PRCTL (2) | System calls | Unix Manual Pages | :man▋
prctl - operations on a process
"int prctl(int "option", unsigned long "arg2", unsigned long "arg3 ", unsigned long "arg4", unsigned long "arg5);
prctl is called with a first argument describing what to do (with values defined in <linux/prctl.h>), and further parameters with a significance depending on the first one. The first argument can be:
| PR_SET_PDEATHSIG |
| || (since Linux 2.1.57) Set the parent process death signal of the current process to arg2 (either a signal value in the range 1..maxsig, or 0 to clear). This is the signal that the current process will get when its parent dies. This value is cleared upon a fork(). |
| PR_GET_PDEATHSIG |
| || (since Linux 2.3.15) Read the current value of the parent process death signal into the (int *) arg2. |
| PR_SET_DUMPABLE |
| || (Since Linux 2.4) Set the state of the flag determining whether core dumps are produced for this process upon delivery of a signal whose default behaviour is to produce a core dump. (Normally this flag is set for a process by default, but it is cleared when a set-UID or set-GID program is executed and also by various system calls that manipulate process UIDs and GIDs). arg2 must be either 0 (process is not dumapable) or 1 (process is dumpable). |
| PR_GET_DUMPABLE |
| || (Since Linux 2.4) Return (as the function result) the current state of the calling processs dumpable flag. |
| PR_SET_KEEPCAPS |
| || Set the state of the processs "keep capabilities" flag, which determines whether the processs effective and permitted capability sets are cleared when a change is made to the processs user IDs such that all of the processs real, effective, and saved set user IDs become non-zero when at least one of them previously had the value 0. (By default, these credential sets are cleared). arg2 must be either 0 (capabilities are cleared) or 1 (capabilities are kept). |
| PR_GET_KEEPCAPS |
| || Return (as the function result) the current state of the calling processs "keep capabilities" flag. |
PR_GET_DUMPABLE and PR_GET_KEEPCAPS return 0 or 1 on success. All other option values return 0 on success. On error, -1 is returned, and errno is set appropriately.
| EINVAL || The value of option is not recognized, or it is PR_SET_PDEATHSIG and arg2 is not zero or a signal number. |
This call is Linux-specific. IRIX has a prctl system call (also introduced in Linux 2.1.44 as irix_prctl on the MIPS architecture), with prototype
"ptrdiff_t prctl(int "option", int "arg2", int "arg3);
and options to get the maximum number of processes per user, get the maximum number of processors the calling process can use, find out whether a specified process is currently blocked, get or set the maximum stack size, etc., etc.
The prctl() systemcall was introduced in Linux 2.1.57. There is no prctl() library call as yet.
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