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/*
* Copyright (C) 2008 The Android Open Source Project
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* * Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
#include <limits.h>
#include <pthread.h>
#include <stdbool.h>
#include <asm/ldt.h>
extern int __set_thread_area(struct user_desc*);
__LIBC_HIDDEN__ void __init_user_desc(struct user_desc* result, bool allocate, void* base_addr) {
if (allocate) {
// Let the kernel choose.
result->entry_number = -1;
} else {
// Get the existing entry number from %gs.
uint32_t gs;
__asm__ __volatile__("movw %%gs, %w0" : "=q"(gs) /*output*/);
result->entry_number = (gs & 0xffff) >> 3;
}
result->base_addr = (uintptr_t) base_addr;
result->limit = PAGE_SIZE;
result->seg_32bit = 1;
result->contents = MODIFY_LDT_CONTENTS_DATA;
result->read_exec_only = 0;
result->limit_in_pages = 1;
result->seg_not_present = 0;
result->useable = 1;
}
__LIBC_HIDDEN__ int __set_tls(void* ptr) {
struct user_desc tls_descriptor;
__init_user_desc(&tls_descriptor, true, ptr);
int rc = __set_thread_area(&tls_descriptor);
if (rc != -1) {
// Change %gs to be new GDT entry.
uint16_t table_indicator = 0; // GDT
uint16_t rpl = 3; // Requested privilege level
uint16_t selector = (tls_descriptor.entry_number << 3) | table_indicator | rpl;
__asm__ __volatile__("movw %w0, %%gs" : /*output*/ : "q"(selector) /*input*/ : /*clobber*/);
}
return rc;
}
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