Re: [PATCH 1/2] add helper for highmem checks

Borislav Petkov
2013-02-09T09:41:34Z

On Fri, Feb 08, 2013 at 12:28:13PM -0800, Dave Hansen wrote:
>
> Boris, could you check that this series also fixes the /dev/mem
> problem you were seeing?
>
> --
>
> We have a new debugging check on x86 that has caught a number
> of long-standing bugs. However, there is a _bit_ of collateral
> damage with things that call __pa(high_memory).
>
> We are now checking that any addresses passed to __pa() are
> *valid* and can be dereferenced.
>
> "high_memory", however, is not valid. It marks the start of
> highmem, and isn't itself a valid pointer. But, those users
> are really just asking "is this vaddr mapped"? So, give them
> a helper that does that, plus is also kind to our new
> debugging check.
>
>
> Signed-off-by: Dave Hansen <dave@linux.vnet.ibm.com>
> ---
>
> linux-2.6.git-dave/arch/x86/mm/pat.c | 11 ++++++-----
> linux-2.6.git-dave/drivers/char/mem.c | 4 ++--
> linux-2.6.git-dave/drivers/mtd/mtdchar.c | 2 +-
> linux-2.6.git-dave/include/linux/mm.h | 13 +++++++++++++
> 4 files changed, 22 insertions(+), 8 deletions(-)
>
> diff -puN drivers/char/mem.c~clean-up-highmem-checks drivers/char/mem.c
> --- linux-2.6.git/drivers/char/mem.c~clean-up-highmem-checks 2013-02-08 08:42:37.291222110 -0800
> +++ linux-2.6.git-dave/drivers/char/mem.c 2013-02-08 12:27:27.837477867 -0800
> @@ -51,7 +51,7 @@ static inline unsigned long size_inside_
> #ifndef ARCH_HAS_VALID_PHYS_ADDR_RANGE
> static inline int valid_phys_addr_range(phys_addr_t addr, size_t count)
> {
> - return addr + count <= __pa(high_memory);
> + return !phys_addr_is_highmem(addr + count);
> }
>
> static inline int valid_mmap_phys_addr_range(unsigned long pfn, size_t size)
> @@ -250,7 +250,7 @@ static int uncached_access(struct file *
> */
> if (file->f_flags & O_DSYNC)
> return 1;
> - return addr >= __pa(high_memory);
> + return phys_addr_is_highmem(addr);
> #endif
> }
> #endif
> diff -puN include/linux/mm.h~clean-up-highmem-checks include/linux/mm.h
> --- linux-2.6.git/include/linux/mm.h~clean-up-highmem-checks 2013-02-08 08:42:37.295222148 -0800
> +++ linux-2.6.git-dave/include/linux/mm.h 2013-02-08 09:01:49.758254468 -0800
> @@ -1771,5 +1771,18 @@ static inline unsigned int debug_guardpa
> static inline bool page_is_guard(struct page *page) { return false; }
> #endif /* CONFIG_DEBUG_PAGEALLOC */
>
> +static inline phys_addr_t last_lowmem_phys_addr(void)
> +{
> + /*
> + * 'high_memory' is not a pointer that can be dereferenced, so
> + * avoid calling __pa() on it directly.
> + */
> + return __pa(high_memory - 1);
> +}
> +static inline bool phys_addr_is_highmem(phys_addr_t addr)
> +{
> + return addr > last_lowmem_paddr();

I think you mean last_lowmem_phys_addr() here:

include/linux/mm.h: In function ‘phys_addr_is_highmem’:
include/linux/mm.h:1764:2: error: implicit declaration of function ‘last_lowmem_paddr’ [-Werror=implicit-function-declaration]
cc1: some warnings being treated as errors
make[1]: *** [arch/x86/kernel/asm-offsets.s] Error 1

Changed.

--
Regards/Gruss,
Boris.

Sent from a fat crate under my desk. Formatting is fine.
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