1 /* 2 * Copyright (C) 2008 The Android Open Source Project 3 * All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * * Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * * Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in 12 * the documentation and/or other materials provided with the 13 * distribution. 14 * 15 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 16 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 17 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS 18 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE 19 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, 20 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, 21 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS 22 * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED 23 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, 24 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT 25 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 26 * SUCH DAMAGE. 27 */ 28 29 #include <limits.h> 30 #include <pthread.h> 31 32 #include <asm/ldt.h> 33 34 extern "C" int __set_thread_area(user_desc*); 35 36 __LIBC_HIDDEN__ void __init_user_desc(user_desc* result, bool allocate, void* base_addr) { 37 if (allocate) { 38 // Let the kernel choose. 39 result->entry_number = -1; 40 } else { 41 // Get the existing entry number from %gs. 42 uint32_t gs; 43 __asm__ __volatile__("movw %%gs, %w0" : "=q"(gs) /*output*/); 44 result->entry_number = (gs & 0xffff) >> 3; 45 } 46 47 result->base_addr = reinterpret_cast<uintptr_t>(base_addr); 48 49 result->limit = 0xfffff; 50 51 result->seg_32bit = 1; 52 result->contents = MODIFY_LDT_CONTENTS_DATA; 53 result->read_exec_only = 0; 54 result->limit_in_pages = 1; 55 result->seg_not_present = 0; 56 result->useable = 1; 57 } 58 59 extern "C" __LIBC_HIDDEN__ int __set_tls(void* ptr) { 60 user_desc tls_descriptor = {}; 61 __init_user_desc(&tls_descriptor, true, ptr); 62 63 int rc = __set_thread_area(&tls_descriptor); 64 if (rc != -1) { 65 // Change %gs to be new GDT entry. 66 uint16_t table_indicator = 0; // GDT 67 uint16_t rpl = 3; // Requested privilege level 68 uint16_t selector = (tls_descriptor.entry_number << 3) | table_indicator | rpl; 69 __asm__ __volatile__("movw %w0, %%gs" : /*output*/ : "q"(selector) /*input*/ : /*clobber*/); 70 } 71 72 return rc; 73 } 74
