_TIMESTAMP .

CAP_CHOWN function:

In a system defined by the _ POSIX_CHOWN_RESTRICTED function. This overrides all permissions to change the owner and group of system files

CAP_DAC_OVERRIED function:

If _ POSIX_ACL is defined, it crosses all DAC access, including ACL execution access, and excludes it with the CAP_LINUX_IMMUTABLE function

Access to DAC

CAP_DAC_READ_SEARCH function:

If _ POSIX_ACL is defined, all DAC read limits are exceeded

And search all files and directories, including ACL restrictions. Use CAP_LINUX_IMMUTABLE to restrict DAC access

CAP_FOWNER function:

The file says that some restrictions are allowed, such as the owner of the file, ID, must be the same as the user ID, except that CAP_FSETID is available. It will not exceed the MAC and DAC restrictions.

CAP_FSETID function:

Beyond the limit that the user's ID must match the owner ID when setting the S_ISUID and S_ISGID bits of the file, when setting the S-ISGID bit, the group ID

Restrictions that must match the owner ID, use chown to set the functional limits for S_ISUID and S_ISGID

CAP_FS_MASK function:

Used to respond to suser () or fsuser ().

CAP_KILL function:

A process with a valid user ID must match the function of a valid user ID when sending a signal

CAP_SETGID function:

Allow setgid () function, allow setgroups ()

Allow counterfeiting of gid in socket

CAP_SETUID function:

Allow set*uid () function to allow forged pid in socket

CAP_SETPCAP function:

Give all permits to all pid. Or delete all licenses.

CAP_LINUX_IMMUTABLE function:

Allow changes to S_IMMUTABLE and S_APPEND file properties

CAP_NET_BIND_SERVICE function:

Allow binding of TCP/UDP sockets under 1024

CAP_NET_BROADCAST function:

Allow broadcast, monitor multicast

CAP_NET_ADMIN function:

Allow configuration of interfac

Allow management of IP Firewall IP masquerading and accounts

Allow configuration of socket debugging options

Allow routing table modification

Allows you to configure the group properties of processes on socket

Allow transparent proxies to bind all addresses

Allow configuration of TOS (service type)

Allow configuration of promiscuous mode

Allow drive status to be cleared

Allow multicasting

Allow you to read or write system records

CAP_NET_RAW function:

Allow RAW sockets

Allow PACKET sockets

CAP_IPC_LOCK function:

Allow trivial fixing of shared memory segments

Allow mlock and mlockall

CAP_IPC_OWNER function:

Beyond the IPC ownership check

CAP_SYS_MODULE function:

Insert or remove kernel modules

CAP_SYS_RAWIO function:

Allow access to ioperm/iopl and / dev/prot

Allow / dev/mem and / dev/kmem access

Allow block devices to access (/ dev/ [sh] dongs? )

CAP_SYS_CHROOT function:

Allow chroot ()

CAP_SYS_PTRACE function:

Allow ptrace () any process

CAP_SYS_PACCT function:

Allow configuration of process accounts

CAP_SYS_ADMIN function:

Allow configuration of security keys

Allow management of random devices

Allow device management

Allows you to check and configure disk limits

Allow configuration of kernel logs

Allow configuration of domain names

Allow configuration of hostname

Allow calls to the bdflush () command

Allow mount () and umount () commands

Allow configuration of smb connections

Allow ioctls for root

Allow nfsservctl

Allow VM86_REQUEST_IRQ

Allow pci configuration to be read and written on alpha

Allow irix_prctl on mips

Allow all m68k caches to be flushed

Allow deletion of semaphores

Replace "chown" IPC message queues, flags and shared memory with CAP_CHOWN

Allow locking or unlocking shared memory segments

Allow switch swap

Allow camouflage of pids in socket

Allows you to set cache refresh for block devices

Allow setting of floppy disk drives

Allow switch DMA switch

Allow management of md devices

Allows you to manage ide drivers

Allow access to nvram Devic

Allows you to manage apm_bios, serial or bttv TV devices

Allow commands to be generated under the driver of isdn CAPI

Allow non-standard configuration of pci to be read

Allow DDI to debug ioctl

Allow qic-117 commands to be sent

Allows you to start or disable the control of SCSI and send SCSI commands that allow you to configure encrypted passwords on the loop file system

