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      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 #pragma once
     30 
     31 #include <pthread.h>
     32 #include <stdatomic.h>
     33 
     34 #if __has_feature(hwaddress_sanitizer)
     35 #include <sanitizer/hwasan_interface.h>
     36 #else
     37 #define __hwasan_thread_enter()
     38 #define __hwasan_thread_exit()
     39 #endif
     40 
     41 #include "private/bionic_elf_tls.h"
     42 #include "private/bionic_lock.h"
     43 #include "private/bionic_tls.h"
     44 
     45 // Has the thread been detached by a pthread_join or pthread_detach call?
     46 #define PTHREAD_ATTR_FLAG_DETACHED 0x00000001
     47 
     48 // Has the thread been joined by another thread?
     49 #define PTHREAD_ATTR_FLAG_JOINED 0x00000002
     50 
     51 // Used for pthread_attr_setinheritsched. We need two flags for this apparent
     52 // boolean because our historical behavior matches neither of the POSIX choices.
     53 #define PTHREAD_ATTR_FLAG_INHERIT 0x00000004
     54 #define PTHREAD_ATTR_FLAG_EXPLICIT 0x00000008
     55 
     56 enum ThreadJoinState {
     57   THREAD_NOT_JOINED,
     58   THREAD_EXITED_NOT_JOINED,
     59   THREAD_JOINED,
     60   THREAD_DETACHED
     61 };
     62 
     63 class thread_local_dtor;
     64 
     65 class pthread_internal_t {
     66  public:
     67   class pthread_internal_t* next;
     68   class pthread_internal_t* prev;
     69 
     70   pid_t tid;
     71 
     72  private:
     73   pid_t cached_pid_;
     74 
     75  public:
     76   pid_t invalidate_cached_pid() {
     77     pid_t old_value;
     78     get_cached_pid(&old_value);
     79     set_cached_pid(0);
     80     return old_value;
     81   }
     82 
     83   void set_cached_pid(pid_t value) {
     84     cached_pid_ = value;
     85   }
     86 
     87   bool get_cached_pid(pid_t* cached_pid) {
     88     *cached_pid = cached_pid_;
     89     return (*cached_pid != 0);
     90   }
     91 
     92   pthread_attr_t attr;
     93 
     94   _Atomic(ThreadJoinState) join_state;
     95 
     96   __pthread_cleanup_t* cleanup_stack;
     97 
     98   void* (*start_routine)(void*);
     99   void* start_routine_arg;
    100   void* return_value;
    101 
    102   void* alternate_signal_stack;
    103 
    104   // The start address of the shadow call stack's guard region (arm64 only).
    105   // This address is only used to deallocate the shadow call stack on thread
    106   // exit; the address of the stack itself is stored only in the x18 register.
    107   // Because the protection offered by SCS relies on the secrecy of the stack
    108   // address, storing the address here weakens the protection, but only
    109   // slightly, because it is relatively easy for an attacker to discover the
    110   // address of the guard region anyway (e.g. it can be discovered by reference
    111   // to other allocations), but not the stack itself, which is <0.1% of the size
    112   // of the guard region.
    113   //
    114   // There are at least two other options for discovering the start address of
    115   // the guard region on thread exit, but they are not as simple as storing in
    116   // TLS.
    117   // 1) Derive it from the value of the x18 register. This is only possible in
    118   //    processes that do not contain legacy code that might clobber x18,
    119   //    therefore each process must declare early during process startup whether
    120   //    it might load legacy code.
    121   // 2) Mark the guard region as such using prctl(PR_SET_VMA_ANON_NAME) and
    122   //    discover its address by reading /proc/self/maps. One issue with this is
    123   //    that reading /proc/self/maps can race with allocations, so we may need
    124   //    code to handle retries.
    125   void* shadow_call_stack_guard_region;
    126 
    127   Lock startup_handshake_lock;
    128 
    129   void* mmap_base;
    130   size_t mmap_size;
    131 
    132   thread_local_dtor* thread_local_dtors;
    133 
    134   /*
    135    * The dynamic linker implements dlerror(3), which makes it hard for us to implement this
    136    * per-thread buffer by simply using malloc(3) and free(3).
