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LinuxEmulation: Don't use clone3 for fork #4195

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merged 1 commit into from
Dec 6, 2024
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LinuxEmulation: Don't use clone3 for fork #4195

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2 changes: 1 addition & 1 deletion Source/Tools/LinuxEmulation/LinuxSyscalls/Syscalls.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -652,7 +652,7 @@ uint64_t CloneHandler(FEXCore::Core::CpuStateFrame* Frame, FEX::HLE::clone3_args
// CLONE_PARENT is ignored (Implied by CLONE_THREAD)
return FEX::HLE::ForkGuest(Thread, Frame, flags, reinterpret_cast<void*>(args->args.stack), args->args.stack_size,
reinterpret_cast<pid_t*>(args->args.parent_tid), reinterpret_cast<pid_t*>(args->args.child_tid),
reinterpret_cast<void*>(args->args.tls));
reinterpret_cast<void*>(args->args.tls), args->args.exit_signal);
} else {
auto NewThread = FEX::HLE::CreateNewThread(Thread->CTX, Frame, args);

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19 changes: 7 additions & 12 deletions Source/Tools/LinuxEmulation/LinuxSyscalls/Syscalls/Thread.cpp
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Expand Up @@ -246,17 +246,12 @@ uint64_t HandleNewClone(FEX::HLE::ThreadStateObject* Thread, FEXCore::Context::C
return Thread->StatusCode;
}

static int Clone3Fork(uint32_t flags) {
struct clone_args cl_args = {
.flags = (flags & (CLONE_FS | CLONE_FILES)),
.exit_signal = SIGCHLD,
};

return syscall(SYS_clone3, cl_args, sizeof(cl_args));
static int CloneFork(uint32_t flags, uint64_t exit_signal) {
return ::syscall(SYSCALL_DEF(clone), (flags & (CLONE_FS | CLONE_FILES)) | exit_signal, nullptr, nullptr, nullptr, nullptr);
}

uint64_t ForkGuest(FEXCore::Core::InternalThreadState* Thread, FEXCore::Core::CpuStateFrame* Frame, uint32_t flags, void* stack,
size_t StackSize, pid_t* parent_tid, pid_t* child_tid, void* tls) {
size_t StackSize, pid_t* parent_tid, pid_t* child_tid, void* tls, uint64_t exit_signal) {
// Just before we fork, we lock all syscall mutexes so that both processes will end up with a locked mutex

uint64_t Mask {~0ULL};
Expand All @@ -275,7 +270,7 @@ uint64_t ForkGuest(FEXCore::Core::InternalThreadState* Thread, FEXCore::Core::Cp

// XXX: We don't currently support a real `vfork` as it causes problems.
// Currently behaves like a fork (with wait after the fact), which isn't correct. Need to find where the problem is
Result = Clone3Fork(flags);
Result = CloneFork(flags, exit_signal);

if (Result == 0) {
// Close the read end of the pipe.
Expand All @@ -286,7 +281,7 @@ uint64_t ForkGuest(FEXCore::Core::InternalThreadState* Thread, FEXCore::Core::Cp
close(VForkFDs[1]);
}
} else {
Result = Clone3Fork(flags);
Result = CloneFork(flags, exit_signal);
}
const bool IsChild = Result == 0;

Expand Down Expand Up @@ -384,11 +379,11 @@ void RegisterThread(FEX::HLE::SyscallHandler* Handler) {
});

REGISTER_SYSCALL_IMPL_FLAGS(fork, SyscallFlags::DEFAULT, [](FEXCore::Core::CpuStateFrame* Frame) -> uint64_t {
return ForkGuest(Frame->Thread, Frame, 0, 0, 0, 0, 0, 0);
return ForkGuest(Frame->Thread, Frame, 0, 0, 0, 0, 0, 0, SIGCHLD);
});

REGISTER_SYSCALL_IMPL_FLAGS(vfork, SyscallFlags::DEFAULT, [](FEXCore::Core::CpuStateFrame* Frame) -> uint64_t {
return ForkGuest(Frame->Thread, Frame, CLONE_VFORK, 0, 0, 0, 0, 0);
return ForkGuest(Frame->Thread, Frame, CLONE_VFORK, 0, 0, 0, 0, 0, SIGCHLD);
});

REGISTER_SYSCALL_IMPL_FLAGS(getpgrp, SyscallFlags::OPTIMIZETHROUGH | SyscallFlags::NOSYNCSTATEONENTRY,
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2 changes: 1 addition & 1 deletion Source/Tools/LinuxEmulation/LinuxSyscalls/Syscalls/Thread.h
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Expand Up @@ -21,5 +21,5 @@ FEX::HLE::ThreadStateObject* CreateNewThread(FEXCore::Context::Context* CTX, FEX
uint64_t HandleNewClone(FEX::HLE::ThreadStateObject* Thread, FEXCore::Context::Context* CTX, FEXCore::Core::CpuStateFrame* Frame,
FEX::HLE::clone3_args* GuestArgs);
uint64_t ForkGuest(FEXCore::Core::InternalThreadState* Thread, FEXCore::Core::CpuStateFrame* Frame, uint32_t flags, void* stack,
size_t StackSize, pid_t* parent_tid, pid_t* child_tid, void* tls);
size_t StackSize, pid_t* parent_tid, pid_t* child_tid, void* tls, uint64_t exit_signal);
} // namespace FEX::HLE
5 changes: 3 additions & 2 deletions Source/Tools/LinuxEmulation/LinuxSyscalls/x64/Thread.cpp
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Expand Up @@ -52,8 +52,9 @@ void RegisterThread(FEX::HLE::SyscallHandler* Handler) {
.Type = TypeOfClone::TYPE_CLONE2,
.args =
{
.flags = flags, // CSIGNAL is contained in here
.pidfd = 0, // For clone, pidfd is duplicated here

.flags = flags & ~CSIGNAL, // This no longer contains CSIGNAL
.pidfd = 0, // For clone, pidfd is duplicated here
.child_tid = reinterpret_cast<uint64_t>(child_tid),
.parent_tid = reinterpret_cast<uint64_t>(parent_tid),
.exit_signal = flags & CSIGNAL,
Expand Down
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