Re: [PATCH v10 17/17] kasan: enable instrumentation of global variables

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



On Thu, 29 Jan 2015 18:12:01 +0300 Andrey Ryabinin <a.ryabinin@xxxxxxxxxxx> wrote:

> This feature let us to detect accesses out of bounds
> of global variables.

global variables *within modules*, I think?  More specificity needed here.

> The idea of this is simple. Compiler increases each global variable
> by redzone size and add constructors invoking __asan_register_globals()
> function. Information about global variable (address, size,
> size with redzone ...) passed to __asan_register_globals() so we could
> poison variable's redzone.
> 
> This patch also forces module_alloc() to return 8*PAGE_SIZE aligned
> address making shadow memory handling ( kasan_module_alloc()/kasan_module_free() )
> more simple. Such alignment guarantees that each shadow page backing
> modules address space correspond to only one module_alloc() allocation.
> 
> ...
>
> +int kasan_module_alloc(void *addr, size_t size)
> +{
> +
> +	size_t shadow_size = round_up(size >> KASAN_SHADOW_SCALE_SHIFT,
> +				PAGE_SIZE);
> +	unsigned long shadow_start = kasan_mem_to_shadow((unsigned long)addr);
> +	void *ret;

Like this:

	size_t shadow_size;
	unsigned long shadow_start;
	void *ret;

	shadow_size = round_up(size >> KASAN_SHADOW_SCALE_SHIFT, PAGE_SIZE);
	shadow_start = kasan_mem_to_shadow((unsigned long)addr);

it's much easier to read and avoids the 80-column trickery.

I do suspect that

	void *kasan_mem_to_shadow(const void *addr);

would clean up lots and lots of code.

> +	if (WARN_ON(!PAGE_ALIGNED(shadow_start)))
> +		return -EINVAL;
> +
> +	ret = __vmalloc_node_range(shadow_size, 1, shadow_start,
> +			shadow_start + shadow_size,
> +			GFP_KERNEL | __GFP_HIGHMEM | __GFP_ZERO,
> +			PAGE_KERNEL, VM_NO_GUARD, NUMA_NO_NODE,
> +			__builtin_return_address(0));
> +	return ret ? 0 : -ENOMEM;
> +}
> +
> 
> ...
>
> +struct kasan_global {
> +	const void *beg;		/* Address of the beginning of the global variable. */
> +	size_t size;			/* Size of the global variable. */
> +	size_t size_with_redzone;	/* Size of the variable + size of the red zone. 32 bytes aligned */
> +	const void *name;
> +	const void *module_name;	/* Name of the module where the global variable is declared. */
> +	unsigned long has_dynamic_init;	/* This needed for C++ */

This can be removed?

> +#if KASAN_ABI_VERSION >= 4
> +	struct kasan_source_location *location;
> +#endif
> +};
> 
> ...
>

--
To unsubscribe from this list: send the line "unsubscribe linux-kbuild" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html




[Index of Archives]     [Linux&nblp;USB Development]     [Linux Media]     [Video for Linux]     [Linux Audio Users]     [Yosemite Secrets]     [Linux Kernel]     [Linux SCSI]

  Powered by Linux