Mercurial > jdk8-mips64-public > hotspot / annotate
src/os_cpu/linux_x86/vm/threadLS_linux_x86.cpp@899ecf76b570 (annotated)
src/os_cpu/linux_x86/vm/threadLS_linux_x86.cpp
Wed, 25 Sep 2013 13:58:13 +0200
- author
- dsimms
- date
- Wed, 25 Sep 2013 13:58:13 +0200
- changeset 5781
- 899ecf76b570
- parent 4299
- f34d701e952e
- child 6876
- 710a3c8b516e
- permissions
- -rw-r--r--
8023956: Provide a work-around to broken Linux 32 bit "Exec Shield" using CS for NX emulation (crashing with SI_KERNEL)
Summary: Execute some code at a high virtual address value, and keep mapped
Reviewed-by: coleenp, zgu
| duke@435 | 1 | /* |
| stefank@2314 | 2 | * Copyright (c) 1999, 2010, Oracle and/or its affiliates. All rights reserved. |
| duke@435 | 3 | * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
| duke@435 | 4 | * |
| duke@435 | 5 | * This code is free software; you can redistribute it and/or modify it |
| duke@435 | 6 | * under the terms of the GNU General Public License version 2 only, as |
| duke@435 | 7 | * published by the Free Software Foundation. |
| duke@435 | 8 | * |
| duke@435 | 9 | * This code is distributed in the hope that it will be useful, but WITHOUT |
| duke@435 | 10 | * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
| duke@435 | 11 | * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
| duke@435 | 12 | * version 2 for more details (a copy is included in the LICENSE file that |
| duke@435 | 13 | * accompanied this code). |
| duke@435 | 14 | * |
| duke@435 | 15 | * You should have received a copy of the GNU General Public License version |
| duke@435 | 16 | * 2 along with this work; if not, write to the Free Software Foundation, |
| duke@435 | 17 | * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
| duke@435 | 18 | * |
| trims@1907 | 19 | * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
| trims@1907 | 20 | * or visit www.oracle.com if you need additional information or have any |
| trims@1907 | 21 | * questions. |
| duke@435 | 22 | * |
| duke@435 | 23 | */ |
| duke@435 | 24 | |
| stefank@2314 | 25 | #include "precompiled.hpp" |
| stefank@4299 | 26 | #include "runtime/thread.inline.hpp" |
| stefank@2314 | 27 | #include "runtime/threadLocalStorage.hpp" |
| duke@435 | 28 | |
| duke@435 | 29 | // Map stack pointer (%esp) to thread pointer for faster TLS access |
| duke@435 | 30 | // |
| duke@435 | 31 | // Here we use a flat table for better performance. Getting current thread |
| duke@435 | 32 | // is down to one memory access (read _sp_map[%esp>>12]) in generated code |
| duke@435 | 33 | // and two in runtime code (-fPIC code needs an extra load for _sp_map). |
| duke@435 | 34 | // |
| duke@435 | 35 | // This code assumes stack page is not shared by different threads. It works |
| duke@435 | 36 | // in 32-bit VM when page size is 4K (or a multiple of 4K, if that matters). |
| duke@435 | 37 | // |
| duke@435 | 38 | // Notice that _sp_map is allocated in the bss segment, which is ZFOD |
| duke@435 | 39 | // (zero-fill-on-demand). While it reserves 4M address space upfront, |
| duke@435 | 40 | // actual memory pages are committed on demand. |
| duke@435 | 41 | // |
| duke@435 | 42 | // If an application creates and destroys a lot of threads, usually the |
| duke@435 | 43 | // stack space freed by a thread will soon get reused by new thread |
| duke@435 | 44 | // (this is especially true in NPTL or LinuxThreads in fixed-stack mode). |
