| /* |
| * Copyright (C) 2019 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. |
| */ |
| |
| #pragma once |
| |
| #include <link.h> |
| #include <pthread.h> |
| #include <stdatomic.h> |
| #include <stdint.h> |
| #include <sys/cdefs.h> |
| |
| __LIBC_HIDDEN__ extern _Atomic(size_t) __libc_tls_generation_copy; |
| |
| struct TlsSegment { |
| size_t size = 0; |
| size_t alignment = 1; |
| const void* init_ptr = ""; // Field is non-null even when init_size is 0. |
| size_t init_size = 0; |
| }; |
| |
| __LIBC_HIDDEN__ bool __bionic_get_tls_segment(const ElfW(Phdr)* phdr_table, size_t phdr_count, |
| ElfW(Addr) load_bias, TlsSegment* out); |
| |
| __LIBC_HIDDEN__ bool __bionic_check_tls_alignment(size_t* alignment); |
| |
| struct StaticTlsLayout { |
| constexpr StaticTlsLayout() {} |
| |
| private: |
| size_t offset_ = 0; |
| size_t alignment_ = 1; |
| bool overflowed_ = false; |
| |
| // Offsets to various Bionic TLS structs from the beginning of static TLS. |
| size_t offset_bionic_tcb_ = SIZE_MAX; |
| size_t offset_bionic_tls_ = SIZE_MAX; |
| |
| public: |
| size_t offset_bionic_tcb() const { return offset_bionic_tcb_; } |
| size_t offset_bionic_tls() const { return offset_bionic_tls_; } |
| size_t offset_thread_pointer() const; |
| |
| size_t size() const { return offset_; } |
| size_t alignment() const { return alignment_; } |
| bool overflowed() const { return overflowed_; } |
| |
| size_t reserve_exe_segment_and_tcb(const TlsSegment* exe_segment, const char* progname); |
| void reserve_bionic_tls(); |
| size_t reserve_solib_segment(const TlsSegment& segment) { |
| return reserve(segment.size, segment.alignment); |
| } |
| void finish_layout(); |
| |
| private: |
| size_t reserve(size_t size, size_t alignment); |
| |
| template <typename T> size_t reserve_type() { |
| return reserve(sizeof(T), alignof(T)); |
| } |
| |
| size_t round_up_with_overflow_check(size_t value, size_t alignment); |
| }; |
| |
| static constexpr size_t kTlsGenerationNone = 0; |
| static constexpr size_t kTlsGenerationFirst = 1; |
| |
| // The first ELF TLS module has ID 1. Zero is reserved for the first word of |
| // the DTV, a generation count. Unresolved weak symbols also use module ID 0. |
| static constexpr size_t kTlsUninitializedModuleId = 0; |
| |
| static inline size_t __tls_module_id_to_idx(size_t id) { return id - 1; } |
| static inline size_t __tls_module_idx_to_id(size_t idx) { return idx + 1; } |
| |
| // A descriptor for a single ELF TLS module. |
| struct TlsModule { |
| TlsSegment segment; |
| |
| // Offset into the static TLS block or SIZE_MAX for a dynamic module. |
| size_t static_offset = SIZE_MAX; |
| |
| // The generation in which this module was loaded. Dynamic TLS lookups use |
| // this field to detect when a module has been unloaded. |
| size_t first_generation = kTlsGenerationNone; |
| |
| // Used by the dynamic linker to track the associated soinfo* object. |
| void* soinfo_ptr = nullptr; |
| }; |
| |
| // Table of the ELF TLS modules. Either the dynamic linker or the static |
| // initialization code prepares this table, and it's then used during thread |
| // creation and for dynamic TLS lookups. |
| struct TlsModules { |
| constexpr TlsModules() {} |
| |
| // A pointer to the TLS generation counter in libc.so. The counter is |
| // incremented each time an solib is loaded or unloaded. |
| _Atomic(size_t) generation = kTlsGenerationFirst; |
| _Atomic(size_t) *generation_libc_so = nullptr; |
| |
| // Access to the TlsModule[] table requires taking this lock. |
| pthread_rwlock_t rwlock = PTHREAD_RWLOCK_INITIALIZER; |
| |
| // Pointer to a block of TlsModule objects. The first module has ID 1 and |
| // is stored at index 0 in this table. |
| size_t module_count = 0; |
| TlsModule* module_table = nullptr; |
| }; |
| |
| void __init_static_tls(void* static_tls); |
| |
| // Dynamic Thread Vector. Each thread has a different DTV. For each module |
| // (executable or solib), the DTV has a pointer to that module's TLS memory. The |
| // DTV is initially empty and is allocated on-demand. It grows as more modules |
| // are dlopen'ed. See https://www.akkadia.org/drepper/tls.pdf. |
| // |
| // The layout of the DTV is specified in various documents, but it is not part |
| // of Bionic's public ABI. A compiler can't generate code to access it directly, |
| // because it can't access libc's global generation counter. |
| struct TlsDtv { |
| // Number of elements in this object's modules field. |
| size_t count; |
| |
| // A pointer to an older TlsDtv object that should be freed when the thread |
| // exits. The objects aren't immediately freed because a DTV could be |
| // reallocated by a signal handler that interrupted __tls_get_addr's fast |
| // path. |
| TlsDtv* next; |
| |
| // The DTV slot points at this field, which allows omitting an add instruction |
| // on the fast path for a TLS lookup. The arm64 tlsdesc_resolver.S depends on |
| // the layout of fields past this point. |
| size_t generation; |
| void* modules[]; |
| }; |
| |
| struct TlsIndex { |
| size_t module_id; |
| size_t offset; |
| }; |
| |
| #if defined(__i386__) |
| #define TLS_GET_ADDR_CCONV __attribute__((regparm(1))) |
| #define TLS_GET_ADDR ___tls_get_addr |
| #else |
| #define TLS_GET_ADDR_CCONV |
| #define TLS_GET_ADDR __tls_get_addr |
| #endif |
| |
| extern "C" void* TLS_GET_ADDR(const TlsIndex* ti) TLS_GET_ADDR_CCONV; |
| |
| struct bionic_tcb; |
| void __free_dynamic_tls(bionic_tcb* tcb); |