    137    */
    138   char* current_dlerror;
    139 #define __BIONIC_DLERROR_BUFFER_SIZE 512
    140   char dlerror_buffer[__BIONIC_DLERROR_BUFFER_SIZE];
    141 
    142   bionic_tls* bionic_tls;
    143 
    144   int errno_value;
    145 };
    146 
    147 struct ThreadMapping {
    148   char* mmap_base;
    149   size_t mmap_size;
    150 
    151   char* static_tls;
    152   char* stack_base;
    153   char* stack_top;
    154 };
    155 
    156 __LIBC_HIDDEN__ void __init_tcb(bionic_tcb* tcb, pthread_internal_t* thread);
    157 __LIBC_HIDDEN__ void __init_tcb_stack_guard(bionic_tcb* tcb);
    158 __LIBC_HIDDEN__ void __init_tcb_dtv(bionic_tcb* tcb);
    159 __LIBC_HIDDEN__ void __init_bionic_tls_ptrs(bionic_tcb* tcb, bionic_tls* tls);
    160 __LIBC_HIDDEN__ bionic_tls* __allocate_temp_bionic_tls();
    161 __LIBC_HIDDEN__ void __free_temp_bionic_tls(bionic_tls* tls);
    162 __LIBC_HIDDEN__ void __init_additional_stacks(pthread_internal_t*);
    163 __LIBC_HIDDEN__ int __init_thread(pthread_internal_t* thread);
    164 __LIBC_HIDDEN__ ThreadMapping __allocate_thread_mapping(size_t stack_size, size_t stack_guard_size);
    165 
    166 __LIBC_HIDDEN__ pthread_t __pthread_internal_add(pthread_internal_t* thread);
    167 __LIBC_HIDDEN__ pthread_internal_t* __pthread_internal_find(pthread_t pthread_id, const char* caller);
    168 __LIBC_HIDDEN__ pid_t __pthread_internal_gettid(pthread_t pthread_id, const char* caller);
    169 __LIBC_HIDDEN__ void __pthread_internal_remove(pthread_internal_t* thread);
    170 __LIBC_HIDDEN__ void __pthread_internal_remove_and_free(pthread_internal_t* thread);
    171 
    172 static inline __always_inline bionic_tcb* __get_bionic_tcb() {
    173   return reinterpret_cast<bionic_tcb*>(&__get_tls()[MIN_TLS_SLOT]);
    174 }
    175 
    176 // Make __get_thread() inlined for performance reason. See http://b/19825434.
    177 static inline __always_inline pthread_internal_t* __get_thread() {
    178   return static_cast<pthread_internal_t*>(__get_tls()[TLS_SLOT_THREAD_ID]);
    179 }
    180 
    181 static inline __always_inline bionic_tls& __get_bionic_tls() {
    182   return *static_cast<bionic_tls*>(__get_tls()[TLS_SLOT_BIONIC_TLS]);
    183 }
    184 
    185 static inline __always_inline TlsDtv* __get_tcb_dtv(bionic_tcb* tcb) {
    186   uintptr_t dtv_slot = reinterpret_cast<uintptr_t>(tcb->tls_slot(TLS_SLOT_DTV));
    187   return reinterpret_cast<TlsDtv*>(dtv_slot - offsetof(TlsDtv, generation));
    188 }
    189 
    190 static inline void __set_tcb_dtv(bionic_tcb* tcb, TlsDtv* val) {
    191   tcb->tls_slot(TLS_SLOT_DTV) = &val->generation;
    192 }
    193 
    194 extern "C" __LIBC_HIDDEN__ int __set_tls(void* ptr);
    195 
    196 __LIBC_HIDDEN__ void pthread_key_clean_all(void);
    197 
    198 // Address space is precious on LP32, so use the minimum unit: one page.
    199 // On LP64, we could use more but there's no obvious advantage to doing
    200 // so, and the various media processes use RLIMIT_AS as a way to limit
    201 // the amount of allocation they'll do.
    202 #define PTHREAD_GUARD_SIZE PAGE_SIZE
    203 
    204 // SIGSTKSZ (8KiB) is not big enough.
    205 // An snprintf to a stack buffer of size PATH_MAX consumes ~7KiB of stack.
    206 // On 64-bit, logging uses more than 8KiB by itself, ucontext is comically
    207 // large on aarch64, and we have effectively infinite address space, so double
    208 // the signal stack size.
    209 #if defined(__LP64__)
    210 #define SIGNAL_STACK_SIZE_WITHOUT_GUARD (32 * 1024)
    211 #else
    212 #define SIGNAL_STACK_SIZE_WITHOUT_GUARD (16 * 1024)
    213 #endif
    214 
    215 // Traditionally we gave threads a 1MiB stack. When we started
    216 // allocating per-thread alternate signal stacks to ease debugging of
    217 // stack overflows, we subtracted the same amount we were using there
    218 // from the default thread stack size. This should keep memory usage
    219 // roughly constant.
    220 #define PTHREAD_STACK_SIZE_DEFAULT ((1 * 1024 * 1024) - SIGNAL_STACK_SIZE_WITHOUT_GUARD)
    221 
    222 // Leave room for a guard page in the internally created signal stacks.
    223 #define SIGNAL_STACK_SIZE (SIGNAL_STACK_SIZE_WITHOUT_GUARD + PTHREAD_GUARD_SIZE)
    224 
    225 // Needed by fork.
    226 __LIBC_HIDDEN__ extern void __bionic_atfork_run_prepare();
    227 __LIBC_HIDDEN__ extern void __bionic_atfork_run_child();
    228 __LIBC_HIDDEN__ extern void __bionic_atfork_run_parent();
    229