fa9e16efaf
If you make clone, fork, or vfork system calls directly, you're still on your own, but we now do the right thing for the clone wrapper. With this implementation, children lose the getpid caching, but we've no reason to think that that covers any significant use cases. Bug: 15387103 Change-Id: Icfab6b63c708fea830960742ec92aeba8ce7680d
83 lines
3.4 KiB
C++
83 lines
3.4 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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// 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 = __bionic_clone(flags, child_stack, parent_tid, new_tls, child_tid, fn, arg);
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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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