linux-kernel - Re: [PATCH v2 34/37] kasan, arm64: print report from tag fault handler

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Message-ID: <20200917170418.GI10662@gaia>
Date:   Thu, 17 Sep 2020 18:04:18 +0100
From:   Catalin Marinas <catalin.marinas@....com>
To:     Andrey Konovalov <andreyknvl@...gle.com>
Cc:     Dmitry Vyukov <dvyukov@...gle.com>,
        Vincenzo Frascino <vincenzo.frascino@....com>,
        kasan-dev@...glegroups.com,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Alexander Potapenko <glider@...gle.com>,
        Marco Elver <elver@...gle.com>,
        Evgenii Stepanov <eugenis@...gle.com>,
        Elena Petrova <lenaptr@...gle.com>,
        Branislav Rankov <Branislav.Rankov@....com>,
        Kevin Brodsky <kevin.brodsky@....com>,
        Will Deacon <will.deacon@....com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        linux-arm-kernel@...ts.infradead.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 34/37] kasan, arm64: print report from tag fault
 handler

On Tue, Sep 15, 2020 at 11:16:16PM +0200, Andrey Konovalov wrote:
> diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c
> index cdc23662691c..ac79819317f2 100644
> --- a/arch/arm64/mm/fault.c
> +++ b/arch/arm64/mm/fault.c
> @@ -14,6 +14,7 @@
>  #include <linux/mm.h>
>  #include <linux/hardirq.h>
>  #include <linux/init.h>
> +#include <linux/kasan.h>
>  #include <linux/kprobes.h>
>  #include <linux/uaccess.h>
>  #include <linux/page-flags.h>
> @@ -295,17 +296,23 @@ static void die_kernel_fault(const char *msg, unsigned long addr,
>  	do_exit(SIGKILL);
>  }
>  
> +#ifdef CONFIG_KASAN_HW_TAGS
>  static void report_tag_fault(unsigned long addr, unsigned int esr,
>  			     struct pt_regs *regs)
>  {
> -	bool is_write = ((esr & ESR_ELx_WNR) >> ESR_ELx_WNR_SHIFT) != 0;
> +	bool is_write  = ((esr & ESR_ELx_WNR) >> ESR_ELx_WNR_SHIFT) != 0;
>  
> -	pr_alert("Memory Tagging Extension Fault in %pS\n", (void *)regs->pc);
> -	pr_alert("  %s at address %lx\n", is_write ? "Write" : "Read", addr);
> -	pr_alert("  Pointer tag: [%02x], memory tag: [%02x]\n",
> -			mte_get_ptr_tag(addr),
> -			mte_get_mem_tag((void *)addr));
> +	/*
> +	 * SAS bits aren't set for all faults reported in EL1, so we can't
> +	 * find out access size.
> +	 */
> +	kasan_report(addr, 0, is_write, regs->pc);
>  }
> +#else
> +/* Tag faults aren't enabled without CONFIG_KASAN_HW_TAGS. */
> +static inline void report_tag_fault(unsigned long addr, unsigned int esr,
> +				    struct pt_regs *regs) { }
> +#endif

So is there a point in introducing this function in an earlier patch,
just to remove its content here?

-- 
Catalin