99 lines · cpp
1//===-- Implementation of tls for aarch64 ---------------------------------===//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-exception6//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 <arm_acle.h>16#include <sys/mman.h>17#include <sys/syscall.h>18 19// Source documentation:20// https://github.com/ARM-software/abi-aa/tree/main/sysvabi6421 22namespace LIBC_NAMESPACE_DECL {23 24#ifdef SYS_mmap225static constexpr long MMAP_SYSCALL_NUMBER = SYS_mmap2;26#elif SYS_mmap27static constexpr long MMAP_SYSCALL_NUMBER = SYS_mmap;28#else29#error "mmap and mmap2 syscalls not available."30#endif31 32void init_tls(TLSDescriptor &tls_descriptor) {33 if (app.tls.size == 0) {34 tls_descriptor.size = 0;35 tls_descriptor.tp = 0;36 return;37 }38 39 // aarch64 follows the variant 1 TLS layout:40 //41 // 1. First entry is the dynamic thread vector pointer42 // 2. Second entry is a 8-byte reserved word.43 // 3. Padding for alignment.44 // 4. The TLS data from the ELF image.45 //46 // The thread pointer points to the first entry.47 48 const uintptr_t size_of_pointers = 2 * sizeof(uintptr_t);49 uintptr_t padding = 0;50 const uintptr_t ALIGNMENT_MASK = app.tls.align - 1;51 uintptr_t diff = size_of_pointers & ALIGNMENT_MASK;52 if (diff != 0)53 padding += (ALIGNMENT_MASK - diff) + 1;54 55 uintptr_t alloc_size = size_of_pointers + padding + app.tls.size;56 57 // We cannot call the mmap function here as the functions set errno on58 // failure. Since errno is implemented via a thread local variable, we cannot59 // use errno before TLS is setup.60 long mmap_ret_val = syscall_impl<long>(MMAP_SYSCALL_NUMBER, nullptr,61 alloc_size, PROT_READ | PROT_WRITE,62 MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);63 // We cannot check the return value with MAP_FAILED as that is the return64 // of the mmap function and not the mmap syscall.65 if (!linux_utils::is_valid_mmap(mmap_ret_val))66 syscall_impl<long>(SYS_exit, 1);67 uintptr_t thread_ptr = uintptr_t(reinterpret_cast<uintptr_t *>(mmap_ret_val));68 uintptr_t tls_addr = thread_ptr + size_of_pointers + padding;69 inline_memcpy(reinterpret_cast<char *>(tls_addr),70 reinterpret_cast<const char *>(app.tls.address),71 app.tls.init_size);72 tls_descriptor.size = alloc_size;73 tls_descriptor.addr = thread_ptr;74 tls_descriptor.tp = thread_ptr;75}76 77void cleanup_tls(uintptr_t addr, uintptr_t size) {78 if (size == 0)79 return;80 syscall_impl<long>(SYS_munmap, addr, size);81}82 83bool set_thread_ptr(uintptr_t val) {84// The PR for __arm_wsr64 support in GCC was merged on Dec 6, 2023, and it is85// not yet usable in 13.3.086// https://github.com/gcc-mirror/gcc/commit/fc42900d21abd5eacb7537c3c8ffc5278d51019587#if __has_builtin(__builtin_arm_wsr64)88 __builtin_arm_wsr64("tpidr_el0", val);89#elif __has_builtin(__builtin_aarch64_wsr)90 __builtin_aarch64_wsr("tpidr_el0", val);91#elif defined(__GNUC__)92 asm volatile("msr tpidr_el0, %0" ::"r"(val));93#else94#error "Unsupported compiler"95#endif96 return true;97}98} // namespace LIBC_NAMESPACE_DECL99