| duke@435 | 45 | // No memory page in _sp_map is wasted. |
| duke@435 | 46 | // |
| duke@435 | 47 | // However, it's still possible that we might end up populating & |
| duke@435 | 48 | // committing a large fraction of the 4M table over time, but the actual |
| duke@435 | 49 | // amount of live data in the table could be quite small. The max wastage |
| duke@435 | 50 | // is less than 4M bytes. If it becomes an issue, we could use madvise() |
| duke@435 | 51 | // with MADV_DONTNEED to reclaim unused (i.e. all-zero) pages in _sp_map. |
| duke@435 | 52 | // MADV_DONTNEED on Linux keeps the virtual memory mapping, but zaps the |
| duke@435 | 53 | // physical memory page (i.e. similar to MADV_FREE on Solaris). |
| duke@435 | 54 | |
| jcoomes@2995 | 55 | #if !defined(AMD64) && !defined(MINIMIZE_RAM_USAGE) |
| duke@435 | 56 | Thread* ThreadLocalStorage::_sp_map[1UL << (SP_BITLENGTH - PAGE_SHIFT)]; |
| duke@435 | 57 | |
| duke@435 | 58 | void ThreadLocalStorage::generate_code_for_get_thread() { |
| duke@435 | 59 | // nothing we can do here for user-level thread |
| duke@435 | 60 | } |
| duke@435 | 61 | |
| duke@435 | 62 | void ThreadLocalStorage::pd_init() { |
| duke@435 | 63 | assert(align_size_down(os::vm_page_size(), PAGE_SIZE) == os::vm_page_size(), |
| duke@435 | 64 | "page size must be multiple of PAGE_SIZE"); |
| duke@435 | 65 | } |
| duke@435 | 66 | |
| duke@435 | 67 | void ThreadLocalStorage::pd_set_thread(Thread* thread) { |
| duke@435 | 68 | os::thread_local_storage_at_put(ThreadLocalStorage::thread_index(), thread); |
| duke@435 | 69 | address stack_top = os::current_stack_base(); |
| duke@435 | 70 | size_t stack_size = os::current_stack_size(); |
| duke@435 | 71 | |
| duke@435 | 72 | for (address p = stack_top - stack_size; p < stack_top; p += PAGE_SIZE) { |
| duke@435 | 73 | // pd_set_thread() is called with non-NULL value when a new thread is |
| duke@435 | 74 | // created/attached, or with NULL value when a thread is about to exit. |
| duke@435 | 75 | // If both "thread" and the corresponding _sp_map[] entry are non-NULL, |
| duke@435 | 76 | // they should have the same value. Otherwise it might indicate that the |
| duke@435 | 77 | // stack page is shared by multiple threads. However, a more likely cause |
| duke@435 | 78 | // for this assertion to fail is that an attached thread exited without |
| duke@435 | 79 | // detaching itself from VM, which is a program error and could cause VM |
| duke@435 | 80 | // to crash. |
| duke@435 | 81 | assert(thread == NULL || _sp_map[(uintptr_t)p >> PAGE_SHIFT] == NULL || |
| duke@435 | 82 | thread == _sp_map[(uintptr_t)p >> PAGE_SHIFT], |
| duke@435 | 83 | "thread exited without detaching from VM??"); |
| duke@435 | 84 | _sp_map[(uintptr_t)p >> PAGE_SHIFT] = thread; |
| duke@435 | 85 | } |
| duke@435 | 86 | } |
| jcoomes@2995 | 87 | #else |
| jcoomes@2995 | 88 | |
| jcoomes@2995 | 89 | void ThreadLocalStorage::generate_code_for_get_thread() { |
| jcoomes@2995 | 90 | // nothing we can do here for user-level thread |
| jcoomes@2995 | 91 | } |
| jcoomes@2995 | 92 | |
| jcoomes@2995 | 93 | void ThreadLocalStorage::pd_init() { |
| jcoomes@2995 | 94 | } |
| jcoomes@2995 | 95 | |
| jcoomes@2995 | 96 | void ThreadLocalStorage::pd_set_thread(Thread* thread) { |
| jcoomes@2995 | 97 | os::thread_local_storage_at_put(ThreadLocalStorage::thread_index(), thread); |
| jcoomes@2995 | 98 | } |
| jcoomes@2995 | 99 | #endif // !AMD64 && !MINIMIZE_RAM_USAGE |
