lkml.org 
[lkml]   [2015]   [Jan]   [29]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH v10 17/17] kasan: enable instrumentation of global variables
On Thu, 29 Jan 2015 18:12:01 +0300 Andrey Ryabinin <a.ryabinin@samsung.com> 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
> +};
>
> ...
>



\
 
 \ /
  Last update: 2015-01-30 00:21    [W:0.221 / U:2.172 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site