linux-kernel - Re: [RFC] x86-64: make compat_start_thread() match start

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Date:	Thu, 08 Oct 2009 19:41:04 -0700
From:	Suresh Siddha <suresh.b.siddha@...el.com>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	LKML <linux-kernel@...r.kernel.org>, Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [RFC] x86-64: make compat_start_thread() match start_thread()

On Thu, 2009-10-08 at 18:09 -0700, H. Peter Anvin wrote:
> diff --git a/arch/x86/kernel/process_64.c
> b/arch/x86/kernel/process_64.c
> index ad535b6..ec223a8 100644
> --- a/arch/x86/kernel/process_64.c
> +++ b/arch/x86/kernel/process_64.c
> @@ -356,7 +356,7 @@ start_thread(struct pt_regs *regs, unsigned long
> new_ip, unsigned long new_sp)
>         percpu_write(old_rsp, new_sp);
>         regs->cs                = __USER_CS;
>         regs->ss                = __USER_DS;
> -       regs->flags             = 0x200;
> +       regs->flags             = X86_EFLAGS_IF;
>         set_fs(USER_DS);
>         /*
>          * Free the old FP and other extended state
> @@ -365,6 +365,27 @@ start_thread(struct pt_regs *regs, unsigned long
> new_ip, unsigned long new_sp)
>  }
>  EXPORT_SYMBOL_GPL(start_thread);
>  
> +#ifdef CONFIG_IA32_EMULATION
> +void compat_start_thread(struct pt_regs *regs, u32 new_ip, u32
> new_sp)
> +{
> +       loadsegment(fs, 0);
> +       loadsegment(ds, __USER32_DS);
> +       loadsegment(es, __USER32_DS);
> +       load_gs_index(0);
> +       regs->ip                = new_ip;
> +       regs->sp                = new_sp;
> +       percpu_write(old_rsp, new_sp);
> +       regs->cs                = __USER32_CS;
> +       regs->ss                = __USER32_DS;
> +       regs->flags             = X86_EFLAGS_IF;
> +       set_fs(USER_DS);
> +       /*
> +        * Free the old FP and other extended state
> +        */
> +       free_thread_xstate(current);
> +}
> +#endif
> +

Peter, While you are it, we should just merge most of the meat into one
common function handling both modes. That will be more cleaner.

thanks,
suresh

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