1/* arch_prctl call for Linux/x32.
2 Copyright (C) 2012-2022 Free Software Foundation, Inc.
3 This file is part of the GNU C Library.
4
5 The GNU C Library is free software; you can redistribute it and/or
6 modify it under the terms of the GNU Lesser General Public
7 License as published by the Free Software Foundation; either
8 version 2.1 of the License, or (at your option) any later version.
9
10 The GNU C Library is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 Lesser General Public License for more details.
14
15 You should have received a copy of the GNU Lesser General Public
16 License along with the GNU C Library; if not, see
17 <https://www.gnu.org/licenses/>. */
18
19#include <errno.h>
20#include <sys/prctl.h>
21#include <sys/syscall.h>
22#include <sysdep.h>
23#include <stdint.h>
24
25/* Since x32 arch_prctl stores 32-bit base address of segment registers
26 %fs and %gs as unsigned 64-bit value via ARCH_GET_FS and ARCH_GET_GS,
27 we use an unsigned 64-bit variable to hold the base address and copy
28 it to ADDR after the system call returns. */
29
30int
31__arch_prctl (int code, uintptr_t *addr)
32{
33 int res;
34 uint64_t addr64;
35 void *prctl_arg = addr;
36
37 switch (code)
38 {
39 case ARCH_GET_FS:
40 case ARCH_GET_GS:
41 prctl_arg = &addr64;
42 break;
43 }
44
45 res = INLINE_SYSCALL (arch_prctl, 2, code, prctl_arg);
46 if (res == 0)
47 switch (code)
48 {
49 case ARCH_GET_FS:
50 case ARCH_GET_GS:
51 /* Check for a large value that overflows. */
52 if ((uintptr_t) addr64 != addr64)
53 {
54 __set_errno (EOVERFLOW);
55 return -1;
56 }
57 *addr = (uintptr_t) addr64;
58 break;
59 }
60
61 return res;
62}
63weak_alias (__arch_prctl, arch_prctl)
64

source code of glibc/sysdeps/unix/sysv/linux/x86_64/x32/arch_prctl.c