Josh Poimboeuf <jpoim...@redhat.com> writes:
> On Mon, Nov 09, 2015 at 02:53:57PM +1030, Rusty Russell wrote:
>
>> @@ -1858,74 +1849,75 @@ static void mod_sysfs_teardown(struct module *mod)
>> /*
>> * LKM RO/NX protection: protect module's text/ro-data
>> * from modification and any data from execution.
>> + *
>> + * General layout of module is:
>> + * [text] [read-only-data] [writable data]
>> + * text_size -----^ ^ ^
>> + * ro_size ------------------------| |
>> + * size -------------------------------------------|
>> + *
>> + * These values are always page-aligned (as is base)
>> */
>> -void set_page_attributes(void *start, void *end, int (*set)(unsigned long
>> start, int num_pages))
>> +static void frob_text(const struct module_layout *layout,
>> + int (*set_memory)(unsigned long start, int num_pages))
>> {
>> - unsigned long begin_pfn = PFN_DOWN((unsigned long)start);
>> - unsigned long end_pfn = PFN_DOWN((unsigned long)end);
>> -
>> - if (end_pfn > begin_pfn)
>> - set(begin_pfn << PAGE_SHIFT, end_pfn - begin_pfn);
>> + BUG_ON((unsigned long)layout->base & (PAGE_SIZE-1));
>> + BUG_ON((unsigned long)layout->text_size & (PAGE_SIZE-1));
>> + set_memory((unsigned long)layout->base,
>> + layout->text_size >> PAGE_SHIFT);
>
> Should the set_memory() call be skipped if text_size is 0?
Not AFAICT. And in practice:
1) Every module on my system has a .text section.
2) Every module has a rodata section (.modinfo)
3) Every module on my system has a .data section.
So I think it would be a premature optimization.
Thanks,
Rusty.
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