Re: [patch V3 02/20] x86/process: Unify copy_thread_tls()

[Linus Torvalds]

On Wed, Nov 13, 2019 at 1:02 PM Thomas Gleixner <tglx@xxxxxxxxxxxxx> wrote:
>
> +int copy_thread_tls(unsigned long clone_flags, unsigned long sp,
> +                   unsigned long arg, struct task_struct *p, unsigned long tls)
...
> +#ifdef CONFIG_X86_64
..
> +#else
> +       /* Clear all status flags including IF and set fixed bit. */
> +       frame->flags = X86_EFLAGS_FIXED;
> +#endif

Hmm. The unification I like, but it also shows these differences that
I don't remember the reason for.

Remind me why __switch_to_asm() on 32-bit safes eflags, but we don't
do it on x86-64?

The comment just talks about callee-saved registers, but flags isn't
callee-saved, so there's something else going on.

This patch clearly doesn't change anything, I'm not complaining about
the patch at all. I'm just wondering about the odd difference that the
patch exposes.

               Linus