arch/arm64: add have fork config

[lipengfei28]

1.ARCH_ARM64 select ARCH_HAVE_FORK

Update this section with information on why change is necessary,
what it exactly does and how, if new feature shows up, provide
references (dependencies, similar problems and solutions), etc.

Impact

Update this section, where applicable, on how change affects users,
build process, hardware, documentation, security, compatibility, etc.

Testing

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and runtime logs from before and after change is highly appreciated.

[pussuw]

I'm pretty sure ostest will crash with arm64 kernel mode.

[xiaoxiang781216]

I'm pretty sure ostest will crash with arm64 kernel mode.

Yes, the current implementation of fork/vfork is only for flat/protected build, the kernel mode need be reimplemented like Linux, which is a huge task I think that.

[pussuw]

I'm pretty sure ostest will crash with arm64 kernel mode.

Yes, the current implementation of fork/vfork is only for flat/protected build, the kernel mode need be reimplemented like Linux, which is a huge task I think that.

I mean arm64 vfork() will cause ostest crash in kernel mode, making the test unusable in arm64.
I did the fix for risc-v, it could be backported to this platform too ?

[xiaoxiang781216]

I'm pretty sure ostest will crash with arm64 kernel mode.

Yes, the current implementation of fork/vfork is only for flat/protected build, the kernel mode need be reimplemented like Linux, which is a huge task I think that.

I mean arm64 vfork() will cause ostest crash in kernel mode, making the test unusable in arm64. I did the fix for risc-v, it could be backported to this platform too ?

how about change to:

	select ARCH_HAVE_FORK if !BUILD_KERNEL

before we port your riscv patch to arm64.

[pussuw]

I'm pretty sure ostest will crash with arm64 kernel mode.

Yes, the current implementation of fork/vfork is only for flat/protected build, the kernel mode need be reimplemented like Linux, which is a huge task I think that.

I mean arm64 vfork() will cause ostest crash in kernel mode, making the test unusable in arm64. I did the fix for risc-v, it could be backported to this platform too ?

how about change to:

	select ARCH_HAVE_FORK if !BUILD_KERNEL

before we port your riscv patch to arm64.

Sounds good to me

[lupyuen]

Sorry I have to cancel the CI Check, there's a problem with CI Test:

• drivers/pipes: return after short write if buffer is full #14667 (comment)