1 //===-- sanitizer_tls_get_addr.h --------------------------------*- C++ -*-===// 2 // 3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 4 // See https://llvm.org/LICENSE.txt for license information. 5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 6 // 7 //===----------------------------------------------------------------------===// 8 // 9 // Handle the __tls_get_addr call. 10 // 11 // All this magic is specific to glibc and is required to workaround 12 // the lack of interface that would tell us about the Dynamic TLS (DTLS). 13 // https://sourceware.org/bugzilla/show_bug.cgi?id=16291 14 // 15 // The matters get worse because the glibc implementation changed between 16 // 2.18 and 2.19: 17 // https://groups.google.com/forum/#!topic/address-sanitizer/BfwYD8HMxTM 18 // 19 // Before 2.19, every DTLS chunk is allocated with __libc_memalign, 20 // which we intercept and thus know where is the DTLS. 21 // Since 2.19, DTLS chunks are allocated with __signal_safe_memalign, 22 // which is an internal function that wraps a mmap call, neither of which 23 // we can intercept. Luckily, __signal_safe_memalign has a simple parseable 24 // header which we can use. 25 // 26 //===----------------------------------------------------------------------===// 27 28 #ifndef SANITIZER_TLS_GET_ADDR_H 29 #define SANITIZER_TLS_GET_ADDR_H 30 31 #include "sanitizer_atomic.h" 32 #include "sanitizer_common.h" 33 34 namespace __sanitizer { 35 36 struct DTLS { 37 // Array of DTLS chunks for the current Thread. 38 // If beg == 0, the chunk is unused. 39 struct DTV { 40 uptr beg, size; 41 }; 42 struct DTVBlock { 43 atomic_uintptr_t next; 44 DTV dtvs[(4096UL - sizeof(next)) / sizeof(DTLS::DTV)]; 45 }; 46 47 static_assert(sizeof(DTVBlock) <= 4096UL, "Unexpected block size"); 48 49 atomic_uintptr_t dtv_block; 50 51 // Auxiliary fields, don't access them outside sanitizer_tls_get_addr.cpp 52 uptr last_memalign_size; 53 uptr last_memalign_ptr; 54 }; 55 56 template <typename Fn> 57 void ForEachDVT(DTLS *dtls, const Fn &fn) { 58 DTLS::DTVBlock *block = 59 (DTLS::DTVBlock *)atomic_load(&dtls->dtv_block, memory_order_acquire); 60 while (block) { 61 int id = 0; 62 for (auto &d : block->dtvs) fn(d, id++); 63 block = (DTLS::DTVBlock *)atomic_load(&block->next, memory_order_acquire); 64 } 65 } 66 67 // Returns pointer and size of a linker-allocated TLS block. 68 // Each block is returned exactly once. 69 DTLS::DTV *DTLS_on_tls_get_addr(void *arg, void *res, uptr static_tls_begin, 70 uptr static_tls_end); 71 void DTLS_on_libc_memalign(void *ptr, uptr size); 72 DTLS *DTLS_Get(); 73 void DTLS_Destroy(); // Make sure to call this before the thread is destroyed. 74 // Returns true if DTLS of suspended thread is in destruction process. 75 bool DTLSInDestruction(DTLS *dtls); 76 77 } // namespace __sanitizer 78 79 #endif // SANITIZER_TLS_GET_ADDR_H 80