um/os-Linux/tls.c

0001 // SPDX-License-Identifier: GPL-2.0
0002 #include <errno.h>
0003 #include <linux/unistd.h>
0004
0005 #include <sys/ptrace.h>
0006 #include <sys/syscall.h>
0007 #include <unistd.h>
0008
0009 #include <sysdep/tls.h>
0010
0011 #ifndef PTRACE_GET_THREAD_AREA
0012 #define PTRACE_GET_THREAD_AREA 25
0013 #endif
0014
0015 #ifndef PTRACE_SET_THREAD_AREA
0016 #define PTRACE_SET_THREAD_AREA 26
0017 #endif
0018
0019 /* Checks whether host supports TLS, and sets *tls_min according to the value
0020  * valid on the host.
0021  * i386 host have it == 6; x86_64 host have it == 12, for i386 emulation. */
0022 void check_host_supports_tls(int *supports_tls, int *tls_min)
0023 {
0024     /* Values for x86 and x86_64.*/
0025     int val[] = {GDT_ENTRY_TLS_MIN_I386, GDT_ENTRY_TLS_MIN_X86_64};
0026     int i;
0027
0028     for (i = 0; i < ARRAY_SIZE(val); i++) {
0029         user_desc_t info;
0030         info.entry_number = val[i];
0031
0032         if (syscall(__NR_get_thread_area, &info) == 0) {
0033             *tls_min = val[i];
0034             *supports_tls = 1;
0035             return;
0036         } else {
0037             if (errno == EINVAL)
0038                 continue;
0039             else if (errno == ENOSYS)
0040                 *supports_tls = 0;
0041             return;
0042         }
0043     }
0044
0045     *supports_tls = 0;
0046 }
0047
0048 int os_set_thread_area(user_desc_t *info, int pid)
0049 {
0050     int ret;
0051
0052     ret = ptrace(PTRACE_SET_THREAD_AREA, pid, info->entry_number,
0053              (unsigned long) info);
0054     if (ret < 0)
0055         ret = -errno;
0056     return ret;
0057 }
0058
0059 int os_get_thread_area(user_desc_t *info, int pid)
0060 {
0061     int ret;
0062
0063     ret = ptrace(PTRACE_GET_THREAD_AREA, pid, info->entry_number,
0064              (unsigned long) info);
0065     if (ret < 0)
0066         ret = -errno;
0067     return ret;
0068 }