linux-kernel - Re: [PATCH v5 03/10] swiotlb: Map the buffer if it was unmapped by XPFO

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Message-ID: <20170810130104.GB2413@localhost.localdomain>
Date:   Thu, 10 Aug 2017 09:01:06 -0400
From:   Konrad Rzeszutek Wilk <konrad@...nok.org>
To:     Tycho Andersen <tycho@...ker.com>
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        kernel-hardening@...ts.openwall.com,
        Marco Benatto <marco.antonio.780@...il.com>,
        Juerg Haefliger <juerg.haefliger@...onical.com>,
        Juerg Haefliger <juerg.haefliger@....com>
Subject: Re: [PATCH v5 03/10] swiotlb: Map the buffer if it was unmapped by
 XPFO

On Wed, Aug 09, 2017 at 02:07:48PM -0600, Tycho Andersen wrote:
> From: Juerg Haefliger <juerg.haefliger@....com>
> 
> Signed-off-by: Juerg Haefliger <juerg.haefliger@...onical.com>
> Tested-by: Tycho Andersen <tycho@...ker.com>
> ---
>  include/linux/xpfo.h | 4 ++++
>  lib/swiotlb.c        | 3 ++-
>  mm/xpfo.c            | 9 +++++++++
>  3 files changed, 15 insertions(+), 1 deletion(-)
> 
> diff --git a/include/linux/xpfo.h b/include/linux/xpfo.h
> index 1ff2d1976837..6b61f7b820f4 100644
> --- a/include/linux/xpfo.h
> +++ b/include/linux/xpfo.h
> @@ -27,6 +27,8 @@ void xpfo_kunmap(void *kaddr, struct page *page);
>  void xpfo_alloc_pages(struct page *page, int order, gfp_t gfp);
>  void xpfo_free_pages(struct page *page, int order);
>  
> +bool xpfo_page_is_unmapped(struct page *page);
> +
>  #else /* !CONFIG_XPFO */
>  
>  static inline void xpfo_kmap(void *kaddr, struct page *page) { }
> @@ -34,6 +36,8 @@ static inline void xpfo_kunmap(void *kaddr, struct page *page) { }
>  static inline void xpfo_alloc_pages(struct page *page, int order, gfp_t gfp) { }
>  static inline void xpfo_free_pages(struct page *page, int order) { }
>  
> +static inline bool xpfo_page_is_unmapped(struct page *page) { return false; }
> +
>  #endif /* CONFIG_XPFO */
>  
>  #endif /* _LINUX_XPFO_H */
> diff --git a/lib/swiotlb.c b/lib/swiotlb.c
> index a8d74a733a38..d4fee5ca2d9e 100644
> --- a/lib/swiotlb.c
> +++ b/lib/swiotlb.c
> @@ -420,8 +420,9 @@ static void swiotlb_bounce(phys_addr_t orig_addr, phys_addr_t tlb_addr,
>  {
>  	unsigned long pfn = PFN_DOWN(orig_addr);
>  	unsigned char *vaddr = phys_to_virt(tlb_addr);
> +	struct page *page = pfn_to_page(pfn);
>  
> -	if (PageHighMem(pfn_to_page(pfn))) {
> +	if (PageHighMem(page) || xpfo_page_is_unmapped(page)) {
>  		/* The buffer does not have a mapping.  Map it in and copy */
>  		unsigned int offset = orig_addr & ~PAGE_MASK;
>  		char *buffer;
> diff --git a/mm/xpfo.c b/mm/xpfo.c
> index 3cd45f68b5ad..3f305f31a072 100644
> --- a/mm/xpfo.c
> +++ b/mm/xpfo.c
> @@ -206,3 +206,12 @@ void xpfo_kunmap(void *kaddr, struct page *page)
>  	spin_unlock_irqrestore(&xpfo->maplock, flags);
>  }
>  EXPORT_SYMBOL(xpfo_kunmap);
> +
> +inline bool xpfo_page_is_unmapped(struct page *page)
> +{
> +	if (!static_branch_unlikely(&xpfo_inited))
> +		return false;
> +
> +	return test_bit(XPFO_PAGE_UNMAPPED, &lookup_xpfo(page)->flags);
> +}
> +EXPORT_SYMBOL(xpfo_page_is_unmapped);

How can it be inline and 'EXPORT_SYMBOL' ? And why make it inline? It
surely does not need to be access that often?

> -- 
> 2.11.0
>