powerpc: copy_thread differentiate kthreads and user mode threads

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When copy_thread is given a kernel function to run in arg->fn, this
does not necessarily mean it is a kernel thread. User threads can be
created this way (e.g., kernel_init, see also x86's copy_thread()).
These threads run a kernel function which may call kernel_execve()
and return, which returns like a userspace exec(2) syscall.

Kernel threads are to  be differentiated with PF_KTHREAD, will always
have arg->fn set, and should never return from that function, instead
calling kthread_exit() to exit.

Create separate paths for the kthread and user kernel thread creation
logic. The kthread path will never exit and does not require a user
interrupt frame, so it gets a minimal stack frame.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/20230325122904.2375060-6-npiggin@gmail.com

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Nicholas Piggin 2023-03-25 22:29:01 +10:00 • committed by Michael Ellerman

parent 5088a6246b

commit eed7c420aa

2 changed files with 64 additions and 36 deletions

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2

arch/powerpc/include/asm/thread_info.h

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98

arch/powerpc/kernel/process.c

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