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/*
* Copyright (c) 2018-2023, Andreas Kling <kling@serenityos.org>
* Copyright (c) 2023, Idan Horowitz <idan.horowitz@serenityos.org>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#include <Kernel/Debug.h>
#include <Kernel/FileSystem/Custody.h>
#include <Kernel/Memory/Region.h>
#include <Kernel/TTY/TTY.h>
#include <Kernel/Tasks/PerformanceManager.h>
#include <Kernel/Tasks/Process.h>
#include <Kernel/Tasks/Scheduler.h>
namespace Kernel {
ErrorOr<FlatPtr> Process::sys$fork(RegisterState& regs)
{
VERIFY_NO_PROCESS_BIG_LOCK(this);
TRY(require_promise(Pledge::proc));
auto child_name = TRY(name().with([](auto& name) { return name->try_clone(); }));
auto credentials = this->credentials();
auto child_and_first_thread = TRY(Process::create(move(child_name), credentials->uid(), credentials->gid(), pid(), m_is_kernel_process, current_directory(), executable(), tty(), this));
auto& child = child_and_first_thread.process;
auto& child_first_thread = child_and_first_thread.first_thread;
ArmedScopeGuard thread_finalizer_guard = [&child_first_thread]() {
SpinlockLocker lock(g_scheduler_lock);
child_first_thread->detach();
child_first_thread->set_state(Thread::State::Dying);
};
// NOTE: All user processes have a leaked ref on them. It's balanced by Thread::WaitBlockerSet::finalize().
child->ref();
TRY(m_unveil_data.with([&](auto& parent_unveil_data) -> ErrorOr<void> {
return child->m_unveil_data.with([&](auto& child_unveil_data) -> ErrorOr<void> {
child_unveil_data.state = parent_unveil_data.state;
child_unveil_data.paths = TRY(parent_unveil_data.paths.deep_copy());
return {};
});
}));
TRY(m_exec_unveil_data.with([&](auto& parent_exec_unveil_data) -> ErrorOr<void> {
return child->m_exec_unveil_data.with([&](auto& child_exec_unveil_data) -> ErrorOr<void> {
child_exec_unveil_data.state = parent_exec_unveil_data.state;
child_exec_unveil_data.paths = TRY(parent_exec_unveil_data.paths.deep_copy());
return {};
});
}));
// Note: We take the spinlock of Process::all_instances list because we need
// to ensure that when we take the jail spinlock of two processes that we don't
// run into a deadlock situation because both processes compete over each other Jail's
// spinlock. Such pattern of taking 3 spinlocks in the same order happens in
// Process::for_each* methods.
TRY(Process::all_instances().with([&](auto const&) -> ErrorOr<void> {
TRY(m_attached_jail.with([&](auto& parent_jail) -> ErrorOr<void> {
return child->m_attached_jail.with([&](auto& child_jail) -> ErrorOr<void> {
child_jail = parent_jail;
if (child_jail) {
child_jail->attach_count().with([&](auto& attach_count) {
attach_count++;
});
}
return {};
});
}));
return {};
}));
ArmedScopeGuard remove_from_jail_process_list = [&]() {
m_jail_process_list.with([&](auto& list_ptr) {
if (list_ptr) {
list_ptr->attached_processes().with([&](auto& list) {
list.remove(*child);
});
}
});
};
m_jail_process_list.with([&](auto& list_ptr) {
if (list_ptr) {
child->m_jail_process_list.with([&](auto& child_list_ptr) {
child_list_ptr = list_ptr;
});
list_ptr->attached_processes().with([&](auto& list) {
list.append(child);
});
}
});
TRY(child->m_fds.with_exclusive([&](auto& child_fds) {
return m_fds.with_exclusive([&](auto& parent_fds) {
return child_fds.try_clone(parent_fds);
});
}));
with_protected_data([&](auto& my_protected_data) {
child->with_mutable_protected_data([&](auto& child_protected_data) {
child_protected_data.promises = my_protected_data.promises.load();
child_protected_data.execpromises = my_protected_data.execpromises.load();
child_protected_data.has_promises = my_protected_data.has_promises.load();
child_protected_data.has_execpromises = my_protected_data.has_execpromises.load();
child_protected_data.credentials = my_protected_data.credentials;
child_protected_data.umask = my_protected_data.umask;
child_protected_data.signal_trampoline = my_protected_data.signal_trampoline;
child_protected_data.dumpable = my_protected_data.dumpable;
child_protected_data.process_group = my_protected_data.process_group;
});
});
dbgln_if(FORK_DEBUG, "fork: child={}", child);
// A child created via fork(2) inherits a copy of its parent's signal mask
child_first_thread->update_signal_mask(Thread::current()->signal_mask());
// A child process created via fork(2) inherits a copy of its parent's alternate signal stack settings.
