| //===-- sanitizer_tls_get_addr.h --------------------------------*- C++ -*-===// |
| // |
| // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. |
| // See https://llvm.org/LICENSE.txt for license information. |
| // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception |
| // |
| //===----------------------------------------------------------------------===// |
| // |
| // Handle the __tls_get_addr call. |
| // |
| // All this magic is specific to glibc and is required to workaround |
| // the lack of interface that would tell us about the Dynamic TLS (DTLS). |
| // https://sourceware.org/bugzilla/show_bug.cgi?id=16291 |
| // |
| // Before 2.25: every DTLS chunk is allocated with __libc_memalign, |
| // which we intercept and thus know where is the DTLS. |
| // |
| // Since 2.25: DTLS chunks are allocated with malloc. We could co-opt |
| // the malloc interceptor to keep track of the last allocation, similar |
| // to how we handle __libc_memalign; however, this adds some overhead |
| // (since malloc, unlike __libc_memalign, is commonly called), and |
| // requires care to avoid false negatives for LeakSanitizer. |
| // Instead, we rely on our internal allocators - which keep track of all |
| // its allocations - to determine if an address points to a malloc |
| // allocation. |
| // |
| // There exists a since-deprecated version of Google's internal glibc fork |
| // that used __signal_safe_memalign. DTLS_on_tls_get_addr relied on a |
| // heuristic check (is the allocation 16 bytes from the start of a page |
| // boundary?), which was sometimes erroneous: |
| // https://bugs.chromium.org/p/chromium/issues/detail?id=1275223#c15 |
| // Since that check has no practical use anymore, we have removed it. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #ifndef SANITIZER_TLS_GET_ADDR_H |
| #define SANITIZER_TLS_GET_ADDR_H |
| |
| #include "sanitizer_atomic.h" |
| #include "sanitizer_common.h" |
| |
| namespace __sanitizer { |
| |
| struct DTLS { |
| // Array of DTLS chunks for the current Thread. |
| // If beg == 0, the chunk is unused. |
| struct DTV { |
| uptr beg, size; |
| }; |
| struct DTVBlock { |
| atomic_uintptr_t next; |
| DTV dtvs[(4096UL - sizeof(next)) / sizeof(DTLS::DTV)]; |
| }; |
| |
| static_assert(sizeof(DTVBlock) <= 4096UL, "Unexpected block size"); |
| |
| atomic_uintptr_t dtv_block; |
| }; |
| |
| template <typename Fn> |
| void ForEachDVT(DTLS *dtls, const Fn &fn) { |
| DTLS::DTVBlock *block = |
| (DTLS::DTVBlock *)atomic_load(&dtls->dtv_block, memory_order_acquire); |
| while (block) { |
| int id = 0; |
| for (auto &d : block->dtvs) fn(d, id++); |
| block = (DTLS::DTVBlock *)atomic_load(&block->next, memory_order_acquire); |
| } |
| } |
| |
| // Returns pointer and size of a linker-allocated TLS block. |
| // Each block is returned exactly once. |
| DTLS::DTV *DTLS_on_tls_get_addr(void *arg, void *res, uptr static_tls_begin, |
| uptr static_tls_end); |
| void DTLS_on_libc_memalign(void *ptr, uptr size); |
| DTLS *DTLS_Get(); |
| void DTLS_Destroy(); // Make sure to call this before the thread is destroyed. |
| // Returns true if DTLS of suspended thread is in destruction process. |
| bool DTLSInDestruction(DTLS *dtls); |
| |
| } // namespace __sanitizer |
| |
| #endif // SANITIZER_TLS_GET_ADDR_H |