linux-kernel - Re: [PATCH v2] MIPS: Fixed __debug_virt_addr

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Date:   Fri, 15 Jul 2022 14:44:21 +0300
From:   Serge Semin <fancer.lancer@...il.com>
To:     Florian Fainelli <f.fainelli@...il.com>
Cc:     linux-mips@...r.kernel.org, gerg@...nel.org,
        Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] MIPS: Fixed __debug_virt_addr_valid()

Hi Florian

On Thu, Jul 14, 2022 at 03:25:12PM -0700, Florian Fainelli wrote:
> It is permissible for kernel code to call virt_to_phys() against virtual
> addresses that are in KSEG0 or KSEG1 and we need to be dealing with both
> types. Rewrite the test condition to ensure that the kernel virtual
> addresses are above PAGE_OFFSET which they must be, and below KSEG2
> where the non-linear mapping starts.
> 
> For EVA, there is not much that we can do given the linear address range
> that is offered, so just return any virtual address as being valid.
> 
> Finally, when HIGHMEM is not enabled, all virtual addresses are assumed
> to be valid as well.
> 
> Fixes: dfad83cb7193 ("MIPS: Add support for CONFIG_DEBUG_VIRTUAL")
> Signed-off-by: Florian Fainelli <f.fainelli@...il.com>

No objections now. Thanks.
Reviewed-by: Serge Semin <fancer.lancer@...il.com>

-Serge(y)

> ---
> Changes in v2:
> 
> - handle lack of HIGHMEM and EVA
> 
>  arch/mips/mm/physaddr.c | 14 ++++----------
>  1 file changed, 4 insertions(+), 10 deletions(-)
> 
> diff --git a/arch/mips/mm/physaddr.c b/arch/mips/mm/physaddr.c
> index a1ced5e44951..f9b8c85e9843 100644
> --- a/arch/mips/mm/physaddr.c
> +++ b/arch/mips/mm/physaddr.c
> @@ -5,6 +5,7 @@
>  #include <linux/mmdebug.h>
>  #include <linux/mm.h>
>  
> +#include <asm/addrspace.h>
>  #include <asm/sections.h>
>  #include <asm/io.h>
>  #include <asm/page.h>
> @@ -12,15 +13,6 @@
>  
>  static inline bool __debug_virt_addr_valid(unsigned long x)
>  {
> -	/* high_memory does not get immediately defined, and there
> -	 * are early callers of __pa() against PAGE_OFFSET
> -	 */
> -	if (!high_memory && x >= PAGE_OFFSET)
> -		return true;
> -
> -	if (high_memory && x >= PAGE_OFFSET && x < (unsigned long)high_memory)
> -		return true;
> -
>  	/*
>  	 * MAX_DMA_ADDRESS is a virtual address that may not correspond to an
>  	 * actual physical address. Enough code relies on
> @@ -30,7 +22,9 @@ static inline bool __debug_virt_addr_valid(unsigned long x)
>  	if (x == MAX_DMA_ADDRESS)
>  		return true;
>  
> -	return false;
> +	return x >= PAGE_OFFSET && (KSEGX(x) < KSEG2 ||
> +	       IS_ENABLED(CONFIG_EVA) ||
> +	       !IS_ENABLED(CONFIG_HIGHMEM));
>  }
>  
>  phys_addr_t __virt_to_phys(volatile const void *x)
> -- 
> 2.25.1
>