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Date: Fri, 11 Nov 2016 20:49:13 -0500 (EST)
From: Nicolas Pitre <nicolas.pitre@linaro.org>
To: Florian Fainelli <f.fainelli@gmail.com>
cc: linux-kernel@vger.kernel.org, Russell King <linux@armlinux.org.uk>,
        Catalin Marinas <catalin.marinas@arm.com>,
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Subject: Re: [PATCH RFC] mm: Add debug_virt_to_phys()
In-Reply-To: <20161112004449.30566-1-f.fainelli@gmail.com>
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References: <20161112004449.30566-1-f.fainelli@gmail.com>
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On Fri, 11 Nov 2016, Florian Fainelli wrote:

> When CONFIG_DEBUG_VM is turned on, virt_to_phys() maps to
> debug_virt_to_phys() which helps catch vmalloc space addresses being
> passed. This is helpful in debugging bogus drivers that just assume
> linear mappings all over the place.
> 
> For ARM, ARM64, Unicore32 and Microblaze, the architectures define
> __virt_to_phys() as being the functional implementation of the address
> translation, so we special case the debug stub to call into
> __virt_to_phys directly.
> 
> Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
> ---
>  arch/arm/include/asm/memory.h      |  4 ++++
>  arch/arm64/include/asm/memory.h    |  4 ++++
>  include/asm-generic/memory_model.h |  4 ++++
>  mm/debug.c                         | 15 +++++++++++++++
>  4 files changed, 27 insertions(+)
> 
> diff --git a/arch/arm/include/asm/memory.h b/arch/arm/include/asm/memory.h
> index 76cbd9c674df..448dec9b8b00 100644
> --- a/arch/arm/include/asm/memory.h
> +++ b/arch/arm/include/asm/memory.h
> @@ -260,11 +260,15 @@ static inline unsigned long __phys_to_virt(phys_addr_t x)
>   * translation for translating DMA addresses.  Use the driver
>   * DMA support - see dma-mapping.h.
>   */
> +#ifndef CONFIG_DEBUG_VM
>  #define virt_to_phys virt_to_phys
>  static inline phys_addr_t virt_to_phys(const volatile void *x)
>  {
>  	return __virt_to_phys((unsigned long)(x));
>  }
> +#else
> +#define virt_to_phys debug_virt_to_phys
> +#endif
[...]

Why don't you do something more like:

 static inline phys_addr_t virt_to_phys(const volatile void *x)
 {
+        debug_virt_to_phys(x);
         return __virt_to_phys((unsigned long)(x));
 }

[...]

static inline void debug_virt_to_phys(const void *address)
{
#ifdef CONFIG_DEBUG_VM
        BUG_ON(is_vmalloc_addr(address));
#endif
}

?


Nicolas