1 //===-- Implementation of tls for riscv -----------------------------------===// 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 #include "src/__support/OSUtil/syscall.h" 10 #include "src/__support/macros/config.h" 11 #include "src/__support/threads/thread.h" 12 #include "src/string/memory_utils/inline_memcpy.h" 13 #include "startup/linux/do_start.h" 14 15 #include <sys/mman.h> 16 #include <sys/syscall.h> 17 18 namespace LIBC_NAMESPACE_DECL { 19 20 #ifdef SYS_mmap2 21 static constexpr long MMAP_SYSCALL_NUMBER = SYS_mmap2; 22 #elif SYS_mmap 23 static constexpr long MMAP_SYSCALL_NUMBER = SYS_mmap; 24 #else 25 #error "mmap and mmap2 syscalls not available." 26 #endif 27 28 void init_tls(TLSDescriptor &tls_descriptor) { 29 if (app.tls.size == 0) { 30 tls_descriptor.size = 0; 31 tls_descriptor.tp = 0; 32 return; 33 } 34 35 // riscv64 follows the variant 1 TLS layout: 36 const uintptr_t size_of_pointers = 2 * sizeof(uintptr_t); 37 uintptr_t padding = 0; 38 const uintptr_t ALIGNMENT_MASK = app.tls.align - 1; 39 uintptr_t diff = size_of_pointers & ALIGNMENT_MASK; 40 if (diff != 0) 41 padding += (ALIGNMENT_MASK - diff) + 1; 42 43 uintptr_t alloc_size = size_of_pointers + padding + app.tls.size; 44 45 // We cannot call the mmap function here as the functions set errno on 46 // failure. Since errno is implemented via a thread local variable, we cannot 47 // use errno before TLS is setup. 48 long mmap_ret_val = syscall_impl<long>(MMAP_SYSCALL_NUMBER, nullptr, 49 alloc_size, PROT_READ | PROT_WRITE, 50 MAP_ANONYMOUS | MAP_PRIVATE, -1, 0); 51 // We cannot check the return value with MAP_FAILED as that is the return 52 // of the mmap function and not the mmap syscall. 53 if (mmap_ret_val < 0 && static_cast<uintptr_t>(mmap_ret_val) > -app.page_size) 54 syscall_impl<long>(SYS_exit, 1); 55 uintptr_t thread_ptr = uintptr_t(reinterpret_cast<uintptr_t *>(mmap_ret_val)); 56 uintptr_t tls_addr = thread_ptr + size_of_pointers + padding; 57 inline_memcpy(reinterpret_cast<char *>(tls_addr), 58 reinterpret_cast<const char *>(app.tls.address), 59 app.tls.init_size); 60 tls_descriptor.size = alloc_size; 61 tls_descriptor.addr = thread_ptr; 62 tls_descriptor.tp = tls_addr; 63 } 64 65 void cleanup_tls(uintptr_t addr, uintptr_t size) { 66 if (size == 0) 67 return; 68 syscall_impl<long>(SYS_munmap, addr, size); 69 } 70 71 bool set_thread_ptr(uintptr_t val) { 72 LIBC_INLINE_ASM("mv tp, %0\n\t" : : "r"(val)); 73 return true; 74 } 75 } // namespace LIBC_NAMESPACE_DECL 76