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/*
* Copyright (C) 2011 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#include "thread.h"
#include <sys/syscall.h>
#include <sys/types.h>
#include "asm_support.h"
#include "base/macros.h"
#include "thread.h"
#include "thread_list.h"
#if defined(__APPLE__)
#include <architecture/i386/table.h>
#include <i386/user_ldt.h>
struct descriptor_table_entry_t {
uint16_t limit0;
uint16_t base0;
unsigned base1: 8, type: 4, s: 1, dpl: 2, p: 1;
unsigned limit: 4, avl: 1, l: 1, d: 1, g: 1, base2: 8;
} __attribute__((packed));
#define MODIFY_LDT_CONTENTS_DATA 0
#else
#include <asm/ldt.h>
#endif
namespace art {
void Thread::InitCpu() {
static Mutex modify_ldt_lock("modify_ldt lock");
MutexLock mu(Thread::Current(), modify_ldt_lock);
const uintptr_t base = reinterpret_cast<uintptr_t>(this);
const size_t limit = kPageSize;
const int contents = MODIFY_LDT_CONTENTS_DATA;
const int seg_32bit = 1;
const int read_exec_only = 0;
const int limit_in_pages = 0;
const int seg_not_present = 0;
const int useable = 1;
int entry_number = -1;
#if defined(__APPLE__)
descriptor_table_entry_t entry;
memset(&entry, 0, sizeof(entry));
entry.limit0 = (limit & 0x0ffff);
entry.limit = (limit & 0xf0000) >> 16;
entry.base0 = (base & 0x0000ffff);
entry.base1 = (base & 0x00ff0000) >> 16;
entry.base2 = (base & 0xff000000) >> 24;
entry.type = ((read_exec_only ^ 1) << 1) | (contents << 2);
entry.s = 1;
entry.dpl = 0x3;
entry.p = seg_not_present ^ 1;
entry.avl = useable;
entry.l = 0;
entry.d = seg_32bit;
entry.g = limit_in_pages;
entry_number = i386_set_ldt(LDT_AUTO_ALLOC, (ldt_entry*)(void*)(&entry), 1);
if (entry_number == -1) {
PLOG(FATAL) << "i386_set_ldt failed";
}
#else
// Read current LDT entries.
CHECK_EQ((size_t)LDT_ENTRY_SIZE, sizeof(uint64_t));
std::vector<uint64_t> ldt(LDT_ENTRIES);
size_t ldt_size(sizeof(uint64_t) * ldt.size());
memset(&ldt[0], 0, ldt_size);
// TODO: why doesn't this return LDT_ENTRY_SIZE * LDT_ENTRIES for the main thread?
syscall(__NR_modify_ldt, 0, &ldt[0], ldt_size);
// Find the first empty slot.
for (entry_number = 0; entry_number < LDT_ENTRIES && ldt[entry_number] != 0; ++entry_number) {
}
if (entry_number >= LDT_ENTRIES) {
LOG(FATAL) << "Failed to find a free LDT slot";
}
// Update LDT entry.
user_desc ldt_entry;
memset(&ldt_entry, 0, sizeof(ldt_entry));
ldt_entry.entry_number = entry_number;
ldt_entry.base_addr = base;
ldt_entry.limit = limit;
ldt_entry.seg_32bit = seg_32bit;
ldt_entry.contents = contents;
ldt_entry.read_exec_only = read_exec_only;
ldt_entry.limit_in_pages = limit_in_pages;
ldt_entry.seg_not_present = seg_not_present;
ldt_entry.useable = useable;
CHECK_EQ(0, syscall(__NR_modify_ldt, 1, &ldt_entry, sizeof(ldt_entry)));
entry_number = ldt_entry.entry_number;
#endif
// Change %fs to be new LDT entry.
uint16_t table_indicator = 1 << 2; // LDT
uint16_t rpl = 3; // Requested privilege level
uint16_t selector = (entry_number << 3) | table_indicator | rpl;
// TODO: use our assembler to generate code
__asm__ __volatile__("movw %w0, %%fs"
: // output
: "q"(selector) // input
:); // clobber
// Allow easy indirection back to Thread*.
self_ = this;
// Sanity check that reads from %fs point to this Thread*.
Thread* self_check;
// TODO: use our assembler to generate code
CHECK_EQ(THREAD_SELF_OFFSET, OFFSETOF_MEMBER(Thread, self_));
__asm__ __volatile__("movl %%fs:(%1), %0"
: "=r"(self_check) // output
: "r"(THREAD_SELF_OFFSET) // input
:); // clobber
CHECK_EQ(self_check, this);
// Sanity check other offsets.
CHECK_EQ(THREAD_EXCEPTION_OFFSET, OFFSETOF_MEMBER(Thread, exception_));
}
} // namespace art
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