1// SPDX-License-Identifier: GPL-2.0
2#include <errno.h>
3#include <linux/unistd.h>
4
5#include <sys/ptrace.h>
6#include <sys/syscall.h>
7#include <unistd.h>
8
9#include <sysdep/tls.h>
10
11#ifndef PTRACE_GET_THREAD_AREA
12#define PTRACE_GET_THREAD_AREA 25
13#endif
14
15#ifndef PTRACE_SET_THREAD_AREA
16#define PTRACE_SET_THREAD_AREA 26
17#endif
18
19/* Checks whether host supports TLS, and sets *tls_min according to the value
20 * valid on the host.
21 * i386 host have it == 6; x86_64 host have it == 12, for i386 emulation. */
22void check_host_supports_tls(int *supports_tls, int *tls_min)
23{
24 /* Values for x86 and x86_64.*/
25 int val[] = {GDT_ENTRY_TLS_MIN_I386, GDT_ENTRY_TLS_MIN_X86_64};
26 int i;
27
28 for (i = 0; i < ARRAY_SIZE(val); i++) {
29 user_desc_t info;
30 info.entry_number = val[i];
31
32 if (syscall(__NR_get_thread_area, &info) == 0) {
33 *tls_min = val[i];
34 *supports_tls = 1;
35 return;
36 } else {
37 if (errno == EINVAL)
38 continue;
39 else if (errno == ENOSYS)
40 *supports_tls = 0;
41 return;
42 }
43 }
44
45 *supports_tls = 0;
46}
47
48int os_set_thread_area(user_desc_t *info, int pid)
49{
50 int ret;
51
52 ret = ptrace(PTRACE_SET_THREAD_AREA, pid, info->entry_number,
53 (unsigned long) info);
54 if (ret < 0)
55 ret = -errno;
56 return ret;
57}
58
59int os_get_thread_area(user_desc_t *info, int pid)
60{
61 int ret;
62
63 ret = ptrace(PTRACE_GET_THREAD_AREA, pid, info->entry_number,
64 (unsigned long) info);
65 if (ret < 0)
66 ret = -errno;
67 return ret;
68}
69

source code of linux/arch/x86/um/os-Linux/tls.c