linux-kernel - Re: [PATCHv2 6/6] arm64: Add support for CONFIG_DEBUG

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Message-ID: <20161102230642.GB19591@remoulade>
Date:   Wed, 2 Nov 2016 23:06:43 +0000
From:   Mark Rutland <mark.rutland@....com>
To:     Laura Abbott <labbott@...hat.com>
Cc:     Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Will Deacon <will.deacon@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCHv2 6/6] arm64: Add support for CONFIG_DEBUG_VIRTUAL

On Wed, Nov 02, 2016 at 03:00:54PM -0600, Laura Abbott wrote:
> +CFLAGS_physaddr.o		:= -DTEXT_OFFSET=$(TEXT_OFFSET)
> +obj-$(CONFIG_DEBUG_VIRTUAL)	+= physaddr.o

> diff --git a/arch/arm64/mm/physaddr.c b/arch/arm64/mm/physaddr.c
> new file mode 100644
> index 0000000..874c782
> --- /dev/null
> +++ b/arch/arm64/mm/physaddr.c
> @@ -0,0 +1,34 @@
> +#include <linux/mm.h>
> +
> +#include <asm/memory.h>
> +
> +unsigned long __virt_to_phys(unsigned long x)
> +{
> +	phys_addr_t __x = (phys_addr_t)x;
> +
> +	if (__x & BIT(VA_BITS - 1)) {
> +		/*
> +		 * The linear kernel range starts in the middle of the virtual
> +		 * adddress space. Testing the top bit for the start of the
> +		 * region is a sufficient check.
> +		 */
> +		return (__x & ~PAGE_OFFSET) + PHYS_OFFSET;
> +	} else {
> +		VIRTUAL_BUG_ON(x < kimage_vaddr || x >= (unsigned long)_end);
> +		return (__x - kimage_voffset);
> +	}
> +}
> +EXPORT_SYMBOL(__virt_to_phys);
> +
> +unsigned long __phys_addr_symbol(unsigned long x)
> +{
> +	phys_addr_t __x = (phys_addr_t)x;
> +
> +	/*
> +	 * This is intentionally different than above to be a tighter check
> +	 * for symbols.
> +	 */
> +	VIRTUAL_BUG_ON(x < kimage_vaddr + TEXT_OFFSET || x > (unsigned long) _end);

Can't we use _text instead of kimage_vaddr + TEXT_OFFSET? That way we don't
need CFLAGS_physaddr.o.

Or KERNEL_START / KERNEL_END from <asm/memory.h>?

Otherwise, this looks good to me (though I haven't grokked the need for
__pa_symbol() yet).

Thanks,
Mark.

> +	return (__x - kimage_voffset);
> +}
> +EXPORT_SYMBOL(__phys_addr_symbol);
> -- 
> 2.10.1
>