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Diffstat (limited to 'libc/src/threads/linux/thrd_create.cpp')
| -rw-r--r-- | libc/src/threads/linux/thrd_create.cpp | 153 |
1 files changed, 0 insertions, 153 deletions
diff --git a/libc/src/threads/linux/thrd_create.cpp b/libc/src/threads/linux/thrd_create.cpp deleted file mode 100644 index 5f25ded38bd3..000000000000 --- a/libc/src/threads/linux/thrd_create.cpp +++ /dev/null @@ -1,153 +0,0 @@ -//===-- Linux implementation of the thrd_create function ------------------===// -// -// 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 -// -//===----------------------------------------------------------------------===// - -#include "Futex.h" - -#include "src/__support/OSUtil/syscall.h" // For syscall function. -#include "src/__support/architectures.h" -#include "src/__support/common.h" -#include "src/threads/linux/Thread.h" -#include "src/threads/thrd_create.h" - -#include <errno.h> // For E* error values. -#include <linux/sched.h> // For CLONE_* flags. -#include <stdint.h> -#include <sys/mman.h> // For PROT_* and MAP_* definitions. -#include <sys/syscall.h> // For syscall numbers. -#include <threads.h> // For thrd_* type definitions. - -#ifdef SYS_mmap2 -constexpr long MMAP_SYSCALL_NUMBER = SYS_mmap2; -#elif SYS_mmap -constexpr long MMAP_SYSCALL_NUMBER = SYS_mmap; -#else -#error "SYS_mmap or SYS_mmap2 not available on the target platform" -#endif - -namespace __llvm_libc { - -// We align the start args to 16-byte boundary as we adjust the allocated -// stack memory with its size. We want the adjusted address to be at a -// 16-byte boundary to satisfy the x86_64 and aarch64 ABI requirements. -// If different architecture in future requires higher alignment, then we -// can add a platform specific alignment spec. -struct alignas(16) StartArgs { - thrd_t *thread; - thrd_start_t func; - void *arg; -}; - -__attribute__((always_inline)) inline uintptr_t get_start_args_addr() { - // NOTE: For __builtin_frame_address to work reliably across compilers, - // architectures and various optimization levels, the TU including this file - // should be compiled with -fno-omit-frame-pointer. - return reinterpret_cast<uintptr_t>(__builtin_frame_address(0)) - // The x86_64 call instruction pushes resume address on to the stack. - // Next, The x86_64 SysV ABI requires that the frame pointer be pushed - // on to the stack. Similarly on aarch64, previous frame pointer and - // the value of the link register are pushed on to the stack. So, in - // both these cases, we have to step past two 64-bit values to get - // to the start args. - + sizeof(uintptr_t) * 2; -} - -static __attribute__((noinline)) void start_thread() { - StartArgs *start_args = reinterpret_cast<StartArgs *>(get_start_args_addr()); - __llvm_libc::syscall(SYS_exit, start_args->thread->__retval = - start_args->func(start_args->arg)); -} - -LLVM_LIBC_FUNCTION(int, thrd_create, - (thrd_t * thread, thrd_start_t func, void *arg)) { - unsigned clone_flags = - CLONE_VM // Share the memory space with the parent. - | CLONE_FS // Share the file system with the parent. - | CLONE_FILES // Share the files with the parent. - | CLONE_SIGHAND // Share the signal handlers with the parent. - | CLONE_THREAD // Same thread group as the parent. - | CLONE_SYSVSEM // Share a single list of System V semaphore adjustment - // values - | CLONE_PARENT_SETTID // Set child thread ID in |ptid| of the parent. - | CLONE_CHILD_CLEARTID; // Let the kernel clear the tid address and futex - // wake the joining thread. - // TODO: Add the CLONE_SETTLS flag and setup the TLS area correctly when - // making the clone syscall. - - // Allocate thread stack. - long mmap_result = - __llvm_libc::syscall(MMAP_SYSCALL_NUMBER, - 0, // No special address - ThreadParams::DEFAULT_STACK_SIZE, - PROT_READ | PROT_WRITE, // Read and write stack - MAP_ANONYMOUS | MAP_PRIVATE, // Process private - -1, // Not backed by any file - 0 // No offset - ); - if (mmap_result < 0 && (uintptr_t(mmap_result) >= - UINTPTR_MAX - ThreadParams::DEFAULT_STACK_SIZE)) { - return -mmap_result == ENOMEM ? thrd_nomem : thrd_error; - } - void *stack = reinterpret_cast<void *>(mmap_result); - - thread->__stack = stack; - thread->__stack_size = ThreadParams::DEFAULT_STACK_SIZE; - thread->__retval = -1; - FutexWordType *clear_tid_address = &thread->__clear_tid.__word; - *clear_tid_address = ThreadParams::CLEAR_TID_VALUE; - - // When the new thread is spawned by the kernel, the new thread gets the - // stack we pass to the clone syscall. However, this stack is empty and does - // not have any local vars present in this function. Hence, one cannot - // pass arguments to the thread start function, or use any local vars from - // here. So, we pack them into the new stack from where the thread can sniff - // them out. - uintptr_t adjusted_stack = reinterpret_cast<uintptr_t>(stack) + - ThreadParams::DEFAULT_STACK_SIZE - - sizeof(StartArgs); - StartArgs *start_args = reinterpret_cast<StartArgs *>(adjusted_stack); - start_args->thread = thread; - start_args->func = func; - start_args->arg = arg; - - // The clone syscall takes arguments in an architecture specific order. - // Also, we want the result of the syscall to be in a register as the child - // thread gets a completely different stack after it is created. The stack - // variables from this function will not be availalbe to the child thread. -#ifdef LLVM_LIBC_ARCH_X86_64 - long register clone_result asm("rax"); - clone_result = __llvm_libc::syscall( - SYS_clone, clone_flags, adjusted_stack, - &thread->__tid, // The address where the child tid is written - clear_tid_address, // The futex where the child thread status is signalled - 0 // Set TLS to null for now. - ); -#elif defined(LLVM_LIBC_ARCH_AARCH64) - long register clone_result asm("x0"); - clone_result = __llvm_libc::syscall( - SYS_clone, clone_flags, adjusted_stack, - &thread->__tid, // The address where the child tid is written - 0, // Set TLS to null for now. - clear_tid_address // The futex where the child thread status is signalled - ); -#else -#error "Unsupported architecture for the clone syscall." -#endif - - if (clone_result == 0) { - start_thread(); - } else if (clone_result < 0) { - __llvm_libc::syscall(SYS_munmap, mmap_result, - ThreadParams::DEFAULT_STACK_SIZE); - int error_val = -clone_result; - return error_val == ENOMEM ? thrd_nomem : thrd_error; - } - - return thrd_success; -} - -} // namespace __llvm_libc |