e104a2edf3
* Allow clone where both the child function and stack are null. It's obviously wrong to ask to call a function without a stack, but it's not necessarily wrong to supply no stack if you're also not supplying a function. * Reimplement fork in terms of the clone function, rather than using the clone system call directly. This is intended as a step towards enabling use of pid namespaces. Change-Id: I03c89bd1dc540d8b4ed1c8fdf6644290744b9e91
97 lines
3.8 KiB
C++
97 lines
3.8 KiB
C++
/*
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* Copyright (C) 2010 The Android Open Source Project
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* * Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* * Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in
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* the documentation and/or other materials provided with the
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* distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
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* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
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* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
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* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
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* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
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* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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#define _GNU_SOURCE 1
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#include <sched.h>
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#include <stdlib.h>
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#include <stdarg.h>
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#include "pthread_internal.h"
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extern "C" pid_t __bionic_clone(uint32_t flags, void* child_stack, int* parent_tid, void* tls, int* child_tid, int (*fn)(void*), void* arg);
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extern "C" __noreturn void __exit(int status);
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// Called from the __bionic_clone assembler to call the thread function then exit.
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extern "C" __LIBC_HIDDEN__ void __start_thread(int (*fn)(void*), void* arg) {
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int status = (*fn)(arg);
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__exit(status);
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}
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int clone(int (*fn)(void*), void* child_stack, int flags, void* arg, ...) {
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int* parent_tid = NULL;
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void* new_tls = NULL;
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int* child_tid = NULL;
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if (fn != nullptr && child_stack == nullptr) {
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errno = EINVAL;
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return -1;
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}
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// Extract any optional parameters required by the flags.
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va_list args;
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va_start(args, arg);
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if ((flags & (CLONE_PARENT_SETTID|CLONE_SETTLS|CLONE_CHILD_SETTID|CLONE_CHILD_CLEARTID)) != 0) {
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parent_tid = va_arg(args, int*);
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}
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if ((flags & (CLONE_SETTLS|CLONE_CHILD_SETTID|CLONE_CHILD_CLEARTID)) != 0) {
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new_tls = va_arg(args, void*);
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}
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if ((flags & (CLONE_CHILD_SETTID|CLONE_CHILD_CLEARTID)) != 0) {
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child_tid = va_arg(args, int*);
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}
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va_end(args);
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// Align 'child_stack' to 16 bytes.
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uintptr_t child_stack_addr = reinterpret_cast<uintptr_t>(child_stack);
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child_stack_addr &= ~0xf;
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child_stack = reinterpret_cast<void*>(child_stack_addr);
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// Remember the parent pid and invalidate the cached value while we clone.
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pthread_internal_t* self = __get_thread();
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pid_t parent_pid = self->invalidate_cached_pid();
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// Actually do the clone.
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int clone_result;
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if (fn != nullptr) {
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clone_result = __bionic_clone(flags, child_stack, parent_tid, new_tls, child_tid, fn, arg);
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} else {
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#if defined(__x86_64__) // sys_clone's last two arguments are flipped on x86-64.
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clone_result = syscall(__NR_clone, flags, child_stack, parent_tid, child_tid, new_tls);
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#else
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clone_result = syscall(__NR_clone, flags, child_stack, parent_tid, new_tls, child_tid);
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#endif
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}
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// We're the parent, so put our known pid back in place.
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// We leave the child without a cached pid, but:
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// 1. pthread_create gives its children their own pthread_internal_t with the correct pid.
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// 2. fork makes a clone system call directly.
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// If any other cases become important, we could use a double trampoline like __pthread_start.
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self->set_cached_pid(parent_pid);
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return clone_result;
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}
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