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Date: Tue, 13 Jul 2021 14:16:46 -0600
From: subashab@codeaurora.org
Subject: Re: UML kernel panic on initialization
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To: Johannes Berg <johannes@sipsolutions.net>
Cc: jdike@addtoit.com, richard@nod.at, anton.ivanov@cambridgegreys.com, linux-um@lists.infradead.org

> Oh, and it looks like 84b2789d6115 actually got some bits that 
> shouldn't
> have been there!
> 
> Assuming it does *not* work with just the first three patches reverted,
> does it work again if you revert the first three patches, and only this
> bit of the fourth?
> 
> --- a/arch/um/kernel/skas/clone.c
> +++ b/arch/um/kernel/skas/clone.c
> @@ -24,29 +24,26 @@
>  void __attribute__ ((__section__ (".__syscall_stub")))
>  stub_clone_handler(void)
>  {
> -       struct stub_data *data = (struct stub_data *) STUB_DATA;
> +       int stack;
> +       struct stub_data *data = (void *) ((unsigned long)&stack &
> ~(UM_KERN_PAGE_SIZE - 1));
>         long err;
> 
> 
> 
> I think we probably have some miscompilation again with this thing - I
> saw a bunch of similar issues with our syscall stubs at some point, and
> I'm not sure we got it all right already.
> 
> johannes

Initialization is successful if only this bit of 
84b2789d61156db0224724806b20110c0d34b07c
is reverted.


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