CAP_SYS_BOOT function:

The reboot () command is allowed

CAP_SYS_NICE function:

Allow you to increase or set the priority of other processes

Allow FISO and real-time scheduling and configuration in your own process

CAP_SYS_RESOURCE function:

Set resource limits beyond resource limits

Exceed the quota limit

Beyond the reserved ext2 file system

Allow real-time clock interrupts greater than 64hz

Over the maximum number of control terminals

Beyond the maximum number of keys

CAP_SYS_TIME function:

Allow processing of the system clock

Allow _ stime

Allows you to set the real-time clock

CAP_SYS_TTY_CONFIG function:

Allow configuration of end devices

Allow vhangup () terminals

Return value

PR_GET_DUMPABLE and PR_GET_KEEPCAPS return 0 or 1 if they are successful. All other option values return 0 on success.

Return-1 in case of error and set the corresponding error number.

The value of EINVAL----option is incorrect, or when it is PR_SET_PDEATHSIG, the value of the parameter arg2 is not 0 or signal number.

EBADF---- invalid descriptor

Example: for multithreaded applications, if you can name each thread, the convenience of debugging is self-evident.

# include

# include

# include

Void* tmain (void*arg)

{

Char name [32]

Prctl (PR_SET_NAME, (unsignedlong) "xx")

Prctl (PR_GET_NAME, (unsignedlong) name)

Printf ("% SSPO", name)

While (1)

Sleep (1)

}

Int main (void)

{

Pthread_t tid

Pthread_create (& tid,NULL, tmain,NULL)

Pthread_join (tid,NULL)

Return 0

}

Compile and run:

Xiaosuo@gentux test $gcc t_threadname.c-lpthread

Xiaosuo@gentux test $. / a.out

Xx

At the other terminal, find a.out 's pid through ps:

Xiaosuo@gentux test $ps aux | grep a.out

Xiaosuo 29882 0.0 0.0 14144 544 pts/6 Sl+ 16:23 0:00. / a.out

See if the naming works:

Xiaosuo@gentux test $cd / proc/29882/task/

Xiaosuo@gentux task $ls

29882 29883

Xiaosuo@gentux task $cd 29883 /

Xiaosuo@gentux 29883$ cat cmdline

. / a.outxiaosuo@gentux 29883 $

It's a little depressing that cmdline still shows. / a.out. Check the return value of prctl through the xx and strace printed at run time to confirm that prctl is indeed running successfully. I suspected that the name could only be obtained through prctl. I was a little lost, but I was still reluctant. Look at ps's man and experiment, and finally find the "xx":

Xiaosuo@gentux 29883$ ps-L-p 29882

PID LWP TTY TIME CMD

29882 29882 pts/6 00:00:00 a.out

29882 29883 pts/6 00:00:00 xx

How to rename a process under Linux:

Using the system function prctl (), declare as follows:

# include

Int prctl (int option, unsigned long arg2, unsigned long arg3, unsigned long arg4, unsigned long arg5)

For specific usage, please refer to http://www.kernel.org/doc/man-pages/online/pages/man2/prctl.2.html

Process rename code:

Prctl (PR_SET_NAME, "process_name", NULL, NULL, NULL)

The first parameter is the operation type. Specify PR_SET_NAME, that is, set the process name.

The second parameter is the process name string, which is up to 16 bytes long

The above is how to apply the prctl () function. The editor believes that there are some knowledge points that we may see or use in our daily work. I hope you can learn more from this article. For more details, please follow the industry information channel.

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