linux-kernel - Re: [PATCH] [7/31] Extract page table dumping code from i386 fault handler into dump

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Date:	Tue, 15 Jan 2008 00:56:17 -0800
From:	Harvey Harrison <harvey.harrison@...il.com>
To:	Andi Kleen <ak@...e.de>
Cc:	linux-kernel@...r.kernel.org, jbeulich@...ell.com, mingo@...e.hu,
	tglx@...utronix.de
Subject: Re: [PATCH] [7/31] Extract page table dumping code from i386 fault
	handler into dump_pagetable()

On Mon, 2008-01-14 at 23:16 +0100, Andi Kleen wrote:
> Similar to x86-64. This is useful in other situations where we want
> the page table dumped too.
> 
> Besides anything that makes i386 do_page_fault shorter is good.
> 
> Signed-off-by: Andi Kleen <ak@...e.de>
> 
> ---
>  arch/x86/mm/fault_32.c |   72 ++++++++++++++++++++++++++-----------------------
>  1 file changed, 39 insertions(+), 33 deletions(-)
> 
> Index: linux/arch/x86/mm/fault_32.c
> ===================================================================
> --- linux.orig/arch/x86/mm/fault_32.c
> +++ linux/arch/x86/mm/fault_32.c
> @@ -28,6 +28,44 @@
>  #include <asm/desc.h>
>  #include <asm/segment.h>
>  
> +void dump_pagetable(unsigned long address)

static?

> +{
> +	typeof(pte_val(__pte(0))) page;

Is there any type that could be picked that would be nicer than
sprinkling ((__typeof__(page) *), typeof(pte_val(__pte(0))) etc
through here, I know it's just moving the code out to another
function, just wondering if you had any better ideas that someone
could follow-up on.

Maybe another helper printk_page()? could help here.

> +
> +	page = read_cr3();
> +	page = ((__typeof__(page) *) __va(page))[address >> PGDIR_SHIFT];
> +#ifdef CONFIG_X86_PAE
> +	printk("*pdpt = %016Lx ", page);
> +	if ((page >> PAGE_SHIFT) < max_low_pfn
> +	    && page & _PAGE_PRESENT) {
> +		page &= PAGE_MASK;
> +		page = ((__typeof__(page) *) __va(page))[(address >> PMD_SHIFT)
> +							 & (PTRS_PER_PMD - 1)];
> +		printk(KERN_CONT "*pde = %016Lx ", page);
> +		page &= ~_PAGE_NX;
> +	}
> +#else
> +	printk("*pde = %08lx ", page);
> +#endif
> +
> +	/*
> +	 * We must not directly access the pte in the highpte
> +	 * case if the page table is located in highmem.
> +	 * And let's rather not kmap-atomic the pte, just in case
> +	 * it's allocated already.
> +	 */
> +	if ((page >> PAGE_SHIFT) < max_low_pfn
> +	    && (page & _PAGE_PRESENT)
> +	    && !(page & _PAGE_PSE)) {
> +		page &= PAGE_MASK;
> +		page = ((__typeof__(page) *) __va(page))[(address >> PAGE_SHIFT)
> +							 & (PTRS_PER_PTE - 1)];
> +		printk("*pte = %0*Lx ", sizeof(page)*2, (u64)page);
> +	}
> +
> +	printk("\n");
> +}
> +

Cheers,

Harvey

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