linux-kernel - Re: [PATCH 10/24] x86/mm/kaiser: Map the entry stack variables

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Message-ID: <20171127172216.vd7ompgabf2bol76@hirez.programming.kicks-ass.net>
Date:   Mon, 27 Nov 2017 18:22:16 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Ingo Molnar <mingo@...nel.org>
Cc:     linux-kernel@...r.kernel.org,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Andy Lutomirski <luto@...capital.net>,
        Thomas Gleixner <tglx@...utronix.de>,
        "H . Peter Anvin" <hpa@...or.com>, Borislav Petkov <bp@...en8.de>,
        Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [PATCH 10/24] x86/mm/kaiser: Map the entry stack variables

On Mon, Nov 27, 2017 at 11:49:09AM +0100, Ingo Molnar wrote:
> diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c
> index 157f81816915..631e229ab428 100644
> --- a/arch/x86/kernel/process_64.c
> +++ b/arch/x86/kernel/process_64.c
> @@ -59,7 +59,7 @@
>  #include <asm/unistd_32_ia32.h>
>  #endif
>  
> -__visible DEFINE_PER_CPU(unsigned long, rsp_scratch);
> +__visible DEFINE_PER_CPU_USER_MAPPED(unsigned long, rsp_scratch);
>  
>  /* Prints also some state that isn't saved in the pt_regs */
>  void __show_regs(struct pt_regs *regs, int all)

Do we still need this one? It appears to me we'll never actually execute
that part of entry_SYSCALL_64 anymore, due to
entry_SYSCALL_64_trampoline.