1PRCTL(2) Linux Programmer's Manual PRCTL(2)
2
6 prctl - operations on a process
7
9 #include <sys/prctl.h>
10 int prctl(int option, unsigned long arg2, unsigned long arg3 , unsigned
12 long arg4, unsigned long arg5);
13
15 prctl() is called with a first argument describing what to do (with
16 values defined in <linux/prctl.h>), and further parameters with a sig‐
17 nificance depending on the first one. The first argument can be:
18 PR_SET_PDEATHSIG
20 (since Linux 2.1.57) Set the parent process death signal of the
21 calling process to arg2 (either a signal value in the range
22 1..maxsig, or 0 to clear). This is the signal that the calling
23 process will get when its parent dies. This value is cleared
24 upon a fork().
25 PR_GET_PDEATHSIG
27 (Since Linux 2.3.15) Read the current value of the parent
28 process death signal into the (int *) arg2.
29 PR_SET_DUMPABLE
31 (Since Linux 2.3.20) Set the state of the flag determining
32 whether core dumps are produced for this process upon delivery
33 of a signal whose default behaviour is to produce a core dump.
34 (Normally this flag is set for a process by default, but it is
35 cleared when a set-user-ID or set-group-ID program is executed
36 and also by various system calls that manipulate process UIDs
37 and GIDs). In kernels up to and including 2.6.12, arg2 must be
38 either 0 (process is not dumpable) or 1 (process is dumpable).
39 Between kernels 2.6.13 and 2.6.17, the value 2 was also permit‐
40 ted, which caused any binary which normally would not be dumped
41 to be dumped readable by root only; for security reasons, this
42 feature has been removed. (See also the description of
43 /proc/sys/fs/suid_dumpable in proc(5).)
44 PR_GET_DUMPABLE
46 (Since Linux 2.3.20) Return (as the function result) the current
47 state of the calling process's dumpable flag.
48 PR_SET_KEEPCAPS
50 (Since Linux 2.2.18) Set the state of the process's "keep capa‐
51 bilities" flag, which determines whether the process's effective
52 and permitted capability sets are cleared when a change is made
53 to the process's user IDs such that the process's real UID,
54 effective UID, and saved set-user-ID all become non-zero when at
55 least one of them previously had the value 0. (By default,
56 these credential sets are cleared). arg2 must be either 0
57 (capabilities are cleared) or 1 (capabilities are kept).
58 PR_GET_KEEPCAPS
60 (Since Linux 2.2.18) Return (as the function result) the current
61 state of the calling process's "keep capabilities" flag.
62 PR_SET_TIMING
64 (Since Linux 2.6.0-test4) Set whether to use (normal, tradi‐
65 tional) statistical process timing or accurate timestamp based
66 process timing, by passing PR_TIMING_STATISTICAL or PR_TIM‐
67 ING_TIMESTAMP to arg2.
68 PR_GET_TIMING
70 (Since Linux 2.6.0-test4) Return (as the function result) which
71 process timing method is currently in use.
72 PR_SET_NAME
74 (Since Linux 2.6.9) Set the process name for the calling process
75 to arg2.
76 PR_GET_NAME
78 (Since Linux 2.6.11) Get the process name for the calling
79 process from arg2.
80 PR_GET_ENDIAN
82 (Since Linux 2.6.18, PowerPC only) Return the endian-ness of the
83 calling process.
84 PR_SET_ENDIAN
86 (Since Linux 2.6.18, PowerPC only) Set the endian-ness of the
87 calling process to the value given in arg2, which should be one
88 of the following: PR_ENDIAN_BIG, PR_ENDIAN_LITTLE, or
89 PR_ENDIAN_PPC_LITTLE (PowerPC pseudo little endian).
90 PR_SET_UNALIGN
92 (Since Linux 2.3.48, only on parisc and ia64) Set unaligned
93 access control bits to arg2. Pass PR_UNALIGN_NOPRINT to silently
94 fix up unaligned user accesses, or PR_UNALIGN_SIGBUS to generate
95 SIGBUS on unaligned user access.
96 PR_GET_UNALIGN
98 (Since Linux 2.3.48, only on parisc and ia64) Get unaligned
99 access control bits from arg2.
100 PR_SET_FPEMU
102 (Since Linux 2.4.18, 2.5.9, only on ia64) Set floating-point
103 emulation control bits to arg2. Pass PR_FPEMU_NOPRINT to
104 silently emulate fp operations accesses, or PR_FPEMU_SIGFPE to
105 not emulate fp operations and send SIGFPE instead.
106 PR_GET_FPEMU
108 (Since Linux 2.4.18, 2.5.9, only on ia64) Get floating-point
109 emulation control bits from arg2.
110 PR_SET_FPEXC
112 (Since Linux 2.4.21, 2.5.32, only on PowerPC) Set floating-point
113 exception mode to arg2. Pass PR_FP_EXC_SW_ENABLE to use FPEXC
114 for FP exception enables, PR_FP_EXC_DIV for floating point
115 divide by zero, PR_FP_EXC_OVF for floating point overflow,
116 PR_FP_EXC_UND for floating point underflow, PR_FP_EXC_RES for
117 floating point inexact result, PR_FP_EXC_INV for floating point
118 invalid operation, PR_FP_EXC_DISABLED for FP exceptions dis‐
119 abled, PR_FP_EXC_NONRECOV for async non-recoverable exception
120 mode, PR_FP_EXC_ASYNC for async recoverable exception mode,
121 PR_FP_EXC_PRECISE for precise exception mode.
122 PR_GET_FPEXC
124 (Since Linux 2.4.21, 2.5.32, only on PowerPC) Get floating-point
125 exception mode from arg2.
126
128 PR_GET_DUMPABLE and PR_GET_KEEPCAPS return 0 or 1 on success. All
129 other option values return 0 on success. On error, -1 is returned, and
130 errno is set appropriately.
131
133 EINVAL The value of option is not recognized, or it is PR_SET_PDEATHSIG
134 and arg2 is not zero or a signal number.
135
137 This call is Linux specific. IRIX has a prctl() system call (also
138 introduced in Linux 2.1.44 as irix_prctl on the MIPS architecture),
139 with prototype
140 ptrdiff_t prctl(int option, int arg2, int arg3);
142 and options to get the maximum number of processes per user, get the
144 maximum number of processors the calling process can use, find out
145 whether a specified process is currently blocked, get or set the maxi‐
146 mum stack size, etc.
147
149 The prctl() system call was introduced in Linux 2.1.57.
150
152 signal(2), core(5)
153Linux 2.6.17 2006-08-30 PRCTL(2)