child_first_thread->m_alternative_signal_stack = Thread::current()->m_alternative_signal_stack;
child_first_thread->m_alternative_signal_stack_size = Thread::current()->m_alternative_signal_stack_size;
auto& child_regs = child_first_thread->m_regs;
#if ARCH(X86_64)
child_regs.rax = 0; // fork() returns 0 in the child :^)
child_regs.rbx = regs.rbx;
child_regs.rcx = regs.rcx;
child_regs.rdx = regs.rdx;
child_regs.rbp = regs.rbp;
child_regs.rsp = regs.userspace_rsp;
child_regs.rsi = regs.rsi;
child_regs.rdi = regs.rdi;
child_regs.r8 = regs.r8;
child_regs.r9 = regs.r9;
child_regs.r10 = regs.r10;
child_regs.r11 = regs.r11;
child_regs.r12 = regs.r12;
child_regs.r13 = regs.r13;
child_regs.r14 = regs.r14;
child_regs.r15 = regs.r15;
child_regs.rflags = regs.rflags;
child_regs.rip = regs.rip;
child_regs.cs = regs.cs;
dbgln_if(FORK_DEBUG, "fork: child will begin executing at {:#04x}:{:p} with stack {:p}, kstack {:p}",
child_regs.cs, child_regs.rip, child_regs.rsp, child_regs.rsp0);
#elif ARCH(AARCH64)
child_regs.x[0] = 0; // fork() returns 0 in the child :^)
for (size_t i = 1; i < array_size(child_regs.x); ++i)
child_regs.x[i] = regs.x[i];
child_regs.spsr_el1 = regs.spsr_el1;
child_regs.elr_el1 = regs.elr_el1;
child_regs.sp_el0 = regs.sp_el0;
#else
# error Unknown architecture
#endif
TRY(address_space().with([&](auto& parent_space) {
return child->address_space().with([&](auto& child_space) -> ErrorOr<void> {
child_space->set_enforces_syscall_regions(parent_space->enforces_syscall_regions());
for (auto& region : parent_space->region_tree().regions()) {
dbgln_if(FORK_DEBUG, "fork: cloning Region '{}' @ {}", region.name(), region.vaddr());
auto region_clone = TRY(region.try_clone());
TRY(region_clone->map(child_space->page_directory(), Memory::ShouldFlushTLB::No));
TRY(child_space->region_tree().place_specifically(*region_clone, region.range()));
auto* child_region = region_clone.leak_ptr();
if (®ion == m_master_tls_region.unsafe_ptr())
child->m_master_tls_region = TRY(child_region->try_make_weak_ptr());
}
return {};
});
}));
thread_finalizer_guard.disarm();
remove_from_jail_process_list.disarm();
Process::register_new(*child);
PerformanceManager::add_process_created_event(*child);
SpinlockLocker lock(g_scheduler_lock);
child_first_thread->set_affinity(Thread::current()->affinity());
child_first_thread->set_state(Thread::State::Runnable);
auto child_pid = child->pid().value();
return child_pid;
}
}
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