linux-kernel - Re: [PATCH v3 2/4] x86/traps: Print non-canonical address on #GP

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Date:   Wed, 20 Nov 2019 13:30:58 +0100
From:   Ingo Molnar <mingo@...nel.org>
To:     Jann Horn <jannh@...gle.com>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        the arch/x86 maintainers <x86@...nel.org>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Alexander Potapenko <glider@...gle.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        kasan-dev <kasan-dev@...glegroups.com>,
        kernel list <linux-kernel@...r.kernel.org>,
        Andrey Konovalov <andreyknvl@...gle.com>,
        Andy Lutomirski <luto@...nel.org>,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Andi Kleen <ak@...ux.intel.com>
Subject: Re: [PATCH v3 2/4] x86/traps: Print non-canonical address on #GP


* Jann Horn <jannh@...gle.com> wrote:

> You mean something like this?
> 
> ========================
> diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
> index 9b23c4bda243..16a6bdaccb51 100644
> --- a/arch/x86/kernel/traps.c
> +++ b/arch/x86/kernel/traps.c
> @@ -516,32 +516,36 @@ dotraplinkage void do_bounds(struct pt_regs
> *regs, long error_code)
>   * On 64-bit, if an uncaught #GP occurs while dereferencing a non-canonical
>   * address, return that address.
>   */
> -static unsigned long get_kernel_gp_address(struct pt_regs *regs)
> +static bool get_kernel_gp_address(struct pt_regs *regs, unsigned long *addr,
> +                                          bool *non_canonical)

Yeah, that's pretty much the perfect end result!

> I guess that could potentially be useful if a #GP is triggered by
> something like an SSE alignment error? I'll add it in unless someone
> else complains.

Yeah - also it's correct information about the context of the fault, so 
it probably cannot *hurt*, and will allow us to debug/validate everything 
in this area faster.

> > > +#define GPFSTR "general protection fault"
> > >  dotraplinkage void
> >
> > Please separate macro and function definitions by an additional newline.
> 
> Will change it.

Thanks!

	Ingo