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    Subject[4/6] go BUG on vmallocspace in __pa() (was: Re: [-mm patch] i386: enable 4k stacks by default)
    On Mon, Apr 30, 2007 at 10:38:19AM -0700, William Lee Irwin III wrote:
    > Here's what I did for i386 for someone concerned about blowing the stack.

    Add checks to __pa() so it goes BUG() on vmallocspace addresses.

    Signed-off-by: William Irwin <wli@holomorphy.com>


    Index: stack-paranoia/arch/i386/kernel/doublefault.c
    ===================================================================
    --- stack-paranoia.orig/arch/i386/kernel/doublefault.c 2007-04-30 10:26:15.959875324 -0700
    +++ stack-paranoia/arch/i386/kernel/doublefault.c 2007-04-30 10:34:55.201465216 -0700
    @@ -62,5 +62,5 @@
    .ss = __KERNEL_DS,
    .ds = __USER_DS,

    - .__cr3 = __pa(swapper_pg_dir)
    + .__cr3 = (unsigned long)swapper_pg_dir - PAGE_OFFSET,
    };
    Index: stack-paranoia/arch/i386/mm/pgtable.c
    ===================================================================
    --- stack-paranoia.orig/arch/i386/mm/pgtable.c 2007-04-30 10:26:16.075881935 -0700
    +++ stack-paranoia/arch/i386/mm/pgtable.c 2007-04-30 10:34:55.201465216 -0700
    @@ -181,6 +181,15 @@
    #endif
    }

    +unsigned long __kvaddr_to_paddr(unsigned long kvaddr)
    +{
    + if (high_memory)
    + BUG_ON(kvaddr >= VMALLOC_START);
    + else
    + BUG_ON(kvaddr >= (unsigned long)__va(MAXMEM));
    + return kvaddr - PAGE_OFFSET;
    +}
    +
    pte_t *pte_alloc_one_kernel(struct mm_struct *mm, unsigned long address)
    {
    return (pte_t *)__get_free_page(GFP_KERNEL|__GFP_REPEAT|__GFP_ZERO);
    Index: stack-paranoia/include/asm-i386/page.h
    ===================================================================
    --- stack-paranoia.orig/include/asm-i386/page.h 2007-04-30 10:26:32.012790127 -0700
    +++ stack-paranoia/include/asm-i386/page.h 2007-04-30 10:34:55.197464988 -0700
    @@ -118,11 +118,17 @@
    #define __PAGE_OFFSET ((unsigned long)CONFIG_PAGE_OFFSET)
    #endif

    -
    #define PAGE_OFFSET ((unsigned long)__PAGE_OFFSET)
    +
    +#ifdef __ASSEMBLY__
    +#define __pa(x) ((unsigned long)(x)-PAGE_OFFSET)
    +#else
    +extern unsigned long __kvaddr_to_paddr(unsigned long);
    +#define __pa(x) __kvaddr_to_paddr((unsigned long)(x))
    +#endif
    +
    #define VMALLOC_RESERVE ((unsigned long)__VMALLOC_RESERVE)
    #define MAXMEM (-__PAGE_OFFSET-__VMALLOC_RESERVE)
    -#define __pa(x) ((unsigned long)(x)-PAGE_OFFSET)
    /* __pa_symbol should be used for C visible symbols.
    This seems to be the official gcc blessed way to do such arithmetic. */
    #define __pa_symbol(x) __pa(RELOC_HIDE((unsigned long)(x),0))
    -
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